1 """Interface to the liblzma compression library. 2 3 This module provides a class for reading and writing compressed files, 4 classes for incremental (de)compression, and convenience functions for 5 one-shot (de)compression. 6 7 These classes and functions support both the XZ and legacy LZMA 8 container formats, as well as raw compressed data streams. 9 """ 10 11 __all__ = [ 12 "CHECK_NONE", "CHECK_CRC32", "CHECK_CRC64", "CHECK_SHA256", 13 "CHECK_ID_MAX", "CHECK_UNKNOWN", 14 "FILTER_LZMA1", "FILTER_LZMA2", "FILTER_DELTA", "FILTER_X86", "FILTER_IA64", 15 "FILTER_ARM", "FILTER_ARMTHUMB", "FILTER_POWERPC", "FILTER_SPARC", 16 "FORMAT_AUTO", "FORMAT_XZ", "FORMAT_ALONE", "FORMAT_RAW", 17 "MF_HC3", "MF_HC4", "MF_BT2", "MF_BT3", "MF_BT4", 18 "MODE_FAST", "MODE_NORMAL", "PRESET_DEFAULT", "PRESET_EXTREME", 19 20 "LZMACompressor", "LZMADecompressor", "LZMAFile", "LZMAError", 21 "open", "compress", "decompress", "is_check_supported", 22 ] 23 24 import builtins 25 import io 26 import os 27 from _lzma import * 28 from _lzma import _encode_filter_properties, _decode_filter_properties 29 import _compression 30 31 32 _MODE_CLOSED = 0 33 _MODE_READ = 1 34 # Value 2 no longer used 35 _MODE_WRITE = 3 36 37 38 class LZMAFile(_compression.BaseStream): 39 40 """A file object providing transparent LZMA (de)compression. 41 42 An LZMAFile can act as a wrapper for an existing file object, or 43 refer directly to a named file on disk. 44 45 Note that LZMAFile provides a *binary* file interface - data read 46 is returned as bytes, and data to be written must be given as bytes. 47 """ 48 49 def __init__(self, filename=None, mode="r", *, 50 format=None, check=-1, preset=None, filters=None): 51 """Open an LZMA-compressed file in binary mode. 52 53 filename can be either an actual file name (given as a str, 54 bytes, or PathLike object), in which case the named file is 55 opened, or it can be an existing file object to read from or 56 write to. 57 58 mode can be "r" for reading (default), "w" for (over)writing, 59 "x" for creating exclusively, or "a" for appending. These can 60 equivalently be given as "rb", "wb", "xb" and "ab" respectively. 61 62 format specifies the container format to use for the file. 63 If mode is "r", this defaults to FORMAT_AUTO. Otherwise, the 64 default is FORMAT_XZ. 65 66 check specifies the integrity check to use. This argument can 67 only be used when opening a file for writing. For FORMAT_XZ, 68 the default is CHECK_CRC64. FORMAT_ALONE and FORMAT_RAW do not 69 support integrity checks - for these formats, check must be 70 omitted, or be CHECK_NONE. 71 72 When opening a file for reading, the *preset* argument is not 73 meaningful, and should be omitted. The *filters* argument should 74 also be omitted, except when format is FORMAT_RAW (in which case 75 it is required). 76 77 When opening a file for writing, the settings used by the 78 compressor can be specified either as a preset compression 79 level (with the *preset* argument), or in detail as a custom 80 filter chain (with the *filters* argument). For FORMAT_XZ and 81 FORMAT_ALONE, the default is to use the PRESET_DEFAULT preset 82 level. For FORMAT_RAW, the caller must always specify a filter 83 chain; the raw compressor does not support preset compression 84 levels. 85 86 preset (if provided) should be an integer in the range 0-9, 87 optionally OR-ed with the constant PRESET_EXTREME. 88 89 filters (if provided) should be a sequence of dicts. Each dict 90 should have an entry for "id" indicating ID of the filter, plus 91 additional entries for options to the filter. 