Add new virtual table 'recover' to src/ and the amalgamation.
Since recover.c is in somewhat active development, it is possible that
the patch below will not reliably re-create the file.
shess@chromium.org
Generated with:
git diff --cached --relative=third_party/sqlite/src --src-prefix='' --dst-prefix='' > third_party/sqlite/recover.patch
[--cached because otherwise the diff adding recover.c wasn't generated.]
diff --git Makefile.in Makefile.in
index f3239f3..216742c 100644
--- Makefile.in
+++ Makefile.in
@@ -251,6 +251,7 @@ SRC = \
$(TOP)/src/prepare.c \
$(TOP)/src/printf.c \
$(TOP)/src/random.c \
+ $(TOP)/src/recover.c \
$(TOP)/src/resolve.c \
$(TOP)/src/rowset.c \
$(TOP)/src/select.c \
diff --git src/sqlite.h.in src/sqlite.h.in
index 62b9326..fb76659 100644
--- src/sqlite.h.in
+++ src/sqlite.h.in
@@ -6403,6 +6403,17 @@ int sqlite3_wal_checkpoint_v2(
#define SQLITE_CHECKPOINT_RESTART 2
+/* Begin recover.patch for Chromium */
+/*
+** Call to initialize the recover virtual-table modules (see recover.c).
+**
+** This could be loaded by default in main.c, but that would make the
+** virtual table available to Web SQL. Breaking it out allows only
+** selected users to enable it (currently sql/recovery.cc).
+*/
+int recoverVtableInit(sqlite3 *db);
+/* End recover.patch for Chromium */
+
/*
** Undo the hack that converts floating point types to integer for
** builds on processors without floating point support.
diff --git tool/mksqlite3c.tcl tool/mksqlite3c.tcl
index fa99f2d..df2df07 100644
--- tool/mksqlite3c.tcl
+++ tool/mksqlite3c.tcl
@@ -293,6 +293,8 @@ foreach file {
main.c
notify.c
+ recover.c
+
fts3.c
fts3_aux.c
fts3_expr.c
diff --git src/recover.c src/recover.c
new file mode 100644
index 0000000..6430c8b
--- /dev/null
+++ src/recover.c
@@ -0,0 +1,2130 @@
+/*
+** 2012 Jan 11
+**
+** The author disclaims copyright to this source code. In place of
+** a legal notice, here is a blessing:
+**
+** May you do good and not evil.
+** May you find forgiveness for yourself and forgive others.
+** May you share freely, never taking more than you give.
+*/
+/* TODO(shess): THIS MODULE IS STILL EXPERIMENTAL. DO NOT USE IT. */
+/* Implements a virtual table "recover" which can be used to recover
+ * data from a corrupt table. The table is walked manually, with
+ * corrupt items skipped. Additionally, any errors while reading will
+ * be skipped.
+ *
+ * Given a table with this definition:
+ *
+ * CREATE TABLE Stuff (
+ * name TEXT PRIMARY KEY,
+ * value TEXT NOT NULL
+ * );
+ *
+ * to recover the data from teh table, you could do something like:
+ *
+ * -- Attach another database, the original is not trustworthy.
+ * ATTACH DATABASE '/tmp/db.db' AS rdb;
+ * -- Create a new version of the table.
+ * CREATE TABLE rdb.Stuff (
+ * name TEXT PRIMARY KEY,
+ * value TEXT NOT NULL
+ * );
+ * -- This will read the original table's data.
+ * CREATE VIRTUAL TABLE temp.recover_Stuff using recover(
+ * main.Stuff,
+ * name TEXT STRICT NOT NULL, -- only real TEXT data allowed
+ * value TEXT STRICT NOT NULL
+ * );
+ * -- Corruption means the UNIQUE constraint may no longer hold for
+ * -- Stuff, so either OR REPLACE or OR IGNORE must be used.
+ * INSERT OR REPLACE INTO rdb.Stuff (rowid, name, value )
+ * SELECT rowid, name, value FROM temp.recover_Stuff;
+ * DROP TABLE temp.recover_Stuff;
+ * DETACH DATABASE rdb;
+ * -- Move db.db to replace original db in filesystem.
+ *
+ *
+ * Usage
+ *
+ * Given the goal of dealing with corruption, it would not be safe to
+ * create a recovery table in the database being recovered. So
+ * recovery tables must be created in the temp database. They are not
+ * appropriate to persist, in any case. [As a bonus, sqlite_master
+ * tables can be recovered. Perhaps more cute than useful, though.]
+ *
+ * The parameters are a specifier for the table to read, and a column
+ * definition for each bit of data stored in that table. The named
+ * table must be convertable to a root page number by reading the
+ * sqlite_master table. Bare table names are assumed to be in
+ * database 0 ("main"), other databases can be specified in db.table
+ * fashion.
+ *
+ * Column definitions are similar to BUT NOT THE SAME AS those
+ * provided to CREATE statements:
+ * column-def: column-name [type-name [STRICT] [NOT NULL]]
+ * type-name: (ANY|ROWID|INTEGER|FLOAT|NUMERIC|TEXT|BLOB)
+ *
+ * Only those exact type names are accepted, there is no type
+ * intuition. The only constraints accepted are STRICT (see below)
+ * and NOT NULL. Anything unexpected will cause the create to fail.
+ *
+ * ANY is a convenience to indicate that manifest typing is desired.
+ * It is equivalent to not specifying a type at all. The results for
+ * such columns will have the type of the data's storage. The exposed
+ * schema will contain no type for that column.
+ *
+ * ROWID is used for columns representing aliases to the rowid
+ * (INTEGER PRIMARY KEY, with or without AUTOINCREMENT), to make the
+ * concept explicit. Such columns are actually stored as NULL, so
+ * they cannot be simply ignored. The exposed schema will be INTEGER
+ * for that column.
+ *
+ * NOT NULL causes rows with a NULL in that column to be skipped. It
+ * also adds NOT NULL to the column in the exposed schema. If the
+ * table has ever had columns added using ALTER TABLE, then those
+ * columns implicitly contain NULL for rows which have not been
+ * updated. [Workaround using COALESCE() in your SELECT statement.]
+ *
+ * The created table is read-only, with no indices. Any SELECT will
+ * be a full-table scan, returning each valid row read from the
+ * storage of the backing table. The rowid will be the rowid of the
+ * row from the backing table. "Valid" means:
+ * - The cell metadata for the row is well-formed. Mainly this means that
+ * the cell header info describes a payload of the size indicated by
+ * the cell's payload size.
+ * - The cell does not run off the page.
+ * - The cell does not overlap any other cell on the page.
+ * - The cell contains doesn't contain too many columns.
+ * - The types of the serialized data match the indicated types (see below).
+ *
+ *
+ * Type affinity versus type storage.
+ *
+ * http://www.sqlite.org/datatype3.html describes SQLite's type
+ * affinity system. The system provides for automated coercion of
+ * types in certain cases, transparently enough that many developers
+ * do not realize that it is happening. Importantly, it implies that
+ * the raw data stored in the database may not have the obvious type.
+ *
+ * Differences between the stored data types and the expected data
+ * types may be a signal of corruption. This module makes some
+ * allowances for automatic coercion. It is important to be concious
+ * of the difference between the schema exposed by the module, and the
+ * data types read from storage. The following table describes how
+ * the module interprets things:
+ *
+ * type schema data STRICT
+ * ---- ------ ---- ------
+ * ANY <none> any any
+ * ROWID INTEGER n/a n/a
+ * INTEGER INTEGER integer integer
+ * FLOAT FLOAT integer or float float
+ * NUMERIC NUMERIC integer, float, or text integer or float
+ * TEXT TEXT text or blob text
+ * BLOB BLOB blob blob
+ *
+ * type is the type provided to the recover module, schema is the
+ * schema exposed by the module, data is the acceptable types of data
+ * decoded from storage, and STRICT is a modification of that.
+ *
+ * A very loose recovery system might use ANY for all columns, then
+ * use the appropriate sqlite3_column_*() calls to coerce to expected
+ * types. This doesn't provide much protection if a page from a
+ * different table with the same column count is linked into an
+ * inappropriate btree.
+ *
+ * A very tight recovery system might use STRICT to enforce typing on
+ * all columns, preferring to skip rows which are valid at the storage
+ * level but don't contain the right types. Note that FLOAT STRICT is
+ * almost certainly not appropriate, since integral values are
+ * transparently stored as integers, when that is more efficient.
+ *
+ * Another option is to use ANY for all columns and inspect each
+ * result manually (using sqlite3_column_*). This should only be
+ * necessary in cases where developers have used manifest typing (test
+ * to make sure before you decide that you aren't using manifest
+ * typing!).
+ *
+ *
+ * Caveats
+ *
+ * Leaf pages not referenced by interior nodes will not be found.
+ *
+ * Leaf pages referenced from interior nodes of other tables will not
+ * be resolved.
+ *
+ * Rows referencing invalid overflow pages will be skipped.
+ *
+ * SQlite rows have a header which describes how to interpret the rest
+ * of the payload. The header can be valid in cases where the rest of
+ * the record is actually corrupt (in the sense that the data is not
+ * the intended data). This can especially happen WRT overflow pages,
+ * as lack of atomic updates between pages is the primary form of
+ * corruption I have seen in the wild.
+ */
+/* The implementation is via a series of cursors. The cursor
+ * implementations follow the pattern:
+ *
+ * // Creates the cursor using various initialization info.
+ * int cursorCreate(...);
+ *
+ * // Returns 1 if there is no more data, 0 otherwise.
+ * int cursorEOF(Cursor *pCursor);
+ *
+ * // Various accessors can be used if not at EOF.
+ *
+ * // Move to the next item.
+ * int cursorNext(Cursor *pCursor);
+ *
+ * // Destroy the memory associated with the cursor.
+ * void cursorDestroy(Cursor *pCursor);
+ *
+ * References in the following are to sections at
+ * http://www.sqlite.org/fileformat2.html .
+ *
+ * RecoverLeafCursor iterates the records in a leaf table node
+ * described in section 1.5 "B-tree Pages". When the node is
+ * exhausted, an interior cursor is used to get the next leaf node,
+ * and iteration continues there.
+ *
+ * RecoverInteriorCursor iterates the child pages in an interior table
+ * node described in section 1.5 "B-tree Pages". When the node is
+ * exhausted, a parent interior cursor is used to get the next
+ * interior node at the same level, and iteration continues there.
+ *
+ * Together these record the path from the leaf level to the root of
+ * the tree. Iteration happens from the leaves rather than the root
+ * both for efficiency and putting the special case at the front of
+ * the list is easier to implement.
+ *
+ * RecoverCursor uses a RecoverLeafCursor to iterate the rows of a
+ * table, returning results via the SQLite virtual table interface.
+ */
+/* TODO(shess): It might be useful to allow DEFAULT in types to
+ * specify what to do for NULL when an ALTER TABLE case comes up.
