From: Kuan-Wei Chiu <[email protected]> Replace the use of strchr() in base64_decode() with precomputed reverse lookup tables for each variant. This avoids repeated string scans and improves performance. Use -1 in the tables to mark invalid characters.
Decode: 64B ~1530ns -> ~80ns (~19.1x) 1KB ~27726ns -> ~1239ns (~22.4x) Signed-off-by: Kuan-Wei Chiu <[email protected]> Co-developed-by: Guan-Chun Wu <[email protected]> Signed-off-by: Guan-Chun Wu <[email protected]> --- lib/base64.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/lib/base64.c b/lib/base64.c index a7c20a8e8..8a0d28908 100644 --- a/lib/base64.c +++ b/lib/base64.c @@ -21,6 +21,21 @@ static const char base64_tables[][65] = { [BASE64_IMAP] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+,", }; +#define BASE64_REV_INIT(ch_62, ch_63) { \ + [0 ... 255] = -1, \ + ['A'] = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, \ + 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, \ + ['a'] = 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, \ + 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, \ + ['0'] = 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, \ + [ch_62] = 62, [ch_63] = 63, \ +} + +static const s8 base64_rev_maps[][256] = { + [BASE64_STD] = BASE64_REV_INIT('+', '/'), + [BASE64_URLSAFE] = BASE64_REV_INIT('-', '_'), + [BASE64_IMAP] = BASE64_REV_INIT('+', ',') +}; /** * base64_encode() - Base64-encode some binary data * @src: the binary data to encode @@ -84,10 +99,9 @@ int base64_decode(const char *src, int srclen, u8 *dst, bool padding, enum base6 int bits = 0; int i; u8 *bp = dst; - const char *base64_table = base64_tables[variant]; + s8 ch; for (i = 0; i < srclen; i++) { - const char *p = strchr(base64_table, src[i]); if (padding) { if (src[i] == '=') { ac = (ac << 6); @@ -97,9 +111,10 @@ int base64_decode(const char *src, int srclen, u8 *dst, bool padding, enum base6 continue; } } - if (p == NULL || src[i] == 0) + ch = base64_rev_maps[variant][(u8)src[i]]; + if (ch == -1) return -1; - ac = (ac << 6) | (p - base64_table); + ac = (ac << 6) | ch; bits += 6; if (bits >= 8) { bits -= 8; -- 2.34.1