92 """ 93 self._fp = None 94 self._closefp = False 95 self._mode = _MODE_CLOSED 96 97 if mode in ("r", "rb"): 98 if check != -1: 99 raise ValueError("Cannot specify an integrity check " 100 "when opening a file for reading") 101 if preset is not None: 102 raise ValueError("Cannot specify a preset compression " 103 "level when opening a file for reading") 104 if format is None: 105 format = FORMAT_AUTO 106 mode_code = _MODE_READ 107 elif mode in ("w", "wb", "a", "ab", "x", "xb"): 108 if format is None: 109 format = FORMAT_XZ 110 mode_code = _MODE_WRITE 111 self._compressor = LZMACompressor(format=format, check=check, 112 preset=preset, filters=filters) 113 self._pos = 0 114 else: 115 raise ValueError("Invalid mode: {!r}".format(mode)) 116 117 if isinstance(filename, (str, bytes, os.PathLike)): 118 if "b" not in mode: 119 mode += "b" 120 self._fp = builtins.open(filename, mode) 121 self._closefp = True 122 self._mode = mode_code 123 elif hasattr(filename, "read") or hasattr(filename, "write"): 124 self._fp = filename 125 self._mode = mode_code 126 else: 127 raise TypeError("filename must be a str, bytes, file or PathLike object") 128 129 if self._mode == _MODE_READ: 130 raw = _compression.DecompressReader(self._fp, LZMADecompressor, 131 trailing_error=LZMAError, format=format, filters=filters) 132 self._buffer = io.BufferedReader(raw) 133 134 def close(self): 135 """Flush and close the file. 136 137 May be called more than once without error. Once the file is 138 closed, any other operation on it will raise a ValueError. 139 """ 140 if self._mode == _MODE_CLOSED: 141 return 142 try: 143 if self._mode == _MODE_READ: 144 self._buffer.close() 145 self._buffer = None 146 elif self._mode == _MODE_WRITE: 147 self._fp.write(self._compressor.flush()) 148 self._compressor = None 149 finally: 150 try: 151 if self._closefp: 152 self._fp.close() 153 finally: 154 self._fp = None 155 self._closefp = False 156 self._mode = _MODE_CLOSED 157 158 @property 159 def closed(self): 160 """True if this file is closed.""" 161 return self._mode == _MODE_CLOSED 162 163 def fileno(self): 164 """Return the file descriptor for the underlying file.""" 165 self._check_not_closed() 166 return self._fp.fileno() 167 168 def seekable(self): 169 """Return whether the file supports seeking.""" 170 return self.readable() and self._buffer.seekable() 171 172 def readable(self): 173 """Return whether the file was opened for reading.""" 174 self._check_not_closed() 175 return self._mode == _MODE_READ 176 177 def writable(self): 178 """Return whether the file was opened for writing.""" 179 self._check_not_closed() 180 return self._mode == _MODE_WRITE 181 182 def peek(self, size=-1): 183 """Return buffered data without advancing the file position. 184 185 Always returns at least one byte of data, unless at EOF. 186 The exact number of bytes returned is unspecified. 187 """ 188 self._check_can_read() 189 # Relies on the undocumented fact that BufferedReader.peek() always 190 # returns at least one byte (except at EOF) 191 return self._buffer.peek(size) 192 193 def read(self, size=-1): 194 """Read up to size uncompressed bytes from the file. 195 196 If size is negative or omitted, read until EOF is reached. 197 Returns b"" if the file is already at EOF. 198 """ 199 self._check_can_read() 200 return self._buffer.read(size) 201 202 def read1(self, size=-1): 203 """Read up to size uncompressed bytes, while trying to avoid 204 making multiple reads from the underlying stream. Reads up to a 205 buffer's worth of data if size is negative. 206 207 Returns b"" if the file is at EOF. 208 """ 209 self._check_can_read() 210 if size < 0: 211 size = io.DEFAULT_BUFFER_SIZE 212 return self._buffer.read1(size) 213 214 def readline(self, size=-1): 215 """Read a line of uncompressed bytes from the file. 216 217 The terminating newline (if present) is retained. If size is 218 non-negative, no more than size bytes will be read (in which 219 case the line may be incomplete). Returns b'' if already at EOF. 220 """ 221 self._check_can_read() 222 return self._buffer.readline(size) 223 224 def write(self, data): 225 """Write a bytes object to the file. 226 227 Returns the number of uncompressed bytes written, which is 228 always len(data). Note that due to buffering, the file on disk 229 may not reflect the data written until close() is called. 