+ * Unfortunately, simply adding it to the exposed schema and using
+ * sqlite3_result_null() does not cause the default to be generate.
+ * Handling it ourselves seems hard, unfortunately.
+ */
+
+#include <assert.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <string.h>
+
+/* Internal SQLite things that are used:
+ * u32, u64, i64 types.
+ * Btree, Pager, and DbPage structs.
+ * DbPage.pData, .pPager, and .pgno
+ * sqlite3 struct.
+ * sqlite3BtreePager() and sqlite3BtreeGetPageSize()
+ * sqlite3PagerAcquire() and sqlite3PagerUnref()
+ * getVarint().
+ */
+#include "sqliteInt.h"
+
+/* For debugging. */
+#if 0
+#define FNENTRY() fprintf(stderr, "In %s\n", __FUNCTION__)
+#else
+#define FNENTRY()
+#endif
+
+/* Generic constants and helper functions. */
+
+static const unsigned char kTableLeafPage = 0x0D;
+static const unsigned char kTableInteriorPage = 0x05;
+
+/* From section 1.5. */
+static const unsigned kiPageTypeOffset = 0;
+static const unsigned kiPageFreeBlockOffset = 1;
+static const unsigned kiPageCellCountOffset = 3;
+static const unsigned kiPageCellContentOffset = 5;
+static const unsigned kiPageFragmentedBytesOffset = 7;
+static const unsigned knPageLeafHeaderBytes = 8;
+/* Interior pages contain an additional field. */
+static const unsigned kiPageRightChildOffset = 8;
+static const unsigned kiPageInteriorHeaderBytes = 12;
+
+/* Accepted types are specified by a mask. */
+#define MASK_ROWID (1<<0)
+#define MASK_INTEGER (1<<1)
+#define MASK_FLOAT (1<<2)
+#define MASK_TEXT (1<<3)
+#define MASK_BLOB (1<<4)
+#define MASK_NULL (1<<5)
+
+/* Helpers to decode fixed-size fields. */
+static u32 decodeUnsigned16(const unsigned char *pData){
+ return (pData[0]<<8) + pData[1];
+}
+static u32 decodeUnsigned32(const unsigned char *pData){
+ return (decodeUnsigned16(pData)<<16) + decodeUnsigned16(pData+2);
+}
+static i64 decodeSigned(const unsigned char *pData, unsigned nBytes){
+ i64 r = (char)(*pData);
+ while( --nBytes ){
+ r <<= 8;
+ r += *(++pData);
+ }
+ return r;
+}
+/* Derived from vdbeaux.c, sqlite3VdbeSerialGet(), case 7. */
+/* TODO(shess): Determine if swapMixedEndianFloat() applies. */
+static double decodeFloat64(const unsigned char *pData){
+#if !defined(NDEBUG)
+ static const u64 t1 = ((u64)0x3ff00000)<<32;
+ static const double r1 = 1.0;
+ u64 t2 = t1;
+ assert( sizeof(r1)==sizeof(t2) && memcmp(&r1, &t2, sizeof(r1))==0 );
+#endif
+ i64 x = decodeSigned(pData, 8);
+ double d;
+ memcpy(&d, &x, sizeof(x));
+ return d;
+}
+
+/* Return true if a varint can safely be read from pData/nData. */
+/* TODO(shess): DbPage points into the middle of a buffer which
+ * contains the page data before DbPage. So code should always be
+ * able to read a small number of varints safely. Consider whether to
+ * trust that or not.
+ */
+static int checkVarint(const unsigned char *pData, unsigned nData){
+ unsigned i;
+
+ /* In the worst case the decoder takes all 8 bits of the 9th byte. */
+ if( nData>=9 ){
+ return 1;
+ }
+
+ /* Look for a high-bit-clear byte in what's left. */
+ for( i=0; i<nData; ++i ){
+ if( !(pData[i]&0x80) ){
+ return 1;
+ }
+ }
+
+ /* Cannot decode in the space given. */
+ return 0;
+}
+
+/* Return 1 if n varints can be read from pData/nData. */
+static int checkVarints(const unsigned char *pData, unsigned nData,
+ unsigned n){
+ unsigned nCur = 0; /* Byte offset within current varint. */
+ unsigned nFound = 0; /* Number of varints found. */
+ unsigned i;
+
+ /* In the worst case the decoder takes all 8 bits of the 9th byte. */
+ if( nData>=9*n ){
+ return 1;
+ }
+
+ for( i=0; nFound<n && i<nData; ++i ){
+ nCur++;
+ if( nCur==9 || !(pData[i]&0x80) ){
+ nFound++;
+ nCur = 0;
+ }
+ }
+
+ return nFound==n;
+}
+
+/* ctype and str[n]casecmp() can be affected by locale (eg, tr_TR).
+ * These versions consider only the ASCII space.
+ */
+/* TODO(shess): It may be reasonable to just remove the need for these
+ * entirely. The module could require "TEXT STRICT NOT NULL", not
+ * "Text Strict Not Null" or whatever the developer felt like typing
+ * that day. Handling corrupt data is a PERFECT place to be pedantic.
+ */
+static int ascii_isspace(char c){
+ /* From fts3_expr.c */
+ return c==' ' || c=='\t' || c=='\n' || c=='\r' || c=='\v' || c=='\f';
+}
+static int ascii_isalnum(int x){
+ /* From fts3_tokenizer1.c */
+ return (x>='0' && x<='9') || (x>='A' && x<='Z') || (x>='a' && x<='z');
+}
+static int ascii_tolower(int x){
+ /* From fts3_tokenizer1.c */
+ return (x>='A' && x<='Z') ? x-'A'+'a' : x;
+}
+/* TODO(shess): Consider sqlite3_strnicmp() */
+static int ascii_strncasecmp(const char *s1, const char *s2, size_t n){
+ const unsigned char *us1 = (const unsigned char *)s1;
+ const unsigned char *us2 = (const unsigned char *)s2;
+ while( *us1 && *us2 && n && ascii_tolower(*us1)==ascii_tolower(*us2) ){
+ us1++, us2++, n--;
+ }
+ return n ? ascii_tolower(*us1)-ascii_tolower(*us2) : 0;
+}
+static int ascii_strcasecmp(const char *s1, const char *s2){
+ /* If s2 is equal through strlen(s1), will exit while() due to s1's
+ * trailing NUL, and return NUL-s2[strlen(s1)].
+ */
+ return ascii_strncasecmp(s1, s2, strlen(s1)+1);
+}
+
+/* For some reason I kept making mistakes with offset calculations. */
+static const unsigned char *PageData(DbPage *pPage, unsigned iOffset){
+ assert( iOffset<=pPage->nPageSize );
+ return (unsigned char *)pPage->pData + iOffset;
+}
+
+/* The first page in the file contains a file header in the first 100
+ * bytes. The page's header information comes after that. Note that
+ * the offsets in the page's header information are relative to the
+ * beginning of the page, NOT the end of the page header.
+ */
+static const unsigned char *PageHeader(DbPage *pPage){
+ if( pPage->pgno==1 ){
+ const unsigned nDatabaseHeader = 100;
+ return PageData(pPage, nDatabaseHeader);
+ }else{
+ return PageData(pPage, 0);
+ }
+}
+
+/* Helper to fetch the pager and page size for the named database. */
+static int GetPager(sqlite3 *db, const char *zName,
+ Pager **pPager, unsigned *pnPageSize){
+ Btree *pBt = NULL;
+ int i;
+ for( i=0; i<db->nDb; ++i ){
+ if( ascii_strcasecmp(db->aDb[i].zName, zName)==0 ){
+ pBt = db->aDb[i].pBt;
+ break;
+ }
+ }
+ if( !pBt ){
+ return SQLITE_ERROR;
+ }
+
+ *pPager = sqlite3BtreePager(pBt);
+ *pnPageSize = sqlite3BtreeGetPageSize(pBt) - sqlite3BtreeGetReserve(pBt);
+ return SQLITE_OK;
+}
+
+/* iSerialType is a type read from a record header. See "2.1 Record Format".
+ */
+
+/* Storage size of iSerialType in bytes. My interpretation of SQLite
+ * documentation is that text and blob fields can have 32-bit length.
+ * Values past 2^31-12 will need more than 32 bits to encode, which is
+ * why iSerialType is u64.
+ */
+static u32 SerialTypeLength(u64 iSerialType){
+ switch( iSerialType ){
+ case 0 : return 0; /* NULL */
+ case 1 : return 1; /* Various integers. */
+ case 2 : return 2;
+ case 3 : return 3;
+ case 4 : return 4;
+ case 5 : return 6;
+ case 6 : return 8;
+ case 7 : return 8; /* 64-bit float. */
+ case 8 : return 0; /* Constant 0. */
+ case 9 : return 0; /* Constant 1. */
+ case 10 : case 11 : assert( !"RESERVED TYPE"); return 0;
+ }
+ return (u32)((iSerialType>>1) - 6);
+}
+
+/* True if iSerialType refers to a blob. */
+static int SerialTypeIsBlob(u64 iSerialType){
+ assert( iSerialType>=12 );
+ return (iSerialType%2)==0;
+}
+
+/* Returns true if the serialized type represented by iSerialType is
+ * compatible with the given type mask.
+ */
+static int SerialTypeIsCompatible(u64 iSerialType, unsigned char mask){
+ switch( iSerialType ){
+ case 0 : return (mask&MASK_NULL)!=0;
+ case 1 : return (mask&MASK_INTEGER)!=0;
+ case 2 : return (mask&MASK_INTEGER)!=0;
+ case 3 : return (mask&MASK_INTEGER)!=0;
+ case 4 : return (mask&MASK_INTEGER)!=0;
+ case 5 : return (mask&MASK_INTEGER)!=0;
+ case 6 : return (mask&MASK_INTEGER)!=0;
+ case 7 : return (mask&MASK_FLOAT)!=0;
+ case 8 : return (mask&MASK_INTEGER)!=0;
+ case 9 : return (mask&MASK_INTEGER)!=0;
+ case 10 : assert( !"RESERVED TYPE"); return 0;
+ case 11 : assert( !"RESERVED TYPE"); return 0;
+ }
+ return (mask&(SerialTypeIsBlob(iSerialType) ? MASK_BLOB : MASK_TEXT));
+}
+
+/* Versions of strdup() with return values appropriate for
+ * sqlite3_free(). malloc.c has sqlite3DbStrDup()/NDup(), but those
+ * need sqlite3DbFree(), which seems intrusive.
+ */
+static char *sqlite3_strndup(const char *z, unsigned n){
+ char *zNew;
+
+ if( z==NULL ){
+ return NULL;
+ }
+
+ zNew = sqlite3_malloc(n+1);
+ if( zNew!=NULL ){
+ memcpy(zNew, z, n);
+ zNew[n] = '\0';
+ }
+ return zNew;
+}
+static char *sqlite3_strdup(const char *z){
+ if( z==NULL ){
+ return NULL;
+ }
+ return sqlite3_strndup(z, strlen(z));
+}
+
+/* Fetch the page number of zTable in zDb from sqlite_master in zDb,
+ * and put it in *piRootPage.
