269 lines
8.2 KiB
Python
269 lines
8.2 KiB
Python
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# Protocol Buffers - Google's data interchange format
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# Copyright 2008 Google Inc. All rights reserved.
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# https://developers.google.com/protocol-buffers/
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are
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# met:
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#
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# * Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following disclaimer
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# in the documentation and/or other materials provided with the
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# distribution.
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# * Neither the name of Google Inc. nor the names of its
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# contributors may be used to endorse or promote products derived from
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# this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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"""Constants and static functions to support protocol buffer wire format."""
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__author__ = 'robinson@google.com (Will Robinson)'
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import struct
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from google.protobuf import descriptor
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from google.protobuf import message
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TAG_TYPE_BITS = 3 # Number of bits used to hold type info in a proto tag.
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TAG_TYPE_MASK = (1 << TAG_TYPE_BITS) - 1 # 0x7
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# These numbers identify the wire type of a protocol buffer value.
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# We use the least-significant TAG_TYPE_BITS bits of the varint-encoded
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# tag-and-type to store one of these WIRETYPE_* constants.
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# These values must match WireType enum in google/protobuf/wire_format.h.
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WIRETYPE_VARINT = 0
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WIRETYPE_FIXED64 = 1
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WIRETYPE_LENGTH_DELIMITED = 2
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WIRETYPE_START_GROUP = 3
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WIRETYPE_END_GROUP = 4
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WIRETYPE_FIXED32 = 5
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_WIRETYPE_MAX = 5
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# Bounds for various integer types.
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INT32_MAX = int((1 << 31) - 1)
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INT32_MIN = int(-(1 << 31))
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UINT32_MAX = (1 << 32) - 1
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INT64_MAX = (1 << 63) - 1
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INT64_MIN = -(1 << 63)
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UINT64_MAX = (1 << 64) - 1
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# "struct" format strings that will encode/decode the specified formats.
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FORMAT_UINT32_LITTLE_ENDIAN = '<I'
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FORMAT_UINT64_LITTLE_ENDIAN = '<Q'
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FORMAT_FLOAT_LITTLE_ENDIAN = '<f'
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FORMAT_DOUBLE_LITTLE_ENDIAN = '<d'
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# We'll have to provide alternate implementations of AppendLittleEndian*() on
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# any architectures where these checks fail.
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if struct.calcsize(FORMAT_UINT32_LITTLE_ENDIAN) != 4:
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raise AssertionError('Format "I" is not a 32-bit number.')
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if struct.calcsize(FORMAT_UINT64_LITTLE_ENDIAN) != 8:
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raise AssertionError('Format "Q" is not a 64-bit number.')
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def PackTag(field_number, wire_type):
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"""Returns an unsigned 32-bit integer that encodes the field number and
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wire type information in standard protocol message wire format.
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Args:
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field_number: Expected to be an integer in the range [1, 1 << 29)
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wire_type: One of the WIRETYPE_* constants.
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"""
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if not 0 <= wire_type <= _WIRETYPE_MAX:
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raise message.EncodeError('Unknown wire type: %d' % wire_type)
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return (field_number << TAG_TYPE_BITS) | wire_type
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def UnpackTag(tag):
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"""The inverse of PackTag(). Given an unsigned 32-bit number,
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returns a (field_number, wire_type) tuple.
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"""
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return (tag >> TAG_TYPE_BITS), (tag & TAG_TYPE_MASK)
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def ZigZagEncode(value):
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"""ZigZag Transform: Encodes signed integers so that they can be
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effectively used with varint encoding. See wire_format.h for
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more details.
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"""
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if value >= 0:
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return value << 1
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return (value << 1) ^ (~0)
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def ZigZagDecode(value):
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"""Inverse of ZigZagEncode()."""
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if not value & 0x1:
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return value >> 1
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return (value >> 1) ^ (~0)
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# The *ByteSize() functions below return the number of bytes required to
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# serialize "field number + type" information and then serialize the value.
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def Int32ByteSize(field_number, int32):
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return Int64ByteSize(field_number, int32)
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def Int32ByteSizeNoTag(int32):
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return _VarUInt64ByteSizeNoTag(0xffffffffffffffff & int32)
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def Int64ByteSize(field_number, int64):
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# Have to convert to uint before calling UInt64ByteSize().
