zig/std/base64.zig

459 lines
19 KiB
Zig

const std = @import("std.zig");
const assert = std.debug.assert;
const testing = std.testing;
const mem = std.mem;
pub const standard_alphabet_chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
pub const standard_pad_char = '=';
pub const standard_encoder = Base64Encoder.init(standard_alphabet_chars, standard_pad_char);
pub const Base64Encoder = struct {
alphabet_chars: []const u8,
pad_char: u8,
/// a bunch of assertions, then simply pass the data right through.
pub fn init(alphabet_chars: []const u8, pad_char: u8) Base64Encoder {
assert(alphabet_chars.len == 64);
var char_in_alphabet = []bool{false} ** 256;
for (alphabet_chars) |c| {
assert(!char_in_alphabet[c]);
assert(c != pad_char);
char_in_alphabet[c] = true;
}
return Base64Encoder{
.alphabet_chars = alphabet_chars,
.pad_char = pad_char,
};
}
/// ceil(source_len * 4/3)
pub fn calcSize(source_len: usize) usize {
return @divTrunc(source_len + 2, 3) * 4;
}
/// dest.len must be what you get from ::calcSize.
pub fn encode(encoder: *const Base64Encoder, dest: []u8, source: []const u8) void {
assert(dest.len == Base64Encoder.calcSize(source.len));
var i: usize = 0;
var out_index: usize = 0;
while (i + 2 < source.len) : (i += 3) {
dest[out_index] = encoder.alphabet_chars[(source[i] >> 2) & 0x3f];
out_index += 1;
dest[out_index] = encoder.alphabet_chars[((source[i] & 0x3) << 4) | ((source[i + 1] & 0xf0) >> 4)];
out_index += 1;
dest[out_index] = encoder.alphabet_chars[((source[i + 1] & 0xf) << 2) | ((source[i + 2] & 0xc0) >> 6)];
out_index += 1;
dest[out_index] = encoder.alphabet_chars[source[i + 2] & 0x3f];
out_index += 1;
}
if (i < source.len) {
dest[out_index] = encoder.alphabet_chars[(source[i] >> 2) & 0x3f];
out_index += 1;
if (i + 1 == source.len) {
dest[out_index] = encoder.alphabet_chars[(source[i] & 0x3) << 4];
out_index += 1;
dest[out_index] = encoder.pad_char;
out_index += 1;
} else {
dest[out_index] = encoder.alphabet_chars[((source[i] & 0x3) << 4) | ((source[i + 1] & 0xf0) >> 4)];
out_index += 1;
dest[out_index] = encoder.alphabet_chars[(source[i + 1] & 0xf) << 2];
out_index += 1;
}
dest[out_index] = encoder.pad_char;
out_index += 1;
}
}
};
pub const standard_decoder = Base64Decoder.init(standard_alphabet_chars, standard_pad_char);
pub const Base64Decoder = struct {
/// e.g. 'A' => 0.
/// undefined for any value not in the 64 alphabet chars.
char_to_index: [256]u8,
/// true only for the 64 chars in the alphabet, not the pad char.
char_in_alphabet: [256]bool,
pad_char: u8,
pub fn init(alphabet_chars: []const u8, pad_char: u8) Base64Decoder {
assert(alphabet_chars.len == 64);
var result = Base64Decoder{
.char_to_index = undefined,
.char_in_alphabet = []bool{false} ** 256,
.pad_char = pad_char,
};
for (alphabet_chars) |c, i| {
assert(!result.char_in_alphabet[c]);
assert(c != pad_char);
result.char_to_index[c] = @intCast(u8, i);
result.char_in_alphabet[c] = true;
}
return result;
}
/// If the encoded buffer is detected to be invalid, returns error.InvalidPadding.
pub fn calcSize(decoder: *const Base64Decoder, source: []const u8) !usize {
if (source.len % 4 != 0) return error.InvalidPadding;
return calcDecodedSizeExactUnsafe(source, decoder.pad_char);
}
/// dest.len must be what you get from ::calcSize.
/// invalid characters result in error.InvalidCharacter.
