[gzip] Add support for gzip archive images

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/errfile.h

@@ -303,6 +303,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_pem		      ( ERRFILE_IMAGE | 0x00090000 )
 #define ERRFILE_archive		      ( ERRFILE_IMAGE | 0x000a0000 )
 #define ERRFILE_zlib		      ( ERRFILE_IMAGE | 0x000b0000 )
+#define ERRFILE_gzip		      ( ERRFILE_IMAGE | 0x000c0000 )
 
 #define ERRFILE_asn1		      ( ERRFILE_OTHER | 0x00000000 )
 #define ERRFILE_chap		      ( ERRFILE_OTHER | 0x00010000 )

src/include/ipxe/gzip.h

@@ -0,0 +1,71 @@
+#ifndef _IPXE_GZIP_H
+#define _IPXE_GZIP_H
+
+/** @file
+ *
+ * gzip compressed images
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <ipxe/image.h>
+
+/** gzip header */
+struct gzip_header {
+	/** Magic ID */
+	uint16_t magic;
+	/** Compression method */
+	uint8_t method;
+	/** Flags */
+	uint8_t flags;
+	/** Modification time */
+	uint32_t mtime;
+	/** Extra flags */
+	uint8_t extra;
+	/** Operating system */
+	uint8_t os;
+} __attribute__ (( packed ));
+
+/** Magic ID */
+#define GZIP_MAGIC 0x1f8b
+
+/** Compression method */
+#define GZIP_METHOD_DEFLATE 0x08
+
+/** CRC header is present */
+#define GZIP_FL_HCRC 0x02
+
+/** Extra header is present */
+#define GZIP_FL_EXTRA 0x04
+
+/** File name is present */
+#define GZIP_FL_NAME 0x08
+
+/** File comment is present */
+#define GZIP_FL_COMMENT 0x10
+
+/** gzip extra header */
+struct gzip_extra_header {
+	/** Extra header length (excluding this field) */
+	uint16_t len;
+} __attribute__ (( packed ));
+
+/** gzip CRC header */
+struct gzip_crc_header {
+	/** CRC-16 */
+	uint16_t crc;
+} __attribute__ (( packed ));
+
+/** gzip footer */
+struct gzip_footer {
+	/** CRC-32 */
+	uint32_t crc;
+	/** Uncompressed size (modulo 2^32) */
+	uint32_t len;
+} __attribute__ (( packed ));
+
+extern struct image_type gzip_image_type __image_type ( PROBE_NORMAL );
+
+#endif /* _IPXE_GZIP_H */