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

* 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
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 127 additions and 0 deletions
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72
src/idl_gen_python.cpp
View File

@ -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);
}
}

26
tests/MyGame/Example/Monster.py
View File

@ -205,6 +205,14 @@ class Monster(object):
return self._tab.GetVectorAsNumpy(flatbuffers.number_types.Uint8Flags, o)
return 0
# Monster
def TestnestedflatbufferNestedRoot(self):
o = flatbuffers.number_types.UOffsetTFlags.py_type(self._tab.Offset(30))
if o != 0:
from MyGame.Example.Monster import Monster
return Monster.GetRootAsMonster(self._tab.Bytes, self._tab.Vector(o))
return 0
# Monster
def TestnestedflatbufferLength(self):
o = flatbuffers.number_types.UOffsetTFlags.py_type(self._tab.Offset(30))
@ -734,6 +742,14 @@ class Monster(object):
return self._tab.GetVectorAsNumpy(flatbuffers.number_types.Uint8Flags, o)
return 0
# Monster
def TestrequirednestedflatbufferNestedRoot(self):
o = flatbuffers.number_types.UOffsetTFlags.py_type(self._tab.Offset(102))
if o != 0:
from MyGame.Example.Monster import Monster
return Monster.GetRootAsMonster(self._tab.Bytes, self._tab.Vector(o))
return 0
# Monster
def TestrequirednestedflatbufferLength(self):
o = flatbuffers.number_types.UOffsetTFlags.py_type(self._tab.Offset(102))
@ -765,6 +781,11 @@ def MonsterStartTestarrayoftablesVector(builder, numElems): return builder.Start
def MonsterAddEnemy(builder, enemy): builder.PrependUOffsetTRelativeSlot(12, flatbuffers.number_types.UOffsetTFlags.py_type(enemy), 0)
def MonsterAddTestnestedflatbuffer(builder, testnestedflatbuffer): builder.PrependUOffsetTRelativeSlot(13, flatbuffers.number_types.UOffsetTFlags.py_type(testnestedflatbuffer), 0)
def MonsterStartTestnestedflatbufferVector(builder, numElems): return builder.StartVector(1, numElems, 1)
def MonsterMakeTestnestedflatbufferVectorFromBytes(builder, bytes):
builder.StartVector(1, len(bytes), 1)
builder.head = builder.head - len(bytes)
builder.Bytes[builder.head : builder.head + len(bytes)] = bytes
return builder.EndVector(len(bytes))
def MonsterAddTestempty(builder, testempty): builder.PrependUOffsetTRelativeSlot(14, flatbuffers.number_types.UOffsetTFlags.py_type(testempty), 0)
def MonsterAddTestbool(builder, testbool): builder.PrependBoolSlot(15, testbool, 0)
def MonsterAddTesthashs32Fnv1(builder, testhashs32Fnv1): builder.PrependInt32Slot(16, testhashs32Fnv1, 0)
@ -815,6 +836,11 @@ def MonsterStartVectorOfEnumsVector(builder, numElems): return builder.StartVect
def MonsterAddSignedEnum(builder, signedEnum): builder.PrependInt8Slot(48, signedEnum, -1)
def MonsterAddTestrequirednestedflatbuffer(builder, testrequirednestedflatbuffer): builder.PrependUOffsetTRelativeSlot(49, flatbuffers.number_types.UOffsetTFlags.py_type(testrequirednestedflatbuffer), 0)
def MonsterStartTestrequirednestedflatbufferVector(builder, numElems): return builder.StartVector(1, numElems, 1)
def MonsterMakeTestrequirednestedflatbufferVectorFromBytes(builder, bytes):
builder.StartVector(1, len(bytes), 1)
builder.head = builder.head - len(bytes)
builder.Bytes[builder.head : builder.head + len(bytes)] = bytes
return builder.EndVector(len(bytes))
def MonsterEnd(builder): return builder.EndObject()
import MyGame.Example.Ability

29
tests/py_test.py
View File

@ -1874,6 +1874,35 @@ class TestAllCodePathsOfExampleSchema(unittest.TestCase):
lambda: mon2.TestnestedflatbufferAsNumpy(),
NumpyRequiredForThisFeature)
def test_nested_monster_testnestedflatbuffer(self):
b = flatbuffers.Builder(0)
# build another monster to nest inside testnestedflatbuffer
nestedB = flatbuffers.Builder(0)
nameStr = nestedB.CreateString("Nested Monster")
MyGame.Example.Monster.MonsterStart(nestedB)
MyGame.Example.Monster.MonsterAddHp(nestedB, 30)
MyGame.Example.Monster.MonsterAddName(nestedB, nameStr)
nestedMon = MyGame.Example.Monster.MonsterEnd(nestedB)
nestedB.Finish(nestedMon)
# write the nested FB bytes
sub_buf = MyGame.Example.Monster.MonsterMakeTestnestedflatbufferVectorFromBytes(
b, nestedB.Output())
# make the parent monster and include the bytes of the nested monster
MyGame.Example.Monster.MonsterStart(b)
MyGame.Example.Monster.MonsterAddTestnestedflatbuffer(b, sub_buf)
mon = MyGame.Example.Monster.MonsterEnd(b)
b.Finish(mon)
# inspect the resulting data:
mon2 = MyGame.Example.Monster.Monster.GetRootAsMonster(b.Bytes,
b.Head())
nestedMon2 = mon2.TestnestedflatbufferNestedRoot()
self.assertEqual(b"Nested Monster", nestedMon2.Name())
self.assertEqual(30, nestedMon2.Hp())
def test_nondefault_monster_testempty(self):
b = flatbuffers.Builder(0)