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      1 // SPDX-License-Identifier: 0BSD
      2 
      3 ///////////////////////////////////////////////////////////////////////////////
      4 //
      5 /// \file       delta_common.c
      6 /// \brief      Common stuff for Delta encoder and decoder
      7 //
      8 //  Author:     Lasse Collin
      9 //
     10 ///////////////////////////////////////////////////////////////////////////////
     11 
     12 #include "delta_common.h"
     13 #include "delta_private.h"
     14 
     15 
     16 static void
     17 delta_coder_end(void *coder_ptr, const lzma_allocator *allocator)
     18 {
     19 	lzma_delta_coder *coder = coder_ptr;
     20 	lzma_next_end(&coder->next, allocator);
     21 	lzma_free(coder, allocator);
     22 	return;
     23 }
     24 
     25 
     26 extern lzma_ret
     27 lzma_delta_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
     28 		const lzma_filter_info *filters)
     29 {
     30 	// Allocate memory for the decoder if needed.
     31 	lzma_delta_coder *coder = next->coder;
     32 	if (coder == NULL) {
     33 		coder = lzma_alloc(sizeof(lzma_delta_coder), allocator);
     34 		if (coder == NULL)
     35 			return LZMA_MEM_ERROR;
     36 
     37 		next->coder = coder;
     38 
     39 		// End function is the same for encoder and decoder.
     40 		next->end = &delta_coder_end;
     41 		coder->next = LZMA_NEXT_CODER_INIT;
     42 	}
     43 
     44 	// Validate the options.
     45 	if (lzma_delta_coder_memusage(filters[0].options) == UINT64_MAX)
     46 		return LZMA_OPTIONS_ERROR;
     47 
     48 	// Set the delta distance.
     49 	const lzma_options_delta *opt = filters[0].options;
     50 	coder->distance = opt->dist;
     51 
     52 	// Initialize the rest of the variables.
     53 	coder->pos = 0;
     54 	memzero(coder->history, LZMA_DELTA_DIST_MAX);
     55 
     56 	// Initialize the next decoder in the chain, if any.
     57 	return lzma_next_filter_init(&coder->next, allocator, filters + 1);
     58 }
     59 
     60 
     61 extern uint64_t
     62 lzma_delta_coder_memusage(const void *options)
     63 {
     64 	const lzma_options_delta *opt = options;
     65 
     66 	if (opt == NULL || opt->type != LZMA_DELTA_TYPE_BYTE
     67 			|| opt->dist < LZMA_DELTA_DIST_MIN
     68 			|| opt->dist > LZMA_DELTA_DIST_MAX)
     69 		return UINT64_MAX;
     70 
     71 	return sizeof(lzma_delta_coder);
     72 }
     73