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Optimize std.base64.standard.Encoder.encode

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This commit is contained in:
Igor Sadikov 2023-08-28 20:30:49 -04:00 committed by Andrew Kelley
parent 3b2b9fcbc5
commit 4635179857
1 changed files with 16 additions and 13 deletions
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29
lib/std/base64.zig
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@ -100,21 +100,24 @@ pub const Base64Encoder = struct {
const out_len = encoder.calcSize(source.len);
assert(dest.len >= out_len);
var acc: u12 = 0;
var acc_len: u4 = 0;
var idx: usize = 0;
var out_idx: usize = 0;
for (source) |v| {
acc = (acc << 8) + v;
acc_len += 8;
while (acc_len >= 6) {
acc_len -= 6;
dest[out_idx] = encoder.alphabet_chars[@as(u6, @truncate((acc >> acc_len)))];
out_idx += 1;
}
while (idx + 2 < source.len) : (idx += 3) {
dest[out_idx] = encoder.alphabet_chars[source[idx] >> 2];
dest[out_idx + 1] = encoder.alphabet_chars[((source[idx] & 0x3) << 4) | (source[idx + 1] >> 4)];
dest[out_idx + 2] = encoder.alphabet_chars[(source[idx + 1] & 0xf) << 2 | (source[idx + 2] >> 6)];
dest[out_idx + 3] = encoder.alphabet_chars[source[idx + 2] & 0x3f];
out_idx += 4;
}
if (acc_len > 0) {
dest[out_idx] = encoder.alphabet_chars[@as(u6, @truncate((acc << 6 - acc_len)))];
out_idx += 1;
if (idx + 1 < source.len) {
dest[out_idx] = encoder.alphabet_chars[source[idx] >> 2];
dest[out_idx + 1] = encoder.alphabet_chars[((source[idx] & 0x3) << 4) | (source[idx + 1] >> 4)];
dest[out_idx + 2] = encoder.alphabet_chars[(source[idx + 1] & 0xf) << 2];
out_idx += 3;
} else if (idx < source.len) {
dest[out_idx] = encoder.alphabet_chars[source[idx] >> 2];
dest[out_idx + 1] = encoder.alphabet_chars[(source[idx] & 0x3) << 4];
out_idx += 2;
}
if (encoder.pad_char) |pad_char| {
for (dest[out_idx..out_len]) |*pad| {