libg1m/src/decode/std/picture.c

/* *****************************************************************************
 * decode/std/picture.c -- decode a picture file.
 * Copyright (C) 2017 Thomas "Cakeisalie5" Touhey <thomas@touhey.fr>
 *
 * This file is part of libg1m.
 * libg1m is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 3.0 of the License,
 * or (at your option) any later version.
 *
 * libg1m 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with libg1m; if not, see <http://www.gnu.org/licenses/>.
 * ************************************************************************** */
#include <libg1m/internals.h>
#include <zlib.h>

/**
 *	g3p_deobfuscate:
 *	De-obfuscate the image data.
 *
 *	@arg	buf			the buffer.
 *	@arg	n			the buffer size.
 */

static void g3p_deobfuscate(uint8_t *buf, size_t n)
{
	while (n--) {
		int byte = *buf;
		*buf++ = (byte >> 3) | ((byte & 0x7) << 5);
	}
}

/**
 *	g1m_decode_std_g3p:
 *	Decode a G3P file.
 *
 *	@arg	handle		the handle.
 *	@arg	buffer		the buffer to read from.
 *	@arg	std			the standard header.
 *	@return				the error code (0 if ok).
 */

int g1m_decode_std_g3p(g1m_t **h, g1m_buffer_t *buffer,
	struct standard_header *std)
{
	/* get the G3P global header */
	DREAD(hd, g3p_subheader)
	hd.g3p_size = be32toh(hd.g3p_size);

	/* check magic */
	if (memcmp(hd.magic, "CP", 2)) {
		log_fatal("could not read 'CP'.");
		return (g1m_error_magic);
	}

	/* read the image header */
	DREAD(ihd, g3p_imageheader)
	ihd.df_size = be32toh(ihd.df_size);
	ihd.width = be16toh(ihd.width);
	ihd.height = be16toh(ihd.height);
	ihd.color_depth = be16toh(ihd.color_depth);
	ihd.data_size = be32toh(ihd.data_size);

	/* check some little things */
	int is_obfuscated =
		((std->obfuscated + 8) & 0xff) != ((std->filesize & 0xff00) >> 8);
	int has_footer = 1; /* might change? */
	size_t deflated_image_size = ihd.data_size - has_footer * 0x4;

	/* log info */
	log_info("Width: %" PRIu16 "px, height: %" PRIu16 "px",
		ihd.width, ihd.height);
	log_info("Pixel depth: %s",
		(ihd.color_depth == g3p_color_4bit) ? "4-bit" : "16-bit");
	log_info("Deflated image length: %" PRIuSIZE "o", deflated_image_size);
	log_info("Is obfuscated: %s", is_obfuscated ? "yes" : "no");

	/* read image */
	uint8_t deflated_image[deflated_image_size];
	READ(deflated_image, deflated_image_size)

	/* read footer and check sum */
	if (has_footer) {
		DREAD(ft, g3p_imagefooter);
		ft.checksum = be32toh(ft.checksum);

		uLong adl = adler32(0, deflated_image, deflated_image_size);
		if (adl != ft.checksum) {
			log_fatal("Incorrect Adler32 checksum!");
			log_fatal("Expected %" PRIu32 ", got %lu",
				ft.checksum, adl);
			return (g1m_error_magic);
		}
	}

	/* unobfuscate if required */
	if (is_obfuscated)
		g3p_deobfuscate(deflated_image, deflated_image_size);

	/* find out length of inflated data */
	uLongf inflated_size = 0L; int z_err;
	if ((z_err = uncompress(Z_NULL, &inflated_size, deflated_image,
		deflated_image_size)) != Z_MEM_ERROR) {
		log_fatal("Zlib error: error #%d", z_err);
		return (g1m_error_magic);
	}
	log_info("Inflated image size is %lu", inflated_size);

	/* allocate space for it, and uncompress */
	uint8_t inflated_image[inflated_size];
	if ((z_err = uncompress(inflated_image, &inflated_size, deflated_image,
		deflated_image_size))) {
		log_fatal("Zlib error: error #%d", z_err);
		return (g1m_error_magic);
	}

	/* allocate picture in handle */
	int err = g1m_make_picture(h, ihd.width, ihd.height);
	if (err) return (err);
	g1m_t *handle = *h;

	/* then store it */
	g1m_decode_picture(handle->pixels, ihd.color_depth == g3p_color_4bit
		? g1m_pictureformat_4bit_code : g1m_pictureformat_16bit,
		inflated_image, handle->width, handle->height);

	/* no error */
	return (0);
}

/**
 *	g1m_decode_std_c2p:
 *	Decode Classpad images.
 *
 *	@arg	handle		the handle.
 *	@arg	buffer		the buffer to read from.
 *	@return				the error code (0 if ok).
 */

int g1m_decode_std_c2p(g1m_t **h, g1m_buffer_t *buffer,
	struct standard_header *std)
{
	(void)std;
	(void)h;
	(void)buffer;
	/* TODO */
	log_info("C2P files are not managed yet.");
	log_info("Size is %" PRIuSIZE "B", sizeof(struct c2p_subheader));

	/* no error */
	return (g1m_error_magic);
}