[zlib] Add support for zlib archive images

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

src/include/ipxe/errfile.h

@@ -302,6 +302,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_der		      ( ERRFILE_IMAGE | 0x00080000 )
 #define ERRFILE_pem		      ( ERRFILE_IMAGE | 0x00090000 )
 #define ERRFILE_archive		      ( ERRFILE_IMAGE | 0x000a0000 )
+#define ERRFILE_zlib		      ( ERRFILE_IMAGE | 0x000b0000 )
 
 #define ERRFILE_asn1		      ( ERRFILE_OTHER | 0x00000000 )
 #define ERRFILE_chap		      ( ERRFILE_OTHER | 0x00010000 )

src/include/ipxe/zlib.h

@@ -0,0 +1,43 @@
+#ifndef _IPXE_ZLIB_H
+#define _IPXE_ZLIB_H
+
+/** @file
+ *
+ * zlib compressed images
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <stdint.h>
+#include <byteswap.h>
+#include <ipxe/image.h>
+#include <ipxe/deflate.h>
+
+/** zlib magic header */
+union zlib_magic {
+	/** Compression method and flags */
+	uint8_t cmf;
+	/** Check value */
+	uint16_t check;
+} __attribute__ (( packed ));
+
+/**
+ * Check that zlib magic header is valid
+ *
+ * @v magic		Magic header
+ * @ret is_valid	Magic header is valid
+ */
+static inline int zlib_magic_is_valid ( union zlib_magic *magic ) {
+
+	/* Check magic value as per RFC 6713 */
+	return ( ( ( magic->cmf & 0x8f ) == 0x08 ) &&
+		 ( ( be16_to_cpu ( magic->check ) % 31 ) == 0 ) );
+}
+
+extern int zlib_deflate ( enum deflate_format format, struct deflate_chunk *in,
+			  struct image *extracted );
+
+extern struct image_type zlib_image_type __image_type ( PROBE_NORMAL );
+
+#endif /* _IPXE_ZLIB_H */