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C++ generated code now has constants for vtable offsets.

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Besides making the generated code looking a lot more readable,
it also allows you to use these offsets in calls to
Table::CheckField, to see if a field is present in a table.

Change-Id: I1b4cc350c4f27c4e474c31add40c701ef4ae63b2
Tested: On Linux.
This commit is contained in:
Wouter van Oortmerssen
2015-11-30 14:27:47 -08:00
parent 3fc5387db7
commit 7b06041a7c
3 changed files with 203 additions and 142 deletions
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29
src/idl_gen_cpp.cpp
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@@ -242,6 +242,12 @@ std::string GenUnderlyingCast(const Parser &parser, const FieldDef &field,
: val;
}
std::string GenFieldOffsetName(const FieldDef &field) {
std::string uname = field.name;
std::transform(uname.begin(), uname.end(), uname.begin(), ::toupper);
return "VT_" + uname;
}
// Generate an accessor struct, builder structs & function for a table.
static void GenTable(const Parser &parser, StructDef &struct_def,
const GeneratorOptions &opts, std::string *code_ptr) {
@@ -254,6 +260,19 @@ static void GenTable(const Parser &parser, StructDef &struct_def,
code += "struct " + struct_def.name;
code += " FLATBUFFERS_FINAL_CLASS : private flatbuffers::Table";
code += " {\n";
// Generate field id constants.
code += " enum {\n";
for (auto it = struct_def.fields.vec.begin();
it != struct_def.fields.vec.end();
++it) {
auto &field = **it;
if (!field.deprecated) { // Deprecated fields won't be accessible.
code += " " + GenFieldOffsetName(field) + " = ";
code += NumToString(field.value.offset) + ",\n";
}
}
code += " };\n";
// Generate the accessors.
for (auto it = struct_def.fields.vec.begin();
it != struct_def.fields.vec.end();
++it) {
@@ -268,7 +287,7 @@ static void GenTable(const Parser &parser, StructDef &struct_def,
auto accessor = is_scalar
? "GetField<"
: (IsStruct(field.value.type) ? "GetStruct<" : "GetPointer<");
auto offsetstr = NumToString(field.value.offset);
auto offsetstr = GenFieldOffsetName(field);
auto call =
accessor +
GenTypeGet(parser, field.value.type, "", "const ", " *", false) +
@@ -347,8 +366,7 @@ static void GenTable(const Parser &parser, StructDef &struct_def,
code += prefix + "VerifyField";
if (field.required) code += "Required";
code += "<" + GenTypeSize(parser, field.value.type);
code += ">(verifier, " + NumToString(field.value.offset);
code += " /* " + field.name + " */)";
code += ">(verifier, " + GenFieldOffsetName(field) + ")";
switch (field.value.type.base_type) {
case BASE_TYPE_UNION:
code += prefix + "Verify" + field.value.type.enum_def->name;
@@ -412,7 +430,7 @@ static void GenTable(const Parser &parser, StructDef &struct_def,
} else {
code += "Offset";
}
code += "(" + NumToString(field.value.offset) + ", ";
code += "(" + struct_def.name + "::" + GenFieldOffsetName(field) + ", ";
code += GenUnderlyingCast(parser, field, false, field.name);
if (IsScalar(field.value.type.base_type))
code += ", " + field.value.constant;
@@ -433,7 +451,8 @@ static void GenTable(const Parser &parser, StructDef &struct_def,
++it) {
auto &field = **it;
if (!field.deprecated && field.required) {
code += " fbb_.Required(o, " + NumToString(field.value.offset);
code += " fbb_.Required(o, ";
code += struct_def.name + "::" + GenFieldOffsetName(field);
code += "); // " + field.name + "\n";
}
}