/*
* Copyright 2014 Google Inc. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// independent from idl_parser, since this code is not needed for most clients
#include <string>
#include "flatbuffers/flatbuffers.h"
#include "flatbuffers/idl.h"
#include "flatbuffers/util.h"
#include "flatbuffers/code_generators.h"
namespace flatbuffers {
namespace python {
static std::string GenGetter(const Type &type);
static std::string GenMethod(const FieldDef &field);
static void GenStructBuilder(const StructDef &struct_def,
std::string *code_ptr);
static void GenReceiver(const StructDef &struct_def, std::string *code_ptr);
static std::string GenTypeBasic(const Type &type);
static std::string GenTypeGet(const Type &type);
static std::string TypeName(const FieldDef &field);
// Hardcode spaces per indentation.
const std::string Indent = " ";
// Most field accessors need to retrieve and test the field offset first,
// this is the prefix code for that.
std::string OffsetPrefix(const FieldDef &field) {
return "\n" + Indent + Indent +
"o = flatbuffers.number_types.UOffsetTFlags.py_type" +
"(self._tab.Offset(" +
NumToString(field.value.offset) +
"))\n" + Indent + Indent + "if o != 0:\n";
}
// Begin a class declaration.
static void BeginClass(const StructDef &struct_def, std::string *code_ptr) {
std::string &code = *code_ptr;
code += "class " + struct_def.name + "(object):\n";
code += Indent + "__slots__ = ['_tab']";
code += "\n\n";
}
// Begin enum code with a class declaration.
static void BeginEnum(const std::string class_name, std::string *code_ptr) {
std::string &code = *code_ptr;
code += "class " + class_name + "(object):\n";
}
// A single enum member.
static void EnumMember(const EnumVal ev, std::string *code_ptr) {
std::string &code = *code_ptr;
code += Indent;
code += ev.name;
code += " = ";
code += NumToString(ev.value) + "\n";
}
// End enum code.
static void EndEnum(std::string *code_ptr) {
std::string &code = *code_ptr;
code += "\n";
}
// Initialize a new struct or table from existing data.
static void NewRootTypeFromBuffer(const StructDef &struct_def,
std::string *code_ptr) {
std::string &code = *code_ptr;
code += Indent + "@classmethod\n";
code += Indent + "def GetRootAs";
code += struct_def.name;
code += "(cls, buf, offset):";
code += "\n";
code += Indent + Indent;
code += "n = flatbuffers.encode.Get";
code += "(flatbuffers.packer.uoffset, buf, offset)\n";
code += Indent + Indent + "x = " + struct_def.name + "()\n";
code += Indent + Indent + "x.Init(buf, n + offset)\n";
code += Indent + Indent + "return x\n";
code += "\n";
}
// Initialize an existing object with other data, to avoid an allocation.
static void InitializeExisting(const StructDef &struct_def,
std::string *code_ptr) {
std::string &code = *code_ptr;
GenReceiver(struct_def, code_ptr);
code += "Init(self, buf, pos):\n";
code += Indent + Indent + "self._tab = flatbuffers.table.Table(buf, pos)\n";
code += "\n";
}
// Get the length of a vector.
static void GetVectorLen(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name) + "Length(self";
code += "):" + OffsetPrefix(field);
code += Indent + Indent + Indent + "return self._tab.VectorLen(o)\n";
code += Indent + Indent + "return 0\n\n";
}
// Get the value of a struct's scalar.
static void GetScalarFieldOfStruct(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
std::string getter = GenGetter(field.value.type);
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name);
code += "(self): return " + getter;
code += "self._tab.Pos + flatbuffers.number_types.UOffsetTFlags.py_type(";
code += NumToString(field.value.offset) + "))\n";
}
// Get the value of a table's scalar.
static void GetScalarFieldOfTable(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
std::string getter = GenGetter(field.value.type);
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name);
code += "(self):";
code += OffsetPrefix(field);
code += Indent + Indent + Indent + "return " + getter;
code += "o + self._tab.Pos)\n";
code += Indent + Indent + "return " + field.value.constant + "\n\n";
}
// Get a struct by initializing an existing struct.
// Specific to Struct.
static void GetStructFieldOfStruct(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name);
code += "(self, obj):\n";
code += Indent + Indent + "obj.Init(self._tab.Bytes, self._tab.Pos + ";
code += NumToString(field.value.offset) + ")";
code += "\n" + Indent + Indent + "return obj\n\n";
}
// Get a struct by initializing an existing struct.
