Slightly refactor some C tools

tools/common.h

@@ -1,40 +1,132 @@
 #ifndef GUARD_COMMON_H
 #define GUARD_COMMON_H
 
-int __getopt_long_i__;
-#define getopt_long(c, v, s, l) getopt_long(c, v, s, l, &__getopt_long_i__)
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <inttypes.h>
+#include <string.h>
+#include <errno.h>
+#include <getopt.h>
 
-FILE *fopen_verbose(char *filename, char *mode) {
+#ifndef PROGRAM_NAME
+#error Define PROGRAM_NAME before including common.h!
+#endif
+#ifndef USAGE_OPTS
+#error Define USAGE_OPTS before including common.h!
+#endif
+
+#define error_exit(...) exit((fprintf(stderr, PROGRAM_NAME ": " __VA_ARGS__), 1))
+
+void usage_exit(int status) {
+	fprintf(stderr, "Usage: " PROGRAM_NAME " " USAGE_OPTS "\n");
+	exit(status);
+}
+
+int getopt_long_index;
+#define getopt_long(argc, argv, optstring, longopts) getopt_long(argc, argv, optstring, longopts, &getopt_long_index)
+
+void *xmalloc(size_t size) {
+	errno = 0;
+	void *m = malloc(size);
+	if (!m) {
+		error_exit("Could not allocate %zu bytes: %s\n", size, strerror(errno));
+	}
+	return m;
+}
+
+void *xcalloc(size_t size) {
+	errno = 0;
+	void *m = calloc(size, 1);
+	if (!m) {
+		error_exit("Could not allocate %zu bytes: %s\n", size, strerror(errno));
+	}
+	return m;
+}
+
+void *xrealloc(void *m, size_t size) {
+	errno = 0;
+	m = realloc(m, size);
+	if (!m) {
+		error_exit("Could not allocate %zu bytes: %s\n", size, strerror(errno));
+	}
+	return m;
+}
+
+FILE *xfopen(const char *filename, char rw) {
+	char mode[3] = {rw, 'b', '\0'};
+	errno = 0;
 	FILE *f = fopen(filename, mode);
 	if (!f) {
-		fprintf(stderr, "Could not open file: \"%s\"\n", filename);
+		error_exit("Could not open file \"%s\": %s\n", filename, strerror(errno));
 	}
 	return f;
 }
 
-uint8_t *read_u8(char *filename, int *size) {
-	FILE *f = fopen_verbose(filename, "rb");
-	if (!f) {
-		exit(1);
+void xfread(uint8_t *data, size_t size, const char *filename, FILE *f) {
+	errno = 0;
+	if (fread(data, 1, size, f) != size) {
+		fclose(f);
+		error_exit("Could not read from file \"%s\": %s\n", filename, strerror(errno));
 	}
-	fseek(f, 0, SEEK_END);
-	*size = ftell(f);
-	rewind(f);
-	uint8_t *data = malloc(*size);
-	if (*size != (int)fread(data, 1, *size, f)) {
-		fprintf(stderr, "Could not read file: \"%s\"\n", filename);
-		exit(1);
+}
+
+void xfwrite(const uint8_t *data, size_t size, const char *filename, FILE *f) {
+	errno = 0;
+	if (fwrite(data, 1, size, f) != size) {
+		fclose(f);
+		error_exit("Could not write to file \"%s\": %s\n", filename, strerror(errno));
 	}
+}
+
+long xfsize(const char *filename, FILE *f) {
+	long size = -1;
+	errno = 0;
+	if (!fseek(f, 0, SEEK_END)) {
+		size = ftell(f);
+		if (size != -1) {
+			rewind(f);
+		}
+	}
+	if (size == -1) {
+		error_exit("Could not measure file \"%s\": %s\n", filename, strerror(errno));
+	}
+	return size;
+}
+
+uint8_t *read_u8(const char *filename, long *size) {
+	FILE *f = xfopen(filename, 'r');
+	*size = xfsize(filename, f);
+	uint8_t *data = xmalloc(*size);
+	xfread(data, *size, filename, f);
 	fclose(f);
 	return data;
 }
 
-void write_u8(char *filename, uint8_t *data, int size) {
-	FILE *f = fopen_verbose(filename, "wb");
-	if (f) {
-		fwrite(data, 1, size, f);
+void write_u8(const char *filename, uint8_t *data, size_t size) {
+	FILE *f = xfopen(filename, 'w');
+	xfwrite(data, size, filename, f);
+	fclose(f);
+}
+
+uint32_t read_png_width(const char *filename) {
+	FILE *f = xfopen(filename, 'r');
+	uint8_t header[16] = {0};
+	xfread(header, sizeof(header), filename, f);
+	static uint8_t expected_header[16] = {
+		0x89, 'P', 'N', 'G', '\r', '\n', 0x1A, '\n', // signature
+		0, 0, 0, 13,                                 // IHDR chunk length
+		'I', 'H', 'D', 'R',                          // IHDR chunk type
+	};
+	if (memcmp(header, expected_header, sizeof(header))) {
 		fclose(f);
+		error_exit("Not a valid PNG file: \"%s\"\n", filename);
 	}
+	uint8_t bytes[4] = {0};
+	xfread(bytes, sizeof(bytes), filename, f);
+	fclose(f);
+	return (bytes[0] << 24) | (bytes[1] << 16) | (bytes[2] << 8) | bytes[3];
 }
 
 #endif // GUARD_COMMON_H