#include "strings/numbers.h"
#include <float.h> // for FLT_DIG
#include <cassert>
#include <memory>
#include "strings/ascii_ctype.h"
namespace dynamic_depth {
namespace strings {
namespace {
// Represents integer values of digits.
// Uses 36 to indicate an invalid character since we support
// bases up to 36.
static const int8 kAsciiToInt[256] = {
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, // 16 36s.
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36,
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 0, 1, 2, 3, 4, 5,
6, 7, 8, 9, 36, 36, 36, 36, 36, 36, 36, 10, 11, 12, 13, 14, 15, 16, 17,
18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36,
36, 36, 36, 36, 36, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,
24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 36, 36, 36, 36, 36, 36,
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36,
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36,
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36,
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36,
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36,
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36,
36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36};
// Parse the sign and optional hex or oct prefix in text.
inline bool safe_parse_sign_and_base(string* text /*inout*/,
int* base_ptr /*inout*/,
bool* negative_ptr /*output*/) {
if (text->data() == NULL) {
return false;
}
const char* start = text->data();
const char* end = start + text->size();
int base = *base_ptr;
// Consume whitespace.
while (start < end && ascii_isspace(start[0])) {
++start;
}
while (start < end && ascii_isspace(end[-1])) {
--end;
}
if (start >= end) {
return false;
}
// Consume sign.
*negative_ptr = (start[0] == '-');
if (*negative_ptr || start[0] == '+') {
++start;
if (start >= end) {
return false;
}
}
// Consume base-dependent prefix.
// base 0: "0x" -> base 16, "0" -> base 8, default -> base 10
// base 16: "0x" -> base 16
// Also validate the base.
if (base == 0) {
if (end - start >= 2 && start[0] == '0' &&
(start[1] == 'x' || start[1] == 'X')) {
base = 16;
start += 2;
if (start >= end) {
// "0x" with no digits after is invalid.
return false;
}
} else if (end - start >= 1 && start[0] == '0') {
base = 8;
start += 1;
} else {
base = 10;
}
} else if (base == 16) {
if (end - start >= 2 && start[0] == '0' &&
(start[1] == 'x' || start[1] == 'X')) {
start += 2;
if (start >= end) {
// "0x" with no digits after is invalid.
return false;
}
}
} else if (base >= 2 && base <= 36) {
// okay
} else {
return false;
}
text->assign(start, end - start);
*base_ptr = base;
return true;
}
// Consume digits.
//
// The classic loop:
//
// for each digit
// value = value * base + digit
// value *= sign
//
// The classic loop needs overflow checking. It also fails on the most
// negative integer, -2147483648 in 32-bit two's complement representation.
//
// My improved loop:
//
// if (!negative)
// for each digit
// value = value * base
// value = value + digit
// else
// for each digit
// value = value * base
// value = value - digit
//
// Overflow checking becomes simple.
// Lookup tables per IntType:
// vmax/base and vmin/base are precomputed because division costs at least 8ns.
// TODO(junyer): Doing this per base instead (i.e. an array of structs, not a
// struct of arrays) would probably be better in terms of d-cache for the most
// commonly used bases.
template <typename IntType>
struct LookupTables {
static const IntType kVmaxOverBase[];
static const IntType kVminOverBase[];
};
// An array initializer macro for X/base where base in [0, 36].
// However, note that lookups for base in [0, 1] should never happen because
// base has been validated to be in [2, 36] by safe_parse_sign_and_base().
#define X_OVER_BASE_INITIALIZER(X) \
{ \
0, 0, X / 2, X / 3, X / 4, X / 5, X / 6, X / 7, \
X / 8, X / 9, X / 10, X / 11, X / 12, X / 13, X / 14, X / 15, \
X / 16, X / 17, X / 18, X / 19, X / 20, X / 21, X / 22, X / 23, \
X / 24, X / 25, X / 26, X / 27, X / 28, X / 29, X / 30, X / 31, \
X / 32, X / 33, X / 34, X / 35, X / 36, \
};
template <typename IntType>
const IntType LookupTables<IntType>::kVmaxOverBase[] =
X_OVER_BASE_INITIALIZER(std::numeric_limits<IntType>::max());
template <typename IntType>
const IntType LookupTables<IntType>::kVminOverBase[] =
X_OVER_BASE_INITIALIZER(std::numeric_limits<IntType>::min());
#undef X_OVER_BASE_INITIALIZER
template <typename IntType>
inline bool safe_parse_positive_int(const string& text, int base,
IntType* value_p) {
IntType value = 0;
const IntType vmax = std::numeric_limits<IntType>::max();
assert(vmax > 0);
assert(vmax >= base);
const IntType vmax_over_base = LookupTables<IntType>::kVmaxOverBase[base];
const char* start = text.data();
const char* end = start + text.size();
// loop over digits
for (; start < end; ++start) {
unsigned char c = static_cast<unsigned char>(start[0]);
int digit = kAsciiToInt[c];
if (digit >= base) {
*value_p = value;
return false;
}
if (value > vmax_over_base) {
*value_p = vmax;
return false;
}
value *= base;
if (value > vmax - digit) {
*value_p = vmax;
return false;
}
value += digit;
}
*value_p = value;
return true;
}
template <typename IntType>
inline bool safe_parse_negative_int(const string& text, int base,
IntType* value_p) {
IntType value = 0;
const IntType vmin = std::numeric_limits<IntType>::min();
assert(vmin < 0);
assert(vmin <= 0 - base);
IntType vmin_over_base = LookupTables<IntType>::kVminOverBase[base];
// 2003 c++ standard [expr.mul]
// "... the sign of the remainder is implementation-defined."
