1# Protocol Buffers - Google's data interchange format 2# Copyright 2008 Google Inc. All rights reserved. 3# http://code.google.com/p/protobuf/ 4# 5# Redistribution and use in source and binary forms, with or without 6# modification, are permitted provided that the following conditions are 7# met: 8# 9# * Redistributions of source code must retain the above copyright 10# notice, this list of conditions and the following disclaimer. 11# * Redistributions in binary form must reproduce the above 12# copyright notice, this list of conditions and the following disclaimer 13# in the documentation and/or other materials provided with the 14# distribution. 15# * Neither the name of Google Inc. nor the names of its 16# contributors may be used to endorse or promote products derived from 17# this software without specific prior written permission. 18# 19# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 22# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 23# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 24# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 25# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 29# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 31"""Constants and static functions to support protocol buffer wire format.""" 32 33__author__ = 'robinson@google.com (Will Robinson)' 34 35import struct 36from google.protobuf import descriptor 37from google.protobuf import message 38 39 40TAG_TYPE_BITS = 3 # Number of bits used to hold type info in a proto tag. 41TAG_TYPE_MASK = (1 << TAG_TYPE_BITS) - 1 # 0x7 42 43# These numbers identify the wire type of a protocol buffer value. 44# We use the least-significant TAG_TYPE_BITS bits of the varint-encoded 45# tag-and-type to store one of these WIRETYPE_* constants. 46# These values must match WireType enum in google/protobuf/wire_format.h. 47WIRETYPE_VARINT = 0 48WIRETYPE_FIXED64 = 1 49WIRETYPE_LENGTH_DELIMITED = 2 50WIRETYPE_START_GROUP = 3 51WIRETYPE_END_GROUP = 4 52WIRETYPE_FIXED32 = 5 53_WIRETYPE_MAX = 5 54 55 56# Bounds for various integer types. 57INT32_MAX = int((1 << 31) - 1) 58INT32_MIN = int(-(1 << 31)) 59UINT32_MAX = (1 << 32) - 1 60 61INT64_MAX = (1 << 63) - 1 62INT64_MIN = -(1 << 63) 63UINT64_MAX = (1 << 64) - 1 64 65# "struct" format strings that will encode/decode the specified formats. 66FORMAT_UINT32_LITTLE_ENDIAN = '<I' 67FORMAT_UINT64_LITTLE_ENDIAN = '<Q' 68FORMAT_FLOAT_LITTLE_ENDIAN = '<f' 69FORMAT_DOUBLE_LITTLE_ENDIAN = '<d' 70 71 72# We'll have to provide alternate implementations of AppendLittleEndian*() on 73# any architectures where these checks fail. 74if struct.calcsize(FORMAT_UINT32_LITTLE_ENDIAN) != 4: 75 raise AssertionError('Format "I" is not a 32-bit number.') 76if struct.calcsize(FORMAT_UINT64_LITTLE_ENDIAN) != 8: 77 raise AssertionError('Format "Q" is not a 64-bit number.') 78 79 80def PackTag(field_number, wire_type): 81 """Returns an unsigned 32-bit integer that encodes the field number and 82 wire type information in standard protocol message wire format. 83 84 Args: 85 field_number: Expected to be an integer in the range [1, 1 << 29) 86 wire_type: One of the WIRETYPE_* constants. 87 """ 88 if not 0 <= wire_type <= _WIRETYPE_MAX: 89 raise message.EncodeError('Unknown wire type: %d' % wire_type) 90 return (field_number << TAG_TYPE_BITS) | wire_type 91 92 93def UnpackTag(tag): 94 """The inverse of PackTag(). Given an unsigned 32-bit number, 95 returns a (field_number, wire_type) tuple. 96 """ 97 return (tag >> TAG_TYPE_BITS), (tag & TAG_TYPE_MASK) 98 99 100def ZigZagEncode(value): 101 """ZigZag Transform: Encodes signed integers so that they can be 102 effectively used with varint encoding. See wire_format.h for 103 more details. 104 """ 105 if value >= 0: 106 return value << 1 107 return (value << 1) ^ (~0) 108 109 110def ZigZagDecode(value): 111 """Inverse of ZigZagEncode().""" 112 if not value & 0x1: 113 return value >> 1 114 return (value >> 1) ^ (~0) 115 116 117 118# The *ByteSize() functions below return the number of bytes required to 119# serialize "field number + type" information and then serialize the value. 