pub const Base64Encoder = structalphabet_chars: [64]u8pad_char: ?u8pub fn init(alphabet_chars: [64]u8, pad_char: ?u8) Base64EncoderA bunch of assertions, then simply pass the data right through.
pub fn calcSize(encoder: *const Base64Encoder, source_len: usize) usizeCompute the encoded length
pub fn encodeWriter(encoder: *const Base64Encoder, dest: *std.Io.Writer, source: []const u8) !voidpub fn encode(encoder: *const Base64Encoder, dest: []u8, source: []const u8) []const u8dest.len must at least be what you get from ::calcSize.
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165pub const Base64Encoder = struct {
alphabet_chars: [64]u8,
pad_char: ?u8,
/// A bunch of assertions, then simply pass the data right through.
pub fn init(alphabet_chars: [64]u8, pad_char: ?u8) Base64Encoder {
assert(alphabet_chars.len == 64);
var char_in_alphabet: [256]bool = @splat(false);
for (alphabet_chars) |c| {
assert(!char_in_alphabet[c]);
assert(pad_char == null or c != pad_char.?);
char_in_alphabet[c] = true;
}
return Base64Encoder{
.alphabet_chars = alphabet_chars,
.pad_char = pad_char,
};
}
/// Compute the encoded length
pub fn calcSize(encoder: *const Base64Encoder, source_len: usize) usize {
if (encoder.pad_char != null) {
return @divTrunc(source_len + 2, 3) * 4;
} else {
const leftover = source_len % 3;
return @divTrunc(source_len, 3) * 4 + @divTrunc(leftover * 4 + 2, 3);
}
}
pub fn encodeWriter(encoder: *const Base64Encoder, dest: *std.Io.Writer, source: []const u8) !void {
var chunker = window(u8, source, 3, 3);
while (chunker.next()) |chunk| {
var temp: [5]u8 = undefined;
const s = encoder.encode(&temp, chunk);
try dest.writeAll(s);
}
}
/// dest.len must at least be what you get from ::calcSize.
pub fn encode(encoder: *const Base64Encoder, dest: []u8, source: []const u8) []const u8 {
const out_len = encoder.calcSize(source.len);
assert(dest.len >= out_len);
var idx: usize = 0;
var out_idx: usize = 0;
while (idx + 15 < source.len) : (idx += 12) {
const bits = std.mem.readInt(u128, source[idx..][0..16], .big);
inline for (0..16) |i| {
dest[out_idx + i] = encoder.alphabet_chars[@truncate((bits >> (122 - i * 6)) & 0x3f)];
}
out_idx += 16;
}
while (idx + 3 < source.len) : (idx += 3) {
const bits = std.mem.readInt(u32, source[idx..][0..4], .big);
dest[out_idx] = encoder.alphabet_chars[(bits >> 26) & 0x3f];
dest[out_idx + 1] = encoder.alphabet_chars[(bits >> 20) & 0x3f];
dest[out_idx + 2] = encoder.alphabet_chars[(bits >> 14) & 0x3f];
dest[out_idx + 3] = encoder.alphabet_chars[(bits >> 8) & 0x3f];
out_idx += 4;
}
if (idx + 2 < 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 | (source[idx + 2] >> 6)];
dest[out_idx + 3] = encoder.alphabet_chars[source[idx + 2] & 0x3f];
out_idx += 4;
} else 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| {
pad.* = pad_char;
}
}
return dest[0..out_len];
}
}