[Python-checkins] r46629 - python/trunk/Demo/zlib/minigzip.py
andrew.kuchling
python-checkins at python.org
Sun Jun 4 01:39:08 CEST 2006
Author: andrew.kuchling
Date: Sun Jun 4 01:39:07 2006
New Revision: 46629
Modified:
python/trunk/Demo/zlib/minigzip.py
Log:
Use functions; modernize code
Modified: python/trunk/Demo/zlib/minigzip.py
==============================================================================
--- python/trunk/Demo/zlib/minigzip.py (original)
+++ python/trunk/Demo/zlib/minigzip.py Sun Jun 4 01:39:07 2006
@@ -1,106 +1,133 @@
#!/usr/bin/env python
# Demo program for zlib; it compresses or decompresses files, but *doesn't*
# delete the original. This doesn't support all of gzip's options.
+#
+# The 'gzip' module in the standard library provides a more complete
+# implementation of gzip-format files.
+
+import zlib, sys, os
FTEXT, FHCRC, FEXTRA, FNAME, FCOMMENT = 1, 2, 4, 8, 16
def write32(output, value):
- output.write(chr(value & 255)) ; value=value / 256
- output.write(chr(value & 255)) ; value=value / 256
- output.write(chr(value & 255)) ; value=value / 256
+ output.write(chr(value & 255)) ; value=value // 256
+ output.write(chr(value & 255)) ; value=value // 256
+ output.write(chr(value & 255)) ; value=value // 256
output.write(chr(value & 255))
def read32(input):
- v=ord(input.read(1))
- v=v+ (ord(input.read(1))<<8 )
- v=v+ (ord(input.read(1))<<16)
- v=v+ (ord(input.read(1))<<24)
+ v = ord(input.read(1))
+ v += (ord(input.read(1)) << 8 )
+ v += (ord(input.read(1)) << 16)
+ v += (ord(input.read(1)) << 24)
return v
-import zlib, sys
-if len(sys.argv)!=2:
- print 'Usage: minigzip.py <filename>'
- print ' The file will be compressed or decompressed.'
- sys.exit(0)
-
-filename=sys.argv[1]
-compressing=1 ; outputname=filename+'.gz'
-if filename[-3:]=='.gz':
- compressing=0 ; outputname=filename[:-3]
-input=open(filename) ; output=open(outputname, 'w')
-
-if compressing:
+def compress (filename, input, output):
output.write('\037\213\010') # Write the header, ...
output.write(chr(FNAME)) # ... flag byte ...
- import os # ... modification time ...
- statval=os.stat(filename)
- mtime=statval[8]
+ statval = os.stat(filename) # ... modification time ...
+ mtime = statval[8]
write32(output, mtime)
output.write('\002') # ... slowest compression alg. ...
output.write('\377') # ... OS (=unknown) ...
output.write(filename+'\000') # ... original filename ...
- crcval=zlib.crc32("")
- compobj=zlib.compressobj(9, zlib.DEFLATED, -zlib.MAX_WBITS,
+ crcval = zlib.crc32("")
+ compobj = zlib.compressobj(9, zlib.DEFLATED, -zlib.MAX_WBITS,
zlib.DEF_MEM_LEVEL, 0)
- while (1):
- data=input.read(1024)
- if data=="": break
- crcval=zlib.crc32(data, crcval)
+ while True:
+ data = input.read(1024)
+ if data == "":
+ break
+ crcval = zlib.crc32(data, crcval)
output.write(compobj.compress(data))
output.write(compobj.flush())
write32(output, crcval) # ... the CRC ...
write32(output, statval[6]) # and the file size.
-else:
- magic=input.read(2)
- if magic!='\037\213':
- print 'Not a gzipped file' ; sys.exit(0)
- if ord(input.read(1))!=8:
- print 'Unknown compression method' ; sys.exit(0)
- flag=ord(input.read(1))
+def decompress (input, output):
+ magic = input.read(2)
+ if magic != '\037\213':
+ print 'Not a gzipped file'
+ sys.exit(0)
+ if ord(input.read(1)) != 8:
+ print 'Unknown compression method'
+ sys.exit(0)
+ flag = ord(input.read(1))
input.read(4+1+1) # Discard modification time,
# extra flags, and OS byte.
if flag & FEXTRA:
# Read & discard the extra field, if present
- xlen=ord(input.read(1))
- xlen=xlen+256*ord(input.read(1))
+ xlen = ord(input.read(1))
+ xlen += 256*ord(input.read(1))
input.read(xlen)
if flag & FNAME:
# Read and discard a null-terminated string containing the filename
- while (1):
- s=input.read(1)
- if s=='\000': break
+ while True:
+ s = input.read(1)
+ if s == '\0': break
if flag & FCOMMENT:
# Read and discard a null-terminated string containing a comment
- while (1):
+ while True:
s=input.read(1)
- if s=='\000': break
+ if s=='\0': break
if flag & FHCRC:
input.read(2) # Read & discard the 16-bit header CRC
- decompobj=zlib.decompressobj(-zlib.MAX_WBITS)
- crcval=zlib.crc32("")
- length=0
- while (1):
+
+ decompobj = zlib.decompressobj(-zlib.MAX_WBITS)
+ crcval = zlib.crc32("")
+ length = 0
+ while True:
data=input.read(1024)
- if data=="": break
- decompdata=decompobj.decompress(data)
- print len(decompdata)
- output.write(decompdata) ; length=length+len(decompdata)
- crcval=zlib.crc32(decompdata, crcval)
- decompdata=decompobj.flush()
- output.write(decompdata) ; length=length+len(decompdata)
- crcval=zlib.crc32(decompdata, crcval)
+ if data == "":
+ break
+ decompdata = decompobj.decompress(data)
+ output.write(decompdata)
+ length += len(decompdata)
+ crcval = zlib.crc32(decompdata, crcval)
+
+ decompdata = decompobj.flush()
+ output.write(decompdata)
+ length += len(decompdata)
+ crcval = zlib.crc32(decompdata, crcval)
# We've read to the end of the file, so we have to rewind in order
# to reread the 8 bytes containing the CRC and the file size. The
# decompressor is smart and knows when to stop, so feeding it
# extra data is harmless.
input.seek(-8, 2)
- crc32=read32(input)
- isize=read32(input)
- if crc32!=crcval: print 'CRC check failed.'
- if isize!=length: print 'Incorrect length of data produced'
+ crc32 = read32(input)
+ isize = read32(input)
+ if crc32 != crcval:
+ print 'CRC check failed.'
+ if isize != length:
+ print 'Incorrect length of data produced'
+
+def main():
+ if len(sys.argv)!=2:
+ print 'Usage: minigzip.py <filename>'
+ print ' The file will be compressed or decompressed.'
+ sys.exit(0)
+
+ filename = sys.argv[1]
+ if filename.endswith('.gz'):
+ compressing = False
+ outputname = filename[:-3]
+ else:
+ compressing = True
+ outputname = filename + '.gz'
+
+ input = open(filename, 'rb')
+ output = open(outputname, 'wb')
+
+ if compressing:
+ compress(filename, input, output)
+ else:
+ decompress(input, output)
+
+ input.close()
+ output.close()
-input.close() ; output.close()
+if __name__ == '__main__':
+ main()
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