/// invalid padding results in error.InvalidPadding.
pub fn decode(decoder: *const Base64Decoder, dest: []u8, source: []const u8) !void {
assert(dest.len == (decoder.calcSize(source) catch unreachable));
assert(source.len % 4 == 0);
var src_cursor: usize = 0;
var dest_cursor: usize = 0;
while (src_cursor < source.len) : (src_cursor += 4) {
if (!decoder.char_in_alphabet[source[src_cursor + 0]]) return error.InvalidCharacter;
if (!decoder.char_in_alphabet[source[src_cursor + 1]]) return error.InvalidCharacter;
if (src_cursor < source.len - 4 or source[src_cursor + 3] != decoder.pad_char) {
// common case
if (!decoder.char_in_alphabet[source[src_cursor + 2]]) return error.InvalidCharacter;
if (!decoder.char_in_alphabet[source[src_cursor + 3]]) return error.InvalidCharacter;
dest[dest_cursor + 0] = decoder.char_to_index[source[src_cursor + 0]] << 2 | decoder.char_to_index[source[src_cursor + 1]] >> 4;
dest[dest_cursor + 1] = decoder.char_to_index[source[src_cursor + 1]] << 4 | decoder.char_to_index[source[src_cursor + 2]] >> 2;
dest[dest_cursor + 2] = decoder.char_to_index[source[src_cursor + 2]] << 6 | decoder.char_to_index[source[src_cursor + 3]];
dest_cursor += 3;
} else if (source[src_cursor + 2] != decoder.pad_char) {
// one pad char
if (!decoder.char_in_alphabet[source[src_cursor + 2]]) return error.InvalidCharacter;
dest[dest_cursor + 0] = decoder.char_to_index[source[src_cursor + 0]] << 2 | decoder.char_to_index[source[src_cursor + 1]] >> 4;
dest[dest_cursor + 1] = decoder.char_to_index[source[src_cursor + 1]] << 4 | decoder.char_to_index[source[src_cursor + 2]] >> 2;
if (decoder.char_to_index[source[src_cursor + 2]] << 6 != 0) return error.InvalidPadding;
dest_cursor += 2;
} else {
// two pad chars
dest[dest_cursor + 0] = decoder.char_to_index[source[src_cursor + 0]] << 2 | decoder.char_to_index[source[src_cursor + 1]] >> 4;
if (decoder.char_to_index[source[src_cursor + 1]] << 4 != 0) return error.InvalidPadding;
dest_cursor += 1;
}
}
assert(src_cursor == source.len);
assert(dest_cursor == dest.len);
}
};
pub const Base64DecoderWithIgnore = struct {
decoder: Base64Decoder,
char_is_ignored: [256]bool,
pub fn init(alphabet_chars: []const u8, pad_char: u8, ignore_chars: []const u8) Base64DecoderWithIgnore {
var result = Base64DecoderWithIgnore{
.decoder = Base64Decoder.init(alphabet_chars, pad_char),
.char_is_ignored = []bool{false} ** 256,
};
for (ignore_chars) |c| {
assert(!result.decoder.char_in_alphabet[c]);
assert(!result.char_is_ignored[c]);
assert(result.decoder.pad_char != c);
result.char_is_ignored[c] = true;
}
return result;
}
/// If no characters end up being ignored or padding, this will be the exact decoded size.
pub fn calcSizeUpperBound(encoded_len: usize) usize {
return @divTrunc(encoded_len, 4) * 3;
}
/// Invalid characters that are not ignored result in error.InvalidCharacter.
/// Invalid padding results in error.InvalidPadding.
/// Decoding more data than can fit in dest results in error.OutputTooSmall. See also ::calcSizeUpperBound.
/// Returns the number of bytes written to dest.
pub fn decode(decoder_with_ignore: *const Base64DecoderWithIgnore, dest: []u8, source: []const u8) !usize {
const decoder = &decoder_with_ignore.decoder;
var src_cursor: usize = 0;
var dest_cursor: usize = 0;
while (true) {
// get the next 4 chars, if available
var next_4_chars: [4]u8 = undefined;
var available_chars: usize = 0;
var pad_char_count: usize = 0;
while (available_chars < 4 and src_cursor < source.len) {
var c = source[src_cursor];
src_cursor += 1;
if (decoder.char_in_alphabet[c]) {
// normal char
next_4_chars[available_chars] = c;
available_chars += 1;
} else if (decoder_with_ignore.char_is_ignored[c]) {
// we're told to skip this one
continue;
} else if (c == decoder.pad_char) {
// the padding has begun. count the pad chars.