+ */
+static int getRootPage(sqlite3 *db, const char *zDb, const char *zTable,
+ u32 *piRootPage){
+ char *zSql; /* SQL selecting root page of named element. */
+ sqlite3_stmt *pStmt;
+ int rc;
+
+ if( strcmp(zTable, "sqlite_master")==0 ){
+ *piRootPage = 1;
+ return SQLITE_OK;
+ }
+
+ zSql = sqlite3_mprintf("SELECT rootpage FROM %s.sqlite_master "
+ "WHERE type = 'table' AND tbl_name = %Q",
+ zDb, zTable);
+ if( !zSql ){
+ return SQLITE_NOMEM;
+ }
+
+ rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+ sqlite3_free(zSql);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+
+ /* Require a result. */
+ rc = sqlite3_step(pStmt);
+ if( rc==SQLITE_DONE ){
+ rc = SQLITE_CORRUPT;
+ }else if( rc==SQLITE_ROW ){
+ *piRootPage = sqlite3_column_int(pStmt, 0);
+
+ /* Require only one result. */
+ rc = sqlite3_step(pStmt);
+ if( rc==SQLITE_DONE ){
+ rc = SQLITE_OK;
+ }else if( rc==SQLITE_ROW ){
+ rc = SQLITE_CORRUPT;
+ }
+ }
+ sqlite3_finalize(pStmt);
+ return rc;
+}
+
+static int getEncoding(sqlite3 *db, const char *zDb, int* piEncoding){
+ sqlite3_stmt *pStmt;
+ int rc;
+ char *zSql = sqlite3_mprintf("PRAGMA %s.encoding", zDb);
+ if( !zSql ){
+ return SQLITE_NOMEM;
+ }
+
+ rc = sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0);
+ sqlite3_free(zSql);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+
+ /* Require a result. */
+ rc = sqlite3_step(pStmt);
+ if( rc==SQLITE_DONE ){
+ /* This case should not be possible. */
+ rc = SQLITE_CORRUPT;
+ }else if( rc==SQLITE_ROW ){
+ if( sqlite3_column_type(pStmt, 0)==SQLITE_TEXT ){
+ const char* z = (const char *)sqlite3_column_text(pStmt, 0);
+ /* These strings match the literals in pragma.c. */
+ if( !strcmp(z, "UTF-16le") ){
+ *piEncoding = SQLITE_UTF16LE;
+ }else if( !strcmp(z, "UTF-16be") ){
+ *piEncoding = SQLITE_UTF16BE;
+ }else if( !strcmp(z, "UTF-8") ){
+ *piEncoding = SQLITE_UTF8;
+ }else{
+ /* This case should not be possible. */
+ *piEncoding = SQLITE_UTF8;
+ }
+ }else{
+ /* This case should not be possible. */
+ *piEncoding = SQLITE_UTF8;
+ }
+
+ /* Require only one result. */
+ rc = sqlite3_step(pStmt);
+ if( rc==SQLITE_DONE ){
+ rc = SQLITE_OK;
+ }else if( rc==SQLITE_ROW ){
+ /* This case should not be possible. */
+ rc = SQLITE_CORRUPT;
+ }
+ }
+ sqlite3_finalize(pStmt);
+ return rc;
+}
+
+/* Cursor for iterating interior nodes. Interior page cells contain a
+ * child page number and a rowid. The child page contains items left
+ * of the rowid (less than). The rightmost page of the subtree is
+ * stored in the page header.
+ *
+ * interiorCursorDestroy - release all resources associated with the
+ * cursor and any parent cursors.
+ * interiorCursorCreate - create a cursor with the given parent and page.
+ * interiorCursorEOF - returns true if neither the cursor nor the
+ * parent cursors can return any more data.
+ * interiorCursorNextPage - fetch the next child page from the cursor.
+ *
+ * Logically, interiorCursorNextPage() returns the next child page
+ * number from the page the cursor is currently reading, calling the
+ * parent cursor as necessary to get new pages to read, until done.
+ * SQLITE_ROW if a page is returned, SQLITE_DONE if out of pages,
+ * error otherwise. Unfortunately, if the table is corrupted
+ * unexpected pages can be returned. If any unexpected page is found,
+ * leaf or otherwise, it is returned to the caller for processing,
+ * with the interior cursor left empty. The next call to
+ * interiorCursorNextPage() will recurse to the parent cursor until an
+ * interior page to iterate is returned.
+ *
+ * Note that while interiorCursorNextPage() will refuse to follow
+ * loops, it does not keep track of pages returned for purposes of
+ * preventing duplication.
+ *
+ * Note that interiorCursorEOF() could return false (not at EOF), and
+ * interiorCursorNextPage() could still return SQLITE_DONE. This
+ * could happen if there are more cells to iterate in an interior
+ * page, but those cells refer to invalid pages.
+ */
+typedef struct RecoverInteriorCursor RecoverInteriorCursor;
+struct RecoverInteriorCursor {
+ RecoverInteriorCursor *pParent; /* Parent node to this node. */
+ DbPage *pPage; /* Reference to leaf page. */
+ unsigned nPageSize; /* Size of page. */
+ unsigned nChildren; /* Number of children on the page. */
+ unsigned iChild; /* Index of next child to return. */
+};
+
+static void interiorCursorDestroy(RecoverInteriorCursor *pCursor){
+ /* Destroy all the cursors to the root. */
+ while( pCursor ){
+ RecoverInteriorCursor *p = pCursor;
+ pCursor = pCursor->pParent;
+
+ if( p->pPage ){
+ sqlite3PagerUnref(p->pPage);
+ p->pPage = NULL;
+ }
+
+ memset(p, 0xA5, sizeof(*p));
+ sqlite3_free(p);
+ }
+}
+
+/* Internal helper. Reset storage in preparation for iterating pPage. */
+static void interiorCursorSetPage(RecoverInteriorCursor *pCursor,
+ DbPage *pPage){
+ assert( PageHeader(pPage)[kiPageTypeOffset]==kTableInteriorPage );
+
+ if( pCursor->pPage ){
+ sqlite3PagerUnref(pCursor->pPage);
+ pCursor->pPage = NULL;
+ }
+ pCursor->pPage = pPage;
+ pCursor->iChild = 0;
+
+ /* A child for each cell, plus one in the header. */
+ /* TODO(shess): Sanity-check the count? Page header plus per-cell
+ * cost of 16-bit offset, 32-bit page number, and one varint
+ * (minimum 1 byte).
+ */
+ pCursor->nChildren = decodeUnsigned16(PageHeader(pPage) +
+ kiPageCellCountOffset) + 1;
+}
+
+static int interiorCursorCreate(RecoverInteriorCursor *pParent,
+ DbPage *pPage, int nPageSize,
+ RecoverInteriorCursor **ppCursor){
+ RecoverInteriorCursor *pCursor =
+ sqlite3_malloc(sizeof(RecoverInteriorCursor));
+ if( !pCursor ){
+ return SQLITE_NOMEM;
+ }
+
+ memset(pCursor, 0, sizeof(*pCursor));
+ pCursor->pParent = pParent;
+ pCursor->nPageSize = nPageSize;
+ interiorCursorSetPage(pCursor, pPage);
+ *ppCursor = pCursor;
+ return SQLITE_OK;
+}
+
+/* Internal helper. Return the child page number at iChild. */
+static unsigned interiorCursorChildPage(RecoverInteriorCursor *pCursor){
+ const unsigned char *pPageHeader; /* Header of the current page. */
+ const unsigned char *pCellOffsets; /* Offset to page's cell offsets. */
+ unsigned iCellOffset; /* Offset of target cell. */
+
+ assert( pCursor->iChild<pCursor->nChildren );
+
+ /* Rightmost child is in the header. */
+ pPageHeader = PageHeader(pCursor->pPage);
+ if( pCursor->iChild==pCursor->nChildren-1 ){
+ return decodeUnsigned32(pPageHeader + kiPageRightChildOffset);
+ }
+
+ /* Each cell is a 4-byte integer page number and a varint rowid
+ * which is greater than the rowid of items in that sub-tree (this
+ * module ignores ordering). The offset is from the beginning of the
+ * page, not from the page header.
+ */
+ pCellOffsets = pPageHeader + kiPageInteriorHeaderBytes;
+ iCellOffset = decodeUnsigned16(pCellOffsets + pCursor->iChild*2);
+ if( iCellOffset<=pCursor->nPageSize-4 ){
+ return decodeUnsigned32(PageData(pCursor->pPage, iCellOffset));
+ }
+
+ /* TODO(shess): Check for cell overlaps? Cells require 4 bytes plus
+ * a varint. Check could be identical to leaf check (or even a
+ * shared helper testing for "Cells starting in this range"?).
+ */
+
+ /* If the offset is broken, return an invalid page number. */
+ return 0;
+}
+
+static int interiorCursorEOF(RecoverInteriorCursor *pCursor){
+ /* Find a parent with remaining children. EOF if none found. */
+ while( pCursor && pCursor->iChild>=pCursor->nChildren ){
+ pCursor = pCursor->pParent;
+ }
+ return pCursor==NULL;
+}
+
+/* Internal helper. Used to detect if iPage would cause a loop. */
+static int interiorCursorPageInUse(RecoverInteriorCursor *pCursor,
+ unsigned iPage){
+ /* Find any parent using the indicated page. */
+ while( pCursor && pCursor->pPage->pgno!=iPage ){
+ pCursor = pCursor->pParent;
+ }
+ return pCursor!=NULL;
+}
+
+/* Get the next page from the interior cursor at *ppCursor. Returns
+ * SQLITE_ROW with the page in *ppPage, or SQLITE_DONE if out of
+ * pages, or the error SQLite returned.
+ *
+ * If the tree is uneven, then when the cursor attempts to get a new
+ * interior page from the parent cursor, it may get a non-interior
+ * page. In that case, the new page is returned, and *ppCursor is
+ * updated to point to the parent cursor (this cursor is freed).
+ */
+/* TODO(shess): I've tried to avoid recursion in most of this code,
+ * but this case is more challenging because the recursive call is in
+ * the middle of operation. One option for converting it without
+ * adding memory management would be to retain the head pointer and
+ * use a helper to "back up" as needed. Another option would be to
+ * reverse the list during traversal.
