[base64] Add ability to decode base64 strings

Inspired-by: Piotr Jaroszyński <p.jaroszynski@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/src/include/ipxe/base64.h b/src/include/ipxe/base64.h
index 88c91563e..5fe134dc8 100644
--- a/src/include/ipxe/base64.h
+++ b/src/include/ipxe/base64.h
@@ -10,6 +10,7 @@
 FILE_LICENCE ( GPL2_OR_LATER );
 
 #include <stdint.h>
+#include <string.h>
 
 /**
  * Calculate length of base64-encoded data
@@ -21,6 +22,20 @@ static inline size_t base64_encoded_len ( size_t raw_len ) {
 	return ( ( ( raw_len + 3 - 1 ) / 3 ) * 4 );
 }
 
+/**
+ * Calculate maximum length of base64-decoded string
+ *
+ * @v encoded		Encoded string
+ * @v max_raw_len	Maximum length of raw data
+ *
+ * Note that the exact length of the raw data cannot be known until
+ * the string is decoded.
+ */
+static inline size_t base64_decoded_max_len ( const char *encoded ) {
+	return ( ( ( strlen ( encoded ) + 4 - 1 ) / 4 ) * 3 );
+}
+
 extern void base64_encode ( const uint8_t *raw, size_t len, char *encoded );
+extern int base64_decode ( const char *encoded, uint8_t *raw );
 
 #endif /* _IPXE_BASE64_H */