The R Project SVN R

/**
 * \file        lzma/delta.h
 * \brief       Delta filter
 */

/*
 * Author: Lasse Collin
 *
 * This file has been put into the public domain.
 * You can do whatever you want with this file.
 *
 * See ../lzma.h for information about liblzma as a whole.
 */

#ifndef LZMA_H_INTERNAL
#   error Never include this file directly. Use <lzma.h> instead.
#endif


/**
 * \brief       Filter ID
 *
 * Filter ID of the Delta filter. This is used as lzma_filter.id.
 */
#define LZMA_FILTER_DELTA       LZMA_VLI_C(0x03)


/**
 * \brief       Type of the delta calculation
 *
 * Currently only byte-wise delta is supported. Other possible types could
 * be, for example, delta of 16/32/64-bit little/big endian integers, but
 * these are not currently planned since byte-wise delta is almost as good.
 */
typedef enum {
    LZMA_DELTA_TYPE_BYTE
} lzma_delta_type;


/**
 * \brief       Options for the Delta filter
 *
 * These options are needed by both encoder and decoder.
 */
typedef struct {
    /** For now, this must always be LZMA_DELTA_TYPE_BYTE. */
    lzma_delta_type type;

    /**
     * \brief       Delta distance
     *
     * With the only currently supported type, LZMA_DELTA_TYPE_BYTE,
     * the distance is as bytes.
     *
     * Examples:
     *  - 16-bit stereo audio: distance = 4 bytes
     *  - 24-bit RGB image data: distance = 3 bytes
     */
    uint32_t dist;
#   define LZMA_DELTA_DIST_MIN 1
#   define LZMA_DELTA_DIST_MAX 256

    /*
     * Reserved space to allow possible future extensions without
     * breaking the ABI. You should not touch these, because the names
     * of these variables may change. These are and will never be used
     * when type is LZMA_DELTA_TYPE_BYTE, so it is safe to leave these
     * uninitialized.
     */
    uint32_t reserved_int1;
    uint32_t reserved_int2;
    uint32_t reserved_int3;
    uint32_t reserved_int4;
    void *reserved_ptr1;
    void *reserved_ptr2;

} lzma_options_delta;