+ */
+static int interiorCursorNextPage(RecoverInteriorCursor **ppCursor,
+ DbPage **ppPage){
+ RecoverInteriorCursor *pCursor = *ppCursor;
+ while( 1 ){
+ int rc;
+ const unsigned char *pPageHeader; /* Header of found page. */
+
+ /* Find a valid child page which isn't on the stack. */
+ while( pCursor->iChild<pCursor->nChildren ){
+ const unsigned iPage = interiorCursorChildPage(pCursor);
+ pCursor->iChild++;
+ if( interiorCursorPageInUse(pCursor, iPage) ){
+ fprintf(stderr, "Loop detected at %d\n", iPage);
+ }else{
+ int rc = sqlite3PagerAcquire(pCursor->pPage->pPager, iPage, ppPage, 0);
+ if( rc==SQLITE_OK ){
+ return SQLITE_ROW;
+ }
+ }
+ }
+
+ /* This page has no more children. Get next page from parent. */
+ if( !pCursor->pParent ){
+ return SQLITE_DONE;
+ }
+ rc = interiorCursorNextPage(&pCursor->pParent, ppPage);
+ if( rc!=SQLITE_ROW ){
+ return rc;
+ }
+
+ /* If a non-interior page is received, that either means that the
+ * tree is uneven, or that a child was re-used (say as an overflow
+ * page). Remove this cursor and let the caller handle the page.
+ */
+ pPageHeader = PageHeader(*ppPage);
+ if( pPageHeader[kiPageTypeOffset]!=kTableInteriorPage ){
+ *ppCursor = pCursor->pParent;
+ pCursor->pParent = NULL;
+ interiorCursorDestroy(pCursor);
+ return SQLITE_ROW;
+ }
+
+ /* Iterate the new page. */
+ interiorCursorSetPage(pCursor, *ppPage);
+ *ppPage = NULL;
+ }
+
+ assert(NULL); /* NOTREACHED() */
+ return SQLITE_CORRUPT;
+}
+
+/* Large rows are spilled to overflow pages. The row's main page
+ * stores the overflow page number after the local payload, with a
+ * linked list forward from there as necessary. overflowMaybeCreate()
+ * and overflowGetSegment() provide an abstraction for accessing such
+ * data while centralizing the code.
+ *
+ * overflowDestroy - releases all resources associated with the structure.
+ * overflowMaybeCreate - create the overflow structure if it is needed
+ * to represent the given record. See function comment.
+ * overflowGetSegment - fetch a segment from the record, accounting
+ * for overflow pages. Segments which are not
+ * entirely contained with a page are constructed
+ * into a buffer which is returned. See function comment.
+ */
+typedef struct RecoverOverflow RecoverOverflow;
+struct RecoverOverflow {
+ RecoverOverflow *pNextOverflow;
+ DbPage *pPage;
+ unsigned nPageSize;
+};
+
+static void overflowDestroy(RecoverOverflow *pOverflow){
+ while( pOverflow ){
+ RecoverOverflow *p = pOverflow;
+ pOverflow = p->pNextOverflow;
+
+ if( p->pPage ){
+ sqlite3PagerUnref(p->pPage);
+ p->pPage = NULL;
+ }
+
+ memset(p, 0xA5, sizeof(*p));
+ sqlite3_free(p);
+ }
+}
+
+/* Internal helper. Used to detect if iPage would cause a loop. */
+static int overflowPageInUse(RecoverOverflow *pOverflow, unsigned iPage){
+ while( pOverflow && pOverflow->pPage->pgno!=iPage ){
+ pOverflow = pOverflow->pNextOverflow;
+ }
+ return pOverflow!=NULL;
+}
+
+/* Setup to access an nRecordBytes record beginning at iRecordOffset
+ * in pPage. If nRecordBytes can be satisfied entirely from pPage,
+ * then no overflow pages are needed an *pnLocalRecordBytes is set to
+ * nRecordBytes. Otherwise, *ppOverflow is set to the head of a list
+ * of overflow pages, and *pnLocalRecordBytes is set to the number of
+ * bytes local to pPage.
+ *
+ * overflowGetSegment() will do the right thing regardless of whether
+ * those values are set to be in-page or not.
+ */
+static int overflowMaybeCreate(DbPage *pPage, unsigned nPageSize,
+ unsigned iRecordOffset, unsigned nRecordBytes,
+ unsigned *pnLocalRecordBytes,
+ RecoverOverflow **ppOverflow){
+ unsigned nLocalRecordBytes; /* Record bytes in the leaf page. */
+ unsigned iNextPage; /* Next page number for record data. */
+ unsigned nBytes; /* Maximum record bytes as of current page. */
+ int rc;
+ RecoverOverflow *pFirstOverflow; /* First in linked list of pages. */
+ RecoverOverflow *pLastOverflow; /* End of linked list. */
+
+ /* Calculations from the "Table B-Tree Leaf Cell" part of section
+ * 1.5 of http://www.sqlite.org/fileformat2.html . maxLocal and
+ * minLocal to match naming in btree.c.
+ */
+ const unsigned maxLocal = nPageSize - 35;
+ const unsigned minLocal = ((nPageSize-12)*32/255)-23; /* m */
+
+ /* Always fit anything smaller than maxLocal. */
+ if( nRecordBytes<=maxLocal ){
+ *pnLocalRecordBytes = nRecordBytes;
+ *ppOverflow = NULL;
+ return SQLITE_OK;
+ }
+
+ /* Calculate the remainder after accounting for minLocal on the leaf
+ * page and what packs evenly into overflow pages. If the remainder
+ * does not fit into maxLocal, then a partially-full overflow page
+ * will be required in any case, so store as little as possible locally.
+ */
+ nLocalRecordBytes = minLocal+((nRecordBytes-minLocal)%(nPageSize-4));
+ if( maxLocal<nLocalRecordBytes ){
+ nLocalRecordBytes = minLocal;
+ }
+
+ /* Don't read off the end of the page. */
+ if( iRecordOffset+nLocalRecordBytes+4>nPageSize ){
+ return SQLITE_CORRUPT;
+ }
+
+ /* First overflow page number is after the local bytes. */
+ iNextPage =
+ decodeUnsigned32(PageData(pPage, iRecordOffset + nLocalRecordBytes));
+ nBytes = nLocalRecordBytes;
+
+ /* While there are more pages to read, and more bytes are needed,
+ * get another page.
+ */
+ pFirstOverflow = pLastOverflow = NULL;
+ rc = SQLITE_OK;
+ while( iNextPage && nBytes<nRecordBytes ){
+ RecoverOverflow *pOverflow; /* New overflow page for the list. */
+
+ rc = sqlite3PagerAcquire(pPage->pPager, iNextPage, &pPage, 0);
+ if( rc!=SQLITE_OK ){
+ break;
+ }
+
+ pOverflow = sqlite3_malloc(sizeof(RecoverOverflow));
+ if( !pOverflow ){
+ sqlite3PagerUnref(pPage);
+ rc = SQLITE_NOMEM;
+ break;
+ }
+ memset(pOverflow, 0, sizeof(*pOverflow));
+ pOverflow->pPage = pPage;
+ pOverflow->nPageSize = nPageSize;
+
+ if( !pFirstOverflow ){
+ pFirstOverflow = pOverflow;
+ }else{
+ pLastOverflow->pNextOverflow = pOverflow;
+ }
+ pLastOverflow = pOverflow;
+
+ iNextPage = decodeUnsigned32(pPage->pData);
+ nBytes += nPageSize-4;
+
+ /* Avoid loops. */
+ if( overflowPageInUse(pFirstOverflow, iNextPage) ){
+ fprintf(stderr, "Overflow loop detected at %d\n", iNextPage);
+ rc = SQLITE_CORRUPT;
+ break;
+ }
+ }
+
+ /* If there were not enough pages, or too many, things are corrupt.
+ * Not having enough pages is an obvious problem, all the data
+ * cannot be read. Too many pages means that the contents of the
+ * row between the main page and the overflow page(s) is
+ * inconsistent (most likely one or more of the overflow pages does
+ * not really belong to this row).
+ */
+ if( rc==SQLITE_OK && (nBytes<nRecordBytes || iNextPage) ){
+ rc = SQLITE_CORRUPT;
+ }
+
+ if( rc==SQLITE_OK ){
+ *ppOverflow = pFirstOverflow;
+ *pnLocalRecordBytes = nLocalRecordBytes;
+ }else if( pFirstOverflow ){
+ overflowDestroy(pFirstOverflow);
+ }
+ return rc;
+}
+
+/* Use in concert with overflowMaybeCreate() to efficiently read parts
+ * of a potentially-overflowing record. pPage and iRecordOffset are
+ * the values passed into overflowMaybeCreate(), nLocalRecordBytes and
+ * pOverflow are the values returned by that call.
+ *
+ * On SQLITE_OK, *ppBase points to nRequestBytes of data at
+ * iRequestOffset within the record. If the data exists contiguously
+ * in a page, a direct pointer is returned, otherwise a buffer from
+ * sqlite3_malloc() is returned with the data. *pbFree is set true if
+ * sqlite3_free() should be called on *ppBase.
+ */
+/* Operation of this function is subtle. At any time, pPage is the
+ * current page, with iRecordOffset and nLocalRecordBytes being record
+ * data within pPage, and pOverflow being the overflow page after
+ * pPage. This allows the code to handle both the initial leaf page
+ * and overflow pages consistently by adjusting the values
+ * appropriately.
+ */
+static int overflowGetSegment(DbPage *pPage, unsigned iRecordOffset,
+ unsigned nLocalRecordBytes,
+ RecoverOverflow *pOverflow,
+ unsigned iRequestOffset, unsigned nRequestBytes,
+ unsigned char **ppBase, int *pbFree){
+ unsigned nBase; /* Amount of data currently collected. */
+ unsigned char *pBase; /* Buffer to collect record data into. */
+
+ /* Skip to the page containing the start of the data. */
+ while( iRequestOffset>=nLocalRecordBytes && pOverflow ){
+ /* Factor out current page's contribution. */
+ iRequestOffset -= nLocalRecordBytes;
+
+ /* Move forward to the next page in the list. */
+ pPage = pOverflow->pPage;
+ iRecordOffset = 4;
+ nLocalRecordBytes = pOverflow->nPageSize - iRecordOffset;
+ pOverflow = pOverflow->pNextOverflow;
+ }
+
+ /* If the requested data is entirely within this page, return a
+ * pointer into the page.
+ */
+ if( iRequestOffset+nRequestBytes<=nLocalRecordBytes ){
+ /* TODO(shess): "assignment discards qualifiers from pointer target type"
+ * Having ppBase be const makes sense, but sqlite3_free() takes non-const.
+ */
+ *ppBase = (unsigned char *)PageData(pPage, iRecordOffset + iRequestOffset);
+ *pbFree = 0;
+ return SQLITE_OK;
+ }
+
+ /* The data range would require additional pages. */
+ if( !pOverflow ){
+ /* Should never happen, the range is outside the nRecordBytes
+ * passed to overflowMaybeCreate().