// Specific to Table.
static void GetStructFieldOfTable(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name);
code += "(self):";
code += OffsetPrefix(field);
if (field.value.type.struct_def->fixed) {
code += Indent + Indent + Indent + "x = o + self._tab.Pos\n";
} else {
code += Indent + Indent + Indent;
code += "x = self._tab.Indirect(o + self._tab.Pos)\n";
}
code += Indent + Indent + Indent;
code += "from ." + TypeName(field) + " import " + TypeName(field) + "\n";
code += Indent + Indent + Indent + "obj = " + TypeName(field) + "()\n";
code += Indent + Indent + Indent + "obj.Init(self._tab.Bytes, x)\n";
code += Indent + Indent + Indent + "return obj\n";
code += Indent + Indent + "return None\n\n";
}
// Get the value of a string.
static void GetStringField(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name);
code += "(self):";
code += OffsetPrefix(field);
code += Indent + Indent + Indent + "return " + GenGetter(field.value.type);
code += "o + self._tab.Pos)\n";
code += Indent + Indent + "return bytes()\n\n";
}
// Get the value of a union from an object.
static void GetUnionField(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name) + "(self):";
code += OffsetPrefix(field);
// TODO(rw): this works and is not the good way to it:
bool is_native_table = TypeName(field) == "*flatbuffers.Table";
if (is_native_table) {
code += Indent + Indent + Indent + "from flatbuffers.table import Table\n";
} else {
code += Indent + Indent + Indent;
code += "from ." + TypeName(field) + " import " + TypeName(field) + "\n";
}
code += Indent + Indent + Indent + "obj = Table(bytearray(), 0)\n";
code += Indent + Indent + Indent + GenGetter(field.value.type);
code += "obj, o)\n" + Indent + Indent + Indent + "return obj\n";
code += Indent + Indent + "return None\n\n";
}
// Get the value of a vector's struct member.
static void GetMemberOfVectorOfStruct(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
auto vectortype = field.value.type.VectorType();
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name);
code += "(self, j):" + OffsetPrefix(field);
code += Indent + Indent + Indent + "x = self._tab.Vector(o)\n";
code += Indent + Indent + Indent;
code += "x += flatbuffers.number_types.UOffsetTFlags.py_type(j) * ";
code += NumToString(InlineSize(vectortype)) + "\n";
if (!(vectortype.struct_def->fixed)) {
code += Indent + Indent + Indent + "x = self._tab.Indirect(x)\n";
}
code += Indent + Indent + Indent;
code += "from ." + TypeName(field) + " import " + TypeName(field) + "\n";
code += Indent + Indent + Indent + "obj = " + TypeName(field) + "()\n";
code += Indent + Indent + Indent + "obj.Init(self._tab.Bytes, x)\n";
code += Indent + Indent + Indent + "return obj\n";
code += Indent + Indent + "return None\n\n";
}
// Get the value of a vector's non-struct member. Uses a named return
// argument to conveniently set the zero value for the result.
static void GetMemberOfVectorOfNonStruct(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
auto vectortype = field.value.type.VectorType();
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name);
code += "(self, j):";
code += OffsetPrefix(field);
code += Indent + Indent + Indent + "a = self._tab.Vector(o)\n";
code += Indent + Indent + Indent;
code += "return " + GenGetter(field.value.type);
code += "a + flatbuffers.number_types.UOffsetTFlags.py_type(j * ";
code += NumToString(InlineSize(vectortype)) + "))\n";
if (vectortype.base_type == BASE_TYPE_STRING) {
code += Indent + Indent + "return \"\"\n";
} else {
code += Indent + Indent + "return 0\n";
}
code += "\n";
}
// Returns a non-struct vector as a numpy array. Much faster
// than iterating over the vector element by element.
static void GetVectorOfNonStructAsNumpy(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
auto vectortype = field.value.type.VectorType();
// Currently, we only support accessing as numpy array if
// the vector type is a scalar.
if (!(IsScalar(vectortype.base_type))) {
return;
}
GenReceiver(struct_def, code_ptr);
code += MakeCamel(field.name) + "AsNumpy(self):";
code += OffsetPrefix(field);
code += Indent + Indent + Indent;
code += "return ";
code += "self._tab.GetVectorAsNumpy(flatbuffers.number_types.";
code += MakeCamel(GenTypeGet(field.value.type));
code += "Flags, o)\n";
if (vectortype.base_type == BASE_TYPE_STRING) {
code += Indent + Indent + "return \"\"\n";
} else {
code += Indent + Indent + "return 0\n";
}
code += "\n";
}
// Begin the creator function signature.
