Chilkat2-Python

Streaming Compression

See more Compression Examples

Compress and decompress using a stream. Chilkat2-Python

import sys
import chilkat2

success = False

# This example assumes the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

fac = chilkat2.FileAccess()
compress = chilkat2.Compression()
compress.Algorithm = "deflate"

streamC = chilkat2.Stream()

# This example sets the source and sink of the stream to files.
# A stream can have use other streams as a source or sink,
# or the application can itself be the source/sink by directly
# reading or writing a stream.  (See below for an example of this..)
streamC.SourceFile = "qa_data/hamlet.xml"
streamC.SinkFile = "qa_output/hamlet_compressed.dat"

# Compress from source to sink.
success = compress.CompressStream(streamC)
if (success != True):
    print(compress.LastErrorText)
    sys.exit()

print("File-to-file deflate compression successful.")
# Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
# the size of the file as a string, then convert to an integer value.
print("Original size = " + str(fac.FileSize(streamC.SourceFile)))
print("Compressed size = " + str(fac.FileSize(streamC.SinkFile)))

# Now do file-to-file decompression
streamD = chilkat2.Stream()
streamD.SourceFile = "qa_output/hamlet_compressed.dat"
streamD.SinkFile = "qa_output/hamlet_restored.xml"

# Decompress from source to sink.
success = compress.DecompressStream(streamD)
if (success != True):
    print(compress.LastErrorText)
    sys.exit()

print("File-to-file deflate decompression successful.")

# Let's double-check to see that the files are equal in size and content:

bFilesEqual = fac.FileContentsEqual(streamC.SourceFile,streamD.SinkFile)
if (bFilesEqual != True):
    print("The output file is not equal to the input file!")
else:
    print("The file was successfully compressed and decompressed.")

# ---------------------------------------------------------------------
# Now let's decompress again, but this time w/ the application reading
# the decompressed data directly from a stream.
streamA = chilkat2.Stream()

streamA.SourceFile = "qa_output/hamlet_compressed.dat"

# Start decompressing in a background thread.
# task is a CkTask
task = compress.DecompressStreamAsync(streamA)
success = task.Run()

# Read decompressed data from streamA:

while (streamA.EndOfStream != True) :
    if (streamA.DataAvailable == True):
        decompressedText = streamA.ReadString()
        print(decompressedText)

# Let's make sure the background task finished and that the decompress was successful.
# It should already be the case that the task is finished.
while (task.Finished != True) :
    task.SleepMs(20)

# The decompressor may have finished, but it is possible that data
# remains to be flushed.  
if (streamA.DataAvailable == True):
    decompressedText = streamA.ReadString()
    print(decompressedText)

# Did streamA succeed in reading the entire file?
if (task.TaskSuccess != True):
    print("async decompress failed:")
    print(task.ResultErrorText)
    success = False

print("The async decompress was successful.")