(Chilkat2-Python) Decompress Large Binary File in Blocks

Decompresses a large binary file in blocks.

Note: This example requires Chilkat v11.0.0 or greater.

Chilkat2 Python Downloads install with pip pip3 install chilkat2 or download... Python Module for Windows, Linux, Alpine Linux, MacOS

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.")