File size: 11,730 Bytes
8377638 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 |
# this is a standalone single-file merge of aplib compression and decompression
# taken from my own library Kabopan http://code.google.com/p/kabopan/
# (no other clean-up or improvement)
# Ange Albertini, BSD Licence, 2007-2011
# from kbp\comp\_lz77.py ##################################################
def find_longest_match(s, sub):
"""returns the number of byte to look backward and the length of byte to copy)"""
if sub == "":
return 0, 0
limit = len(s)
dic = s[:]
l = 0
offset = 0
length = 0
first = 0
word = ""
word += sub[l]
pos = dic.rfind(word, 0, limit + 1)
if pos == -1:
return offset, length
offset = limit - pos
length = len(word)
dic += sub[l]
while l < len(sub) - 1:
l += 1
word += sub[l]
pos = dic.rfind(word, 0, limit + 1)
if pos == -1:
return offset, length
offset = limit - pos
length = len(word)
dic += sub[l]
return offset, length
# from _misc.py ###############################
def int2lebin(value, size):
"""ouputs value in binary, as little-endian"""
result = ""
for i in xrange(size):
result = result + chr((value >> (8 * i)) & 0xFF )
return result
def modifystring(s, sub, offset):
"""overwrites 'sub' at 'offset' of 's'"""
return s[:offset] + sub + s[offset + len(sub):]
def getbinlen(value):
"""return the bit length of an integer"""
result = 0
if value == 0:
return 1
while value != 0:
value >>= 1
result += 1
return result
# from kbp\_bits.py #################################
class _bits_compress():
"""bit machine for variable-sized auto-reloading tag compression"""
def __init__(self, tagsize):
"""tagsize is the number of bytes that takes the tag"""
self.out = ""
self.__tagsize = tagsize
self.__tag = 0
self.__tagoffset = -1
self.__maxbit = (self.__tagsize * 8) - 1
self.__curbit = 0
self.__isfirsttag = True
def getdata(self):
"""builds an output string of what's currently compressed:
currently output bit + current tag content"""
tagstr = int2lebin(self.__tag, self.__tagsize)
return modifystring(self.out, tagstr, self.__tagoffset)
def write_bit(self, value):
"""writes a bit, make space for the tag if necessary"""
if self.__curbit != 0:
self.__curbit -= 1
else:
if self.__isfirsttag:
self.__isfirsttag = False
else:
self.out = self.getdata()
self.__tagoffset = len(self.out)
self.out += "".join(["\x00"] * self.__tagsize)
self.__curbit = self.__maxbit
self.__tag = 0
if value:
self.__tag |= (1 << self.__curbit)
return
def write_bitstring(self, s):
"""write a string of bits"""
for c in s:
self.write_bit(0 if c == "0" else 1)
return
def write_byte(self, b):
"""writes a char or a number"""
assert len(b) == 1 if isinstance(b, str) else 0 <= b <= 255
self.out += b[0:1] if isinstance(b, str) else chr(b)
return
def write_fixednumber(self, value, nbbit):
"""write a value on a fixed range of bits"""
for i in xrange(nbbit - 1, -1, -1):
self.write_bit( (value >> i) & 1)
return
def write_variablenumber(self, value):
assert value >= 2
length = getbinlen(value) - 2 # the highest bit is 1
self.write_bit(value & (1 << length))
for i in xrange(length - 1, -1, -1):
self.write_bit(1)
self.write_bit(value & (1 << i))
self.write_bit(0)
return
class _bits_decompress():
"""bit machine for variable-sized auto-reloading tag decompression"""
def __init__(self, data, tagsize):
self.__curbit = 0
self.__offset = 0
self.__tag = None
self.__tagsize = tagsize
self.__in = data
self.out = ""
def getoffset(self):
"""return the current byte offset"""
return self.__offset
# def getdata(self):
# return self.__lzdata
def read_bit(self):
"""read next bit from the stream, reloads the tag if necessary"""
if self.__curbit != 0:
self.__curbit -= 1
else:
self.__curbit = (self.__tagsize * 8) - 1
self.__tag = ord(self.read_byte())
for i in xrange(self.__tagsize - 1):
self.__tag += ord(self.read_byte()) << (8 * (i + 1))
bit = (self.__tag >> ((self.__tagsize * 8) - 1)) & 0x01
self.__tag <<= 1
return bit
def is_end(self):
return self.__offset == len(self.__in) and self.__curbit == 1
def read_byte(self):
"""read next byte from the stream"""
if type(self.__in) == str:
result = self.__in[self.__offset]
elif type(self.__in) == file:
result = self.__in.read(1)
self.__offset += 1
return result
def read_fixednumber(self, nbbit, init=0):
"""reads a fixed bit-length number"""
result = init
for i in xrange(nbbit):
result = (result << 1) + self.read_bit()
return result
def read_variablenumber(self):
"""return a variable bit-length number x, x >= 2
reads a bit until the next bit in the pair is not set"""
result = 1
result = (result << 1) + self.read_bit()
while self.read_bit():
