path: root/src/gzip.c

/*
 * Copyright (C) 2023  Patrick McDermott
 *
 * This file is part of opkg-opkg.
 *
 * opkg-opkg 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 3 of the License, or
 * (at your option) any later version.
 *
 * opkg-opkg 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 opkg-opkg.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stdlib.h>
#include <zlib.h>
#include "defs.h"
#include "gzip.h"
#include "ustar.h"

#define OPKG_OPK_GZIP_WINDOW_BITS_ (15 + 16)

enum _opkg_opk_gzip_dir {
	_OPKG_OPK_GZIP_DIR_READ,
	_OPKG_OPK_GZIP_DIR_WRITE,
};

struct opkg_opk_gzip {
	enum _opkg_opk_gzip_dir   dir;
	char                     *buffer;
	size_t                    buffer_size;
	opkg_opk_gzip_read_func  *read_func;
	opkg_opk_gzip_write_func *write_func;
	void                     *user_data;
	z_stream                  stream;
	gz_header                 gz_header;
};

static struct opkg_opk_gzip *
_opkg_opk_gzip_init(enum _opkg_opk_gzip_dir dir,
		opkg_opk_gzip_read_func *read_func,
		opkg_opk_gzip_write_func *write_func, void *user_data)
{
	struct opkg_opk_gzip *gzip;

	gzip = malloc(sizeof(*gzip));
	if (gzip == NULL) {
		return NULL;
	}

	gzip->dir        = dir;
	gzip->read_func  = read_func;
	gzip->write_func = write_func;
	gzip->user_data  = user_data;

	gzip->stream.zalloc   = Z_NULL;
	gzip->stream.zfree    = Z_NULL;
	gzip->stream.opaque   = Z_NULL;

	if (dir == _OPKG_OPK_GZIP_DIR_READ) {
		gzip->stream.next_in  = Z_NULL;
		gzip->stream.avail_in = 0;
		if (inflateInit2(&gzip->stream, OPKG_OPK_GZIP_WINDOW_BITS_) !=
				Z_OK) {
			free(gzip);
			return NULL;
		}
	} else {
		gzip->stream.next_out  = Z_NULL;
		gzip->stream.avail_out = 0;
		if (deflateInit2(&gzip->stream, 9, Z_DEFLATED,
					OPKG_OPK_GZIP_WINDOW_BITS_, 9,
					Z_DEFAULT_STRATEGY) != Z_OK) {
			free(gzip);
			return NULL;
		}
		gzip->gz_header.text    = 0;
		gzip->gz_header.time    = 0;       /* Stored as 32-bit uint */
		gzip->gz_header.os      = 3;       /* Unix, per RFC 1952 */
		gzip->gz_header.extra   = Z_NULL;
		gzip->gz_header.name    = Z_NULL;
		gzip->gz_header.comment = Z_NULL;
		gzip->gz_header.hcrc    = 0;
		if (deflateSetHeader(&gzip->stream, &gzip->gz_header) != Z_OK) {
			deflateEnd(&gzip->stream);
			free(gzip);
			return NULL;
		}
	}

	return gzip;
}

struct opkg_opk_gzip *
opkg_opk_gzip_init_read(opkg_opk_gzip_read_func *read, void *user_data)
{
	return _opkg_opk_gzip_init(_OPKG_OPK_GZIP_DIR_READ,
			read, NULL, user_data);
}

struct opkg_opk_gzip *
opkg_opk_gzip_init_write(opkg_opk_gzip_write_func *write, void *user_data)
{
	return _opkg_opk_gzip_init(_OPKG_OPK_GZIP_DIR_WRITE,
			NULL, write, user_data);
}

int
opkg_opk_gzip_set_write_buffer(struct opkg_opk_gzip *gzip, char *buffer,
		size_t size)
{
	gzip->buffer      = buffer;
	gzip->buffer_size = size;
	return OPKG_OPK_OK;
}

int
opkg_opk_gzip_read(struct opkg_opk_gzip *gzip, void *record)
{
	int end;

	/* Sanity check */
	if (gzip->dir != _OPKG_OPK_GZIP_DIR_READ) {
		return OPKG_OPK_ERROR;
	}

	gzip->stream.next_out  = record;
	gzip->stream.avail_out = OPKG_OPK_USTAR_RECORD_SIZE;

	for (;;) {
		end = 0;
		if (gzip->stream.avail_in == 0) {
			/* Input buffer is empty and needs refilled. */
			switch (gzip->read_func(gzip->user_data,
						(char **) &gzip->stream.next_in,
						(size_t *) &gzip->stream.
							avail_in)) {
				case OPKG_OPK_OK:
					break;
				case OPKG_OPK_END:
					end = 1;
					break;
				case OPKG_OPK_ERROR:
				default:
					return OPKG_OPK_ERROR;
			}
		}
		switch (inflate(&gzip->stream, Z_SYNC_FLUSH)) {
			case Z_OK:
				break;
			case Z_BUF_ERROR:
				if (end == 1) {
					return OPKG_OPK_ERROR;
				}
				break;
			case Z_STREAM_END:
				if (gzip->stream.avail_out != 0) {
					/* Premature end */
					return OPKG_OPK_ERROR;
				}
				return OPKG_OPK_END;
			default:
				return OPKG_OPK_ERROR;
		}
		if (gzip->stream.avail_out == 0) {
			/* Output buffer is filled and ready for use. */
			return OPKG_OPK_OK;
		}
	}
}

int
opkg_opk_gzip_write(struct opkg_opk_gzip *gzip, void *record, size_t size,
		int last)
{
//	memcpy(gzip->buffer, record, size);
//	gzip->write_func(gzip->user_data, size);
//	if (last == 0) {
//		return OPKG_OPK_OK;
//	} else {
//		return OPKG_OPK_END;
//	}

