1 files changed, 78 insertions, 0 deletions
diff --git a/gzip2deflate.c b/gzip2deflate.c
new file mode 100644
index 0000000..7edf6ac
--- /dev/null
+++ b/gzip2deflate.c
@@ -0,0 +1,78 @@
+// gzip2deflate by Piotr Fusik <fox@scene.pl>
+// http://xasm.atari.org
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#ifdef __WIN32
+#include <fcntl.h>
+#endif
+
+static int get_byte(void)
+{
+	int b = getchar();
+	if (b == EOF) {
+		fputs("gzip2deflate: unexpected end of stream\n", stderr);
+		exit(1);
+	}
+	return b;
+}
+
+static void skip_bytes(int n)
+{
+	while (--n >= 0)
+		get_byte();
+}
+
+static void skip_string(void)
+{
+	while (get_byte() != 0);
+}
+
+int main (int argc, char *argv[])
+{
+	int flg;
+	char buf[8 + 4096];
+	size_t len;
+#ifdef __WIN32
+	_setmode(_fileno(stdin), _O_BINARY);
+	_setmode(_fileno(stdout), _O_BINARY);
+#endif
+	if (get_byte() != 0x1f || get_byte() != 0x8b || get_byte() != 8) {
+		fputs("gzip2deflate: not a gzip file on stdin\n", stderr);
+		return 1;
+	}
+	flg = get_byte();
+	skip_bytes(6);
+	if ((flg & 4) != 0) {
+		int xlen = get_byte();
+		xlen += get_byte() << 8;
+		skip_bytes(xlen);
+	}
+	if ((flg & 8) != 0)
+		skip_string();
+	if ((flg & 16) != 0)
+		skip_string();
+	if ((flg & 2) != 0)
+		skip_bytes(2);
+	/* copy everything except the last 8 bytes */
+	len = 0;
+	for (;;) {
+		len += fread(buf + len, 1, sizeof(buf) - len, stdin);
+		if (len != sizeof(buf))
+			break;
+		fwrite(buf, 1, sizeof(buf) - 8, stdout);
+		memcpy(buf, buf + sizeof(buf) - 8, 8);
+		len = 8;
+	}
+	if (ferror(stdin)) {
+		fputs("gzip2deflate: read error\n", stderr);
+		return 1;
+	}
+	if (len < 8) {
+		fputs("gzip2deflate: unexpected end of stream\n", stderr);
+		return 1;
+	}
+	fwrite(buf, 1, len - 8, stdout);
+	return 0;
+}