Function decode [src]
dest.len must be what you get from ::calcSize.
Invalid characters result in error.InvalidCharacter.
Invalid padding results in error.InvalidPadding.
Prototype
pub fn decode(decoder: *const Base64Decoder, dest: []u8, source: []const u8) Error!void Parameters
decoder: *const Base64Decoderdest: []u8source: []const u8 Possible Errors
Source
pub fn decode(decoder: *const Base64Decoder, dest: []u8, source: []const u8) Error!void {
if (decoder.pad_char != null and source.len % 4 != 0) return error.InvalidPadding;
var dest_idx: usize = 0;
var fast_src_idx: usize = 0;
var acc: u12 = 0;
var acc_len: u4 = 0;
var leftover_idx: ?usize = null;
while (fast_src_idx + 16 < source.len and dest_idx + 15 < dest.len) : ({
fast_src_idx += 16;
dest_idx += 12;
}) {
var bits: u128 = 0;
inline for (0..4) |i| {
var new_bits: u128 = decoder.fast_char_to_index[0][source[fast_src_idx + i * 4]];
new_bits |= decoder.fast_char_to_index[1][source[fast_src_idx + 1 + i * 4]];
new_bits |= decoder.fast_char_to_index[2][source[fast_src_idx + 2 + i * 4]];
new_bits |= decoder.fast_char_to_index[3][source[fast_src_idx + 3 + i * 4]];
if ((new_bits & invalid_char_tst) != 0) return error.InvalidCharacter;
bits |= (new_bits << (24 * i));
}
std.mem.writeInt(u128, dest[dest_idx..][0..16], bits, .little);
}
while (fast_src_idx + 4 < source.len and dest_idx + 3 < dest.len) : ({
fast_src_idx += 4;
dest_idx += 3;
}) {
var bits = decoder.fast_char_to_index[0][source[fast_src_idx]];
bits |= decoder.fast_char_to_index[1][source[fast_src_idx + 1]];
bits |= decoder.fast_char_to_index[2][source[fast_src_idx + 2]];
bits |= decoder.fast_char_to_index[3][source[fast_src_idx + 3]];
if ((bits & invalid_char_tst) != 0) return error.InvalidCharacter;
std.mem.writeInt(u32, dest[dest_idx..][0..4], bits, .little);
}
const remaining = source[fast_src_idx..];
for (remaining, fast_src_idx..) |c, src_idx| {
const d = decoder.char_to_index[c];
if (d == invalid_char) {
if (decoder.pad_char == null or c != decoder.pad_char.?) return error.InvalidCharacter;
leftover_idx = src_idx;
break;
}
acc = (acc << 6) + d;
acc_len += 6;
if (acc_len >= 8) {
acc_len -= 8;
dest[dest_idx] = @as(u8, @truncate(acc >> acc_len));
dest_idx += 1;
}
}
if (acc_len > 4 or (acc & (@as(u12, 1) << acc_len) - 1) != 0) {
return error.InvalidPadding;
}
if (leftover_idx == null) return;
const leftover = source[leftover_idx.?..];
if (decoder.pad_char) |pad_char| {
const padding_len = acc_len / 2;
var padding_chars: usize = 0;
for (leftover) |c| {
if (c != pad_char) {
return if (c == Base64Decoder.invalid_char) error.InvalidCharacter else error.InvalidPadding;
}
padding_chars += 1;
}
if (padding_chars != padding_len) return error.InvalidPadding;
}
}