hare

base64.ha (13005B)

---

 // SPDX-License-Identifier: MPL-2.0
 // (c) Hare authors <https://harelang.org>
 
 use ascii;
 use bytes;
 use errors;
 use io;
 use memio;
 use os;
 use strings;
 
 def PADDING: u8 = '=';
 
 export type encoding = struct {
 	encmap: [64]u8,
 	decmap: [128]u8,
 };
 
 // Represents the standard base-64 encoding alphabet as defined in RFC 4648.
 export const std_encoding: encoding = encoding { ... };
 
 // Represents the "base64url" alphabet as defined in RFC 4648, suitable for use
 // in URLs and file paths.
 export const url_encoding: encoding = encoding { ... };
 
 // Initializes a new encoding based on the passed alphabet, which must be a
 // 64-byte ASCII string.
 export fn encoding_init(enc: *encoding, alphabet: str) void = {
 	const alphabet = strings::toutf8(alphabet);
 	enc.decmap[..] = [-1...];
 	assert(len(alphabet) == 64);
 	for (let i: u8 = 0; i < 64; i += 1) {
 		const ch = alphabet[i];
 		assert(ascii::valid(ch: rune) && enc.decmap[ch] == -1);
 		enc.encmap[i] = ch;
 		enc.decmap[ch] = i;
 	};
 };
 
 @init fn init() void = {
 	const std_alpha: str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 	const url_alpha: str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
 	encoding_init(&std_encoding, std_alpha);
 	encoding_init(&url_encoding, url_alpha);
 };
 
 export type encoder = struct {
 	stream: io::stream,
 	out: io::handle,
 	enc: *encoding,
 	ibuf: [3]u8,
 	obuf: [4]u8,
 	iavail: u8,
 	oavail: u8,
 };
 
 const encoder_vtable: io::vtable = io::vtable {
 	writer = &encode_writer,
 	closer = &encode_closer,
 	...
 };
 
 // Creates a stream that encodes writes as base64 before writing them to a
 // secondary stream. Afterwards [[io::close]] must be called to write any
 // unwritten bytes, in case of padding. Closing this stream will not close the
 // underlying stream. After a write returns an error, the stream must not be
 // written to again or closed.
 export fn newencoder(
 	enc: *encoding,
 	out: io::handle,
 ) encoder = {
 	return encoder {
 		stream = &encoder_vtable,
 		out = out,
 		enc = enc,
 		...
 	};
 };
 
 fn encode_writer(
 	s: *io::stream,
 	in: const []u8
 ) (size | io::error) = {
 	let s = s: *encoder;
 	let i = 0z;
 	for (i < len(in)) {
 		let b = s.ibuf[..];
 		// fill ibuf
 		for (let j = s.iavail; j < 3 && i < len(in); j += 1) {
 			b[j] = in[i];
 			i += 1;
 			s.iavail += 1;
 		};
 
 		if (s.iavail != 3) {
 			return i;
 		};
 
 		fillobuf(s);
 
 		match (writeavail(s)) {
 		case let e: io::error =>
 			if (i == 0) {
 				return e;
 			};
 			return i;
 		case void => void;
 		};
 	};
 
 	return i;
 };
 
 fn fillobuf(s: *encoder) void = {
 	assert(s.iavail == 3);
 	let b = s.ibuf[..];
 	s.obuf[..] = [
 		s.enc.encmap[b[0] >> 2],
 		s.enc.encmap[(b[0] & 0x3) << 4 | b[1] >> 4],
 		s.enc.encmap[(b[1] & 0xf) << 2 | b[2] >> 6],
 		s.enc.encmap[b[2] & 0x3f],
 	][..];
 	s.oavail = 4;
 };
 
 fn writeavail(s: *encoder) (void | io::error) = {
 	if (s.oavail == 0) {
 		return;
 	};
 
 	for (s.oavail > 0) {
 		let n = io::write(s.out, s.obuf[len(s.obuf) - s.oavail..])?;
 		s.oavail -= n: u8;
 	};
 
 	if (s.oavail == 0) {
 		s.iavail = 0;
 	};
 };
 
 // Flushes pending writes to the underlying stream.
 fn encode_closer(s: *io::stream) (void | io::error) = {
 	let s = s: *encoder;
 	let finished = false;
 	defer if (finished) clear(s);
 
 	if (s.oavail > 0) {
 		for (s.oavail > 0) {
 			writeavail(s)?;
 		};
 		finished = true;
 		return;
 	};
 
 	if (s.iavail == 0) {
 		finished = true;
 		return;
 	};
 
