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Compression

Functions

Name
int wc_Compress(byte * out, word32 outSz, const byte * in, word32 inSz, word32 flags)
This function compresses the given input data using Huffman coding and stores the output in out. Note that the output buffer should still be larger than the input buffer because there exists a certain input for which there will be no compression possible, which will still require a lookup table. It is recommended that one allocate srcSz + 0.1% + 12 for the output buffer.
int wc_DeCompress(byte * out, word32 outSz, const byte * in, word32 inSz)
This function decompresses the given compressed data using Huffman coding and stores the output in out.
int wc_Compress_ex(byte * out, word32 outSz, const byte * in, word32 inSz, word32 flags, word32 windowBits)
This function compresses the given input data using Huffman coding with extended parameters. This is similar to wc_Compress but allows specification of compression flags and window bits for more control over the compression process.
int wc_DeCompress_ex(byte * out, word32 outSz, const byte * in, word32 inSz, int windowBits)
This function decompresses the given compressed data using Huffman coding with extended parameters. This is similar to wc_DeCompress but allows specification of window bits for more control over the decompression process.
int wc_DeCompressDynamic(byte ** out, int max, int memoryType, const byte * in, word32 inSz, int windowBits, void * heap)
This function decompresses the given compressed data using Huffman coding with dynamic memory allocation. The output buffer is allocated dynamically and the caller is responsible for freeing it.

Functions Documentation

function wc_Compress

int wc_Compress(
    byte * out,
    word32 outSz,
    const byte * in,
    word32 inSz,
    word32 flags
)

This function compresses the given input data using Huffman coding and stores the output in out. Note that the output buffer should still be larger than the input buffer because there exists a certain input for which there will be no compression possible, which will still require a lookup table. It is recommended that one allocate srcSz + 0.1% + 12 for the output buffer.

Parameters:

  • out pointer to the output buffer in which to store the compressed data
  • outSz size available in the output buffer for storage
  • in pointer to the buffer containing the message to compress
  • inSz size of the input message to compress
  • flags flags to control how compression operates. Use 0 for normal decompression

See: wc_DeCompress

Return:

  • On successfully compressing the input data, returns the number of bytes stored in the output buffer
  • COMPRESS_INIT_E Returned if there is an error initializing the stream for compression
  • COMPRESS_E Returned if an error occurs during compression

Example

byte message[] = { // initialize text to compress };
byte compressed[(sizeof(message) + sizeof(message) * .001 + 12 )];
// Recommends at least srcSz + .1% + 12

if( wc_Compress(compressed, sizeof(compressed), message, sizeof(message),
0) != 0){
    // error compressing data
}

function wc_DeCompress

int wc_DeCompress(
    byte * out,
    word32 outSz,
    const byte * in,
    word32 inSz
)

This function decompresses the given compressed data using Huffman coding and stores the output in out.

Parameters:

  • out pointer to the output buffer in which to store the decompressed data
  • outSz size available in the output buffer for storage
  • in pointer to the buffer containing the message to decompress
  • inSz size of the input message to decompress

See: wc_Compress

Return:

  • Success On successfully decompressing the input data, returns the number of bytes stored in the output buffer
  • COMPRESS_INIT_E: Returned if there is an error initializing the stream for compression
  • COMPRESS_E: Returned if an error occurs during compression

Example

byte compressed[] = { // initialize compressed message };
byte decompressed[MAX_MESSAGE_SIZE];

if( wc_DeCompress(decompressed, sizeof(decompressed),
compressed, sizeof(compressed)) != 0 ) {
    // error decompressing data
}

function wc_Compress_ex

int wc_Compress_ex(
    byte * out,
    word32 outSz,
    const byte * in,
    word32 inSz,
    word32 flags,
    word32 windowBits
)

This function compresses the given input data using Huffman coding with extended parameters. This is similar to wc_Compress but allows specification of compression flags and window bits for more control over the compression process.

Parameters:

  • out pointer to the output buffer in which to store the compressed data
  • outSz size available in the output buffer for storage
  • in pointer to the buffer containing the message to compress
  • inSz size of the input message to compress
  • flags flags to control how compression operates
  • windowBits the base two logarithm of the window size (8..15)

See:

Return:

  • On successfully compressing the input data, returns the number of bytes stored in the output buffer
  • COMPRESS_INIT_E Returned if there is an error initializing the stream for compression
  • COMPRESS_E Returned if an error occurs during compression

Example

byte message[] = { // initialize text to compress };
byte compressed[(sizeof(message) + sizeof(message) * .001 + 12)];
word32 flags = 0;
word32 windowBits = 15; // 32KB window

int ret = wc_Compress_ex(compressed, sizeof(compressed), message,
                         sizeof(message), flags, windowBits);
if (ret < 0) {
    // error compressing data
}

function wc_DeCompress_ex

int wc_DeCompress_ex(
    byte * out,
    word32 outSz,
    const byte * in,
    word32 inSz,
    int windowBits
)

This function decompresses the given compressed data using Huffman coding with extended parameters. This is similar to wc_DeCompress but allows specification of window bits for more control over the decompression process.

Parameters:

  • out pointer to the output buffer in which to store the decompressed data
  • outSz size available in the output buffer for storage
  • in pointer to the buffer containing the message to decompress
  • inSz size of the input message to decompress
  • windowBits the base two logarithm of the window size (8..15)

See:

Return:

  • On successfully decompressing the input data, returns the number of bytes stored in the output buffer
  • COMPRESS_INIT_E Returned if there is an error initializing the stream for decompression
  • COMPRESS_E Returned if an error occurs during decompression

Example

byte compressed[] = { // initialize compressed message };
byte decompressed[MAX_MESSAGE_SIZE];
int windowBits = 15;

int ret = wc_DeCompress_ex(decompressed, sizeof(decompressed),
                           compressed, sizeof(compressed),
                           windowBits);
if (ret < 0) {
    // error decompressing data
}

function wc_DeCompressDynamic

int wc_DeCompressDynamic(
    byte ** out,
    int max,
    int memoryType,
    const byte * in,
    word32 inSz,
    int windowBits,
    void * heap
)

This function decompresses the given compressed data using Huffman coding with dynamic memory allocation. The output buffer is allocated dynamically and the caller is responsible for freeing it.

Parameters:

  • out pointer to pointer that will be set to the allocated output buffer
  • max maximum size to allocate for output buffer
  • memoryType type of memory to allocate (DYNAMIC_TYPE_TMP_BUFFER)
  • in pointer to the buffer containing the message to decompress
  • inSz size of the input message to decompress
  • windowBits the base two logarithm of the window size (8..15)
  • heap heap hint for memory allocation (can be NULL)

See:

Return:

  • On successfully decompressing the input data, returns the number of bytes stored in the output buffer
  • COMPRESS_INIT_E Returned if there is an error initializing the stream for decompression
  • COMPRESS_E Returned if an error occurs during decompression
  • MEMORY_E Returned if memory allocation fails

Example

byte compressed[] = { // initialize compressed message };
byte* decompressed = NULL;
int max = 1024 * 1024; // 1MB max

int ret = wc_DeCompressDynamic(&decompressed, max,
                               DYNAMIC_TYPE_TMP_BUFFER, compressed,
                               sizeof(compressed), 15, NULL);
if (ret < 0) {
    // error decompressing data
}
else {
    // use decompressed data
    XFREE(decompressed, NULL, DYNAMIC_TYPE_TMP_BUFFER);
}

Updated on 2025-12-31 at 01:16:02 +0000