// Although (vmin/base)*base + vmin%base is always vmin.
// 2011 c++ standard tightens the spec but we cannot rely on it.
// TODO(junyer): Handle this in the lookup table generation.
if (vmin % base > 0) {
vmin_over_base += 1;
}
const char* start = text.data();
const char* end = start + text.size();
// loop over digits
for (; start < end; ++start) {
unsigned char c = static_cast<unsigned char>(start[0]);
int digit = kAsciiToInt[c];
if (digit >= base) {
*value_p = value;
return false;
}
if (value < vmin_over_base) {
*value_p = vmin;
return false;
}
value *= base;
if (value < vmin + digit) {
*value_p = vmin;
return false;
}
value -= digit;
}
*value_p = value;
return true;
}
// Input format based on POSIX.1-2008 strtol
// http://pubs.opengroup.org/onlinepubs/9699919799/functions/strtol.html
template <typename IntType>
inline bool safe_int_internal(const string& text, IntType* value_p, int base) {
*value_p = 0;
bool negative;
string text_copy(text);
if (!safe_parse_sign_and_base(&text_copy, &base, &negative)) {
return false;
}
if (!negative) {
return safe_parse_positive_int(text_copy, base, value_p);
} else {
return safe_parse_negative_int(text_copy, base, value_p);
}
}
template <typename IntType>
inline bool safe_uint_internal(const string& text, IntType* value_p, int base) {
*value_p = 0;
bool negative;
string text_copy(text);
if (!safe_parse_sign_and_base(&text_copy, &base, &negative) || negative) {
return false;
}
return safe_parse_positive_int(text_copy, base, value_p);
}
// Writes a two-character representation of 'i' to 'buf'. 'i' must be in the
// range 0 <= i < 100, and buf must have space for two characters. Example:
// char buf[2];
// PutTwoDigits(42, buf);
// // buf[0] == '4'
// // buf[1] == '2'
inline void PutTwoDigits(size_t i, char* buf) {
static const char two_ASCII_digits[100][2] = {
{'0', '0'}, {'0', '1'}, {'0', '2'}, {'0', '3'}, {'0', '4'}, {'0', '5'},
{'0', '6'}, {'0', '7'}, {'0', '8'}, {'0', '9'}, {'1', '0'}, {'1', '1'},
{'1', '2'}, {'1', '3'}, {'1', '4'}, {'1', '5'}, {'1', '6'}, {'1', '7'},
{'1', '8'}, {'1', '9'}, {'2', '0'}, {'2', '1'}, {'2', '2'}, {'2', '3'},
{'2', '4'}, {'2', '5'}, {'2', '6'}, {'2', '7'}, {'2', '8'}, {'2', '9'},
{'3', '0'}, {'3', '1'}, {'3', '2'}, {'3', '3'}, {'3', '4'}, {'3', '5'},
{'3', '6'}, {'3', '7'}, {'3', '8'}, {'3', '9'}, {'4', '0'}, {'4', '1'},
{'4', '2'}, {'4', '3'}, {'4', '4'}, {'4', '5'}, {'4', '6'}, {'4', '7'},
{'4', '8'}, {'4', '9'}, {'5', '0'}, {'5', '1'}, {'5', '2'}, {'5', '3'},
{'5', '4'}, {'5', '5'}, {'5', '6'}, {'5', '7'}, {'5', '8'}, {'5', '9'},
{'6', '0'}, {'6', '1'}, {'6', '2'}, {'6', '3'}, {'6', '4'}, {'6', '5'},
{'6', '6'}, {'6', '7'}, {'6', '8'}, {'6', '9'}, {'7', '0'}, {'7', '1'},
{'7', '2'}, {'7', '3'}, {'7', '4'}, {'7', '5'}, {'7', '6'}, {'7', '7'},
{'7', '8'}, {'7', '9'}, {'8', '0'}, {'8', '1'}, {'8', '2'}, {'8', '3'},
{'8', '4'}, {'8', '5'}, {'8', '6'}, {'8', '7'}, {'8', '8'}, {'8', '9'},
{'9', '0'}, {'9', '1'}, {'9', '2'}, {'9', '3'}, {'9', '4'}, {'9', '5'},
{'9', '6'}, {'9', '7'}, {'9', '8'}, {'9', '9'}};
assert(i < 100);
memcpy(buf, two_ASCII_digits[i], 2);
}
} // anonymous namespace
// ----------------------------------------------------------------------
// FastInt32ToBufferLeft()
// FastUInt32ToBufferLeft()
// FastInt64ToBufferLeft()
// FastUInt64ToBufferLeft()
//
// Like the Fast*ToBuffer() functions above, these are intended for speed.
