kble-c/src/level.c

/* SPDX-License-Identifier: GPL-3.0-or-later */
/* Copyright (C) 2021 KikooDX */

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

#include "level.h"

static const int kble_fmt_version = 0;

static char read_byte(FILE *file);
static tile_t read_byte_group(FILE *file, int size);
static void write_byte(FILE *file, char byte);
static void write_byte_group(FILE *file, tile_t value, int size);

void level_read(struct Level *level, char *path) {
	FILE *file = NULL;
	char byte = 0;
	unsigned int tile_size = 0;
	int level_size = 0;
	int i = 0;
	tile_t tile = 0;

	/* open file in read mode */
	file = fopen(path, "rb");
	if (file == NULL) {
		fprintf(stderr, "ERROR: cannot open input file %s\n", path);
		exit(EXIT_FAILURE);
	}

	/* check KBLE format version */
	byte = read_byte(file);
	if (byte != kble_fmt_version) {
		fprintf(stderr, "ERROR: KBLE format version doesn't match ; "
			"expected %d, got %d\n", kble_fmt_version, byte);
		exit(EXIT_FAILURE);
	}

	/* get tile size (in bytes) */
	tile_size = read_byte(file);
	/* check than tile size is in boundaries */
	if (tile_size > sizeof(tile_t) / sizeof(char)) {
    		fprintf(stderr, "ERROR: tile size is too big ; "
    			"maximum is %ld, found %d", sizeof(tile_t), tile_size);
    		exit(EXIT_FAILURE);
	}
	/* get width */
	level->width = read_byte_group(file, 2);
	/* get height */
	level->height = read_byte_group(file, 2);

	/* allocate memory for data */
	level_size = level->width * level->height;
	if (level->data == NULL) {
		level->data = malloc(level_size * sizeof(tile_t));
	} else {
		level->data = realloc(level->data, level_size * sizeof(tile_t));
	}
	/* check for allocation failure */
	if (level->data == NULL) {
		fprintf(stderr, "ERROR: memory allocation failure\n");
		exit(EXIT_FAILURE);
	}

	/* read file content */
	for (i = 0; i < level_size; i += 1) {
		tile = read_byte_group(file, tile_size);
		level->data[i] = tile;
	}

	/* close file */
	fclose(file);
}

void level_free(struct Level *level) {
	free(level->data);
}

void level_write(struct Level level, char *path) {
	FILE *file = NULL;
	int tile = 0;
	int tile_size = 0;
	int max_tile_size = 1;
	int i = 0;
	const int level_size = level.width * level.height;

	/* open file in write mode */
	file = fopen(path, "wb");
	if (file == NULL) {
		fprintf(stderr, "ERROR: cannot open output file %s\n", path);
		exit(EXIT_FAILURE);
	}

	/* find longest value in data (in bytes) */
	for (i = 0; i < level_size; i += 1) {
		tile = level.data[i];
		tile_size = 1;
		while (tile >>= 8)
			tile_size += 1;
		if (tile_size > max_tile_size)
			max_tile_size = tile_size;
	}

	/* write KBLE format version */
	write_byte(file, kble_fmt_version);
	/* write tile size (in bytes) */
	write_byte(file, max_tile_size);
	/* write width */
	write_byte_group(file, level.width, 2);
	/* write height */
	write_byte_group(file, level.height, 2);

	/* write level content */
	for (i = 0; i < level_size; i += 1) {
		write_byte_group(file, level.data[i], max_tile_size);
	}

	/* close file */
	fclose(file);
}

/* Read a single byte safely (handle EOF). */
static char read_byte(FILE *file) {
	const int byte = fgetc(file);
	if (byte == EOF) {
		fprintf(stderr, "ERROR: unexpected EOF\n");
		exit(EXIT_FAILURE);
	}
	return (char)byte;
}

/* Read multiple bytes and "merge" them into one integer. */
static tile_t read_byte_group(FILE *file, int size) {
	int group = 0;
	char *byte_ptr = (char*)&group;
	int i = 0;
	byte_ptr += size;
	for (i = 0; i < size; i += 1) {
		byte_ptr -= 1,
		*byte_ptr = read_byte(file);
	}
	return group;
}

/* Write a single byte safely (handle EOF). */
static void write_byte(FILE *file, char byte) {
	const int result = fputc(byte, file);
	if (result == EOF) {
		fprintf(stderr, "ERROR: file write error\n");
		exit(EXIT_FAILURE);
	}
}

/* Write an integer as multiple bytes. */
static void write_byte_group(FILE *file, tile_t value, int size) {
	char *value_ptr = (char*)&value;
	value_ptr += size;
	int i = 0;
	for (i = 0; i < size; i += 1) {
		value_ptr -= 1;
		write_byte(file, *value_ptr);
	}
}