[base16] Add generic base16 encoding and decoding routines

Base16 encoding is currently implemented in both iSCSI and SRP.

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

src/core/base16.c

@@ -0,0 +1,106 @@
+/*
+ * Copyright (C) 2010 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <errno.h>
+#include <ipxe/base16.h>
+
+/** @file
+ *
+ * Base16 encoding
+ *
+ */
+
+/**
+ * Base16-encode data
+ *
+ * @v raw		Raw data
+ * @v len		Length of raw data
+ * @v encoded		Buffer for encoded string
+ *
+ * The buffer must be the correct length for the encoded string.  Use
+ * something like
+ *
+ *     char buf[ base16_encoded_len ( len ) + 1 ];
+ *
+ * (the +1 is for the terminating NUL) to provide a buffer of the
+ * correct size.
+ */
+void base16_encode ( const uint8_t *raw, size_t len, char *encoded ) {
+	const uint8_t *raw_bytes = raw;
+	char *encoded_bytes = encoded;
+	size_t remaining = len;
+
+	for ( ; remaining-- ; encoded_bytes += 2 ) {
+		sprintf ( encoded_bytes, "%02x", *(raw_bytes++) );
+	}
+
+	DBG ( "Base16-encoded to \"%s\":\n", encoded );
+	DBG_HDA ( 0, raw, len );
+	assert ( strlen ( encoded ) == base16_encoded_len ( len ) );
+}
+
+/**
+ * Base16-decode data
+ *
+ * @v encoded		Encoded string
+ * @v raw		Raw data
+ * @ret len		Length of raw data, or negative error
+ *
+ * The buffer must be large enough to contain the decoded data.  Use
+ * something like
+ *
+ *     char buf[ base16_decoded_max_len ( encoded ) ];
+ *
+ * to provide a buffer of the correct size.
+ */
+int base16_decode ( const char *encoded, uint8_t *raw ) {
+	const char *encoded_bytes = encoded;
+	uint8_t *raw_bytes = raw;
+	char buf[3];
+	char *endp;
+	size_t len;
+
+	while ( encoded_bytes[0] ) {
+		if ( ! encoded_bytes[1] ) {
+			DBG ( "Base16-encoded string \"%s\" has invalid "
+			      "length\n", encoded );
+			return -EINVAL;
+		}
+		memcpy ( buf, encoded_bytes, 2 );
+		buf[2] = '\0';
+		*(raw_bytes++) = strtoul ( buf, &endp, 16 );
+		if ( *endp != '\0' ) {
+			DBG ( "Base16-encoded string \"%s\" has invalid "
+			      "byte \"%s\"\n", encoded, buf );
+			return -EINVAL;
+		}
+		encoded_bytes += 2;
+	}
+	len = ( raw_bytes - raw );
+
+	DBG ( "Base16-decoded \"%s\" to:\n", encoded );
+	DBG_HDA ( 0, raw, len );
+	assert ( len <= base16_decoded_max_len ( encoded ) );
+
+	return ( len );
+}