static void BeginBuilderArgs(const StructDef &struct_def,
std::string *code_ptr) {
std::string &code = *code_ptr;
code += "\n";
code += "def Create" + struct_def.name;
code += "(builder";
}
// Recursively generate arguments for a constructor, to deal with nested
// structs.
static void StructBuilderArgs(const StructDef &struct_def,
const char *nameprefix,
std::string *code_ptr) {
for (auto it = struct_def.fields.vec.begin();
it != struct_def.fields.vec.end();
++it) {
auto &field = **it;
if (IsStruct(field.value.type)) {
// Generate arguments for a struct inside a struct. To ensure names
// don't clash, and to make it obvious these arguments are constructing
// a nested struct, prefix the name with the field name.
StructBuilderArgs(*field.value.type.struct_def,
(nameprefix + (field.name + "_")).c_str(),
code_ptr);
} else {
std::string &code = *code_ptr;
code += (std::string)", " + nameprefix;
code += MakeCamel(field.name, false);
}
}
}
// End the creator function signature.
static void EndBuilderArgs(std::string *code_ptr) {
std::string &code = *code_ptr;
code += "):\n";
}
// Recursively generate struct construction statements and instert manual
// padding.
static void StructBuilderBody(const StructDef &struct_def,
const char *nameprefix,
std::string *code_ptr) {
std::string &code = *code_ptr;
code += " builder.Prep(" + NumToString(struct_def.minalign) + ", ";
code += NumToString(struct_def.bytesize) + ")\n";
for (auto it = struct_def.fields.vec.rbegin();
it != struct_def.fields.vec.rend();
++it) {
auto &field = **it;
if (field.padding)
code += " builder.Pad(" + NumToString(field.padding) + ")\n";
if (IsStruct(field.value.type)) {
StructBuilderBody(*field.value.type.struct_def,
(nameprefix + (field.name + "_")).c_str(),
code_ptr);
} else {
code += " builder.Prepend" + GenMethod(field) + "(";
code += nameprefix + MakeCamel(field.name, false) + ")\n";
}
}
}
static void EndBuilderBody(std::string *code_ptr) {
std::string &code = *code_ptr;
code += " return builder.Offset()\n";
}
// Get the value of a table's starting offset.
static void GetStartOfTable(const StructDef &struct_def,
std::string *code_ptr) {
std::string &code = *code_ptr;
code += "def " + struct_def.name + "Start";
code += "(builder): ";
code += "builder.StartObject(";
code += NumToString(struct_def.fields.vec.size());
code += ")\n";
}
// Set the value of a table's field.
static void BuildFieldOfTable(const StructDef &struct_def,
const FieldDef &field,
const size_t offset,
std::string *code_ptr) {
std::string &code = *code_ptr;
code += "def " + struct_def.name + "Add" + MakeCamel(field.name);
code += "(builder, ";
code += MakeCamel(field.name, false);
code += "): ";
code += "builder.Prepend";
code += GenMethod(field) + "Slot(";
code += NumToString(offset) + ", ";
if (!IsScalar(field.value.type.base_type) && (!struct_def.fixed)) {
code += "flatbuffers.number_types.UOffsetTFlags.py_type";
code += "(";
code += MakeCamel(field.name, false) + ")";
} else {
code += MakeCamel(field.name, false);
}
code += ", " + field.value.constant;
code += ")\n";
}
// Set the value of one of the members of a table's vector.
static void BuildVectorOfTable(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
std::string &code = *code_ptr;
code += "def " + struct_def.name + "Start";
code += MakeCamel(field.name);
code += "Vector(builder, numElems): return builder.StartVector(";
auto vector_type = field.value.type.VectorType();
auto alignment = InlineAlignment(vector_type);
auto elem_size = InlineSize(vector_type);
code += NumToString(elem_size);
code += ", numElems, " + NumToString(alignment);
code += ")\n";
}
// Get the offset of the end of a table.