120 121 122def Int32ByteSize(field_number, int32): 123 return Int64ByteSize(field_number, int32) 124 125 126def Int32ByteSizeNoTag(int32): 127 return _VarUInt64ByteSizeNoTag(0xffffffffffffffff & int32) 128 129 130def Int64ByteSize(field_number, int64): 131 # Have to convert to uint before calling UInt64ByteSize(). 132 return UInt64ByteSize(field_number, 0xffffffffffffffff & int64) 133 134 135def UInt32ByteSize(field_number, uint32): 136 return UInt64ByteSize(field_number, uint32) 137 138 139def UInt64ByteSize(field_number, uint64): 140 return TagByteSize(field_number) + _VarUInt64ByteSizeNoTag(uint64) 141 142 143def SInt32ByteSize(field_number, int32): 144 return UInt32ByteSize(field_number, ZigZagEncode(int32)) 145 146 147def SInt64ByteSize(field_number, int64): 148 return UInt64ByteSize(field_number, ZigZagEncode(int64)) 149 150 151def Fixed32ByteSize(field_number, fixed32): 152 return TagByteSize(field_number) + 4 153 154 155def Fixed64ByteSize(field_number, fixed64): 156 return TagByteSize(field_number) + 8 157 158 159def SFixed32ByteSize(field_number, sfixed32): 160 return TagByteSize(field_number) + 4 161 162 163def SFixed64ByteSize(field_number, sfixed64): 164 return TagByteSize(field_number) + 8 165 166 167def FloatByteSize(field_number, flt): 168 return TagByteSize(field_number) + 4 169 170 171def DoubleByteSize(field_number, double): 172 return TagByteSize(field_number) + 8 173 174 175def BoolByteSize(field_number, b): 176 return TagByteSize(field_number) + 1 177 178 179def EnumByteSize(field_number, enum): 180 return UInt32ByteSize(field_number, enum) 181 182 183def StringByteSize(field_number, string): 184 return BytesByteSize(field_number, string.encode('utf-8')) 185 186 187def BytesByteSize(field_number, b): 188 return (TagByteSize(field_number) 189 + _VarUInt64ByteSizeNoTag(len(b)) 190 + len(b)) 191 192 193def GroupByteSize(field_number, message): 194 return (2 * TagByteSize(field_number) # START and END group. 195 + message.ByteSize()) 196 197 198def MessageByteSize(field_number, message): 199 return (TagByteSize(field_number) 200 + _VarUInt64ByteSizeNoTag(message.ByteSize()) 201 + message.ByteSize()) 202 203 204def MessageSetItemByteSize(field_number, msg): 205 # First compute the sizes of the tags. 206 # There are 2 tags for the beginning and ending of the repeated group, that 207 # is field number 1, one with field number 2 (type_id) and one with field 208 # number 3 (message). 209 total_size = (2 * TagByteSize(1) + TagByteSize(2) + TagByteSize(3)) 210 211 # Add the number of bytes for type_id. 212 total_size += _VarUInt64ByteSizeNoTag(field_number) 213 214 message_size = msg.ByteSize() 215 216 # The number of bytes for encoding the length of the message. 217 total_size += _VarUInt64ByteSizeNoTag(message_size) 218 219 # The size of the message. 220 total_size += message_size 221 return total_size 222 223 224def TagByteSize(field_number): 225 """Returns the bytes required to serialize a tag with this field number.""" 226 # Just pass in type 0, since the type won't affect the tag+type size. 227 return _VarUInt64ByteSizeNoTag(PackTag(field_number, 0)) 228 229 230# Private helper function for the *ByteSize() functions above. 231 232def _VarUInt64ByteSizeNoTag(uint64): 233 """Returns the number of bytes required to serialize a single varint 234 using boundary value comparisons. (unrolled loop optimization -WPierce) 235 uint64 must be unsigned. 236 """ 237 if uint64 <= 0x7f: return 1 238 if uint64 <= 0x3fff: return 2 239 if uint64 <= 0x1fffff: return 3 240 if uint64 <= 0xfffffff: return 4 241 if uint64 <= 0x7ffffffff: return 5 242 if uint64 <= 0x3ffffffffff: return 6 243 if uint64 <= 0x1ffffffffffff: return 7 244 if uint64 <= 0xffffffffffffff: return 8 245 if uint64 <= 0x7fffffffffffffff: return 9 246 if uint64 > UINT64_MAX: 247 raise message.EncodeError('Value out of range: %d' % uint64) 248 return 10 249 250 251NON_PACKABLE_TYPES = ( 252 descriptor.FieldDescriptor.TYPE_STRING, 253 descriptor.FieldDescriptor.TYPE_GROUP, 254 descriptor.FieldDescriptor.TYPE_MESSAGE, 255 descriptor.FieldDescriptor.TYPE_BYTES 256) 257 258 259def IsTypePackable(field_type): 260 """Return true iff packable = true is valid for fields of this type. 261 262 Args: 263 field_type: a FieldDescriptor::Type value. 264 265 Returns: 266 True iff fields of this type are packable. 267 """ 268 return field_type not in NON_PACKABLE_TYPES 269