(Chilkat2-Python) Transition from Compression.BeginCompressBytes to FirstChunk/LastChunk

Provides instructions for replacing deprecated BeginCompressBytes method calls with using FirstChunk and LastChunk properties.

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

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

# Open a large binary file for reading.
success = facSrc.OpenForRead("qa_data/bmp/big.bmp")
if (success == False):
    print(facSrc.LastErrorText)
    sys.exit()

# If we compress in 64K chunks, find out how many blocks there will be.
blockSize = 65536
numBlocks = facSrc.GetNumBlocks(blockSize)

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

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

# ----------------------------------------------------------------------------------
# This is the deprecated way of compressing in chunks using Begin/More/End methods..
# ----------------------------------------------------------------------------------
i = 0
while i < numBlocks :
    # fileBytes is a memoryview
    fileBytes = facSrc.ReadBlock(i,blockSize)
    if (i == 0):
        # compressedBytes is a memoryview
        compressedBytes = compress.BeginCompressBytes(fileBytes)
    else:
        # compressedBytes is a memoryview
        compressedBytes = compress.MoreCompressBytes(fileBytes)

    facDest.FileWrite(compressedBytes)

    i = i + 1

# At the very end, flush any remaining compressed bytes, if any.
# compressedBytes is a memoryview
compressedBytes = compress.EndCompressBytes()
facDest.FileWrite(compressedBytes)

facSrc.FileClose()
facDest.FileClose()

print("Finished compressing file.")

# ----------------------------------------------------------------------------------
# This is new way of compressing in chunks using FirstChunk and LastChunk properties
# ----------------------------------------------------------------------------------

success = facSrc.OpenForRead("qa_data/bmp/big.bmp")
if (success == False):
    print(facSrc.LastErrorText)
    sys.exit()

success = facDest.OpenForWrite("c:/temp/qa_output/compressedBmp2.dat")
if (success == False):
    print(facDest.LastErrorText)
    sys.exit()

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

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

    facDest.FileWrite(compressedBytes)

    i = i + 1

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

facSrc.FileClose()
facDest.FileClose()

print("Finished compressing file 2.")