/*

* 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/code_generators.h"

#include "flatbuffers/flatbuffers.h"

#include "flatbuffers/idl.h"

#include "flatbuffers/util.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[] = {

// clang-format off

#define FLATBUFFERS_TD(ENUM, IDLTYPE, \

CTYPE, JTYPE, GTYPE, NTYPE, PTYPE) \

#PTYPE,

FLATBUFFERS_GEN_TYPES(FLATBUFFERS_TD)

#undef FLATBUFFERS_TD

// clang-format on

};

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