+ */
+ assert(NULL); /* NOTREACHED */
+ return SQLITE_ERROR;
+ }
+
+ /* Get a buffer to construct into. */
+ nBase = 0;
+ pBase = sqlite3_malloc(nRequestBytes);
+ if( !pBase ){
+ return SQLITE_NOMEM;
+ }
+ while( nBase<nRequestBytes ){
+ /* Copy over data present on this page. */
+ unsigned nCopyBytes = nRequestBytes - nBase;
+ if( nLocalRecordBytes-iRequestOffset<nCopyBytes ){
+ nCopyBytes = nLocalRecordBytes - iRequestOffset;
+ }
+ memcpy(pBase + nBase, PageData(pPage, iRecordOffset + iRequestOffset),
+ nCopyBytes);
+ nBase += nCopyBytes;
+
+ if( pOverflow ){
+ /* Copy from start of record data in future pages. */
+ iRequestOffset = 0;
+
+ /* Move forward to the next page in the list. Should match
+ * first while() loop.
+ */
+ pPage = pOverflow->pPage;
+ iRecordOffset = 4;
+ nLocalRecordBytes = pOverflow->nPageSize - iRecordOffset;
+ pOverflow = pOverflow->pNextOverflow;
+ }else if( nBase<nRequestBytes ){
+ /* Ran out of overflow pages with data left to deliver. Not
+ * possible if the requested range fits within nRecordBytes
+ * passed to overflowMaybeCreate() when creating pOverflow.
+ */
+ assert(NULL); /* NOTREACHED */
+ sqlite3_free(pBase);
+ return SQLITE_ERROR;
+ }
+ }
+ assert( nBase==nRequestBytes );
+ *ppBase = pBase;
+ *pbFree = 1;
+ return SQLITE_OK;
+}
+
+/* Primary structure for iterating the contents of a table.
+ *
+ * leafCursorDestroy - release all resources associated with the cursor.
+ * leafCursorCreate - create a cursor to iterate items from tree at
+ * the provided root page.
+ * leafCursorNextValidCell - get the cursor ready to access data from
+ * the next valid cell in the table.
+ * leafCursorCellRowid - get the current cell's rowid.
+ * leafCursorCellColumns - get current cell's column count.
+ * leafCursorCellColInfo - get type and data for a column in current cell.
+ *
+ * leafCursorNextValidCell skips cells which fail simple integrity
+ * checks, such as overlapping other cells, or being located at
+ * impossible offsets, or where header data doesn't correctly describe
+ * payload data. Returns SQLITE_ROW if a valid cell is found,
+ * SQLITE_DONE if all pages in the tree were exhausted.
+ *
+ * leafCursorCellColInfo() accounts for overflow pages in the style of
+ * overflowGetSegment().
+ */
+typedef struct RecoverLeafCursor RecoverLeafCursor;
+struct RecoverLeafCursor {
+ RecoverInteriorCursor *pParent; /* Parent node to this node. */
+ DbPage *pPage; /* Reference to leaf page. */
+ unsigned nPageSize; /* Size of pPage. */
+ unsigned nCells; /* Number of cells in pPage. */
+ unsigned iCell; /* Current cell. */
+
+ /* Info parsed from data in iCell. */
+ i64 iRowid; /* rowid parsed. */
+ unsigned nRecordCols; /* how many items in the record. */
+ u64 iRecordOffset; /* offset to record data. */
+ /* TODO(shess): nRecordBytes and nRecordHeaderBytes are used in
+ * leafCursorCellColInfo() to prevent buffer overruns.
+ * leafCursorCellDecode() already verified that the cell is valid, so
+ * those checks should be redundant.
+ */
+ u64 nRecordBytes; /* Size of record data. */
+ unsigned nLocalRecordBytes; /* Amount of record data in-page. */
+ unsigned nRecordHeaderBytes; /* Size of record header data. */
+ unsigned char *pRecordHeader; /* Pointer to record header data. */
+ int bFreeRecordHeader; /* True if record header requires free. */
+ RecoverOverflow *pOverflow; /* Cell overflow info, if needed. */
+};
+
+/* Internal helper shared between next-page and create-cursor. If
+ * pPage is a leaf page, it will be stored in the cursor and state
+ * initialized for reading cells.
+ *
+ * If pPage is an interior page, a new parent cursor is created and
+ * injected on the stack. This is necessary to handle trees with
+ * uneven depth, but also is used during initial setup.
+ *
+ * If pPage is not a table page at all, it is discarded.
+ *
+ * If SQLITE_OK is returned, the caller no longer owns pPage,
+ * otherwise the caller is responsible for discarding it.
+ */
+static int leafCursorLoadPage(RecoverLeafCursor *pCursor, DbPage *pPage){
+ const unsigned char *pPageHeader; /* Header of *pPage */
+
+ /* Release the current page. */
+ if( pCursor->pPage ){
+ sqlite3PagerUnref(pCursor->pPage);
+ pCursor->pPage = NULL;
+ pCursor->iCell = pCursor->nCells = 0;
+ }
+
+ /* If the page is an unexpected interior node, inject a new stack
+ * layer and try again from there.
+ */
+ pPageHeader = PageHeader(pPage);
+ if( pPageHeader[kiPageTypeOffset]==kTableInteriorPage ){
+ RecoverInteriorCursor *pParent;
+ int rc = interiorCursorCreate(pCursor->pParent, pPage, pCursor->nPageSize,
+ &pParent);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+ pCursor->pParent = pParent;
+ return SQLITE_OK;
+ }
+
+ /* Not a leaf page, skip it. */
+ if( pPageHeader[kiPageTypeOffset]!=kTableLeafPage ){
+ sqlite3PagerUnref(pPage);
+ return SQLITE_OK;
+ }
+
+ /* Take ownership of the page and start decoding. */
+ pCursor->pPage = pPage;
+ pCursor->iCell = 0;
+ pCursor->nCells = decodeUnsigned16(pPageHeader + kiPageCellCountOffset);
+ return SQLITE_OK;
+}
+
+/* Get the next leaf-level page in the tree. Returns SQLITE_ROW when
+ * a leaf page is found, SQLITE_DONE when no more leaves exist, or any
+ * error which occurred.
+ */
+static int leafCursorNextPage(RecoverLeafCursor *pCursor){
+ if( !pCursor->pParent ){
+ return SQLITE_DONE;
+ }
+
+ /* Repeatedly load the parent's next child page until a leaf is found. */
+ do {
+ DbPage *pNextPage;
+ int rc = interiorCursorNextPage(&pCursor->pParent, &pNextPage);
+ if( rc!=SQLITE_ROW ){
+ assert( rc==SQLITE_DONE );
+ return rc;
+ }
+
+ rc = leafCursorLoadPage(pCursor, pNextPage);
+ if( rc!=SQLITE_OK ){
+ sqlite3PagerUnref(pNextPage);
+ return rc;
+ }
+ } while( !pCursor->pPage );
+
+ return SQLITE_ROW;
+}
+
+static void leafCursorDestroyCellData(RecoverLeafCursor *pCursor){
+ if( pCursor->bFreeRecordHeader ){
+ sqlite3_free(pCursor->pRecordHeader);
+ }
+ pCursor->bFreeRecordHeader = 0;
+ pCursor->pRecordHeader = NULL;
+
+ if( pCursor->pOverflow ){
+ overflowDestroy(pCursor->pOverflow);
+ pCursor->pOverflow = NULL;
+ }
+}
+
+static void leafCursorDestroy(RecoverLeafCursor *pCursor){
+ leafCursorDestroyCellData(pCursor);
+
+ if( pCursor->pParent ){
+ interiorCursorDestroy(pCursor->pParent);
+ pCursor->pParent = NULL;
+ }
+
+ if( pCursor->pPage ){
+ sqlite3PagerUnref(pCursor->pPage);
+ pCursor->pPage = NULL;
+ }
+
+ memset(pCursor, 0xA5, sizeof(*pCursor));
+ sqlite3_free(pCursor);
+}
+
+/* Create a cursor to iterate the rows from the leaf pages of a table
+ * rooted at iRootPage.
+ */
+/* TODO(shess): recoverOpen() calls this to setup the cursor, and I
+ * think that recoverFilter() may make a hard assumption that the
+ * cursor returned will turn up at least one valid cell.
+ *
+ * The cases I can think of which break this assumption are:
+ * - pPage is a valid leaf page with no valid cells.
+ * - pPage is a valid interior page with no valid leaves.
+ * - pPage is a valid interior page who's leaves contain no valid cells.
+ * - pPage is not a valid leaf or interior page.
+ */
+static int leafCursorCreate(Pager *pPager, unsigned nPageSize,
+ u32 iRootPage, RecoverLeafCursor **ppCursor){
+ DbPage *pPage; /* Reference to page at iRootPage. */
+ RecoverLeafCursor *pCursor; /* Leaf cursor being constructed. */
+ int rc;
+
+ /* Start out with the root page. */
+ rc = sqlite3PagerAcquire(pPager, iRootPage, &pPage, 0);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+
+ pCursor = sqlite3_malloc(sizeof(RecoverLeafCursor));
+ if( !pCursor ){
+ sqlite3PagerUnref(pPage);
+ return SQLITE_NOMEM;
+ }
+ memset(pCursor, 0, sizeof(*pCursor));
+
+ pCursor->nPageSize = nPageSize;
+
+ rc = leafCursorLoadPage(pCursor, pPage);
+ if( rc!=SQLITE_OK ){
+ sqlite3PagerUnref(pPage);
+ leafCursorDestroy(pCursor);
+ return rc;
+ }
+
+ /* pPage wasn't a leaf page, find the next leaf page. */
+ if( !pCursor->pPage ){
+ rc = leafCursorNextPage(pCursor);
+ if( rc!=SQLITE_DONE && rc!=SQLITE_ROW ){
+ leafCursorDestroy(pCursor);
+ return rc;
+ }
+ }
+
+ *ppCursor = pCursor;
+ return SQLITE_OK;
+}
+
+/* Useful for setting breakpoints. */
+static int ValidateError(){
+ return SQLITE_ERROR;
+}
+
+/* Setup the cursor for reading the information from cell iCell. */
+static int leafCursorCellDecode(RecoverLeafCursor *pCursor){
+ const unsigned char *pPageHeader; /* Header of current page. */
+ const unsigned char *pCellOffsets; /* Pointer to page's cell offsets. */
+ unsigned iCellOffset; /* Offset of current cell (iCell). */
+ const unsigned char *pCell; /* Pointer to data at iCellOffset. */
+ unsigned nCellMaxBytes; /* Maximum local size of iCell. */
+ unsigned iEndOffset; /* End of iCell's in-page data. */
+ u64 nRecordBytes; /* Expected size of cell, w/overflow. */
+ u64 iRowid; /* iCell's rowid (in table). */
+ unsigned nRead; /* Amount of cell read. */
+ unsigned nRecordHeaderRead; /* Header data read. */
+ u64 nRecordHeaderBytes; /* Header size expected. */
+ unsigned nRecordCols; /* Columns read from header. */
+ u64 nRecordColBytes; /* Bytes in payload for those columns. */
+ unsigned i;
+ int rc;
+
+ assert( pCursor->iCell<pCursor->nCells );
+
+ leafCursorDestroyCellData(pCursor);
+
+ /* Find the offset to the row. */
+ pPageHeader = PageHeader(pCursor->pPage);
+ pCellOffsets = pPageHeader + knPageLeafHeaderBytes;
+ iCellOffset = decodeUnsigned16(pCellOffsets + pCursor->iCell*2);
+ if( iCellOffset>=pCursor->nPageSize ){
+ return ValidateError();
+ }
+
+ pCell = PageData(pCursor->pPage, iCellOffset);
+ nCellMaxBytes = pCursor->nPageSize - iCellOffset;
+
+ /* B-tree leaf cells lead with varint record size, varint rowid and
+ * varint header size.