// Unlike the Fast*ToBuffer() functions, however, these functions write
// their output to the beginning of the buffer (hence the name, as the
// output is left-aligned). The caller is responsible for ensuring that
// the buffer has enough space to hold the output.
//
// Returns a pointer to the end of the string (i.e. the null character
// terminating the string).
// ----------------------------------------------------------------------
// Used to optimize printing a decimal number's final digit.
const char one_ASCII_final_digits[10][2]{
{'0', 0}, {'1', 0}, {'2', 0}, {'3', 0}, {'4', 0},
{'5', 0}, {'6', 0}, {'7', 0}, {'8', 0}, {'9', 0},
};
char* FastUInt32ToBufferLeft(uint32 u, char* buffer) {
uint32 digits;
// The idea of this implementation is to trim the number of divides to as few
// as possible, and also reducing memory stores and branches, by going in
// steps of two digits at a time rather than one whenever possible.
// The huge-number case is first, in the hopes that the compiler will output
// that case in one branch-free block of code, and only output conditional
// branches into it from below.
if (u >= 1000000000) { // >= 1,000,000,000
digits = u / 100000000; // 100,000,000
u -= digits * 100000000;
PutTwoDigits(digits, buffer);
buffer += 2;
lt100_000_000:
digits = u / 1000000; // 1,000,000
u -= digits * 1000000;
PutTwoDigits(digits, buffer);
buffer += 2;
lt1_000_000:
digits = u / 10000; // 10,000
u -= digits * 10000;
PutTwoDigits(digits, buffer);
buffer += 2;
lt10_000:
digits = u / 100;
u -= digits * 100;
PutTwoDigits(digits, buffer);
buffer += 2;
lt100:
digits = u;
PutTwoDigits(digits, buffer);
buffer += 2;
*buffer = 0;
return buffer;
}
if (u < 100) {
digits = u;
if (u >= 10) goto lt100;
memcpy(buffer, one_ASCII_final_digits[u], 2);
return buffer + 1;
}
if (u < 10000) { // 10,000
if (u >= 1000) goto lt10_000;
digits = u / 100;
u -= digits * 100;
*buffer++ = '0' + digits;
goto lt100;
}
if (u < 1000000) { // 1,000,000
if (u >= 100000) goto lt1_000_000;
digits = u / 10000; // 10,000
u -= digits * 10000;
*buffer++ = '0' + digits;
goto lt10_000;
}
if (u < 100000000) { // 100,000,000
if (u >= 10000000) goto lt100_000_000;
digits = u / 1000000; // 1,000,000
u -= digits * 1000000;
*buffer++ = '0' + digits;
goto lt1_000_000;
}
// we already know that u < 1,000,000,000
digits = u / 100000000; // 100,000,000
u -= digits * 100000000;
*buffer++ = '0' + digits;
goto lt100_000_000;
}
char* FastInt32ToBufferLeft(int32 i, char* buffer) {
uint32 u = i;
if (i < 0) {
*buffer++ = '-';
// We need to do the negation in modular (i.e., "unsigned")
// arithmetic; MSVC++ apprently warns for plain "-u", so
// we write the equivalent expression "0 - u" instead.
u = 0 - u;
}
return FastUInt32ToBufferLeft(u, buffer);
}
char* FastUInt64ToBufferLeft(uint64 u64, char* buffer) {
uint32 u32 = static_cast<uint32>(u64);
if (u32 == u64) return FastUInt32ToBufferLeft(u32, buffer);
// Here we know u64 has at least 10 decimal digits.
uint64 top_1to11 = u64 / 1000000000;
u32 = static_cast<uint32>(u64 - top_1to11 * 1000000000);
uint32 top_1to11_32 = static_cast<uint32>(top_1to11);
if (top_1to11_32 == top_1to11) {
buffer = FastUInt32ToBufferLeft(top_1to11_32, buffer);
} else {
// top_1to11 has more than 32 bits too; print it in two steps.
