src/liblzma/lzma/fastpos_tablegen.c

// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////
//
/// \file       fastpos_tablegen.c
/// \brief      Generates the lzma_fastpos[] lookup table
///
//  Authors:    Igor Pavlov
//              Lasse Collin
//
///////////////////////////////////////////////////////////////////////////////

#include <inttypes.h>
#include <stdio.h>

#define lzma_attr_visibility_hidden
#include "fastpos.h"


int
main(void)
{
	uint8_t fastpos[1 << FASTPOS_BITS];

	const uint8_t fast_slots = 2 * FASTPOS_BITS;
	uint32_t c = 2;

	fastpos[0] = 0;
	fastpos[1] = 1;

	for (uint8_t slot_fast = 2; slot_fast < fast_slots; ++slot_fast) {
		const uint32_t k = 1 << ((slot_fast >> 1) - 1);
		for (uint32_t j = 0; j < k; ++j, ++c)
			fastpos[c] = slot_fast;
	}

	// Split the SPDX string so that it won't accidentally match
	// when tools search for the string.
	printf("// SPDX" "-License-Identifier" ": 0BSD\n\n"
		"// This file has been generated by fastpos_tablegen.c.\n\n"
		"#include \"common.h\"\n"
		"#include \"fastpos.h\"\n\n"
		"const uint8_t lzma_fastpos[1 << FASTPOS_BITS] = {");

	for (size_t i = 0; i < (1 << FASTPOS_BITS); ++i) {
		if (i % 16 == 0)
			printf("\n\t");

		printf("%3u", (unsigned int)(fastpos[i]));

		if (i != (1 << FASTPOS_BITS) - 1)
			printf(",");
	}

	printf("\n};\n");

	return 0;
}