mirror of
https://github.com/protocolbuffers/protobuf
synced 2026-08-26 02:23:14 -04:00
194 lines
6.9 KiB
Python
Executable file
194 lines
6.9 KiB
Python
Executable file
# 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 decoding protocol buffer primitives.
|
|
|
|
Contains the logic for decoding every logical protocol field type
|
|
from 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 input_stream
|
|
from google.protobuf.internal import wire_format
|
|
|
|
|
|
|
|
# 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 Decoder(object):
|
|
|
|
"""Decodes logical protocol buffer fields from the wire."""
|
|
|
|
def __init__(self, s):
|
|
"""Initializes the decoder to read from s.
|
|
|
|
Args:
|
|
s: An immutable sequence of bytes, which must be accessible
|
|
via the Python buffer() primitive (i.e., buffer(s)).
|
|
"""
|
|
self._stream = input_stream.InputStream(s)
|
|
|
|
def EndOfStream(self):
|
|
"""Returns true iff we've reached the end of the bytes we're reading."""
|
|
return self._stream.EndOfStream()
|
|
|
|
def Position(self):
|
|
"""Returns the 0-indexed position in |s|."""
|
|
return self._stream.Position()
|
|
|
|
def ReadFieldNumberAndWireType(self):
|
|
"""Reads a tag from the wire. Returns a (field_number, wire_type) pair."""
|
|
tag_and_type = self.ReadUInt32()
|
|
return wire_format.UnpackTag(tag_and_type)
|
|
|
|
def SkipBytes(self, bytes):
|
|
"""Skips the specified number of bytes on the wire."""
|
|
self._stream.SkipBytes(bytes)
|
|
|
|
# Note that the Read*() methods below are not exactly symmetrical with the
|
|
# corresponding Encoder.Append*() methods. Those Encoder methods first
|
|
# encode a tag, but the Read*() methods below assume that the tag has already
|
|
# been read, and that the client wishes to read a field of the specified type
|
|
# starting at the current position.
|
|
|
|
def ReadInt32(self):
|
|
"""Reads and returns a signed, varint-encoded, 32-bit integer."""
|
|
return self._stream.ReadVarint32()
|
|
|
|
def ReadInt64(self):
|
|
"""Reads and returns a signed, varint-encoded, 64-bit integer."""
|
|
return self._stream.ReadVarint64()
|
|
|
|
def ReadUInt32(self):
|
|
"""Reads and returns an signed, varint-encoded, 32-bit integer."""
|
|
return self._stream.ReadVarUInt32()
|
|
|
|
def ReadUInt64(self):
|
|
"""Reads and returns an signed, varint-encoded,64-bit integer."""
|
|
return self._stream.ReadVarUInt64()
|
|
|
|
def ReadSInt32(self):
|
|
"""Reads and returns a signed, zigzag-encoded, varint-encoded,
|
|
32-bit integer."""
|
|
return wire_format.ZigZagDecode(self._stream.ReadVarUInt32())
|
|
|
|
def ReadSInt64(self):
|
|
"""Reads and returns a signed, zigzag-encoded, varint-encoded,
|
|
64-bit integer."""
|
|
return wire_format.ZigZagDecode(self._stream.ReadVarUInt64())
|
|
|
|
def ReadFixed32(self):
|
|
"""Reads and returns an unsigned, fixed-width, 32-bit integer."""
|
|
return self._stream.ReadLittleEndian32()
|
|
|
|
def ReadFixed64(self):
|
|
"""Reads and returns an unsigned, fixed-width, 64-bit integer."""
|
|
return self._stream.ReadLittleEndian64()
|
|
|
|
def ReadSFixed32(self):
|
|
"""Reads and returns a signed, fixed-width, 32-bit integer."""
|
|
value = self._stream.ReadLittleEndian32()
|
|
if value >= (1 << 31):
|
|
value -= (1 << 32)
|
|
return value
|
|
|
|
def ReadSFixed64(self):
|
|
"""Reads and returns a signed, fixed-width, 64-bit integer."""
|
|
value = self._stream.ReadLittleEndian64()
|
|
if value >= (1 << 63):
|
|
value -= (1 << 64)
|
|
return value
|
|
|
|
def ReadFloat(self):
|
|
"""Reads and returns a 4-byte floating-point number."""
|
|
serialized = self._stream.ReadString(4)
|
|
return struct.unpack('f', serialized)[0]
|
|
|
|
def ReadDouble(self):
|
|
"""Reads and returns an 8-byte floating-point number."""
|
|
serialized = self._stream.ReadString(8)
|
|
return struct.unpack('d', serialized)[0]
|
|
|
|
def ReadBool(self):
|
|
"""Reads and returns a bool."""
|
|
i = self._stream.ReadVarUInt32()
|
|
return bool(i)
|
|
|
|
def ReadEnum(self):
|
|
"""Reads and returns an enum value."""
|
|
return self._stream.ReadVarUInt32()
|
|
|
|
def ReadString(self):
|
|
"""Reads and returns a length-delimited string."""
|
|
length = self._stream.ReadVarUInt32()
|
|
return self._stream.ReadString(length)
|
|
|
|
def ReadBytes(self):
|
|
"""Reads and returns a length-delimited byte sequence."""
|
|
return self.ReadString()
|
|
|
|
def ReadMessageInto(self, msg):
|
|
"""Calls msg.MergeFromString() to merge
|
|
length-delimited serialized message data into |msg|.
|
|
|
|
REQUIRES: The decoder must be positioned at the serialized "length"
|
|
prefix to a length-delmiited serialized message.
|
|
|
|
POSTCONDITION: The decoder is positioned just after the
|
|
serialized message, and we have merged those serialized
|
|
contents into |msg|.
|
|
"""
|
|
length = self._stream.ReadVarUInt32()
|
|
sub_buffer = self._stream.GetSubBuffer(length)
|
|
num_bytes_used = msg.MergeFromString(sub_buffer)
|
|
if num_bytes_used != length:
|
|
raise message.DecodeError(
|
|
'Submessage told to deserialize from %d-byte encoding, '
|
|
'but used only %d bytes' % (length, num_bytes_used))
|
|
self._stream.SkipBytes(num_bytes_used)
|
|
|
|
def ReadGroupInto(self, expected_field_number, group):
|
|
"""Calls group.MergeFromString() to merge
|
|
END_GROUP-delimited serialized message data into |group|.
|
|
We'll raise an exception if we don't find an END_GROUP
|
|
tag immediately after the serialized message contents.
|
|
|
|
REQUIRES: The decoder is positioned just after the START_GROUP
|
|
tag for this group.
|
|
|
|
POSTCONDITION: The decoder is positioned just after the
|
|
END_GROUP tag for this group, and we have merged
|
|
the contents of the group into |group|.
|
|
"""
|
|
sub_buffer = self._stream.GetSubBuffer() # No a priori length limit.
|
|
num_bytes_used = group.MergeFromString(sub_buffer)
|
|
if num_bytes_used < 0:
|
|
raise message.DecodeError('Group message reported negative bytes read.')
|
|
self._stream.SkipBytes(num_bytes_used)
|
|
field_number, field_type = self.ReadFieldNumberAndWireType()
|
|
if field_type != wire_format.WIRETYPE_END_GROUP:
|
|
raise message.DecodeError('Group message did not end with an END_GROUP.')
|
|
if field_number != expected_field_number:
|
|
raise message.DecodeError('END_GROUP tag had field '
|
|
'number %d, was expecting field number %d' % (
|
|
field_number, expected_field_number))
|
|
# We're now positioned just after the END_GROUP tag. Perfect.
|