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Generate code to encode and decode nested flatbuffers in Python. (#6354)

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* Generate code to encode and decode nested flatbuffers in Python.

* Delete accidental trailing whitespace.

* Fully delete trailing whitespace.
This commit is contained in:
Richard A Hofer
2021-01-04 15:18:19 -05:00
committed by GitHub
parent 57f68e2896
commit 24dd85fd28
3 changed files with 127 additions and 0 deletions
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72
src/idl_gen_python.cpp
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@@ -408,6 +408,39 @@ class PythonGenerator : public BaseGenerator {
code += "\n";
}
// Returns a nested flatbuffer as itself.
void GetVectorAsNestedFlatbuffer(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
auto nested = field.attributes.Lookup("nested_flatbuffer");
if (!nested) { return; } // There is no nested flatbuffer.
std::string unqualified_name = nested->constant;
std::string qualified_name = nested->constant;
auto nested_root = parser_.LookupStruct(nested->constant);
if (nested_root == nullptr) {
qualified_name = parser_.current_namespace_->GetFullyQualifiedName(
nested->constant);
nested_root = parser_.LookupStruct(qualified_name);
}
FLATBUFFERS_ASSERT(nested_root); // Guaranteed to exist by parser.
(void)nested_root;
auto &code = *code_ptr;
GenReceiver(struct_def, code_ptr);
code += MakeCamel(NormalizedName(field)) + "NestedRoot(self):";
code += OffsetPrefix(field);
code += Indent + Indent + Indent;
code += "from " + qualified_name + " import " + unqualified_name + "\n";
code += Indent + Indent + Indent + "return " + unqualified_name;
code += ".GetRootAs" + unqualified_name;
code += "(self._tab.Bytes, self._tab.Vector(o))\n";
code += Indent + Indent + "return 0\n";
code += "\n";
}
// Begin the creator function signature.
void BeginBuilderArgs(const StructDef &struct_def, std::string *code_ptr) {
auto &code = *code_ptr;
@@ -561,6 +594,43 @@ class PythonGenerator : public BaseGenerator {
code += ")\n";
}
// Set the value of one of the members of a table's vector and fills in the
// elements from a bytearray. This is for simplifying the use of nested
// flatbuffers.
void BuildVectorOfTableFromBytes(const StructDef &struct_def,
const FieldDef &field,
std::string *code_ptr) {
auto nested = field.attributes.Lookup("nested_flatbuffer");
if (!nested) { return; } // There is no nested flatbuffer.
std::string unqualified_name = nested->constant;
std::string qualified_name = nested->constant;
auto nested_root = parser_.LookupStruct(nested->constant);
if (nested_root == nullptr) {
qualified_name =
parser_.current_namespace_->GetFullyQualifiedName(nested->constant);
nested_root = parser_.LookupStruct(qualified_name);
}
FLATBUFFERS_ASSERT(nested_root); // Guaranteed to exist by parser.
(void)nested_root;
auto &code = *code_ptr;
code += "def " + NormalizedName(struct_def) + "Make";
code += MakeCamel(NormalizedName(field));
code += "VectorFromBytes(builder, bytes):\n";
code += Indent + "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 += ", len(bytes), " + NumToString(alignment);
code += ")\n";
code += Indent + "builder.head = builder.head - len(bytes)\n";
code += Indent + "builder.Bytes[builder.head : builder.head + len(bytes)]";
code += " = bytes\n";
code += Indent + "return builder.EndVector(len(bytes))\n";
}
// Get the offset of the end of a table.
void GetEndOffsetOnTable(const StructDef &struct_def, std::string *code_ptr) {
auto &code = *code_ptr;
@@ -607,6 +677,7 @@ class PythonGenerator : public BaseGenerator {
} else {
GetMemberOfVectorOfNonStruct(struct_def, field, code_ptr);
GetVectorOfNonStructAsNumpy(struct_def, field, code_ptr);
GetVectorAsNestedFlatbuffer(struct_def, field, code_ptr);
}
break;
}
@@ -643,6 +714,7 @@ class PythonGenerator : public BaseGenerator {
BuildFieldOfTable(struct_def, field, offset, code_ptr);
if (IsVector(field.value.type)) {
BuildVectorOfTable(struct_def, field, code_ptr);
BuildVectorOfTableFromBytes(struct_def, field, code_ptr);
}
}