/*
 * Copyright (c) 2009, 2010, 2013, 2014, 2021, 2022
 * Phillip Lougher <phillip@squashfs.org.uk>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2,
 * or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * gzip_wrapper.c
 *
 * Support for ZLIB compression http://www.zlib.net
 */

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <zlib.h>

#include "squashfs_fs.h"
#include "gzip_wrapper.h"
#include "compressor.h"

static struct strategy strategy[] = {
	{ "default", Z_DEFAULT_STRATEGY, 0 },
	{ "filtered", Z_FILTERED, 0 },
	{ "huffman_only", Z_HUFFMAN_ONLY, 0 },
	{ "run_length_encoded", Z_RLE, 0 },
	{ "fixed", Z_FIXED, 0 },
	{ NULL, 0, 0 }
};

static int strategy_count = 0;

/* default compression level */
static int compression_level = GZIP_DEFAULT_COMPRESSION_LEVEL;

/* default window size */
static int window_size = GZIP_DEFAULT_WINDOW_SIZE;

/*
 * This function is called by the options parsing code in mksquashfs.c
 * to parse any -X compressor option.
 *
 * This function returns:
 *	>=0 (number of additional args parsed) on success
 *	-1 if the option was unrecognised, or
 *	-2 if the option was recognised, but otherwise bad in
 *	   some way (e.g. invalid parameter)
 *
 * Note: this function sets internal compressor state, but does not
 * pass back the results of the parsing other than success/failure.
 * The gzip_dump_options() function is called later to get the options in
 * a format suitable for writing to the filesystem.
 */
static int gzip_options(char *argv[], int argc)
{
	if(strcmp(argv[0], "-Xcompression-level") == 0) {
		if(argc < 2) {
			fprintf(stderr, "gzip: -Xcompression-level missing "
				"compression level\n");
			fprintf(stderr, "gzip: -Xcompression-level it "
				"should be 1 >= n <= 9\n");
			goto failed;
		}

		compression_level = atoi(argv[1]);
		if(compression_level < 1 || compression_level > 9) {
			fprintf(stderr, "gzip: -Xcompression-level invalid, it "
				"should be 1 >= n <= 9\n");
			goto failed;
		}

		return 1;
	} else if(strcmp(argv[0], "-Xwindow-size") == 0) {
		if(argc < 2) {
			fprintf(stderr, "gzip: -Xwindow-size missing window "
				"	size\n");
			fprintf(stderr, "gzip: -Xwindow-size <window-size>\n");
			goto failed;
		}

		window_size = atoi(argv[1]);
		if(window_size < 8 || window_size > 15) {
			fprintf(stderr, "gzip: -Xwindow-size invalid, it "
				"should be 8 >= n <= 15\n");
			goto failed;
		}

		return 1;
	} else if(strcmp(argv[0], "-Xstrategy") == 0) {
		char *name;
		int i;

		if(argc < 2) {
			fprintf(stderr, "gzip: -Xstrategy missing "
							"strategies\n");
			goto failed;
		}

		name = argv[1];
		while(name[0] != '\0') {
			for(i = 0; strategy[i].name; i++) {
				int n = strlen(strategy[i].name);
				if((strncmp(name, strategy[i].name, n) == 0) &&
						(name[n] == '\0' ||
						 name[n] == ',')) {
					if(strategy[i].selected == 0) {
				 		strategy[i].selected = 1;
						strategy_count++;
					}
					name += name[n] == ',' ? n + 1 : n;
					break;
				}
			}
			if(strategy[i].name == NULL) {
				fprintf(stderr, "gzip: -Xstrategy unrecognised "
					"strategy\n");
				goto failed;
			}
		}
	
		return 1;
	}

	return -1;

failed:
	return -2;
}


/*
 * This function is called after all options have been parsed.
 * It is used to do post-processing on the compressor options using
 * values that were not expected to be known at option parse time.
 *
 * This function returns 0 on successful post processing, or
 *			-1 on error
 */
static int gzip_options_post(int block_size)
{
	if(strategy_count == 1 && strategy[0].selected) {
		strategy_count = 0;
		strategy[0].selected = 0;
	}

	return 0;
}


/*
 * This function is called by mksquashfs to dump the parsed
 * compressor options in a format suitable for writing to the
 * compressor options field in the filesystem (stored immediately
 * after the superblock).
 *
 * This function returns a pointer to the compression options structure
 * to be stored (and the size), or NULL if there are no compression
 * options
 *
 */
static void *gzip_dump_options(int block_size, int *size)
{
	static struct gzip_comp_opts comp_opts;
	int i, strategies = 0;

