[pnm] Add support for PNM images

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

src/include/ipxe/errfile.h

@@ -227,6 +227,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #define ERRFILE_segment		      ( ERRFILE_IMAGE | 0x00030000 )
 #define ERRFILE_efi_image	      ( ERRFILE_IMAGE | 0x00040000 )
 #define ERRFILE_embedded	      ( ERRFILE_IMAGE | 0x00050000 )
+#define ERRFILE_pnm		      ( ERRFILE_IMAGE | 0x00060000 )
 
 #define ERRFILE_asn1		      ( ERRFILE_OTHER | 0x00000000 )
 #define ERRFILE_chap		      ( ERRFILE_OTHER | 0x00010000 )

src/include/ipxe/pnm.h

@@ -0,0 +1,86 @@
+#ifndef _IPXE_PNM_H
+#define _IPXE_PNM_H
+
+/** @file
+ *
+ * Portable anymap format (PNM)
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <ipxe/uaccess.h>
+#include <ipxe/image.h>
+
+/** PNM signature */
+struct pnm_signature {
+	/** Magic byte ('P') */
+	char magic;
+	/** PNM type */
+	char type;
+	/** Whitespace */
+	char space;
+} __attribute__ (( packed ));
+
+/** PNM magic byte */
+#define PNM_MAGIC 'P'
+
+/** PNM context */
+struct pnm_context {
+	/** PNM type */
+	struct pnm_type *type;
+	/** Current byte offset */
+	size_t offset;
+	/** Maximum length of ASCII values */
+	size_t ascii_len;
+	/** Maximum pixel value */
+	unsigned int max;
+};
+
+/** Default maximum length of ASCII values */
+#define PNM_ASCII_LEN 16
+
+/** PNM type */
+struct pnm_type {
+	/** PNM type */
+	char type;
+	/** Number of scalar values per pixel */
+	uint8_t depth;
+	/** Number of pixels per composite value */
+	uint8_t packing;
+	/** Flags */
+	uint8_t flags;
+	/** Extract scalar value
+	 *
+	 * @v image		PNM image
+	 * @v pnm		PNM context
+	 * @ret value		Value, or negative error
+	 */
+	int ( * scalar ) ( struct image *image, struct pnm_context *pnm );
+	/** Convert composite value to 24-bit RGB
+	 *
+	 * @v composite		Composite value
+	 * @v index		Pixel index within this composite value
+	 * @ret rgb		24-bit RGB value
+	 */
+	uint32_t ( * rgb ) ( uint32_t composite, unsigned int index );
+};
+
+/** PNM flags */
+enum pnm_flags {
+	/** Bitmap format
+	 *
+	 * If set, this flag indicates that:
+	 *
+	 * - the maximum scalar value is predefined as being equal to
+	 *   (2^packing-1), and is not present within the file, and
+	 *
+	 * - the maximum length of ASCII values is 1.
+	 */
+	PNM_BITMAP = 0x01,
+};
+
+extern struct image_type pnm_image_type __image_type ( PROBE_NORMAL );
+
+#endif /* _IPXE_PNM_H */