mirror of
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143 lines
4.1 KiB
TypeScript
143 lines
4.1 KiB
TypeScript
// Ported from Go
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// https://github.com/golang/go/blob/go1.12.5/src/encoding/hex/hex.go
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
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const hextable = new TextEncoder().encode("0123456789abcdef");
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export function errInvalidByte(byte: number): Error {
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return new Error(
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"encoding/hex: invalid byte: " +
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new TextDecoder().decode(new Uint8Array([byte]))
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);
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}
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export function errLength(): Error {
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return new Error("encoding/hex: odd length hex string");
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}
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// fromHexChar converts a hex character into its value and a success flag.
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function fromHexChar(byte: number): [number, boolean] {
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switch (true) {
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case 48 <= byte && byte <= 57: // '0' <= byte && byte <= '9'
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return [byte - 48, true];
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case 97 <= byte && byte <= 102: // 'a' <= byte && byte <= 'f'
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return [byte - 97 + 10, true];
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case 65 <= byte && byte <= 70: // 'A' <= byte && byte <= 'F'
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return [byte - 65 + 10, true];
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}
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return [0, false];
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}
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/**
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* EncodedLen returns the length of an encoding of n source bytes. Specifically,
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* it returns n * 2.
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* @param n
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*/
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export function encodedLen(n: number): number {
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return n * 2;
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}
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/**
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* Encode encodes `src` into `encodedLen(src.length)` bytes of `dst`.
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* As a convenience, it returns the number of bytes written to `dst`
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* but this value is always `encodedLen(src.length)`.
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* Encode implements hexadecimal encoding.
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* @param dst
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* @param src
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*/
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export function encode(dst: Uint8Array, src: Uint8Array): number {
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const srcLength = encodedLen(src.length);
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if (dst.length !== srcLength) {
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throw new Error("Out of index.");
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}
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for (let i = 0; i < src.length; i++) {
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const v = src[i];
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dst[i * 2] = hextable[v >> 4];
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dst[i * 2 + 1] = hextable[v & 0x0f];
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}
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return srcLength;
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}
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/**
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* EncodeToString returns the hexadecimal encoding of `src`.
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* @param src
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*/
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export function encodeToString(src: Uint8Array): string {
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const dest = new Uint8Array(encodedLen(src.length));
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encode(dest, src);
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return new TextDecoder().decode(dest);
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}
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/**
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* Decode decodes `src` into `decodedLen(src.length)` bytes
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* returning the actual number of bytes written to `dst`.
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* Decode expects that `src` contains only hexadecimal characters and that `src`
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* has even length.
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* If the input is malformed, Decode returns the number of bytes decoded before
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* the error.
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* @param dst
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* @param src
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*/
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export function decode(
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dst: Uint8Array,
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src: Uint8Array
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): [number, Error | void] {
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let i = 0;
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for (; i < Math.floor(src.length / 2); i++) {
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const [a, aOK] = fromHexChar(src[i * 2]);
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if (!aOK) {
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return [i, errInvalidByte(src[i * 2])];
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}
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const [b, bOK] = fromHexChar(src[i * 2 + 1]);
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if (!bOK) {
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return [i, errInvalidByte(src[i * 2 + 1])];
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}
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dst[i] = (a << 4) | b;
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}
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if (src.length % 2 == 1) {
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// Check for invalid char before reporting bad length,
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// since the invalid char (if present) is an earlier problem.
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const [, ok] = fromHexChar(src[i * 2]);
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if (!ok) {
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return [i, errInvalidByte(src[i * 2])];
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}
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return [i, errLength()];
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}
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return [i, undefined];
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}
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/**
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* DecodedLen returns the length of a decoding of `x` source bytes.
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* Specifically, it returns `x / 2`.
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* @param x
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*/
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export function decodedLen(x: number): number {
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return Math.floor(x / 2);
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}
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/**
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* DecodeString returns the bytes represented by the hexadecimal string `s`.
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* DecodeString expects that src contains only hexadecimal characters and that
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* src has even length.
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* If the input is malformed, DecodeString will throws an error.
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* @param s the `string` need to decode to `Uint8Array`
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*/
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export function decodeString(s: string): Uint8Array {
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const src = new TextEncoder().encode(s);
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// We can use the source slice itself as the destination
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// because the decode loop increments by one and then the 'seen' byte is not
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// used anymore.
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const [n, err] = decode(src, src);
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if (err) {
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throw err;
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}
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return src.slice(0, n);
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}
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