	/*
	 * If default compression options of:
	 * compression-level: 8 and
	 * window-size: 15 and
	 * strategy_count == 0 then
	 * don't store a compression options structure (this is compatible
	 * with the legacy implementation of GZIP for Squashfs)
	 */
	if(compression_level == GZIP_DEFAULT_COMPRESSION_LEVEL &&
				window_size == GZIP_DEFAULT_WINDOW_SIZE &&
				strategy_count == 0)
		return NULL;

	for(i = 0; strategy[i].name; i++)
		strategies |= strategy[i].selected << i;

	comp_opts.compression_level = compression_level;
	comp_opts.window_size = window_size;
	comp_opts.strategy = strategies;

	SQUASHFS_INSWAP_COMP_OPTS(&comp_opts);

	*size = sizeof(comp_opts);
	return &comp_opts;
}


/*
 * This function is a helper specifically for the append mode of
 * mksquashfs.  Its purpose is to set the internal compressor state
 * to the stored compressor options in the passed compressor options
 * structure.
 *
 * In effect this function sets up the compressor options
 * to the same state they were when the filesystem was originally
 * generated, this is to ensure on appending, the compressor uses
 * the same compression options that were used to generate the
 * original filesystem.
 *
 * Note, even if there are no compressor options, this function is still
 * called with an empty compressor structure (size == 0), to explicitly
 * set the default options, this is to ensure any user supplied
 * -X options on the appending mksquashfs command line are over-ridden
 *
 * This function returns 0 on sucessful extraction of options, and
 *			-1 on error
 */
static int gzip_extract_options(int block_size, void *buffer, int size)
{
	struct gzip_comp_opts *comp_opts = buffer;
	int i;

	if(size == 0) {
		/* Set default values */
		compression_level = GZIP_DEFAULT_COMPRESSION_LEVEL;
		window_size = GZIP_DEFAULT_WINDOW_SIZE;
		strategy_count = 0;
		return 0;
	}

	/* we expect a comp_opts structure of sufficient size to be present */
	if(size < sizeof(*comp_opts))
		goto failed;

	SQUASHFS_INSWAP_COMP_OPTS(comp_opts);

	/* Check comp_opts structure for correctness */
	if(comp_opts->compression_level < 1 ||
			comp_opts->compression_level > 9) {
		fprintf(stderr, "gzip: bad compression level in "
			"compression options structure\n");
		goto failed;
	}
	compression_level = comp_opts->compression_level;

	if(comp_opts->window_size < 8 ||
			comp_opts->window_size > 15) {
		fprintf(stderr, "gzip: bad window size in "
			"compression options structure\n");
		goto failed;
	}
	window_size = comp_opts->window_size;

	strategy_count = 0;
	for(i = 0; strategy[i].name; i++) {
		if((comp_opts->strategy >> i) & 1) {
			strategy[i].selected = 1;
			strategy_count ++;
		} else
			strategy[i].selected = 0;
	}
	
	return 0;

failed:
	fprintf(stderr, "gzip: error reading stored compressor options from "
		"filesystem!\n");

	return -1;
}


static void gzip_display_options(void *buffer, int size)
{
	struct gzip_comp_opts *comp_opts = buffer;
	int i, printed;

	/* we expect a comp_opts structure of sufficient size to be present */
	if(size < sizeof(*comp_opts))
		goto failed;

	SQUASHFS_INSWAP_COMP_OPTS(comp_opts);

	/* Check comp_opts structure for correctness */
	if(comp_opts->compression_level < 1 ||
			comp_opts->compression_level > 9) {
		fprintf(stderr, "gzip: bad compression level in "
			"compression options structure\n");
		goto failed;
	}
	printf("\tcompression-level %d\n", comp_opts->compression_level);

	if(comp_opts->window_size < 8 ||
			comp_opts->window_size > 15) {
		fprintf(stderr, "gzip: bad window size in "
			"compression options structure\n");
		goto failed;
	}
	printf("\twindow-size %d\n", comp_opts->window_size);

	for(i = 0, printed = 0; strategy[i].name; i++) {
		if((comp_opts->strategy >> i) & 1) {
			if(printed)
				printf(", ");
			else
				printf("\tStrategies selected: ");
			printf("%s", strategy[i].name);
			printed = 1;
		}
	}

	if(!printed)
		printf("\tStrategies selected: default\n");
	else
		printf("\n");

	return;

failed:
	fprintf(stderr, "gzip: error reading stored compressor options from "
		"filesystem!\n");
}	


