Chilkat2-Python

Transition from Compression.BeginCompressBytes to FirstChunk/LastChunk

Provides instructions for replacing deprecated BeginCompressBytes method calls with using FirstChunk and LastChunk properties. Chilkat2-Python

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.")