+ */
+ /* TODO(shess): The smallest page size is 512 bytes, which has an m
+ * of 39. Three varints need at most 27 bytes to encode. I think.
+ */
+ if( !checkVarints(pCell, nCellMaxBytes, 3) ){
+ return ValidateError();
+ }
+
+ nRead = getVarint(pCell, &nRecordBytes);
+ assert( iCellOffset+nRead<=pCursor->nPageSize );
+ pCursor->nRecordBytes = nRecordBytes;
+
+ nRead += getVarint(pCell + nRead, &iRowid);
+ assert( iCellOffset+nRead<=pCursor->nPageSize );
+ pCursor->iRowid = (i64)iRowid;
+
+ pCursor->iRecordOffset = iCellOffset + nRead;
+
+ /* Start overflow setup here because nLocalRecordBytes is needed to
+ * check cell overlap.
+ */
+ rc = overflowMaybeCreate(pCursor->pPage, pCursor->nPageSize,
+ pCursor->iRecordOffset, pCursor->nRecordBytes,
+ &pCursor->nLocalRecordBytes,
+ &pCursor->pOverflow);
+ if( rc!=SQLITE_OK ){
+ return ValidateError();
+ }
+
+ /* Check that no other cell starts within this cell. */
+ iEndOffset = pCursor->iRecordOffset + pCursor->nLocalRecordBytes;
+ for( i=0; i<pCursor->nCells; ++i ){
+ const unsigned iOtherOffset = decodeUnsigned16(pCellOffsets + i*2);
+ if( iOtherOffset>iCellOffset && iOtherOffset<iEndOffset ){
+ return ValidateError();
+ }
+ }
+
+ nRecordHeaderRead = getVarint(pCell + nRead, &nRecordHeaderBytes);
+ assert( nRecordHeaderBytes<=nRecordBytes );
+ pCursor->nRecordHeaderBytes = nRecordHeaderBytes;
+
+ /* Large headers could overflow if pages are small. */
+ rc = overflowGetSegment(pCursor->pPage,
+ pCursor->iRecordOffset, pCursor->nLocalRecordBytes,
+ pCursor->pOverflow, 0, nRecordHeaderBytes,
+ &pCursor->pRecordHeader, &pCursor->bFreeRecordHeader);
+ if( rc!=SQLITE_OK ){
+ return ValidateError();
+ }
+
+ /* Tally up the column count and size of data. */
+ nRecordCols = 0;
+ nRecordColBytes = 0;
+ while( nRecordHeaderRead<nRecordHeaderBytes ){
+ u64 iSerialType; /* Type descriptor for current column. */
+ if( !checkVarint(pCursor->pRecordHeader + nRecordHeaderRead,
+ nRecordHeaderBytes - nRecordHeaderRead) ){
+ return ValidateError();
+ }
+ nRecordHeaderRead += getVarint(pCursor->pRecordHeader + nRecordHeaderRead,
+ &iSerialType);
+ if( iSerialType==10 || iSerialType==11 ){
+ return ValidateError();
+ }
+ nRecordColBytes += SerialTypeLength(iSerialType);
+ nRecordCols++;
+ }
+ pCursor->nRecordCols = nRecordCols;
+
+ /* Parsing the header used as many bytes as expected. */
+ if( nRecordHeaderRead!=nRecordHeaderBytes ){
+ return ValidateError();
+ }
+
+ /* Calculated record is size of expected record. */
+ if( nRecordHeaderBytes+nRecordColBytes!=nRecordBytes ){
+ return ValidateError();
+ }
+
+ return SQLITE_OK;
+}
+
+static i64 leafCursorCellRowid(RecoverLeafCursor *pCursor){
+ return pCursor->iRowid;
+}
+
+static unsigned leafCursorCellColumns(RecoverLeafCursor *pCursor){
+ return pCursor->nRecordCols;
+}
+
+/* Get the column info for the cell. Pass NULL for ppBase to prevent
+ * retrieving the data segment. If *pbFree is true, *ppBase must be
+ * freed by the caller using sqlite3_free().
+ */
+static int leafCursorCellColInfo(RecoverLeafCursor *pCursor,
+ unsigned iCol, u64 *piColType,
+ unsigned char **ppBase, int *pbFree){
+ const unsigned char *pRecordHeader; /* Current cell's header. */
+ u64 nRecordHeaderBytes; /* Bytes in pRecordHeader. */
+ unsigned nRead; /* Bytes read from header. */
+ u64 iColEndOffset; /* Offset to end of column in cell. */
+ unsigned nColsSkipped; /* Count columns as procesed. */
+ u64 iSerialType; /* Type descriptor for current column. */
+
+ /* Implicit NULL for columns past the end. This case happens when
+ * rows have not been updated since an ALTER TABLE added columns.
+ * It is more convenient to address here than in callers.
+ */
+ if( iCol>=pCursor->nRecordCols ){
+ *piColType = 0;
+ if( ppBase ){
+ *ppBase = 0;
+ *pbFree = 0;
+ }
+ return SQLITE_OK;
+ }
+
+ /* Must be able to decode header size. */
+ pRecordHeader = pCursor->pRecordHeader;
+ if( !checkVarint(pRecordHeader, pCursor->nRecordHeaderBytes) ){
+ return SQLITE_CORRUPT;
+ }
+
+ /* Rather than caching the header size and how many bytes it took,
+ * decode it every time.
+ */
+ nRead = getVarint(pRecordHeader, &nRecordHeaderBytes);
+ assert( nRecordHeaderBytes==pCursor->nRecordHeaderBytes );
+
+ /* Scan forward to the indicated column. Scans to _after_ column
+ * for later range checking.
+ */
+ /* TODO(shess): This could get expensive for very wide tables. An
+ * array of iSerialType could be built in leafCursorCellDecode(), but
+ * the number of columns is dynamic per row, so it would add memory
+ * management complexity. Enough info to efficiently forward
+ * iterate could be kept, if all clients forward iterate
+ * (recoverColumn() may not).
+ */
+ iColEndOffset = 0;
+ nColsSkipped = 0;
+ while( nColsSkipped<=iCol && nRead<nRecordHeaderBytes ){
+ if( !checkVarint(pRecordHeader + nRead, nRecordHeaderBytes - nRead) ){
+ return SQLITE_CORRUPT;
+ }
+ nRead += getVarint(pRecordHeader + nRead, &iSerialType);
+ iColEndOffset += SerialTypeLength(iSerialType);
+ nColsSkipped++;
+ }
+
+ /* Column's data extends past record's end. */
+ if( nRecordHeaderBytes+iColEndOffset>pCursor->nRecordBytes ){
+ return SQLITE_CORRUPT;
+ }
+
+ *piColType = iSerialType;
+ if( ppBase ){
+ const u32 nColBytes = SerialTypeLength(iSerialType);
+
+ /* Offset from start of record to beginning of column. */
+ const unsigned iColOffset = nRecordHeaderBytes+iColEndOffset-nColBytes;
+
+ return overflowGetSegment(pCursor->pPage, pCursor->iRecordOffset,
+ pCursor->nLocalRecordBytes, pCursor->pOverflow,
+ iColOffset, nColBytes, ppBase, pbFree);
+ }
+ return SQLITE_OK;
+}
+
+static int leafCursorNextValidCell(RecoverLeafCursor *pCursor){
+ while( 1 ){
+ int rc;
+
+ /* Move to the next cell. */
+ pCursor->iCell++;
+
+ /* No more cells, get the next leaf. */
+ if( pCursor->iCell>=pCursor->nCells ){
+ rc = leafCursorNextPage(pCursor);
+ if( rc!=SQLITE_ROW ){
+ return rc;
+ }
+ assert( pCursor->iCell==0 );
+ }
+
+ /* If the cell is valid, indicate that a row is available. */
+ rc = leafCursorCellDecode(pCursor);
+ if( rc==SQLITE_OK ){
+ return SQLITE_ROW;
+ }
+
+ /* Iterate until done or a valid row is found. */
+ /* TODO(shess): Remove debugging output. */
+ fprintf(stderr, "Skipping invalid cell\n");
+ }
+ return SQLITE_ERROR;
+}
+
+typedef struct Recover Recover;
+struct Recover {
+ sqlite3_vtab base;
+ sqlite3 *db; /* Host database connection */
+ char *zDb; /* Database containing target table */
+ char *zTable; /* Target table */
+ unsigned nCols; /* Number of columns in target table */
+ unsigned char *pTypes; /* Types of columns in target table */
+};
+
+/* Internal helper for deleting the module. */
+static void recoverRelease(Recover *pRecover){
+ sqlite3_free(pRecover->zDb);
+ sqlite3_free(pRecover->zTable);
+ sqlite3_free(pRecover->pTypes);
+ memset(pRecover, 0xA5, sizeof(*pRecover));
+ sqlite3_free(pRecover);
+}
+
+/* Helper function for initializing the module. Forward-declared so
+ * recoverCreate() and recoverConnect() can see it.
