sparse_img.py revision 5ece99d64efe82fc1ca97a96f079ce69ea588a24
1# Copyright (C) 2014 The Android Open Source Project 2# 3# Licensed under the Apache License, Version 2.0 (the "License"); 4# you may not use this file except in compliance with the License. 5# You may obtain a copy of the License at 6# 7# http://www.apache.org/licenses/LICENSE-2.0 8# 9# Unless required by applicable law or agreed to in writing, software 10# distributed under the License is distributed on an "AS IS" BASIS, 11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12# See the License for the specific language governing permissions and 13# limitations under the License. 14 15import bisect 16import os 17import struct 18from hashlib import sha1 19 20import rangelib 21 22 23class SparseImage(object): 24 """Wraps a sparse image file into an image object. 25 26 Wraps a sparse image file (and optional file map and clobbered_blocks) into 27 an image object suitable for passing to BlockImageDiff. file_map contains 28 the mapping between files and their blocks. clobbered_blocks contains the set 29 of blocks that should be always written to the target regardless of the old 30 contents (i.e. copying instead of patching). clobbered_blocks should be in 31 the form of a string like "0" or "0 1-5 8". 32 """ 33 34 def __init__(self, simg_fn, file_map_fn=None, clobbered_blocks=None): 35 self.simg_f = f = open(simg_fn, "rb") 36 37 header_bin = f.read(28) 38 header = struct.unpack("<I4H4I", header_bin) 39 40 magic = header[0] 41 major_version = header[1] 42 minor_version = header[2] 43 file_hdr_sz = header[3] 44 chunk_hdr_sz = header[4] 45 self.blocksize = blk_sz = header[5] 46 self.total_blocks = total_blks = header[6] 47 total_chunks = header[7] 48 49 if magic != 0xED26FF3A: 50 raise ValueError("Magic should be 0xED26FF3A but is 0x%08X" % (magic,)) 51 if major_version != 1 or minor_version != 0: 52 raise ValueError("I know about version 1.0, but this is version %u.%u" % 53 (major_version, minor_version)) 54 if file_hdr_sz != 28: 55 raise ValueError("File header size was expected to be 28, but is %u." % 56 (file_hdr_sz,)) 57 if chunk_hdr_sz != 12: 58 raise ValueError("Chunk header size was expected to be 12, but is %u." % 59 (chunk_hdr_sz,)) 60 61 print("Total of %u %u-byte output blocks in %u input chunks." 62 % (total_blks, blk_sz, total_chunks)) 63 64 pos = 0 # in blocks 65 care_data = [] 66 self.offset_map = offset_map = [] 67 self.clobbered_blocks = rangelib.RangeSet(data=clobbered_blocks) 68 69 for i in range(total_chunks): 70 header_bin = f.read(12) 71 header = struct.unpack("<2H2I", header_bin) 72 chunk_type = header[0] 73 chunk_sz = header[2] 74 total_sz = header[3] 75 data_sz = total_sz - 12 76 77 if chunk_type == 0xCAC1: 78 if data_sz != (chunk_sz * blk_sz): 79 raise ValueError( 80 "Raw chunk input size (%u) does not match output size (%u)" % 81 (data_sz, chunk_sz * blk_sz)) 82 else: 83 care_data.append(pos) 84 care_data.append(pos + chunk_sz) 85 offset_map.append((pos, chunk_sz, f.tell(), None)) 86 pos += chunk_sz 87 f.seek(data_sz, os.SEEK_CUR) 88 89 elif chunk_type == 0xCAC2: 90 fill_data = f.read(4) 91 care_data.append(pos) 92 care_data.append(pos + chunk_sz) 93 offset_map.append((pos, chunk_sz, None, fill_data)) 94 pos += chunk_sz 95 96 elif chunk_type == 0xCAC3: 97 if data_sz != 0: 98 raise ValueError("Don't care chunk input size is non-zero (%u)" % 99 (data_sz)) 100 else: 101 pos += chunk_sz 102 103 elif chunk_type == 0xCAC4: 104 raise ValueError("CRC32 chunks are not supported") 105 106 else: 107 raise ValueError("Unknown chunk type 0x%04X not supported" % 108 (chunk_type,)) 109 110 self.care_map = rangelib.RangeSet(care_data) 111 self.offset_index = [i[0] for i in offset_map] 112 113 if file_map_fn: 114 self.LoadFileBlockMap(file_map_fn, self.clobbered_blocks) 115 else: 116 self.file_map = {"__DATA": self.care_map} 117 118 def ReadRangeSet(self, ranges): 119 return [d for d in self._GetRangeData(ranges)] 120 121 def TotalSha1(self): 122 """Return the SHA-1 hash of all data in the 'care' regions but not in 123 clobbered_blocks of this image.""" 