PPMD Streaming String Compression

Demonstrates streaming string compression using PPMD. Data may be compressed in chunks by initially calling one of the BeginCompress* methods, followed by 0 or more calls to a MoreCompress* method, and terminating with a call to an EndCompress* method.

Likewise, data may be decompressed by calling a BeginDecompress* method, followed by 0 or more MoreDecompress* calls, and ending with an EndDecompress* method call.

This example demonstrates string-to-string compression and decompression in chunks.

The functionality in this example is available in pre-release only:

Download Chilkat Python Library (Pre-Release)

import sys
import chilkat

compress = chilkat.CkCompression()

#  Any string argument automatically begins a 30-day trial.
success = compress.UnlockComponent("30-day trial")
if (success != True):
    print "Compression component unlock failed"
    sys.exit()

compress.put_Algorithm("ppmd")
compress.put_Charset("ansi")
compress.put_EncodingMode("base64")

#  Create a long string to compress.
strData = "abcdefg1122334455667788"
strData = strData + "\r\n"

#  Note: BeginCompressStringENC may return a zero-length
#  string.  This is normal if the input is buffered and no
#  compressed data is yet available.
#  However, a null reference indicates an error -- which is
#  generally only possible if the component was never unlocked.
strCompressed = compress.beginCompressStringENC(strData)
if (strCompressed == None ):
    print compress.lastErrorText()
    sys.exit()

#  Compress 100 more chunks of data.  Each call to
#  MoreCompressStringENC may or may not produce additional
#  compressed output.
for i in range(0,100):
    strData = "abcdefg1122334455667788"
    strData = strData + "\r\n"

    strCompressed = strCompressed + compress.moreCompressStringENC(strData)

#  Finalize the compression with a single call to EndCompressStringENC:
strCompressed = strCompressed + compress.endCompressStringENC()

#  Display the compressed string.
#  The result will be:
#  ec8YZ5vk9za18d0plwuV7R65em9OZge9gJXht/QAAAAAAAAAABNOZQAAKw==

print strCompressed

#  Decompress back to the original in a single call.

strOriginal = compress.decompressStringENC(strCompressed)

#  Display the uncompressed original:
print "--- Original ---"
print strOriginal

#  Decompress in multiple calls.  It doesn't matter how the
#  compressed data is split -- it could be fed to the decompressor
#  one char at a time if desired.
chunk1 = "ec8YZ5vk9za1"
chunk2 = "8d0p"
chunk3 = "lwuV7R65em9OZge9gJXht/QAAAA"
chunk4 = "AAAAAABNOZQAAKw=="

strOriginal = ""
strOriginal = compress.beginDecompressStringENC(chunk1)
strOriginal = strOriginal + compress.moreDecompressStringENC(chunk2)
strOriginal = strOriginal + compress.moreDecompressStringENC(chunk3)
strOriginal = strOriginal + compress.moreDecompressStringENC(chunk4)
strOriginal = strOriginal + compress.endDecompressStringENC()

#  Display the uncompressed original after decompressing in chunks:
print "--- Original after Decompressing from Chunks ---"
print strOriginal