+ */
+static int recoverInit(
+ sqlite3 *, void *, int, const char *const*, sqlite3_vtab **, char **
+);
+
+static int recoverCreate(
+ sqlite3 *db,
+ void *pAux,
+ int argc, const char *const*argv,
+ sqlite3_vtab **ppVtab,
+ char **pzErr
+){
+ FNENTRY();
+ return recoverInit(db, pAux, argc, argv, ppVtab, pzErr);
+}
+
+/* This should never be called. */
+static int recoverConnect(
+ sqlite3 *db,
+ void *pAux,
+ int argc, const char *const*argv,
+ sqlite3_vtab **ppVtab,
+ char **pzErr
+){
+ FNENTRY();
+ return recoverInit(db, pAux, argc, argv, ppVtab, pzErr);
+}
+
+/* No indices supported. */
+static int recoverBestIndex(sqlite3_vtab *tab, sqlite3_index_info *pIdxInfo){
+ FNENTRY();
+ return SQLITE_OK;
+}
+
+/* Logically, this should never be called. */
+static int recoverDisconnect(sqlite3_vtab *pVtab){
+ FNENTRY();
+ recoverRelease((Recover*)pVtab);
+ return SQLITE_OK;
+}
+
+static int recoverDestroy(sqlite3_vtab *pVtab){
+ FNENTRY();
+ recoverRelease((Recover*)pVtab);
+ return SQLITE_OK;
+}
+
+typedef struct RecoverCursor RecoverCursor;
+struct RecoverCursor {
+ sqlite3_vtab_cursor base;
+ RecoverLeafCursor *pLeafCursor;
+ int iEncoding;
+ int bEOF;
+};
+
+static int recoverOpen(sqlite3_vtab *pVTab, sqlite3_vtab_cursor **ppCursor){
+ Recover *pRecover = (Recover*)pVTab;
+ u32 iRootPage; /* Root page of the backing table. */
+ int iEncoding; /* UTF encoding for backing database. */
+ unsigned nPageSize; /* Size of pages in backing database. */
+ Pager *pPager; /* Backing database pager. */
+ RecoverLeafCursor *pLeafCursor; /* Cursor to read table's leaf pages. */
+ RecoverCursor *pCursor; /* Cursor to read rows from leaves. */
+ int rc;
+
+ FNENTRY();
+
+ iRootPage = 0;
+ rc = getRootPage(pRecover->db, pRecover->zDb, pRecover->zTable,
+ &iRootPage);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+
+ iEncoding = 0;
+ rc = getEncoding(pRecover->db, pRecover->zDb, &iEncoding);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+
+ rc = GetPager(pRecover->db, pRecover->zDb, &pPager, &nPageSize);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+
+ rc = leafCursorCreate(pPager, nPageSize, iRootPage, &pLeafCursor);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+
+ pCursor = sqlite3_malloc(sizeof(RecoverCursor));
+ if( !pCursor ){
+ leafCursorDestroy(pLeafCursor);
+ return SQLITE_NOMEM;
+ }
+ memset(pCursor, 0, sizeof(*pCursor));
+ pCursor->base.pVtab = pVTab;
+ pCursor->pLeafCursor = pLeafCursor;
+ pCursor->iEncoding = iEncoding;
+
+ *ppCursor = (sqlite3_vtab_cursor*)pCursor;
+ return SQLITE_OK;
+}
+
+static int recoverClose(sqlite3_vtab_cursor *cur){
+ RecoverCursor *pCursor = (RecoverCursor*)cur;
+ FNENTRY();
+ if( pCursor->pLeafCursor ){
+ leafCursorDestroy(pCursor->pLeafCursor);
+ pCursor->pLeafCursor = NULL;
+ }
+ memset(pCursor, 0xA5, sizeof(*pCursor));
+ sqlite3_free(cur);
+ return SQLITE_OK;
+}
+
+/* Helpful place to set a breakpoint. */
+static int RecoverInvalidCell(){
+ return SQLITE_ERROR;
+}
+
+/* Returns SQLITE_OK if the cell has an appropriate number of columns
+ * with the appropriate types of data.
+ */
+static int recoverValidateLeafCell(Recover *pRecover, RecoverCursor *pCursor){
+ unsigned i;
+
+ /* If the row's storage has too many columns, skip it. */
+ if( leafCursorCellColumns(pCursor->pLeafCursor)>pRecover->nCols ){
+ return RecoverInvalidCell();
+ }
+
+ /* Skip rows with unexpected types. */
+ for( i=0; i<pRecover->nCols; ++i ){
+ u64 iType; /* Storage type of column i. */
+ int rc;
+
+ /* ROWID alias. */
+ if( (pRecover->pTypes[i]&MASK_ROWID) ){
+ continue;
+ }
+
+ rc = leafCursorCellColInfo(pCursor->pLeafCursor, i, &iType, NULL, NULL);
+ assert( rc==SQLITE_OK );
+ if( rc!=SQLITE_OK || !SerialTypeIsCompatible(iType, pRecover->pTypes[i]) ){
+ return RecoverInvalidCell();
+ }
+ }
+
+ return SQLITE_OK;
+}
+
+static int recoverNext(sqlite3_vtab_cursor *pVtabCursor){
+ RecoverCursor *pCursor = (RecoverCursor*)pVtabCursor;
+ Recover *pRecover = (Recover*)pCursor->base.pVtab;
+ int rc;
+
+ FNENTRY();
+
+ /* Scan forward to the next cell with valid storage, then check that
+ * the stored data matches the schema.
+ */
+ while( (rc = leafCursorNextValidCell(pCursor->pLeafCursor))==SQLITE_ROW ){
+ if( recoverValidateLeafCell(pRecover, pCursor)==SQLITE_OK ){
+ return SQLITE_OK;
+ }
+ }
+
+ if( rc==SQLITE_DONE ){
+ pCursor->bEOF = 1;
+ return SQLITE_OK;
+ }
+
+ assert( rc!=SQLITE_OK );
+ return rc;
+}
+
+static int recoverFilter(
+ sqlite3_vtab_cursor *pVtabCursor,
+ int idxNum, const char *idxStr,
+ int argc, sqlite3_value **argv
+){
+ RecoverCursor *pCursor = (RecoverCursor*)pVtabCursor;
+ Recover *pRecover = (Recover*)pCursor->base.pVtab;
+ int rc;
+
+ FNENTRY();
+
+ /* Load the first cell, and iterate forward if it's not valid. */
+ /* TODO(shess): What happens if no cells at all are valid? */
+ rc = leafCursorCellDecode(pCursor->pLeafCursor);
+ if( rc!=SQLITE_OK || recoverValidateLeafCell(pRecover, pCursor)!=SQLITE_OK ){
+ return recoverNext(pVtabCursor);
+ }
+
+ return SQLITE_OK;
+}
+
+static int recoverEof(sqlite3_vtab_cursor *pVtabCursor){
+ RecoverCursor *pCursor = (RecoverCursor*)pVtabCursor;
+ FNENTRY();
+ return pCursor->bEOF;
+}
+
+static int recoverColumn(sqlite3_vtab_cursor *cur, sqlite3_context *ctx, int i){
+ RecoverCursor *pCursor = (RecoverCursor*)cur;
+ Recover *pRecover = (Recover*)pCursor->base.pVtab;
+ u64 iColType; /* Storage type of column i. */
+ unsigned char *pColData; /* Column i's data. */
+ int shouldFree; /* Non-zero if pColData should be freed. */
+ int rc;
+
+ FNENTRY();
+
+ if( i>=pRecover->nCols ){
+ return SQLITE_ERROR;
+ }
+
+ /* ROWID alias. */
+ if( (pRecover->pTypes[i]&MASK_ROWID) ){
+ sqlite3_result_int64(ctx, leafCursorCellRowid(pCursor->pLeafCursor));
+ return SQLITE_OK;
+ }
+
+ pColData = NULL;
+ shouldFree = 0;
+ rc = leafCursorCellColInfo(pCursor->pLeafCursor, i, &iColType,
+ &pColData, &shouldFree);
+ if( rc!=SQLITE_OK ){
+ return rc;
+ }
+ /* recoverValidateLeafCell() should guarantee that this will never
+ * occur.
+ */
+ if( !SerialTypeIsCompatible(iColType, pRecover->pTypes[i]) ){
+ if( shouldFree ){
+ sqlite3_free(pColData);
+ }
+ return SQLITE_ERROR;
+ }
+
+ switch( iColType ){
+ case 0 : sqlite3_result_null(ctx); break;
+ case 1 : sqlite3_result_int64(ctx, decodeSigned(pColData, 1)); break;
+ case 2 : sqlite3_result_int64(ctx, decodeSigned(pColData, 2)); break;
+ case 3 : sqlite3_result_int64(ctx, decodeSigned(pColData, 3)); break;
+ case 4 : sqlite3_result_int64(ctx, decodeSigned(pColData, 4)); break;
+ case 5 : sqlite3_result_int64(ctx, decodeSigned(pColData, 6)); break;
+ case 6 : sqlite3_result_int64(ctx, decodeSigned(pColData, 8)); break;
+ case 7 : sqlite3_result_double(ctx, decodeFloat64(pColData)); break;
+ case 8 : sqlite3_result_int(ctx, 0); break;
+ case 9 : sqlite3_result_int(ctx, 1); break;
+ case 10 : assert( iColType!=10 ); break;
+ case 11 : assert( iColType!=11 ); break;
+
+ default : {
+ u32 l = SerialTypeLength(iColType);
+
+ /* If pColData was already allocated, arrange to pass ownership. */
+ sqlite3_destructor_type pFn = SQLITE_TRANSIENT;
+ if( shouldFree ){
+ pFn = sqlite3_free;
+ shouldFree = 0;
+ }
+
+ if( SerialTypeIsBlob(iColType) ){
+ sqlite3_result_blob(ctx, pColData, l, pFn);
+ }else{
+ if( pCursor->iEncoding==SQLITE_UTF16LE ){
+ sqlite3_result_text16le(ctx, (const void*)pColData, l, pFn);
+ }else if( pCursor->iEncoding==SQLITE_UTF16BE ){
+ sqlite3_result_text16be(ctx, (const void*)pColData, l, pFn);
+ }else{
+ sqlite3_result_text(ctx, (const char*)pColData, l, pFn);
+ }
+ }
+ } break;
+ }
+ if( shouldFree ){
+ sqlite3_free(pColData);
+ }
+ return SQLITE_OK;
+}
+
+static int recoverRowid(sqlite3_vtab_cursor *pVtabCursor, sqlite_int64 *pRowid){
+ RecoverCursor *pCursor = (RecoverCursor*)pVtabCursor;
+ FNENTRY();
+ *pRowid = leafCursorCellRowid(pCursor->pLeafCursor);
+ return SQLITE_OK;
+}
+
+static sqlite3_module recoverModule = {
+ 0, /* iVersion */
+ recoverCreate, /* xCreate - create a table */
+ recoverConnect, /* xConnect - connect to an existing table */
+ recoverBestIndex, /* xBestIndex - Determine search strategy */
+ recoverDisconnect, /* xDisconnect - Disconnect from a table */
+ recoverDestroy, /* xDestroy - Drop a table */
+ recoverOpen, /* xOpen - open a cursor */
+ recoverClose, /* xClose - close a cursor */
+ recoverFilter, /* xFilter - configure scan constraints */
+ recoverNext, /* xNext - advance a cursor */
+ recoverEof, /* xEof */
+ recoverColumn, /* xColumn - read data */
+ recoverRowid, /* xRowid - read data */
+ 0, /* xUpdate - write data */
+ 0, /* xBegin - begin transaction */
+ 0, /* xSync - sync transaction */
+ 0, /* xCommit - commit transaction */
+ 0, /* xRollback - rollback transaction */
+ 0, /* xFindFunction - function overloading */
+ 0, /* xRename - rename the table */
+};
+
+int recoverVtableInit(sqlite3 *db){
+ return sqlite3_create_module_v2(db, "recover", &recoverModule, NULL, 0);
+}
+
+/* This section of code is for parsing the create input and
+ * initializing the module.
+ */
+
+/* Find the next word in zText and place the endpoints in pzWord*.
+ * Returns true if the word is non-empty. "Word" is defined as
+ * ASCII alphanumeric plus '_' at this time.