/*
 * This function is called by mksquashfs to initialise the
 * compressor, before compress() is called.
 *
 * This function returns 0 on success, and
 *			-1 on error
 */
static int gzip_init(void **strm, int block_size, int datablock)
{
	int i, j, res;
	struct gzip_stream *stream;

	if(!datablock || !strategy_count) {
		stream = malloc(sizeof(*stream) + sizeof(struct gzip_strategy));
		if(stream == NULL)
			goto failed;

		stream->strategies = 1;
		stream->strategy[0].strategy = Z_DEFAULT_STRATEGY;
	} else {
		stream = malloc(sizeof(*stream) +
			sizeof(struct gzip_strategy) * strategy_count);
		if(stream == NULL)
			goto failed;

		memset(stream->strategy, 0, sizeof(struct gzip_strategy) *
			strategy_count);

		stream->strategies = strategy_count;

		for(i = 0, j = 0; strategy[i].name; i++) {
			if(!strategy[i].selected)
				continue;

			stream->strategy[j].strategy = strategy[i].strategy;
			if(j) {
				stream->strategy[j].buffer = malloc(block_size);
				if(stream->strategy[j].buffer == NULL)
					goto failed2;
			}
			j++;
		}
	}
		
	stream->stream.zalloc = Z_NULL;
	stream->stream.zfree = Z_NULL;
	stream->stream.opaque = 0;

	res = deflateInit2(&stream->stream, compression_level, Z_DEFLATED,
		window_size, 8, stream->strategy[0].strategy);
	if(res != Z_OK)
		goto failed2;

	*strm = stream;
	return 0;

failed2:
	for(i = 1; i < stream->strategies; i++)
		free(stream->strategy[i].buffer);
	free(stream);
failed:
	return -1;
}


static int gzip_compress(void *strm, void *d, void *s, int size, int block_size,
		int *error)
{
	int i, res;
	struct gzip_stream *stream = strm;
	struct gzip_strategy *selected = NULL;

	stream->strategy[0].buffer = d;

	for(i = 0; i < stream->strategies; i++) {
		struct gzip_strategy *strategy = &stream->strategy[i];

		res = deflateReset(&stream->stream);
		if(res != Z_OK)
			goto failed;

		stream->stream.next_in = s;
		stream->stream.avail_in = size;
		stream->stream.next_out = strategy->buffer;
		stream->stream.avail_out = block_size;

		if(stream->strategies > 1) {
			res = deflateParams(&stream->stream,
				compression_level, strategy->strategy);
			if(res != Z_OK)
				goto failed;
		}

		stream->stream.total_out = 0;
		res = deflate(&stream->stream, Z_FINISH);
		strategy->length = stream->stream.total_out;
		if(res == Z_STREAM_END) {
			if(!selected || selected->length > strategy->length)
				selected = strategy;
		} else if(res != Z_OK)
			goto failed;
	}

	if(!selected)
		/*
		 * Output buffer overflow.  Return out of buffer space
		 */
		return 0;

	if(selected->buffer != d)
		memcpy(d, selected->buffer, selected->length);

	return (int) selected->length;

failed:
	/*
	 * All other errors return failure, with the compressor
	 * specific error code in *error
	 */
	*error = res;
	return -1;
}


static int gzip_uncompress(void *d, void *s, int size, int outsize, int *error)
{
	int res;
	unsigned long bytes = outsize;

	res = uncompress(d, &bytes, s, size);

	if(res == Z_OK)
		return (int) bytes;
	else {
		*error = res;
		return -1;
	}
}


static void gzip_usage(FILE *stream)
{
	fprintf(stream, "\t  -Xcompression-level <compression-level>\n");
	fprintf(stream, "\t\t<compression-level> should be 1 .. 9 (default "
		"%d)\n", GZIP_DEFAULT_COMPRESSION_LEVEL);
	fprintf(stream, "\t  -Xwindow-size <window-size>\n");
	fprintf(stream, "\t\t<window-size> should be 8 .. 15 (default "
		"%d)\n", GZIP_DEFAULT_WINDOW_SIZE);
	fprintf(stream, "\t  -Xstrategy strategy1,strategy2,...,strategyN\n");
	fprintf(stream, "\t\tCompress using strategy1,strategy2,...,strategyN"
		" in turn\n");
	fprintf(stream, "\t\tand choose the best compression.\n");
	fprintf(stream, "\t\tAvailable strategies: default, filtered, "
		"huffman_only,\n\t\trun_length_encoded and fixed\n");
}


static int option_args(char *option)
{
	if(strcmp(option, "-Xcompression-level") == 0 ||
				strcmp(option, "-Xwindow-size") == 0 ||
				strcmp(option, "-Xstrategy") == 0)
		return 1;

	return 0;
}


struct compressor gzip_comp_ops = {
	.init = gzip_init,
	.compress = gzip_compress,
	.uncompress = gzip_uncompress,
	.options = gzip_options,
	.options_post = gzip_options_post,
	.dump_options = gzip_dump_options,
	.extract_options = gzip_extract_options,
	.display_options = gzip_display_options,
	.usage = gzip_usage,
	.option_args = option_args,
	.id = ZLIB_COMPRESSION,
	.name = "gzip",
	.supported = 1
};