 	// prepare padding as input length was not a multiple of 3
 	//                        0  1  2
 	static const npa: []u8 = [0, 2, 1];
 	const np = npa[s.iavail];
 
 	for (let i = s.iavail; i < 3; i += 1) {
 		s.ibuf[i] = 0;
 		s.iavail += 1;
 	};
 
 	fillobuf(s);
 	for (let i = 0z; i < np; i += 1) {
 		s.obuf[3 - i] = PADDING;
 	};
 
 	for (s.oavail > 0) {
 		writeavail(s)?;
 	};
 	finished = true;
 };
 
 fn clear(e: *encoder) void = {
 	bytes::zero(e.ibuf);
 	bytes::zero(e.obuf);
 };
 
 @test fn partialwrite() void = {
 	const raw: [_]u8 = [
 		0x00, 0x00, 0x00, 0x07, 0x73, 0x73, 0x68, 0x2d, 0x72, 0x73,
 		0x61, 0x00,
 	];
 	const expected: str = `AAAAB3NzaC1yc2EA`;
 
 	let buf = memio::dynamic();
 	let e = newencoder(&std_encoding, &buf);
 	io::writeall(&e, raw[..4])!;
 	io::writeall(&e, raw[4..11])!;
 	io::writeall(&e, raw[11..])!;
 	io::close(&e)!;
 
 	assert(memio::string(&buf)! == expected);
 
 	let encb = memio::buffer(&buf);
 	free(encb);
 };
 
 // Encodes a byte slice in base 64, using the given encoding, returning a slice
 // of ASCII bytes. The caller must free the return value.
 export fn encodeslice(enc: *encoding, in: []u8) []u8 = {
 	let out = memio::dynamic();
 	let encoder = newencoder(enc, &out);
 	io::writeall(&encoder, in)!;
 	io::close(&encoder)!;
 	return memio::buffer(&out);
 };
 
 // Encodes base64 data using the given alphabet and writes it to a stream,
 // returning the number of bytes of data written (i.e. len(buf)).
 export fn encode(
 	out: io::handle,
 	enc: *encoding,
 	buf: []u8,
 ) (size | io::error) = {
 	const enc = newencoder(enc, out);
 	match (io::writeall(&enc, buf)) {
 	case let z: size =>
 		io::close(&enc)?;
 		return z;
 	case let err: io::error =>
 		clear(&enc);
 		return err;
 	};
 };
 
 // Encodes a byte slice in base 64, using the given encoding, returning a
 // string. The caller must free the return value.
 export fn encodestr(enc: *encoding, in: []u8) str = {
 	return strings::fromutf8(encodeslice(enc, in))!;
 };
 
 @test fn encode() void = {
 	// RFC 4648 test vectors
 	const in: [_]u8 = ['f', 'o', 'o', 'b', 'a', 'r'];
 	const expect: [_]str = [
 		"",
 		"Zg==",
 		"Zm8=",
 		"Zm9v",
 		"Zm9vYg==",
 		"Zm9vYmE=",
 		"Zm9vYmFy"
 	];
 	for (let i = 0z; i <= len(in); i += 1) {
 		let out = memio::dynamic();
 		let encoder = newencoder(&std_encoding, &out);
 		io::writeall(&encoder, in[..i])!;
 		io::close(&encoder)!;
 		let encb = memio::buffer(&out);
 		defer free(encb);
 		assert(bytes::equal(encb, strings::toutf8(expect[i])));
 
 		// Testing encodestr should cover encodeslice too
 		let s = encodestr(&std_encoding, in[..i]);
 		defer free(s);
 		assert(s == expect[i]);
 	};
 };
 
 export type decoder = struct {
 	stream: io::stream,
 	in: io::handle,
 	enc: *encoding,
 	obuf: [3]u8, // leftover decoded output
 	ibuf: [4]u8,
 	iavail: u8,
 	oavail: u8,
 	pad: bool, // if padding was seen in a previous read
 };
 
 const decoder_vtable: io::vtable = io::vtable {
 	reader = &decode_reader,
 	...
 };
 