230 """ 231 self._check_can_write() 232 compressed = self._compressor.compress(data) 233 self._fp.write(compressed) 234 self._pos += len(data) 235 return len(data) 236 237 def seek(self, offset, whence=io.SEEK_SET): 238 """Change the file position. 239 240 The new position is specified by offset, relative to the 241 position indicated by whence. Possible values for whence are: 242 243 0: start of stream (default): offset must not be negative 244 1: current stream position 245 2: end of stream; offset must not be positive 246 247 Returns the new file position. 248 249 Note that seeking is emulated, so depending on the parameters, 250 this operation may be extremely slow. 251 """ 252 self._check_can_seek() 253 return self._buffer.seek(offset, whence) 254 255 def tell(self): 256 """Return the current file position.""" 257 self._check_not_closed() 258 if self._mode == _MODE_READ: 259 return self._buffer.tell() 260 return self._pos 261 262 263 def open(filename, mode="rb", *, 264 format=None, check=-1, preset=None, filters=None, 265 encoding=None, errors=None, newline=None): 266 """Open an LZMA-compressed file in binary or text mode. 267 268 filename can be either an actual file name (given as a str, bytes, 269 or PathLike object), in which case the named file is opened, or it 270 can be an existing file object to read from or write to. 271 272 The mode argument can be "r", "rb" (default), "w", "wb", "x", "xb", 273 "a", or "ab" for binary mode, or "rt", "wt", "xt", or "at" for text 274 mode. 275 276 The format, check, preset and filters arguments specify the 277 compression settings, as for LZMACompressor, LZMADecompressor and 278 LZMAFile. 279 280 For binary mode, this function is equivalent to the LZMAFile 281 constructor: LZMAFile(filename, mode, ...). In this case, the 282 encoding, errors and newline arguments must not be provided. 283 284 For text mode, an LZMAFile object is created, and wrapped in an 285 io.TextIOWrapper instance with the specified encoding, error 286 handling behavior, and line ending(s). 287 288 """ 289 if "t" in mode: 290 if "b" in mode: 291 raise ValueError("Invalid mode: %r" % (mode,)) 292 else: 293 if encoding is not None: 294 raise ValueError("Argument 'encoding' not supported in binary mode") 295 if errors is not None: 296 raise ValueError("Argument 'errors' not supported in binary mode") 297 if newline is not None: 298 raise ValueError("Argument 'newline' not supported in binary mode") 299 300 lz_mode = mode.replace("t", "") 301 binary_file = LZMAFile(filename, lz_mode, format=format, check=check, 302 preset=preset, filters=filters) 303 304 if "t" in mode: 305 return io.TextIOWrapper(binary_file, encoding, errors, newline) 306 else: 307 return binary_file 308 309 310 def compress(data, format=FORMAT_XZ, check=-1, preset=None, filters=None): 311 """Compress a block of data. 312 313 Refer to LZMACompressor's docstring for a description of the 314 optional arguments *format*, *check*, *preset* and *filters*. 315 316 For incremental compression, use an LZMACompressor instead. 317 """ 318 comp = LZMACompressor(format, check, preset, filters) 319 return comp.compress(data) + comp.flush() 320 321 322 def decompress(data, format=FORMAT_AUTO, memlimit=None, filters=None): 323 """Decompress a block of data. 324 325 Refer to LZMADecompressor's docstring for a description of the 326 optional arguments *format*, *check* and *filters*. 327 328 For incremental decompression, use an LZMADecompressor instead. 329 """ 330 results = [] 331 while True: 332 decomp = LZMADecompressor(format, memlimit, filters) 333 try: 334 res = decomp.decompress(data) 335 except LZMAError: 336 if results: 337 break # Leftover data is not a valid LZMA/XZ stream; ignore it. 338 else: 339 raise # Error on the first iteration; bail out. 340 results.append(res) 341 if not decomp.eof: 342 raise LZMAError("Compressed data ended before the " 343 "end-of-stream marker was reached") 344 data = decomp.unused_data 345 if not data: 346 break 347 return b"".join(results) 348