124 h = sha1() 125 for d in self._GetRangeData(self.care_map.subtract(self.clobbered_blocks)): 126 h.update(d) 127 return h.hexdigest() 128 129 def _GetRangeData(self, ranges): 130 """Generator that produces all the image data in 'ranges'. The 131 number of individual pieces returned is arbitrary (and in 132 particular is not necessarily equal to the number of ranges in 133 'ranges'. 134 135 This generator is stateful -- it depends on the open file object 136 contained in this SparseImage, so you should not try to run two 137 instances of this generator on the same object simultaneously.""" 138 139 f = self.simg_f 140 for s, e in ranges: 141 to_read = e-s 142 idx = bisect.bisect_right(self.offset_index, s) - 1 143 chunk_start, chunk_len, filepos, fill_data = self.offset_map[idx] 144 145 # for the first chunk we may be starting partway through it. 146 remain = chunk_len - (s - chunk_start) 147 this_read = min(remain, to_read) 148 if filepos is not None: 149 p = filepos + ((s - chunk_start) * self.blocksize) 150 f.seek(p, os.SEEK_SET) 151 yield f.read(this_read * self.blocksize) 152 else: 153 yield fill_data * (this_read * (self.blocksize >> 2)) 154 to_read -= this_read 155 156 while to_read > 0: 157 # continue with following chunks if this range spans multiple chunks. 158 idx += 1 159 chunk_start, chunk_len, filepos, fill_data = self.offset_map[idx] 160 this_read = min(chunk_len, to_read) 161 if filepos is not None: 162 f.seek(filepos, os.SEEK_SET) 163 yield f.read(this_read * self.blocksize) 164 else: 165 yield fill_data * (this_read * (self.blocksize >> 2)) 166 to_read -= this_read 167 168 def LoadFileBlockMap(self, fn, clobbered_blocks): 169 remaining = self.care_map 170 self.file_map = out = {} 171 172 with open(fn) as f: 173 for line in f: 174 fn, ranges = line.split(None, 1) 175 ranges = rangelib.RangeSet.parse(ranges) 176 out[fn] = ranges 177 assert ranges.size() == ranges.intersect(remaining).size() 178 179 # Currently we assume that blocks in clobbered_blocks are not part of 180 # any file. 181 assert not clobbered_blocks.overlaps(ranges) 182 remaining = remaining.subtract(ranges) 183 184 remaining = remaining.subtract(clobbered_blocks) 185 186 # For all the remaining blocks in the care_map (ie, those that 187 # aren't part of the data for any file nor part of the clobbered_blocks), 188 # divide them into blocks that are all zero and blocks that aren't. 189 # (Zero blocks are handled specially because (1) there are usually 190 # a lot of them and (2) bsdiff handles files with long sequences of 191 # repeated bytes especially poorly.) 192 193 zero_blocks = [] 194 nonzero_blocks = [] 195 reference = '\0' * self.blocksize 196 197 f = self.simg_f 198 for s, e in remaining: 199 for b in range(s, e): 200 idx = bisect.bisect_right(self.offset_index, b) - 1 201 chunk_start, _, filepos, fill_data = self.offset_map[idx] 202 if filepos is not None: 203 filepos += (b-chunk_start) * self.blocksize 204 f.seek(filepos, os.SEEK_SET) 205 data = f.read(self.blocksize) 206 else: 207 if fill_data == reference[:4]: # fill with all zeros 208 data = reference 209 else: 210 data = None 211 212 if data == reference: 213 zero_blocks.append(b) 214 zero_blocks.append(b+1) 215 else: 216 nonzero_blocks.append(b) 217 nonzero_blocks.append(b+1) 218 219 out["__ZERO"] = rangelib.RangeSet(data=zero_blocks) 220 out["__NONZERO"] = rangelib.RangeSet(data=nonzero_blocks) 221 out["__COPY"] = clobbered_blocks 222 223 def ResetFileMap(self): 224 """Throw away the file map and treat the entire image as 225 undifferentiated data.""" 226 self.file_map = {"__DATA": self.care_map} 227