uint32 top_8to9 = static_cast<uint32>(top_1to11 / 100);
uint32 mid_2 = static_cast<uint32>(top_1to11 - top_8to9 * 100);
buffer = FastUInt32ToBufferLeft(top_8to9, buffer);
PutTwoDigits(mid_2, buffer);
buffer += 2;
}
// We have only 9 digits now, again the maximum uint32 can handle fully.
uint32 digits = u32 / 10000000; // 10,000,000
u32 -= digits * 10000000;
PutTwoDigits(digits, buffer);
buffer += 2;
digits = u32 / 100000; // 100,000
u32 -= digits * 100000;
PutTwoDigits(digits, buffer);
buffer += 2;
digits = u32 / 1000; // 1,000
u32 -= digits * 1000;
PutTwoDigits(digits, buffer);
buffer += 2;
digits = u32 / 10;
u32 -= digits * 10;
PutTwoDigits(digits, buffer);
buffer += 2;
memcpy(buffer, one_ASCII_final_digits[u32], 2);
return buffer + 1;
}
char* FastInt64ToBufferLeft(int64 i, char* buffer) {
uint64 u = i;
if (i < 0) {
*buffer++ = '-';
u = 0 - u;
}
return FastUInt64ToBufferLeft(u, buffer);
}
bool safe_strto32_base(const string& text, int32* value, int base) {
return safe_int_internal<int32>(text, value, base);
}
bool safe_strto64_base(const string& text, int64* value, int base) {
return safe_int_internal<int64>(text, value, base);
}
bool safe_strtou32_base(const string& text, uint32* value, int base) {
return safe_uint_internal<uint32>(text, value, base);
}
bool safe_strtou64_base(const string& text, uint64* value, int base) {
return safe_uint_internal<uint64>(text, value, base);
}
bool safe_strtof(const string& piece, float* value) {
*value = 0.0;
if (piece.empty()) return false;
char buf[32];
std::unique_ptr<char[]> bigbuf;
char* str = buf;
if (piece.size() > sizeof(buf) - 1) {
bigbuf.reset(new char[piece.size() + 1]);
str = bigbuf.get();
}
memcpy(str, piece.data(), piece.size());
str[piece.size()] = '\0';
char* endptr;
#ifdef COMPILER_MSVC // has no strtof()
*value = strtod(str, &endptr);
#else
*value = strtof(str, &endptr);
#endif
if (endptr != str) {
while (ascii_isspace(*endptr)) ++endptr;
}
// Ignore range errors from strtod/strtof.
// The values it returns on underflow and
// overflow are the right fallback in a
// robust setting.
return *str != '\0' && *endptr == '\0';
}
bool safe_strtod(const string& piece, double* value) {
*value = 0.0;
if (piece.empty()) return false;
char buf[32];
std::unique_ptr<char[]> bigbuf;
char* str = buf;
if (piece.size() > sizeof(buf) - 1) {
bigbuf.reset(new char[piece.size() + 1]);
str = bigbuf.get();
}
memcpy(str, piece.data(), piece.size());
str[piece.size()] = '\0';
char* endptr;
*value = strtod(str, &endptr);
if (endptr != str) {
while (ascii_isspace(*endptr)) ++endptr;
}
// Ignore range errors from strtod. The values it
// returns on underflow and overflow are the right
// fallback in a robust setting.
return *str != '\0' && *endptr == '\0';
}
string SimpleFtoa(float value) {
char buffer[kFastToBufferSize];
return FloatToBuffer(value, buffer);
}
char* FloatToBuffer(float value, char* buffer) {
// FLT_DIG is 6 for IEEE-754 floats, which are used on almost all
// platforms these days. Just in case some system exists where FLT_DIG
// is significantly larger -- and risks overflowing our buffer -- we have
// this assert.
assert(FLT_DIG < 10);
int snprintf_result =
snprintf(buffer, kFastToBufferSize, "%.*g", FLT_DIG, value);
// The snprintf should never overflow because the buffer is significantly
// larger than the precision we asked for.
assert(snprintf_result > 0 && snprintf_result < kFastToBufferSize);
float parsed_value;
if (!safe_strtof(buffer, &parsed_value) || parsed_value != value) {
snprintf_result =
snprintf(buffer, kFastToBufferSize, "%.*g", FLT_DIG + 2, value);
// Should never overflow; see above.
assert(snprintf_result > 0 && snprintf_result < kFastToBufferSize);
}
return buffer;
}
} // namespace strings
} // namespace dynamic_depth