static void GetEndOffsetOnTable(const StructDef &struct_def,
std::string *code_ptr) {
std::string &code = *code_ptr;
code += "def " + struct_def.name + "End";
code += "(builder): ";
code += "return builder.EndObject()\n";
}
// Generate the receiver for function signatures.
static void GenReceiver(const StructDef &struct_def, std::string *code_ptr) {
std::string &code = *code_ptr;
code += Indent + "# " + struct_def.name + "\n";
code += Indent + "def ";
}
// Generate a struct field, conditioned on its child type(s).
static void GenStructAccessor(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
GenComment(field.doc_comment, code_ptr, nullptr, "# ");
if (IsScalar(field.value.type.base_type)) {
if (struct_def.fixed) {
GetScalarFieldOfStruct(struct_def, field, code_ptr);
} else {
GetScalarFieldOfTable(struct_def, field, code_ptr);
}
} else {
switch (field.value.type.base_type) {
case BASE_TYPE_STRUCT:
if (struct_def.fixed) {
GetStructFieldOfStruct(struct_def, field, code_ptr);
} else {
GetStructFieldOfTable(struct_def, field, code_ptr);
}
break;
case BASE_TYPE_STRING:
GetStringField(struct_def, field, code_ptr);
break;
case BASE_TYPE_VECTOR: {
auto vectortype = field.value.type.VectorType();
if (vectortype.base_type == BASE_TYPE_STRUCT) {
GetMemberOfVectorOfStruct(struct_def, field, code_ptr);
} else {
GetMemberOfVectorOfNonStruct(struct_def, field, code_ptr);
GetVectorOfNonStructAsNumpy(struct_def, field, code_ptr);
}
break;
}
case BASE_TYPE_UNION:
GetUnionField(struct_def, field, code_ptr);
break;
default:
assert(0);
}
}
if (field.value.type.base_type == BASE_TYPE_VECTOR) {
GetVectorLen(struct_def, field, code_ptr);
}
}
// Generate table constructors, conditioned on its members' types.
static void GenTableBuilders(const StructDef &struct_def,
std::string *code_ptr) {
GetStartOfTable(struct_def, code_ptr);
for (auto it = struct_def.fields.vec.begin();
it != struct_def.fields.vec.end();
++it) {
auto &field = **it;
if (field.deprecated) continue;
auto offset = it - struct_def.fields.vec.begin();
BuildFieldOfTable(struct_def, field, offset, code_ptr);
if (field.value.type.base_type == BASE_TYPE_VECTOR) {
BuildVectorOfTable(struct_def, field, code_ptr);
}
}
GetEndOffsetOnTable(struct_def, code_ptr);
}
// Generate struct or table methods.
static void GenStruct(const StructDef &struct_def,
std::string *code_ptr) {
if (struct_def.generated) return;
GenComment(struct_def.doc_comment, code_ptr, nullptr, "# ");
BeginClass(struct_def, code_ptr);
if (!struct_def.fixed) {
// Generate a special accessor for the table that has been declared as
// the root type.
NewRootTypeFromBuffer(struct_def, code_ptr);
}
// Generate the Init method that sets the field in a pre-existing
// accessor object. This is to allow object reuse.
InitializeExisting(struct_def, code_ptr);
for (auto it = struct_def.fields.vec.begin();
it != struct_def.fields.vec.end();
++it) {
auto &field = **it;
if (field.deprecated) continue;
GenStructAccessor(struct_def, field, code_ptr);
}
if (struct_def.fixed) {
// create a struct constructor function
GenStructBuilder(struct_def, code_ptr);
} else {
// Create a set of functions that allow table construction.
GenTableBuilders(struct_def, code_ptr);
}
}
// Generate enum declarations.
static void GenEnum(const EnumDef &enum_def, std::string *code_ptr) {
if (enum_def.generated) return;
GenComment(enum_def.doc_comment, code_ptr, nullptr, "# ");
BeginEnum(enum_def.name, code_ptr);
for (auto it = enum_def.vals.vec.begin();
it != enum_def.vals.vec.end();
++it) {
auto &ev = **it;
GenComment(ev.doc_comment, code_ptr, nullptr, "# ");
EnumMember(ev, code_ptr);
}
EndEnum(code_ptr);
}
// Returns the function name that is able to read a value of the given type.
