[uuid] Add uuid_aton() to parse a UUID from a string

Add uuid_aton() to parse a UUID value from a string (analogous to
inet_aton(), inet6_aton(), sock_aton(), etc), treating it as a
32-digit hex string with optional hyphen separators.  The placement of
the separators is not checked: each byte within the hex string may be
separated by a hyphen, or not separated at all.

Add dedicated self-tests for UUID parsing and formatting (already
partially covered by the ":uuid" and ":guid" settings self-tests).

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

src/include/ipxe/base16.h

@@ -12,6 +12,9 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #include <stdint.h>
 #include <string.h>
 
+/** Treat separator as optional while decoding */
+#define HEX_DECODE_OPTIONAL 0x80
+
 /**
  * Calculate length of base16-encoded data
  *

src/include/ipxe/errfile.h

@@ -79,6 +79,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_cachedhcp	       ( ERRFILE_CORE | 0x00270000 )
 #define ERRFILE_acpimac		       ( ERRFILE_CORE | 0x00280000 )
 #define ERRFILE_efi_strings	       ( ERRFILE_CORE | 0x00290000 )
+#define ERRFILE_uuid		       ( ERRFILE_CORE | 0x002a0000 )
 
 #define ERRFILE_eisa		     ( ERRFILE_DRIVER | 0x00000000 )
 #define ERRFILE_isa		     ( ERRFILE_DRIVER | 0x00010000 )

src/include/ipxe/uuid.h

@@ -48,5 +48,6 @@ static inline void uuid_mangle ( union uuid *uuid ) {
 }
 
 extern const char * uuid_ntoa ( const union uuid *uuid );
+extern int uuid_aton ( const char *string, union uuid *uuid );
 
 #endif /* _IPXE_UUID_H */