1 files changed, 60 insertions, 0 deletions
diff --git a/xex1to2.c b/xex1to2.c
new file mode 100644
index 0000000..36a33a2
--- /dev/null
+++ b/xex1to2.c
@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+
+#define SELF "xex1to2"
+
+FILE *open_file(const char *name, const char *mode) {
+	FILE *f = fopen(name, mode);
+	if(f) return f;
+
+	fprintf(stderr, SELF ": %s: %s\n", name, strerror(errno));
+	exit(1);
+}
+
+void invalid(void) {
+	fprintf(stderr, SELF ": input is not a valid Atari DOS 1.0 executable.\n");
+	exit(1);
+}
+
+void read_header(FILE *in) {
+	int c;
+
+	c = getc(in);
+	if(c < 0 || c != 0x84) invalid();
+	c = getc(in);
+	if(c < 0 || c != 0x09) invalid();
+}
+
+int main(int argc, char **argv) {
+	int c;
+	FILE *in = stdin, *out = stdout;
+
+	if(argc > 3) {
+		fprintf(stderr, "Usage: " SELF " [dos1_input.xex] [dos2_output.xex]\n");
+		exit(1);
+	}
+
+	if(argc > 1) in  = open_file(argv[1], "rb");
+	if(argc > 2) out = open_file(argv[2], "wb");
+
+	if(isatty(fileno(out))) {
+		fprintf(stderr,
+				SELF ": Standard output is a terminal; not writing binary data\n");
+		exit(1);
+	}
+
+	read_header(in);
+	fputc(0xff, out);
+	fputc(0xff, out);
+
+	while( (c = fgetc(in)) >= 0 )
+		fputc(c, out);
+
+	fclose(in);
+	fclose(out);
+
+	return 0;
+}