Tcl

Compress and Decompress Hex String

See more Compression Examples

Imagine we have data represented as a hex string. This example demonstrates how to decode, compress, and re-encode to a smaller hex string representing the compressed data. An even better choice is to re-encode to a more compact encoding such as base64.

Note: This example requires Chilkat v9.5.0.66 or greater.

Tcl

load ./chilkat.dll

set success 0

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

set strHex "54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A0D0A"

set compress [new_CkCompression]

CkCompression_put_Algorithm $compress "deflate"

set binDat [new_CkBinData]

# Load the hex string into a BinData object.
# This decodes the hexidecimal. The decoded bytes will be contained in the BinData.
CkBinData_AppendEncoded $binDat $strHex "hex"

# Compress the BinData.
CkCompression_CompressBd $compress $binDat

# Get the compressed data in hex format:
set compressedHex [CkBinData_getEncoded $binDat "hex"]
puts "compressed hex:"
puts "$compressedHex"

# The compressed hex is: 0BC94855282CCD4CCE56482ACA2FCF5348CBAF50C82ACD2D484D51C82F4B2D522801CAE72456552AA4E4A7EBF172850C61E5BC5C00

# Even better, get the compressed data in base64 format:
# (base64url and modbase64 are other valid choices...)
set compressedBase64 [CkBinData_getEncoded $binDat "base64"]
puts "compressed base64:"
puts "$compressedBase64"

# The compressed base64 is: C8lIVSgszUzOVkgqyi/PU0jLr1DIKs0tSE1RyC9LLVIoAcrnJFZVKqTkp+vxcoUMYeW8XAA=

# Now decompress:
CkBinData_Clear $binDat
CkBinData_AppendEncoded $binDat $compressedHex "hex"
CkCompression_DecompressBd $compress $binDat

set decompressedHex [CkBinData_getEncoded $binDat "hex"]
puts "decompressed hex:"
puts "$decompressedHex"

# The output is the original hex string:
# 54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A0D0A

delete_CkCompression $compress
delete_CkBinData $binDat