 // Creates a stream that reads and decodes base 64 data from a secondary stream.
 // This stream does not need to be closed, and closing it will not close the
 // underlying stream. If a read returns an error, the stream must not be read
 // from again.
 export fn newdecoder(
 	enc: *encoding,
 	in: io::handle,
 ) decoder = {
 	return decoder {
 		stream = &decoder_vtable,
 		in = in,
 		enc = enc,
 		...
 	};
 };
 
 fn decode_reader(
 	s: *io::stream,
 	out: []u8
 ) (size | io::EOF | io::error) = {
 	let s = s: *decoder;
 	if (len(out) == 0) {
 		return 0z;
 	};
 	let n = 0z;
 	if (s.oavail != 0) {
 		if (len(out) <= s.oavail) {
 			out[..] = s.obuf[..len(out)];
 			s.obuf[..len(s.obuf) - len(out)] = s.obuf[len(out)..];
 			s.oavail = s.oavail - len(out): u8;
 			return len(out);
 		};
 		n = s.oavail;
 		s.oavail = 0;
 		out[..n] = s.obuf[..n];
 		out = out[n..];
 	};
 	let buf: [os::BUFSZ]u8 = [0...];
 	buf[..s.iavail] = s.ibuf[..s.iavail];
 
 	let want = encodedsize(len(out));
 	let nr = s.iavail: size;
 	let lim = if (want > len(buf)) len(buf) else want;
 	match (io::readall(s.in, buf[s.iavail..lim])) {
 	case let n: size =>
 		nr += n;
 	case io::EOF =>
 		return if (s.iavail != 0) errors::invalid
 			else if (n != 0) n
 			else io::EOF;
 	case let err: io::error =>
 		if (!(err is io::underread)) {
 			return err;
 		};
 		nr += err: io::underread;
 	};
 	if (s.pad) {
 		return errors::invalid;
 	};
 	s.iavail = nr: u8 % 4;
 	s.ibuf[..s.iavail] = buf[nr - s.iavail..nr];
 	nr -= s.iavail;
 	if (nr == 0) {
 		return 0z;
 	};
 	// Validating read buffer
 	let np = 0z; // Number of padding chars.
 	for (let i = 0z; i < nr; i += 1) {
 		if (buf[i] == PADDING) {
 			for (i + np < nr; np += 1) {
 				if (np > 2 || buf[i + np] != PADDING) {
 					return errors::invalid;
 				};
 			};
 			s.pad = true;
 			break;
 		};
 		if (!ascii::valid(buf[i]: u32: rune) || s.enc.decmap[buf[i]] == -1) {
 			return errors::invalid;
 		};
 		buf[i] = s.enc.decmap[buf[i]];
 	};
 
 	if (nr / 4 * 3 - np < len(out)) {
 		out = out[..nr / 4 * 3 - np];
 	};
 	let i = 0z, j = 0z;
 	nr -= 4;
 	for (i < nr) {
 		out[j    ] = buf[i    ] << 2 | buf[i + 1] >> 4;
 		out[j + 1] = buf[i + 1] << 4 | buf[i + 2] >> 2;
 		out[j + 2] = buf[i + 2] << 6 | buf[i + 3];
 
 		i += 4;
 		j += 3;
 	};
 	s.obuf = [
 		buf[i    ] << 2 | buf[i + 1] >> 4,
 		buf[i + 1] << 4 | buf[i + 2] >> 2,
 		buf[i + 2] << 6 | buf[i + 3],
 	];
 	out[j..] = s.obuf[..len(out) - j];
 	s.oavail = (len(s.obuf) - (len(out) - j)): u8;
 	s.obuf[..s.oavail] = s.obuf[len(s.obuf) - s.oavail..];
 	s.oavail -= np: u8;
 	return n + len(out);
 };
 
 // Decodes a byte slice of ASCII-encoded base 64 data, using the given encoding,
 // returning a slice of decoded bytes. The caller must free the return value.
 export fn decodeslice(
 	enc: *encoding,
 	in: []u8,
 ) ([]u8 | errors::invalid) = {
 	if (len(in) == 0) {
 		return [];
 	};
 	if (len(in) % 4 != 0) {
 		return errors::invalid;
 	};
 	let ins = memio::fixed(in);
 	let decoder = newdecoder(enc, &ins);
 	let out = alloc([0u8...], decodedsize(len(in)))!;
 	let outs = memio::fixed(out);
 	match (io::copy(&outs, &decoder)) {
 	case io::error =>
 		free(out);
 		return errors::invalid;
 	case let sz: size =>
 		return memio::buffer(&outs)[..sz];
 	};
 };
 
