base64: import from barebox

Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

2 files changed, 120 insertions, 0 deletions

diff --git a/src/base64.c b/src/base64.c
new file mode 100644
index 0000000..02cac16
--- /dev/null
+++ b/src/base64.c
@@ -0,0 +1,114 @@
+/*
+ * Code based on busybox-1.23.2
+ *
+ * Copyright 2003, Glenn McGrath
+ * Copyright 2006, Rob Landley <rob@landley.net>
+ * Copyright 2010, Denys Vlasenko
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#include <common.h>
+#include <base64.h>
+
+/* Conversion table.  for base 64 */
+static const char const uuenc_tbl_base64[65 + 1] = {
+	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
+	'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
+	'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
+	'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
+	'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
+	'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
+	'w', 'x', 'y', 'z', '0', '1', '2', '3',
+	'4', '5', '6', '7', '8', '9', '+', '/',
+	'=' /* termination character */,
+	'\0' /* needed for uudecode.c only */
+};
+
+/*
+ * Decode base64 encoded string. Stops on '\0'.
+ *
+ */
+int decode_base64(char *p_dst, int dst_len, const char *src)
+{
+	const char *src_tail;
+	char *dst = p_dst;
+	int length = 0;
+
+	while (dst_len > 0) {
+		unsigned char six_bit[4];
+		int count = 0;
+
+		/* Fetch up to four 6-bit values */
+		src_tail = src;
+		while (count < 4) {
+			const char *table_ptr;
+			int ch;
+
+			/*
+			 * Get next _valid_ character.
+			 * uuenc_tbl_base64[] contains this string:
+			 *  0         1         2         3         4         5         6
+			 *  01234567890123456789012345678901234567890123456789012345678901234
+			 * "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
+			 */
+			do {
+				ch = *src;
+				if (ch == '\0') {
+					/*
+					 * Example:
+					 * If we decode "QUJD <NUL>", we want
+					 * to return ptr to NUL, not to ' ',
+					 * because we did fully decode
+					 * the string (to "ABC").
+					 */
+					if (count == 0)
+						src_tail = src;
+					goto ret;
+				}
+				src++;
+				table_ptr = strchr(uuenc_tbl_base64, ch);
+			} while (!table_ptr);
+
+			/* Convert encoded character to decimal */
+			ch = table_ptr - uuenc_tbl_base64;
+
+			/* ch is 64 if char was '=', otherwise 0..63 */
+			if (ch == 64)
+				break;
+
+			six_bit[count] = ch;
+			count++;
+		}
+
+		/*
+		 * Transform 6-bit values to 8-bit ones.
+		 * count can be < 4 when we decode the tail:
+		 * "eQ==" -> "y", not "y NUL NUL".
+		 * Note that (count > 1) is always true,
+		 * "x===" encoding is not valid:
+		 * even a single zero byte encodes as "AA==".
+		 * However, with current logic we come here with count == 1
+		 * when we decode "==" tail.
+		 */
+		if (count > 1)
+			*dst++ = six_bit[0] << 2 | six_bit[1] >> 4;
+		if (count > 2)
+			*dst++ = six_bit[1] << 4 | six_bit[2] >> 2;
+		if (count > 3)
+			*dst++ = six_bit[2] << 6 | six_bit[3];
+		/*
+		 * Note that if we decode "AA==" and ate first '=',
+		 * we just decoded one char (count == 2) and now we'll
+		 * do the loop once more to decode second '='.
+		 */
+		dst_len -= count-1;
+		/* last character was "=" */
+		if (count != 0)
+			length += count - 1;
+	}
+ret:
+	p_dst = dst;
+
+	return length;
+}
diff --git a/src/base64.h b/src/base64.h
new file mode 100644
index 0000000..6ce0885
--- /dev/null
+++ b/src/base64.h
@@ -0,0 +1,6 @@
+#ifndef __BASE64_H
+#define __BASE64_H
+
+int decode_base64(char *dst, int dst_len, const char *src);
+
+#endif /* __BASE64_H */