result = (result << 1) + self.read_bit()
return result
def read_setbits(self, max_, set_=1):
"""read bits as long as their set or a maximum is reached"""
result = 0
while result < max_ and self.read_bit() == set_:
result += 1
return result
def back_copy(self, offset, length=1):
for i in xrange(length):
self.out += self.out[-offset]
return
def read_literal(self, value=None):
if value is None:
self.out += self.read_byte()
else:
self.out += value
return False
# from kbp\comp\aplib.py ###################################################
"""
aPLib, LZSS based lossless compression algorithm
Jorgen Ibsen U{http://www.ibsensoftware.com}
"""
def lengthdelta(offset):
if offset < 0x80 or 0x7D00 <= offset:
return 2
elif 0x500 <= offset:
return 1
return 0
class compress(_bits_compress):
"""
aplib compression is based on lz77
"""
def __init__(self, data, length=None):
_bits_compress.__init__(self, 1)
self.__in = data
self.__length = length if length is not None else len(data)
self.__offset = 0
self.__lastoffset = 0
self.__pair = True
return
def __literal(self, marker=True):
if marker:
self.write_bit(0)
self.write_byte(self.__in[self.__offset])
self.__offset += 1
self.__pair = True
return
def __block(self, offset, length):
assert offset >= 2
self.write_bitstring("10")
# if the last operations were literal or single byte
# and the offset is unchanged since the last block copy
# we can just store a 'null' offset and the length
if self.__pair and self.__lastoffset == offset:
self.write_variablenumber(2) # 2-
self.write_variablenumber(length)
else:
high = (offset >> 8) + 2
if self.__pair:
high += 1
self.write_variablenumber(high)
low = offset & 0xFF
self.write_byte(low)
self.write_variablenumber(length - lengthdelta(offset))
self.__offset += length
self.__lastoffset = offset
self.__pair = False
return
def __shortblock(self, offset, length):
assert 2 <= length <= 3
assert 0 < offset <= 127
self.write_bitstring("110")
b = (offset << 1 ) + (length - 2)
self.write_byte(b)
self.__offset += length
self.__lastoffset = offset
self.__pair = False
return
def __singlebyte(self, offset):
assert 0 <= offset < 16
self.write_bitstring("111")
self.write_fixednumber(offset, 4)
self.__offset += 1
self.__pair = True
return
def __end(self):
self.write_bitstring("110")
self.write_byte(chr(0))
return
def do(self):
self.__literal(False)
while self.__offset < self.__length:
offset, length = find_longest_match(self.__in[:self.__offset],
self.__in[self.__offset:])
if length == 0:
c = self.__in[self.__offset]
if c == "\x00":
self.__singlebyte(0)
else:
self.__literal()
elif length == 1 and 0 <= offset < 16:
self.__singlebyte(offset)
elif 2 <= length <= 3 and 0 < offset <= 127:
self.__shortblock(offset, length)
elif 3 <= length and 2 <= offset:
self.__block(offset, length)
else:
self.__literal()
#raise ValueError("no parsing found", offset, length)
self.__end()
return self.getdata()
class decompress(_bits_decompress):
def __init__(self, data):
_bits_decompress.__init__(self, data, tagsize=1)
self.__pair = True # paired sequence
self.__lastoffset = 0
self.__functions = [
self.__literal,
self.__block,
self.__shortblock,
self.__singlebyte]
return
def __literal(self):
self.read_literal()
self.__pair = True
return False
def __block(self):
b = self.read_variablenumber() # 2-
if b == 2 and self.__pair : # reuse the same offset
offset = self.__lastoffset
length = self.read_variablenumber() # 2-
else:
high = b - 2 # 0-
if self.__pair:
high -= 1
offset = (high << 8) + ord(self.read_byte())
length = self.read_variablenumber() # 2-
length += lengthdelta(offset)
self.__lastoffset = offset
self.back_copy(offset, length)
self.__pair = False
return False
def __shortblock(self):
b = ord(self.read_byte())
if b <= 1: # likely 0
return True
length = 2 + (b & 0x01) # 2-3
offset = b >> 1 # 1-127
self.back_copy(offset, length)
self.__lastoffset = offset
self.__pair = False
return False
def __singlebyte(self):
offset = self.read_fixednumber(4) # 0-15
if offset:
self.back_copy(offset)
else:
self.read_literal('\x00')
self.__pair = True
return False
def do(self):
"""returns decompressed buffer and consumed bytes counter"""
self.read_literal()
while True:
if self.__functions[self.read_setbits(3)]():
break
return self.out, self.getoffset()
if __name__ == "__main__":
# from kbp\test\aplib_test.py ######################################################################
assert decompress(compress("a").do()).do() == ("a", 3)
assert decompress(compress("ababababababab").do()).do() == ('ababababababab', 9)
assert decompress(compress("aaaaaaaaaaaaaacaaaaaa").do()).do() == ('aaaaaaaaaaaaaacaaaaaa', 11)
|