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# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc.
# http://code.google.com/p/protobuf/
#
# 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.
"""Class for encoding protocol message primitives.
Contains the logic for encoding every logical protocol field type
into one of the 5 physical wire types.
"""
__author__ = 'robinson@google.com (Will Robinson)'
import struct
from google.protobuf import message
from google.protobuf.internal import wire_format
from google.protobuf.internal import output_stream
# Note that much of this code is ported from //net/proto/ProtocolBuffer, and
# that the interface is strongly inspired by WireFormat from the C++ proto2
# implementation.
class Encoder(object):
"""Encodes logical protocol buffer fields to the wire format."""
def __init__(self):
self._stream = output_stream.OutputStream()
def ToString(self):
"""Returns all values encoded in this object as a string."""
return self._stream.ToString()
# All the Append*() methods below first append a tag+type pair to the buffer
# before appending the specified value.
def AppendInt32(self, field_number, value):
"""Appends a 32-bit integer to our buffer, varint-encoded."""
self._AppendTag(field_number, wire_format.WIRETYPE_VARINT)
self._stream.AppendVarint32(value)
def AppendInt64(self, field_number, value):
"""Appends a 64-bit integer to our buffer, varint-encoded."""
self._AppendTag(field_number, wire_format.WIRETYPE_VARINT)
self._stream.AppendVarint64(value)
def AppendUInt32(self, field_number, unsigned_value):
"""Appends an unsigned 32-bit integer to our buffer, varint-encoded."""
self._AppendTag(field_number, wire_format.WIRETYPE_VARINT)
self._stream.AppendVarUInt32(unsigned_value)
def AppendUInt64(self, field_number, unsigned_value):
"""Appends an unsigned 64-bit integer to our buffer, varint-encoded."""
self._AppendTag(field_number, wire_format.WIRETYPE_VARINT)
self._stream.AppendVarUInt64(unsigned_value)
def AppendSInt32(self, field_number, value):
"""Appends a 32-bit integer to our buffer, zigzag-encoded and then
varint-encoded.
"""
self._AppendTag(field_number, wire_format.WIRETYPE_VARINT)
zigzag_value = wire_format.ZigZagEncode(value)
self._stream.AppendVarUInt32(zigzag_value)
def AppendSInt64(self, field_number, value):
"""Appends a 64-bit integer to our buffer, zigzag-encoded and then
varint-encoded.
"""
self._AppendTag(field_number, wire_format.WIRETYPE_VARINT)
zigzag_value = wire_format.ZigZagEncode(value)
self._stream.AppendVarUInt64(zigzag_value)
def AppendFixed32(self, field_number, unsigned_value):
"""Appends an unsigned 32-bit integer to our buffer, in little-endian
byte-order.
"""
self._AppendTag(field_number, wire_format.WIRETYPE_FIXED32)
self._stream.AppendLittleEndian32(unsigned_value)
def AppendFixed64(self, field_number, unsigned_value):
"""Appends an unsigned 64-bit integer to our buffer, in little-endian
byte-order.
"""
self._AppendTag(field_number, wire_format.WIRETYPE_FIXED64)
self._stream.AppendLittleEndian64(unsigned_value)
def AppendSFixed32(self, field_number, value):
"""Appends a signed 32-bit integer to our buffer, in little-endian
byte-order.
"""
sign = (value & 0x80000000) and -1 or 0
if value >> 32 != sign:
raise message.EncodeError('SFixed32 out of range: %d' % value)
self._AppendTag(field_number, wire_format.WIRETYPE_FIXED32)
self._stream.AppendLittleEndian32(value & 0xffffffff)
def AppendSFixed64(self, field_number, value):
"""Appends a signed 64-bit integer to our buffer, in little-endian
byte-order.
"""
sign = (value & 0x8000000000000000) and -1 or 0
if value >> 64 != sign:
raise message.EncodeError('SFixed64 out of range: %d' % value)
self._AppendTag(field_number, wire_format.WIRETYPE_FIXED64)
self._stream.AppendLittleEndian64(value & 0xffffffffffffffff)
def AppendFloat(self, field_number, value):
"""Appends a floating-point number to our buffer."""
self._AppendTag(field_number, wire_format.WIRETYPE_FIXED32)
self._stream.AppendRawBytes(struct.pack('f', value))
def AppendDouble(self, field_number, value):
"""Appends a double-precision floating-point number to our buffer."""
self._AppendTag(field_number, wire_format.WIRETYPE_FIXED64)
self._stream.AppendRawBytes(struct.pack('d', value))
def AppendBool(self, field_number, value):
"""Appends a boolean to our buffer."""
self.AppendInt32(field_number, value)
def AppendEnum(self, field_number, value):
"""Appends an enum value to our buffer."""
self.AppendInt32(field_number, value)
def AppendString(self, field_number, value):
"""Appends a length-prefixed string to our buffer, with the
length varint-encoded.
"""
self._AppendTag(field_number, wire_format.WIRETYPE_LENGTH_DELIMITED)
self._stream.AppendVarUInt32(len(value))
self._stream.AppendRawBytes(value)
def AppendBytes(self, field_number, value):
"""Appends a length-prefixed sequence of bytes to our buffer, with the
length varint-encoded.
"""
self.AppendString(field_number, value)
# TODO(robinson): For AppendGroup() and AppendMessage(), we'd really like to
# avoid the extra string copy here. We can do so if we widen the Message
# interface to be able to serialize to a stream in addition to a string. The
# challenge when thinking ahead to the Python/C API implementation of Message
# is finding a stream-like Python thing to which we can write raw bytes
# from C. I'm not sure such a thing exists(?). (array.array is pretty much
# what we want, but it's not directly exposed in the Python/C API).
def AppendGroup(self, field_number, group):
"""Appends a group to our buffer.
"""
self._AppendTag(field_number, wire_format.WIRETYPE_START_GROUP)
self._stream.AppendRawBytes(group.SerializeToString())
self._AppendTag(field_number, wire_format.WIRETYPE_END_GROUP)
def AppendMessage(self, field_number, msg):
"""Appends a nested message to our buffer.
"""
self._AppendTag(field_number, wire_format.WIRETYPE_LENGTH_DELIMITED)
self._stream.AppendVarUInt32(msg.ByteSize())
self._stream.AppendRawBytes(msg.SerializeToString())
def AppendMessageSetItem(self, field_number, msg):
"""Appends an item using the message set wire format.
The message set message looks like this:
message MessageSet {
repeated group Item = 1 {
required int32 type_id = 2;
required string message = 3;
}
}
"""
self._AppendTag(1, wire_format.WIRETYPE_START_GROUP)
self.AppendInt32(2, field_number)
self.AppendMessage(3, msg)
self._AppendTag(1, wire_format.WIRETYPE_END_GROUP)
def _AppendTag(self, field_number, wire_type):
"""Appends a tag containing field number and wire type information."""
self._stream.AppendVarUInt32(wire_format.PackTag(field_number, wire_type))
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