1 // SPDX-License-Identifier: GPL-2.0
3  * base64.c - RFC4648-compliant base64 encoding
8  * (which are using the URL-safe base64 encoding),
22  * base64_encode() - base64-encode some binary data
23  * @src: the binary data to encode
25  * @dst: (output) the base64-encoded string.  Not NUL-terminated.
27  * Encodes data using base64 encoding, i.e. the "Base 64 Encoding" specified
28  * by RFC 4648, including the  '='-padding.
30  * Return: the length of the resulting base64-encoded string in bytes.
35 	int bits = 0;  in base64_encode()  local
41 		bits += 8;  in base64_encode()
43 			bits -= 6;  in base64_encode()
44 			*cp++ = base64_table[(ac >> bits) & 0x3f];  in base64_encode()
45 		} while (bits >= 6);  in base64_encode()
47 	if (bits) {  in base64_encode()
48 		*cp++ = base64_table[(ac << (6 - bits)) & 0x3f];  in base64_encode()
49 		bits -= 6;  in base64_encode()
51 	while (bits < 0) {  in base64_encode()
53 		bits += 2;  in base64_encode()
55 	return cp - dst;  in base64_encode()
60  * base64_decode() - base64-decode a string
61  * @src: the string to decode.  Doesn't need to be NUL-terminated.
63  * @dst: (output) the decoded binary data
66  * specified by RFC 4648, including the  '='-padding.
70  * Return: the length of the resulting decoded binary data in bytes,
71  *	   or -1 if the string isn't a valid base64 string.
76 	int bits = 0;  in base64_decode()  local
85 			bits += 6;  in base64_decode()
86 			if (bits >= 8)  in base64_decode()
87 				bits -= 8;  in base64_decode()
91 			return -1;  in base64_decode()
92 		ac = (ac << 6) | (p - base64_table);  in base64_decode()
93 		bits += 6;  in base64_decode()
94 		if (bits >= 8) {  in base64_decode()
95 			bits -= 8;  in base64_decode()
96 			*bp++ = (u8)(ac >> bits);  in base64_decode()
99 	if (ac & ((1 << bits) - 1))  in base64_decode()
100 		return -1;  in base64_decode()
101 	return bp - dst;  in base64_decode()