pad_char_count += 1;
while (src_cursor < source.len) {
c = source[src_cursor];
src_cursor += 1;
if (c == decoder.pad_char) {
pad_char_count += 1;
if (pad_char_count > 2) return error.InvalidCharacter;
} else if (decoder_with_ignore.char_is_ignored[c]) {
// we can even ignore chars during the padding
continue;
} else
return error.InvalidCharacter;
}
break;
} else
return error.InvalidCharacter;
}
switch (available_chars) {
4 => {
// common case
if (dest_cursor + 3 > dest.len) return error.OutputTooSmall;
assert(pad_char_count == 0);
dest[dest_cursor + 0] = decoder.char_to_index[next_4_chars[0]] << 2 | decoder.char_to_index[next_4_chars[1]] >> 4;
dest[dest_cursor + 1] = decoder.char_to_index[next_4_chars[1]] << 4 | decoder.char_to_index[next_4_chars[2]] >> 2;
dest[dest_cursor + 2] = decoder.char_to_index[next_4_chars[2]] << 6 | decoder.char_to_index[next_4_chars[3]];
dest_cursor += 3;
continue;
},
3 => {
if (dest_cursor + 2 > dest.len) return error.OutputTooSmall;
if (pad_char_count != 1) return error.InvalidPadding;
dest[dest_cursor + 0] = decoder.char_to_index[next_4_chars[0]] << 2 | decoder.char_to_index[next_4_chars[1]] >> 4;
dest[dest_cursor + 1] = decoder.char_to_index[next_4_chars[1]] << 4 | decoder.char_to_index[next_4_chars[2]] >> 2;
if (decoder.char_to_index[next_4_chars[2]] << 6 != 0) return error.InvalidPadding;
dest_cursor += 2;
break;
},
2 => {
if (dest_cursor + 1 > dest.len) return error.OutputTooSmall;
if (pad_char_count != 2) return error.InvalidPadding;
dest[dest_cursor + 0] = decoder.char_to_index[next_4_chars[0]] << 2 | decoder.char_to_index[next_4_chars[1]] >> 4;
if (decoder.char_to_index[next_4_chars[1]] << 4 != 0) return error.InvalidPadding;
dest_cursor += 1;
break;
},
1 => {
return error.InvalidPadding;
},
0 => {
if (pad_char_count != 0) return error.InvalidPadding;
break;
},
else => unreachable,
}
}
assert(src_cursor == source.len);
return dest_cursor;
}
};
pub const standard_decoder_unsafe = Base64DecoderUnsafe.init(standard_alphabet_chars, standard_pad_char);
pub const Base64DecoderUnsafe = struct {
/// e.g. 'A' => 0.
/// undefined for any value not in the 64 alphabet chars.
char_to_index: [256]u8,
pad_char: u8,
pub fn init(alphabet_chars: []const u8, pad_char: u8) Base64DecoderUnsafe {
assert(alphabet_chars.len == 64);
var result = Base64DecoderUnsafe{
.char_to_index = undefined,
.pad_char = pad_char,
};
for (alphabet_chars) |c, i| {
assert(c != pad_char);
result.char_to_index[c] = @intCast(u8, i);
}
return result;
}
/// The source buffer must be valid.
pub fn calcSize(decoder: *const Base64DecoderUnsafe, source: []const u8) usize {
return calcDecodedSizeExactUnsafe(source, decoder.pad_char);
}
/// dest.len must be what you get from ::calcDecodedSizeExactUnsafe.
/// invalid characters or padding will result in undefined values.
pub fn decode(decoder: *const Base64DecoderUnsafe, dest: []u8, source: []const u8) void {
assert(dest.len == decoder.calcSize(source));
var src_index: usize = 0;
var dest_index: usize = 0;
var in_buf_len: usize = source.len;
while (in_buf_len > 0 and source[in_buf_len - 1] == decoder.pad_char) {
in_buf_len -= 1;
}
while (in_buf_len > 4) {
dest[dest_index] = decoder.char_to_index[source[src_index + 0]] << 2 | decoder.char_to_index[source[src_index + 1]] >> 4;
dest_index += 1;
dest[dest_index] = decoder.char_to_index[source[src_index + 1]] << 4 | decoder.char_to_index[source[src_index + 2]] >> 2;
dest_index += 1;
dest[dest_index] = decoder.char_to_index[source[src_index + 2]] << 6 | decoder.char_to_index[source[src_index + 3]];
dest_index += 1;
src_index += 4;
in_buf_len -= 4;
}
if (in_buf_len > 1) {
dest[dest_index] = decoder.char_to_index[source[src_index + 0]] << 2 | decoder.char_to_index[source[src_index + 1]] >> 4;
dest_index += 1;
}
if (in_buf_len > 2) {
dest[dest_index] = decoder.char_to_index[source[src_index + 1]] << 4 | decoder.char_to_index[source[src_index + 2]] >> 2;
dest_index += 1;
}
if (in_buf_len > 3) {
dest[dest_index] = decoder.char_to_index[source[src_index + 2]] << 6 | decoder.char_to_index[source[src_index + 3]];
dest_index += 1;
}
}
};
fn calcDecodedSizeExactUnsafe(source: []const u8, pad_char: u8) usize {
if (source.len == 0) return 0;
var result = @divExact(source.len, 4) * 3;