	/* Sanity check */
	if (gzip->dir != _OPKG_OPK_GZIP_DIR_WRITE) {
		return OPKG_OPK_ERROR;
	}

	gzip->stream.next_in  = record;
	gzip->stream.avail_in = size;

	do {
		gzip->stream.next_out  = gzip->buffer;
		gzip->stream.avail_out = gzip->buffer_size;
		switch (deflate(&gzip->stream,
					(last > 0 ? Z_FINISH : Z_NO_FLUSH))) {
			case Z_OK:
			case Z_BUF_ERROR:
			case Z_STREAM_END:
				break;
			default:
				return OPKG_OPK_ERROR;
		}
		/* Process output buffer. */
		switch (gzip->write_func(gzip->user_data,
					gzip->buffer_size
					- gzip->stream.avail_out)) {
			case OPKG_OPK_OK:
				break;
			case OPKG_OPK_END:
			case OPKG_OPK_ERROR:
			default:
				return OPKG_OPK_ERROR;
		}
	} while (gzip->stream.avail_out == 0);

	if (gzip->stream.avail_in != 0) {
		return OPKG_OPK_ERROR;
	}
	if (last == 0) {
		/* Input buffer is empty and needs refilled. */
		return OPKG_OPK_OK;
	} else {
		return OPKG_OPK_END;
	}
}

int
opkg_opk_gzip_free(struct opkg_opk_gzip *gzip)
{
	int ret;

	ret = OPKG_OPK_OK;
	if (gzip->dir == _OPKG_OPK_GZIP_DIR_READ) {
		if (inflateEnd(&gzip->stream) != Z_OK) {
			ret = OPKG_OPK_ERROR;
		}
	} else {
		if (deflateEnd(&gzip->stream) != Z_OK) {
			ret = OPKG_OPK_ERROR;
		}
	}
	free(gzip);
	return ret;
}

#if 0  /* Test code */

/*
 * echo 2.0 >debian-binary
 * tar -cf test.tar debian-binary          # if using GNU tar...
 * truncate -s 2048 test.tar               # ...remove extra trailer records
 * busybox tar -cf test.tar debian-binary  # or just use BB tar
 * flags=$(pkg-config --cflags --libs zlib)
 * gcc -Wall -Wextra -pedantic -g -O0 -o gzip src/gzip.c ${flags}
 * ./gzip test.tar test.tar.gz
 * gunzip -c test.tar.gz 1>test.tar.ungz
 * ls -l test.tar*             # test.tar and test.tar.ungz should be 2048 bytes
 *                             # test.tar.gz should be 108 bytes or so
 * cmp test.tar test.tar.ungz  # should be quiet
 * bvi test.tar.gz             # compare to RFC 1952
 * gzip -9cn test.tar 1>test.tar.gzip
 * ls -l test.tar.gz*          # both should be 108 bytes or so
 * cmp test.tar.gz*            # should be quiet
 */

#include <stdio.h>

FILE *_out_fp;
char  _out_buffer[8192];

static int
_write(void *user_data __attribute__((__unused__)), size_t size)
{
	if (fwrite(_out_buffer, 1, size, _out_fp) == size) {
		return OPKG_OPK_OK;
	} else {
		return OPKG_OPK_ERROR;
	}
}

int
main(int argc __attribute__((__unused__)), char *argv[])
{
	int                   ret;
	FILE                 *in_fp;
	char                  in_buffer[512];
	struct opkg_opk_gzip *gzip;
	size_t                in_size;

	ret = EXIT_SUCCESS;
	in_fp = fopen(argv[1], "rb");
	if (in_fp == NULL) {
		fputs("Error opening input", stderr);
		ret = EXIT_FAILURE;
		goto out0;
	}
	_out_fp = fopen(argv[2], "wb");
	if (_out_fp == NULL) {
		fputs("Error opening output", stderr);
		ret = EXIT_FAILURE;
		goto out1;
	}
	gzip = opkg_opk_gzip_init_write(_write, NULL);
	if (gzip == NULL) {
		fputs("Error initializing compressor", stderr);
		ret = EXIT_FAILURE;
		goto out2;
	}
	opkg_opk_gzip_set_write_buffer(gzip, _out_buffer, sizeof(_out_buffer));
	while ((in_size = fread(in_buffer, 1, sizeof(in_buffer), in_fp)) > 0) {
		if (opkg_opk_gzip_write(gzip, in_buffer, in_size, 0) !=
				OPKG_OPK_OK) {
			fputs("Error compressing", stderr);
			ret = EXIT_FAILURE;
			goto out3;
		}
	}
	if (feof(in_fp)) {
		if (opkg_opk_gzip_write(gzip, in_buffer, in_size, 1) !=
				OPKG_OPK_END) {
			fputs("Error finishing compression", stderr);
			ret = EXIT_FAILURE;
			goto out3;
		}
	}
 out3:
	if (opkg_opk_gzip_free(gzip) != OPKG_OPK_OK) {
		fputs("Error freeing compressor", stderr);
		ret = EXIT_FAILURE;
	}
 out2:
	fclose(_out_fp);
 out1:
	fclose(in_fp);
 out0:
	return ret;
}

#endif