+ */
+static int findWord(const char *zText,
+ const char **pzWordStart, const char **pzWordEnd){
+ int r;
+ while( ascii_isspace(*zText) ){
+ zText++;
+ }
+ *pzWordStart = zText;
+ while( ascii_isalnum(*zText) || *zText=='_' ){
+ zText++;
+ }
+ r = zText>*pzWordStart; /* In case pzWordStart==pzWordEnd */
+ *pzWordEnd = zText;
+ return r;
+}
+
+/* Return true if the next word in zText is zWord, also setting
+ * *pzContinue to the character after the word.
+ */
+static int expectWord(const char *zText, const char *zWord,
+ const char **pzContinue){
+ const char *zWordStart, *zWordEnd;
+ if( findWord(zText, &zWordStart, &zWordEnd) &&
+ ascii_strncasecmp(zWord, zWordStart, zWordEnd - zWordStart)==0 ){
+ *pzContinue = zWordEnd;
+ return 1;
+ }
+ return 0;
+}
+
+/* Parse the name and type information out of parameter. In case of
+ * success, *pzNameStart/End contain the name of the column,
+ * *pzTypeStart/End contain the top-level type, and *pTypeMask has the
+ * type mask to use for the column.
+ */
+static int findNameAndType(const char *parameter,
+ const char **pzNameStart, const char **pzNameEnd,
+ const char **pzTypeStart, const char **pzTypeEnd,
+ unsigned char *pTypeMask){
+ unsigned nNameLen; /* Length of found name. */
+ const char *zEnd; /* Current end of parsed column information. */
+ int bNotNull; /* Non-zero if NULL is not allowed for name. */
+ int bStrict; /* Non-zero if column requires exact type match. */
+ const char *zDummy; /* Dummy parameter, result unused. */
+ unsigned i;
+
+ /* strictMask is used for STRICT, strictMask|otherMask if STRICT is
+ * not supplied. zReplace provides an alternate type to expose to
+ * the caller.
+ */
+ static struct {
+ const char *zName;
+ unsigned char strictMask;
+ unsigned char otherMask;
+ const char *zReplace;
+ } kTypeInfo[] = {
+ { "ANY",
+ MASK_INTEGER | MASK_FLOAT | MASK_BLOB | MASK_TEXT | MASK_NULL,
+ 0, "",
+ },
+ { "ROWID", MASK_INTEGER | MASK_ROWID, 0, "INTEGER", },
+ { "INTEGER", MASK_INTEGER | MASK_NULL, 0, NULL, },
+ { "FLOAT", MASK_FLOAT | MASK_NULL, MASK_INTEGER, NULL, },
+ { "NUMERIC", MASK_INTEGER | MASK_FLOAT | MASK_NULL, MASK_TEXT, NULL, },
+ { "TEXT", MASK_TEXT | MASK_NULL, MASK_BLOB, NULL, },
+ { "BLOB", MASK_BLOB | MASK_NULL, 0, NULL, },
+ };
+
+ if( !findWord(parameter, pzNameStart, pzNameEnd) ){
+ return SQLITE_MISUSE;
+ }
+
+ /* Manifest typing, accept any storage type. */
+ if( !findWord(*pzNameEnd, pzTypeStart, pzTypeEnd) ){
+ *pzTypeEnd = *pzTypeStart = "";
+ *pTypeMask = MASK_INTEGER | MASK_FLOAT | MASK_BLOB | MASK_TEXT | MASK_NULL;
+ return SQLITE_OK;
+ }
+
+ nNameLen = *pzTypeEnd - *pzTypeStart;
+ for( i=0; i<ArraySize(kTypeInfo); ++i ){
+ if( ascii_strncasecmp(kTypeInfo[i].zName, *pzTypeStart, nNameLen)==0 ){
+ break;
+ }
+ }
+ if( i==ArraySize(kTypeInfo) ){
+ return SQLITE_MISUSE;
+ }
+
+ zEnd = *pzTypeEnd;
+ bStrict = 0;
+ if( expectWord(zEnd, "STRICT", &zEnd) ){
+ /* TODO(shess): Ick. But I don't want another single-purpose
+ * flag, either.
+ */
+ if( kTypeInfo[i].zReplace && !kTypeInfo[i].zReplace[0] ){
+ return SQLITE_MISUSE;
+ }
+ bStrict = 1;
+ }
+
+ bNotNull = 0;
+ if( expectWord(zEnd, "NOT", &zEnd) ){
+ if( expectWord(zEnd, "NULL", &zEnd) ){
+ bNotNull = 1;
+ }else{
+ /* Anything other than NULL after NOT is an error. */
+ return SQLITE_MISUSE;
+ }
+ }
+
+ /* Anything else is an error. */
+ if( findWord(zEnd, &zDummy, &zDummy) ){
+ return SQLITE_MISUSE;
+ }
+
+ *pTypeMask = kTypeInfo[i].strictMask;
+ if( !bStrict ){
+ *pTypeMask |= kTypeInfo[i].otherMask;
+ }
+ if( bNotNull ){
+ *pTypeMask &= ~MASK_NULL;
+ }
+ if( kTypeInfo[i].zReplace ){
+ *pzTypeStart = kTypeInfo[i].zReplace;
+ *pzTypeEnd = *pzTypeStart + strlen(*pzTypeStart);
+ }
+ return SQLITE_OK;
+}
+
+/* Parse the arguments, placing type masks in *pTypes and the exposed
+ * schema in *pzCreateSql (for sqlite3_declare_vtab).
+ */
+static int ParseColumnsAndGenerateCreate(unsigned nCols,
+ const char *const *pCols,
+ char **pzCreateSql,
+ unsigned char *pTypes,
+ char **pzErr){
+ unsigned i;
+ char *zCreateSql = sqlite3_mprintf("CREATE TABLE x(");
+ if( !zCreateSql ){
+ return SQLITE_NOMEM;
+ }
+
+ for( i=0; i<nCols; i++ ){
+ const char *zSep = (i < nCols - 1 ? ", " : ")");
+ const char *zNotNull = "";
+ const char *zNameStart, *zNameEnd;
+ const char *zTypeStart, *zTypeEnd;
+ int rc = findNameAndType(pCols[i],
+ &zNameStart, &zNameEnd,
+ &zTypeStart, &zTypeEnd,
+ &pTypes[i]);
+ if( rc!=SQLITE_OK ){
+ *pzErr = sqlite3_mprintf("unable to parse column %d", i);
+ sqlite3_free(zCreateSql);
+ return rc;
+ }
+
+ if( !(pTypes[i]&MASK_NULL) ){
+ zNotNull = " NOT NULL";
+ }
+
+ /* Add name and type to the create statement. */
+ zCreateSql = sqlite3_mprintf("%z%.*s %.*s%s%s",
+ zCreateSql,
+ zNameEnd - zNameStart, zNameStart,
+ zTypeEnd - zTypeStart, zTypeStart,
+ zNotNull, zSep);
+ if( !zCreateSql ){
+ return SQLITE_NOMEM;
+ }
+ }
+
+ *pzCreateSql = zCreateSql;
+ return SQLITE_OK;
+}
+
+/* Helper function for initializing the module. */
+/* argv[0] module name
+ * argv[1] db name for virtual table
+ * argv[2] virtual table name
+ * argv[3] backing table name
+ * argv[4] columns
+ */
+/* TODO(shess): Since connect isn't supported, could inline into
+ * recoverCreate().
+ */
+/* TODO(shess): Explore cases where it would make sense to set *pzErr. */
+static int recoverInit(
+ sqlite3 *db, /* Database connection */
+ void *pAux, /* unused */
+ int argc, const char *const*argv, /* Parameters to CREATE TABLE statement */
+ sqlite3_vtab **ppVtab, /* OUT: New virtual table */
+ char **pzErr /* OUT: Error message, if any */
+){
+ const unsigned kTypeCol = 4; /* First argument with column type info. */
+ Recover *pRecover; /* Virtual table structure being created. */
+ char *zDot; /* Any dot found in "db.table" backing. */
+ u32 iRootPage; /* Root page of backing table. */
+ char *zCreateSql; /* Schema of created virtual table. */
+ int rc;
+
+ /* Require to be in the temp database. */
+ if( ascii_strcasecmp(argv[1], "temp")!=0 ){
+ *pzErr = sqlite3_mprintf("recover table must be in temp database");
+ return SQLITE_MISUSE;
+ }
+
+ /* Need the backing table and at least one column. */
+ if( argc<=kTypeCol ){
+ *pzErr = sqlite3_mprintf("no columns specified");
+ return SQLITE_MISUSE;
+ }
+
+ pRecover = sqlite3_malloc(sizeof(Recover));
+ if( !pRecover ){
+ return SQLITE_NOMEM;
+ }
+ memset(pRecover, 0, sizeof(*pRecover));
+ pRecover->base.pModule = &recoverModule;
+ pRecover->db = db;
+
+ /* Parse out db.table, assuming main if no dot. */
+ zDot = strchr(argv[3], '.');
+ if( !zDot ){
+ pRecover->zDb = sqlite3_strdup(db->aDb[0].zName);
+ pRecover->zTable = sqlite3_strdup(argv[3]);
+ }else if( zDot>argv[3] && zDot[1]!='\0' ){
+ pRecover->zDb = sqlite3_strndup(argv[3], zDot - argv[3]);
+ pRecover->zTable = sqlite3_strdup(zDot + 1);
+ }else{
+ /* ".table" or "db." not allowed. */
+ *pzErr = sqlite3_mprintf("ill-formed table specifier");
+ recoverRelease(pRecover);
+ return SQLITE_ERROR;
+ }
+
+ pRecover->nCols = argc - kTypeCol;
+ pRecover->pTypes = sqlite3_malloc(pRecover->nCols);
+ if( !pRecover->zDb || !pRecover->zTable || !pRecover->pTypes ){
+ recoverRelease(pRecover);
+ return SQLITE_NOMEM;
+ }
+
+ /* Require the backing table to exist. */
+ /* TODO(shess): Be more pedantic about the form of the descriptor
+ * string. This already fails for poorly-formed strings, simply
+ * because there won't be a root page, but it would make more sense
+ * to be explicit.
+ */
+ rc = getRootPage(pRecover->db, pRecover->zDb, pRecover->zTable, &iRootPage);
+ if( rc!=SQLITE_OK ){
+ *pzErr = sqlite3_mprintf("unable to find backing table");
+ recoverRelease(pRecover);
+ return rc;
+ }
+
+ /* Parse the column definitions. */
+ rc = ParseColumnsAndGenerateCreate(pRecover->nCols, argv + kTypeCol,
+ &zCreateSql, pRecover->pTypes, pzErr);
+ if( rc!=SQLITE_OK ){
+ recoverRelease(pRecover);
+ return rc;
+ }
+
+ rc = sqlite3_declare_vtab(db, zCreateSql);
+ sqlite3_free(zCreateSql);
+ if( rc!=SQLITE_OK ){
+ recoverRelease(pRecover);
+ return rc;
+ }
+
+ *ppVtab = (sqlite3_vtab *)pRecover;
+ return SQLITE_OK;
+}