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return UInt64ByteSize(field_number, 0xffffffffffffffff & int64)
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def UInt32ByteSize(field_number, uint32):
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return UInt64ByteSize(field_number, uint32)
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def UInt64ByteSize(field_number, uint64):
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return TagByteSize(field_number) + _VarUInt64ByteSizeNoTag(uint64)
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def SInt32ByteSize(field_number, int32):
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return UInt32ByteSize(field_number, ZigZagEncode(int32))
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def SInt64ByteSize(field_number, int64):
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return UInt64ByteSize(field_number, ZigZagEncode(int64))
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def Fixed32ByteSize(field_number, fixed32):
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return TagByteSize(field_number) + 4
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def Fixed64ByteSize(field_number, fixed64):
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return TagByteSize(field_number) + 8
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def SFixed32ByteSize(field_number, sfixed32):
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return TagByteSize(field_number) + 4
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def SFixed64ByteSize(field_number, sfixed64):
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return TagByteSize(field_number) + 8
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def FloatByteSize(field_number, flt):
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return TagByteSize(field_number) + 4
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def DoubleByteSize(field_number, double):
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return TagByteSize(field_number) + 8
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def BoolByteSize(field_number, b):
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return TagByteSize(field_number) + 1
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def EnumByteSize(field_number, enum):
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return UInt32ByteSize(field_number, enum)
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def StringByteSize(field_number, string):
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return BytesByteSize(field_number, string.encode('utf-8'))
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def BytesByteSize(field_number, b):
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return (TagByteSize(field_number)
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+ _VarUInt64ByteSizeNoTag(len(b))
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+ len(b))
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def GroupByteSize(field_number, message):
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return (2 * TagByteSize(field_number) # START and END group.
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+ message.ByteSize())
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def MessageByteSize(field_number, message):
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return (TagByteSize(field_number)
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+ _VarUInt64ByteSizeNoTag(message.ByteSize())
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+ message.ByteSize())
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def MessageSetItemByteSize(field_number, msg):
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# First compute the sizes of the tags.
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# There are 2 tags for the beginning and ending of the repeated group, that
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# is field number 1, one with field number 2 (type_id) and one with field
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# number 3 (message).
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total_size = (2 * TagByteSize(1) + TagByteSize(2) + TagByteSize(3))
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# Add the number of bytes for type_id.
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total_size += _VarUInt64ByteSizeNoTag(field_number)
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message_size = msg.ByteSize()
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# The number of bytes for encoding the length of the message.
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total_size += _VarUInt64ByteSizeNoTag(message_size)
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# The size of the message.
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total_size += message_size
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return total_size
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def TagByteSize(field_number):
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"""Returns the bytes required to serialize a tag with this field number."""
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# Just pass in type 0, since the type won't affect the tag+type size.
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return _VarUInt64ByteSizeNoTag(PackTag(field_number, 0))
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# Private helper function for the *ByteSize() functions above.
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def _VarUInt64ByteSizeNoTag(uint64):
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"""Returns the number of bytes required to serialize a single varint
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using boundary value comparisons. (unrolled loop optimization -WPierce)
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uint64 must be unsigned.
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"""
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if uint64 <= 0x7f: return 1
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if uint64 <= 0x3fff: return 2
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if uint64 <= 0x1fffff: return 3
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if uint64 <= 0xfffffff: return 4
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if uint64 <= 0x7ffffffff: return 5
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if uint64 <= 0x3ffffffffff: return 6
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if uint64 <= 0x1ffffffffffff: return 7
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if uint64 <= 0xffffffffffffff: return 8
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if uint64 <= 0x7fffffffffffffff: return 9
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if uint64 > UINT64_MAX:
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raise message.EncodeError('Value out of range: %d' % uint64)
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return 10
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NON_PACKABLE_TYPES = (
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descriptor.FieldDescriptor.TYPE_STRING,
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descriptor.FieldDescriptor.TYPE_GROUP,
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descriptor.FieldDescriptor.TYPE_MESSAGE,
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descriptor.FieldDescriptor.TYPE_BYTES
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)
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def IsTypePackable(field_type):
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"""Return true iff packable = true is valid for fields of this type.
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Args:
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field_type: a FieldDescriptor::Type value.
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Returns:
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True iff fields of this type are packable.
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"""
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return field_type not in NON_PACKABLE_TYPES
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