Chilkat2-Python

Decompress Large Binary File in Blocks

See more Compression Examples

Decompresses a large binary file in blocks. Chilkat2-Python

import sys
import chilkat2

success = False

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

facSrc = chilkat2.FileAccess()
facDest = chilkat2.FileAccess()

# Open a previously compressed file for decompressing.
# See Compress Large File in Blocks

success = facSrc.OpenForRead("c:/temp/qa_output/compressedBmp.dat")
if (success == False):
    print(facSrc.LastErrorText)
    sys.exit()

# If we compress in 32K chunks, find out how many blocks there will be.
blockSize = 32768
numBlocks = facSrc.GetNumBlocks(blockSize)

# Open an output file for the decompressed data.
success = facDest.OpenForWrite("c:/temp/qa_output/decompressed.bmp")
if (success == False):
    print(facDest.LastErrorText)
    sys.exit()

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

# Assuming numBlocks > 1
compress.FirstChunk = True
compress.LastChunk = False

i = 0
while i < numBlocks :
    # compressedBytes is a memoryview
    compressedBytes = facSrc.ReadBlock(i,blockSize)

    # decompressedBytes is a memoryview
    decompressedBytes = compress.DecompressBytes(compressedBytes)
    facDest.FileWrite(decompressedBytes)

    i = i + 1

    compress.FirstChunk = False
    if (i == (numBlocks - 1)):
        compress.LastChunk = True

facSrc.FileClose()
facDest.FileClose()

print("Finished decompressing file.")