 // Decodes a string of ASCII-encoded base 64 data, using the given encoding,
 // returning a slice of decoded bytes. The caller must free the return value.
 export fn decodestr(enc: *encoding, in: str) ([]u8 | errors::invalid) = {
 	return decodeslice(enc, strings::toutf8(in));
 };
 
 // Decodes base64 data from a stream using the given alphabet, returning the
 // number of bytes of bytes read (i.e. len(buf)).
 export fn decode(
 	in: io::handle,
 	enc: *encoding,
 	buf: []u8,
 ) (size | io::EOF | io::error) = {
 	const dec = newdecoder(enc, in);
 	return io::readall(&dec, buf);
 };
 
 @test fn decode() void = {
 	// RFC 4648 test vectors
 	const cases: [_](str, str, *encoding) = [
 		("", "", &std_encoding),
 		("Zg==", "f", &std_encoding),
 		("Zm8=", "fo", &std_encoding),
 		("Zm9v", "foo", &std_encoding),
 		("Zm9vYg==", "foob", &std_encoding),
 		("Zm9vYmE=", "fooba", &std_encoding),
 		("Zm9vYmFy", "foobar", &std_encoding),
 	];
 	const invalid: [_](str, *encoding) = [
 		// invalid padding
 		("=", &std_encoding),
 		("==", &std_encoding),
 	        ("===", &std_encoding),
 	        ("=====", &std_encoding),
 	        ("======", &std_encoding),
 	        // invalid characters
 	        ("@Zg=", &std_encoding),
 	        ("ê==", &std_encoding),
 	        ("êg==", &std_encoding),
 		("$3d==", &std_encoding),
 		("%3d==", &std_encoding),
 		("[==", &std_encoding),
 		("!", &std_encoding),
 	        // data after padding is encountered
 	        ("Zg===", &std_encoding),
 	        ("Zg====", &std_encoding),
 	        ("Zg==Zg==", &std_encoding),
 	        ("Zm8=Zm8=", &std_encoding),
 	];
 	let buf: [12]u8 = [0...];
 	for (let bufsz = 1z; bufsz <= 12; bufsz += 1) {
 		for (let (input, expected, encoding) .. cases) {
 			let in = memio::fixed(strings::toutf8(input));
 			let decoder = newdecoder(encoding, &in);
 			let buf = buf[..bufsz];
 			let decb: []u8 = [];
 			defer free(decb);
 			for (true) match (io::read(&decoder, buf)!) {
 			case let z: size =>
 				if (z > 0) {
 					append(decb, buf[..z]...)!;
 				};
 			case io::EOF =>
 				break;
 			};
 			assert(bytes::equal(decb, strings::toutf8(expected)));
 
 			// Testing decodestr should cover decodeslice too
 			let decb = decodestr(encoding, input) as []u8;
 			defer free(decb);
 			assert(bytes::equal(decb, strings::toutf8(expected)));
 		};
 
 		for (let (input, encoding) .. invalid) {
 			let in = memio::fixed(strings::toutf8(input));
 			let decoder = newdecoder(encoding, &in);
 			let buf = buf[..bufsz];
 			let valid = false;
 			for (true) match(io::read(&decoder, buf)) {
 			case errors::invalid =>
 				break;
 			case size =>
 				void;
 			case io::EOF =>
 				abort();
 			};
 
 			// Testing decodestr should cover decodeslice too
 			assert(decodestr(encoding, input) is errors::invalid);
 		};
 	};
 };
 
 // Given the length of the message, returns the size of its base64 encoding
 export fn encodedsize(sz: size) size = if (sz == 0) 0 else ((sz - 1)/ 3 + 1) * 4;
 
 // Given the size of base64 encoded data, returns maximal length of decoded message.
 // The message may be at most 2 bytes shorter than the returned value. Input
 // size must be a multiple of 4.
 export fn decodedsize(sz: size) size = {
 	assert(sz % 4 == 0);
 	return sz / 4 * 3;
 };
 
 @test fn sizecalc() void = {
 	let enc: [_](size, size) = [(1, 4), (2, 4), (3, 4), (4, 8), (10, 16),
 		(119, 160), (120, 160), (121, 164), (122, 164), (123, 164)
 	];
 	assert(encodedsize(0) == 0 && decodedsize(0) == 0);
 	for (let i = 0z; i < len(enc); i += 1) {
 		let (decoded, encoded) = enc[i];
 		assert(encodedsize(decoded) == encoded);
 		assert(decodedsize(encoded) == ((decoded - 1) / 3 + 1) * 3);
 	};
 };