delta_common.c

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//
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
 
#include "delta_common.h"
#include "delta_private.h"
 
 
static void
delta_coder_end(void *coder_ptr, const lzma_allocator *allocator)
{
    lzma_delta_coder *coder = coder_ptr;
    lzma_next_end(&coder->next, allocator);
    lzma_free(coder, allocator);
    return;
}
 
 
extern lzma_ret
lzma_delta_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
        const lzma_filter_info *filters)
{
    // Allocate memory for the decoder if needed.
    lzma_delta_coder *coder = next->coder;
    if (coder == NULL) {
        coder = lzma_alloc(sizeof(lzma_delta_coder), allocator);
        if (coder == NULL)
            return LZMA_MEM_ERROR;
 
        next->coder = coder;
 
        // End function is the same for encoder and decoder.
        next->end = &delta_coder_end;
        coder->next = LZMA_NEXT_CODER_INIT;
    }
 
    // Validate the options.
    if (lzma_delta_coder_memusage(filters[0].options) == UINT64_MAX)
        return LZMA_OPTIONS_ERROR;
 
    // Set the delta distance.
    const lzma_options_delta *opt = filters[0].options;
    coder->distance = opt->dist;
 
    // Initialize the rest of the variables.
    coder->pos = 0;
    memzero(coder->history, LZMA_DELTA_DIST_MAX);
 
    // Initialize the next decoder in the chain, if any.
    return lzma_next_filter_init(&coder->next, allocator, filters + 1);
}
 
 
extern uint64_t
lzma_delta_coder_memusage(const void *options)
{
    const lzma_options_delta *opt = options;
 
    if (opt == NULL || opt->type != LZMA_DELTA_TYPE_BYTE
            || opt->dist < LZMA_DELTA_DIST_MIN
            || opt->dist > LZMA_DELTA_DIST_MAX)
        return UINT64_MAX;
 
    return sizeof(lzma_delta_coder);
}