[image] Add "imgextract" command for extracting archive images

Add the concept of extracting an image from an archive (which could be
a single-file archive such as a gzip-compressed file), along with an
"imgextract" command to expose this functionality to scripts.

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

src/include/ipxe/errfile.h

@@ -301,6 +301,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_png		      ( ERRFILE_IMAGE | 0x00070000 )
 #define ERRFILE_der		      ( ERRFILE_IMAGE | 0x00080000 )
 #define ERRFILE_pem		      ( ERRFILE_IMAGE | 0x00090000 )
+#define ERRFILE_archive		      ( ERRFILE_IMAGE | 0x000a0000 )
 
 #define ERRFILE_asn1		      ( ERRFILE_OTHER | 0x00000000 )
 #define ERRFILE_chap		      ( ERRFILE_OTHER | 0x00010000 )

src/include/ipxe/image.h

@@ -113,6 +113,14 @@ struct image_type {
 	 */
 	int ( * asn1 ) ( struct image *image, size_t offset,
 			 struct asn1_cursor **cursor );
+	/**
+	 * Extract archive image
+	 *
+	 * @v image		Image
+	 * @v extracted		Extracted image
+	 * @ret rc		Return status code
+	 */
+	int ( * extract ) ( struct image *image, struct image *extracted );
 };
 
 /**
@@ -190,6 +198,8 @@ extern struct image * image_memory ( const char *name, userptr_t data,
 extern int image_pixbuf ( struct image *image, struct pixel_buffer **pixbuf );
 extern int image_asn1 ( struct image *image, size_t offset,
 			struct asn1_cursor **cursor );
+extern int image_extract ( struct image *image, const char *name,
+			   struct image **extracted );
 
 /**
  * Increment reference count on an image

src/include/usr/imgarchive.h

@@ -0,0 +1,16 @@
+#ifndef _USR_IMGARCHIVE_H
+#define _USR_IMGARCHIVE_H
+
+/** @file
+ *
+ * Archive image management
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <ipxe/image.h>
+
+extern int imgextract ( struct image *image, const char *name );
+
+#endif /* _USR_IMGARCHIVE_H */