static std::string GenGetter(const Type &type) {
switch (type.base_type) {
case BASE_TYPE_STRING: return "self._tab.String(";
case BASE_TYPE_UNION: return "self._tab.Union(";
case BASE_TYPE_VECTOR: return GenGetter(type.VectorType());
default:
return "self._tab.Get(flatbuffers.number_types." + \
MakeCamel(GenTypeGet(type)) + \
"Flags, ";
}
}
// Returns the method name for use with add/put calls.
static std::string GenMethod(const FieldDef &field) {
return IsScalar(field.value.type.base_type)
? MakeCamel(GenTypeBasic(field.value.type))
: (IsStruct(field.value.type) ? "Struct" : "UOffsetTRelative");
}
static std::string GenTypeBasic(const Type &type) {
static const char *ctypename[] = {
#define FLATBUFFERS_TD(ENUM, IDLTYPE, \
CTYPE, JTYPE, GTYPE, NTYPE, PTYPE) \
#PTYPE,
FLATBUFFERS_GEN_TYPES(FLATBUFFERS_TD)
#undef FLATBUFFERS_TD
};
return ctypename[type.base_type];
}
static std::string GenTypePointer(const Type &type) {
switch (type.base_type) {
case BASE_TYPE_STRING:
return "string";
case BASE_TYPE_VECTOR:
return GenTypeGet(type.VectorType());
case BASE_TYPE_STRUCT:
return type.struct_def->name;
case BASE_TYPE_UNION:
// fall through
default:
return "*flatbuffers.Table";
}
}
static std::string GenTypeGet(const Type &type) {
return IsScalar(type.base_type)
? GenTypeBasic(type)
: GenTypePointer(type);
}
static std::string TypeName(const FieldDef &field) {
return GenTypeGet(field.value.type);
}
// Create a struct with a builder and the struct's arguments.
static void GenStructBuilder(const StructDef &struct_def,
std::string *code_ptr) {
BeginBuilderArgs(struct_def, code_ptr);
StructBuilderArgs(struct_def, "", code_ptr);
EndBuilderArgs(code_ptr);
StructBuilderBody(struct_def, "", code_ptr);
EndBuilderBody(code_ptr);
}
class PythonGenerator : public BaseGenerator {
public:
PythonGenerator(const Parser &parser, const std::string &path,
const std::string &file_name)
: BaseGenerator(parser, path, file_name, "" /* not used */,
"" /* not used */){};
bool generate() {
if (!generateEnums()) return false;
if (!generateStructs()) return false;
return true;
}
private:
bool generateEnums() {
for (auto it = parser_.enums_.vec.begin(); it != parser_.enums_.vec.end();
++it) {
auto &enum_def = **it;
std::string enumcode;
GenEnum(enum_def, &enumcode);
if (!SaveType(enum_def, enumcode, false)) return false;
}
return true;
}
bool generateStructs() {
for (auto it = parser_.structs_.vec.begin();
it != parser_.structs_.vec.end(); ++it) {
auto &struct_def = **it;
std::string declcode;
GenStruct(struct_def, &declcode);
if (!SaveType(struct_def, declcode, true)) return false;
}
return true;
}
// Begin by declaring namespace and imports.
void BeginFile(const std::string name_space_name, const bool needs_imports,
std::string *code_ptr) {
std::string &code = *code_ptr;
code = code + "# " + FlatBuffersGeneratedWarning() + "\n\n";
code += "# namespace: " + name_space_name + "\n\n";
if (needs_imports) {
code += "import flatbuffers\n\n";
}
}
// Save out the generated code for a Python Table type.
bool SaveType(const Definition &def, const std::string &classcode,
bool needs_imports) {
if (!classcode.length()) return true;
std::string namespace_dir = path_;
auto &namespaces = def.defined_namespace->components;
for (auto it = namespaces.begin(); it != namespaces.end(); ++it) {
if (it != namespaces.begin()) namespace_dir += kPathSeparator;
namespace_dir += *it;
std::string init_py_filename = namespace_dir + "/__init__.py";
SaveFile(init_py_filename.c_str(), "", false);
}
std::string code = "";
BeginFile(LastNamespacePart(*def.defined_namespace), needs_imports, &code);
code += classcode;
std::string filename = NamespaceDir(*def.defined_namespace) +
def.name + ".py";
return SaveFile(filename.c_str(), code, false);
}
};
} // namespace python
bool GeneratePython(const Parser &parser, const std::string &path,
const std::string &file_name) {
python::PythonGenerator generator(parser, path, file_name);
return generator.generate();
}
} // namespace flatbuffers