if (source[source.len - 1] == pad_char) {
result -= 1;
if (source[source.len - 2] == pad_char) {
result -= 1;
}
}
return result;
}
test "base64" {
@setEvalBranchQuota(8000);
testBase64() catch unreachable;
comptime (testBase64() catch unreachable);
}
fn testBase64() !void {
try testAllApis("", "");
try testAllApis("f", "Zg==");
try testAllApis("fo", "Zm8=");
try testAllApis("foo", "Zm9v");
try testAllApis("foob", "Zm9vYg==");
try testAllApis("fooba", "Zm9vYmE=");
try testAllApis("foobar", "Zm9vYmFy");
try testDecodeIgnoreSpace("", " ");
try testDecodeIgnoreSpace("f", "Z g= =");
try testDecodeIgnoreSpace("fo", " Zm8=");
try testDecodeIgnoreSpace("foo", "Zm9v ");
try testDecodeIgnoreSpace("foob", "Zm9vYg = = ");
try testDecodeIgnoreSpace("fooba", "Zm9v YmE=");
try testDecodeIgnoreSpace("foobar", " Z m 9 v Y m F y ");
// test getting some api errors
try testError("A", error.InvalidPadding);
try testError("AA", error.InvalidPadding);
try testError("AAA", error.InvalidPadding);
try testError("A..A", error.InvalidCharacter);
try testError("AA=A", error.InvalidCharacter);
try testError("AA/=", error.InvalidPadding);
try testError("A/==", error.InvalidPadding);
try testError("A===", error.InvalidCharacter);
try testError("====", error.InvalidCharacter);
try testOutputTooSmallError("AA==");
try testOutputTooSmallError("AAA=");
try testOutputTooSmallError("AAAA");
try testOutputTooSmallError("AAAAAA==");
}
fn testAllApis(expected_decoded: []const u8, expected_encoded: []const u8) !void {
// Base64Encoder
{
var buffer: [0x100]u8 = undefined;
var encoded = buffer[0..Base64Encoder.calcSize(expected_decoded.len)];
standard_encoder.encode(encoded, expected_decoded);
testing.expectEqualSlices(u8, expected_encoded, encoded);
}
// Base64Decoder
{
var buffer: [0x100]u8 = undefined;
var decoded = buffer[0..try standard_decoder.calcSize(expected_encoded)];
try standard_decoder.decode(decoded, expected_encoded);
testing.expectEqualSlices(u8, expected_decoded, decoded);
}
// Base64DecoderWithIgnore
{
const standard_decoder_ignore_nothing = Base64DecoderWithIgnore.init(standard_alphabet_chars, standard_pad_char, "");
var buffer: [0x100]u8 = undefined;
var decoded = buffer[0..Base64DecoderWithIgnore.calcSizeUpperBound(expected_encoded.len)];
var written = try standard_decoder_ignore_nothing.decode(decoded, expected_encoded);
testing.expect(written <= decoded.len);
testing.expectEqualSlices(u8, expected_decoded, decoded[0..written]);
}
// Base64DecoderUnsafe
{
var buffer: [0x100]u8 = undefined;
var decoded = buffer[0..standard_decoder_unsafe.calcSize(expected_encoded)];
standard_decoder_unsafe.decode(decoded, expected_encoded);
testing.expectEqualSlices(u8, expected_decoded, decoded);
}
}
fn testDecodeIgnoreSpace(expected_decoded: []const u8, encoded: []const u8) !void {
const standard_decoder_ignore_space = Base64DecoderWithIgnore.init(standard_alphabet_chars, standard_pad_char, " ");
var buffer: [0x100]u8 = undefined;
var decoded = buffer[0..Base64DecoderWithIgnore.calcSizeUpperBound(encoded.len)];
var written = try standard_decoder_ignore_space.decode(decoded, encoded);
testing.expectEqualSlices(u8, expected_decoded, decoded[0..written]);
}
fn testError(encoded: []const u8, expected_err: anyerror) !void {
const standard_decoder_ignore_space = Base64DecoderWithIgnore.init(standard_alphabet_chars, standard_pad_char, " ");
var buffer: [0x100]u8 = undefined;
if (standard_decoder.calcSize(encoded)) |decoded_size| {
var decoded = buffer[0..decoded_size];
if (standard_decoder.decode(decoded, encoded)) |_| {
return error.ExpectedError;
} else |err| if (err != expected_err) return err;
} else |err| if (err != expected_err) return err;
if (standard_decoder_ignore_space.decode(buffer[0..], encoded)) |_| {
return error.ExpectedError;
} else |err| if (err != expected_err) return err;
}
fn testOutputTooSmallError(encoded: []const u8) !void {
const standard_decoder_ignore_space = Base64DecoderWithIgnore.init(standard_alphabet_chars, standard_pad_char, " ");
var buffer: [0x100]u8 = undefined;
var decoded = buffer[0 .. calcDecodedSizeExactUnsafe(encoded, standard_pad_char) - 1];
if (standard_decoder_ignore_space.decode(decoded, encoded)) |_| {
return error.ExpectedError;
} else |err| if (err != error.OutputTooSmall) return err;
}