Command-line converter from ZIP to DEFLATE.

zip2deflate.c

@@ -0,0 +1,82 @@
+// zip2deflate 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("zip2deflate: unexpected end of stream\n", stderr);
+		exit(1);
+	}
+	return b;
+}
+
+static void skip_bytes(size_t n)
+{
+	for (; n > 0; n--)
+		get_byte();
+}
+
+static size_t get_word(void)
+{
+	size_t lo = get_byte();
+	return lo + (get_byte() << 8);
+}
+
+static size_t get_long(void)
+{
+	size_t lo = get_word();
+	return lo + (get_word() << 16);
+}
+
+int main (int argc, char *argv[])
+{
+	size_t compressed_size;
+	size_t filename_length;
+	size_t extra_field_length;
+#ifdef _WIN32
+	_setmode(_fileno(stdin), _O_BINARY);
+	_setmode(_fileno(stdout), _O_BINARY);
+#endif
+	if (get_long() != 0x04034b50) {
+		fputs("zip2deflate: not a ZIP file on stdin\n", stderr);
+		return 1;
+	}
+	if (get_word() != 20 /* version needed to extract */
+	 || (get_word() & 0x41) != 0 /* general purpose bit flag */
+	 || get_word() != 8 /* compression method */
+	) {
+		fputs("zip2deflate: unexpected header (not compressed? encrypted?)\n", stderr);
+		return 1;
+	}
+	skip_bytes(8); /* last mod file time, date, crc-32 */
+	compressed_size = get_long();
+	skip_bytes(4); /* uncompressed size */
+	filename_length = get_word();
+	extra_field_length = get_word();
+	skip_bytes(filename_length + extra_field_length);
+	while (compressed_size > 0) {
+		char buf[4096];
+		size_t len = compressed_size < 4096 ? compressed_size : 4096;
+		len = fread(buf, 1, len, stdin);
+		if (len == 0) {
+			fputs("zip2deflate: unexpected end of stream\n", stderr);
+			return 1;
+		}
+		fwrite(buf, 1, len, stdout);
+		compressed_size -= len;
+	}
+
+	if (get_long() != 0x02014b50) {
+		fputs("zip2deflate: unexpected header (more than one file?)\n", stderr);
+		return 1;
+	}
+	return 0;
+}