Checking in zlib demo.
diff --git a/Demo/zlib/minigzip.py b/Demo/zlib/minigzip.py
new file mode 100755
index 0000000..0bfe355
--- /dev/null
+++ b/Demo/zlib/minigzip.py
@@ -0,0 +1,107 @@
+#!/usr/local/bin/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.
+
+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))
+
+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)
+ 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:
+ 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]
+ 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,
+ zlib.DEF_MEM_LEVEL, 0)
+ while (1):
+ 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))
+ 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))
+ 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
+ if flag & FCOMMENT:
+ # Read and discard a null-terminated string containing a comment
+ while (1):
+ s=input.read(1)
+ if s=='\000': 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):
+ 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)
+
+ # 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'
+
+input.close() ; output.close()
+