add encoding/hex module

encoding/hex.ts

@@ -0,0 +1,222 @@
+// Ported from Go
+// https://github.com/golang/go/blob/go1.12.5/src/encoding/hex/hex.go
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import { copyBytes } from "../io/util.ts";
+
+const hextable = new TextEncoder().encode("0123456789abcdef");
+const bufferSize = 1024;
+
+export function errInvalidByte(byte: number): Error {
+  return new Error(
+    "encoding/hex: invalid byte: " +
+      new TextDecoder().decode(new Uint8Array([byte]))
+  );
+}
+
+export function errLength(): Error {
+  return new Error("encoding/hex: odd length hex string");
+}
+
+// fromHexChar converts a hex character into its value and a success flag.
+function fromHexChar(byte: number): [number, boolean] {
+  switch (true) {
+    case 48 <= byte && byte <= 57: // '0' <= byte && byte <= '9'
+      return [byte - 48, true];
+    case 97 <= byte && byte <= 102: // 'a' <= byte && byte <= 'f'
+      return [byte - 97 + 10, true];
+    case 65 <= byte && byte <= 70: // 'A' <= byte && byte <= 'F'
+      return [byte - 65 + 10, true];
+  }
+  return [0, false];
+}
+
+/**
+ * EncodedLen returns the length of an encoding of n source bytes. Specifically, it returns n * 2.
+ * @param n
+ */
+export function encodedLen(n: number): number {
+  return n * 2;
+}
+
+/**
+ * Encode encodes `src` into `encodedLen(src.length)` bytes of `dst`.
+ * As a convenience, it returns the number of bytes written to `dst`, but this value is always `encodedLen(src.length)`.
+ * Encode implements hexadecimal encoding.
+ * @param dst
+ * @param src
+ */
+export function encode(dst: Uint8Array, src: Uint8Array): number {
+  if (dst.length !== encodedLen(src.length)) {
+    throw new Error("Out of index.");
+  }
+  for (let i = 0; i < src.length; i++) {
+    const v = src[i];
+    dst[i * 2] = hextable[v >> 4];
+    dst[i * 2 + 1] = hextable[v & 0x0f];
+  }
+  return encodedLen(src.length);
+}
+
+/**
+ * EncodeToString returns the hexadecimal encoding of `src`.
+ * @param src
+ */
+export function encodeToString(src: Uint8Array): string {
+  const dest = new Uint8Array(encodedLen(src.length));
+  encode(dest, src);
+  return new TextDecoder().decode(dest);
+}
+
+/**
+ * Decode decodes `src` into `decodedLen(src.length)` bytes, returning the actual number of bytes written to `dst`.
+ * Decode expects that `src` contains only hexadecimal characters and that `src` has even length.
+ * If the input is malformed, Decode returns the number of bytes decoded before the error.
+ * @param dst
+ * @param src
+ */
+export function decode(dst: Uint8Array, src: Uint8Array): [number, Error] {
+  var i = 0;
+  for (; i < Math.floor(src.length / 2); i++) {
+    const [a, aOK] = fromHexChar(src[i * 2]);
+    if (!aOK) {
+      return [i, errInvalidByte(src[i * 2])];
+    }
+    const [b, bOK] = fromHexChar(src[i * 2 + 1]);
+    if (!bOK) {
+      return [i, errInvalidByte(src[i * 2 + 1])];
+    }
+
+    dst[i] = (a << 4) | b;
+  }
+
+  if (src.length % 2 == 1) {
+    // Check for invalid char before reporting bad length,
+    // since the invalid char (if present) is an earlier problem.
+    const [, ok] = fromHexChar(src[i * 2]);
+    if (!ok) {
+      return [i, errInvalidByte(src[i * 2])];
+    }
+    return [i, errLength()];
+  }
+
+  return [i, undefined];
+}
+
+/**
+ * DecodedLen returns the length of a decoding of `x` source bytes. Specifically, it returns `x / 2`.
+ * @param x
+ */
+export function decodedLen(x: number): number {
+  return Math.floor(x / 2);
+}
+
+/**
+ * DecodeString returns the bytes represented by the hexadecimal string `s`.
+ * DecodeString expects that src contains only hexadecimal characters and that src has even length.
+ * If the input is malformed, DecodeString will throws an error.
+ * @param s
+ */
+export function decodeString(s: string): Uint8Array {
+  const src = new TextEncoder().encode(s);
+  // We can use the source slice itself as the destination
+  // because the decode loop increments by one and then the 'seen' byte is not used anymore.
+  const [n, err] = decode(src, src);
+
+  if (err) {
+    throw err;
+  }
+
+  return src.slice(0, n);
+}
+
+/**
+ * A `deno.Writer` implements that writes lowercase hexadecimal characters to `w`.
+ */
+export class Encoder implements Deno.Writer {
+  private out = new Uint8Array(bufferSize);
+  constructor(private w: Deno.Writer) {}
+  async write(p: Uint8Array): Promise<number> {
+    let n = 0;
+
+    for (; p.length > 0; ) {
+      let chunkSize = bufferSize / 2;
+      if (p.length < chunkSize) {
+        chunkSize = p.length;
+      }
+
+      const encoded = encode(this.out.slice(), p.slice(chunkSize));
+      const written = await this.w.write(this.out.slice(0, encoded));
+
+      n += written / 2;
+      p = p.slice(chunkSize);
+    }
+
+    return n;
+  }
+}
+
+/**
+ * A `deno.Reader` implements that decodes hexadecimal characters from `r`.
+ * Decoder expects that `r` contain only an even number of hexadecimal characters.
+ */
+export class Decoder implements Deno.Reader {
+  private in = new Uint8Array(); // input buffer (encoded form)
+  private arr = new Uint8Array(bufferSize); // backing array for in
+  private err: Error;
+  constructor(private r: Deno.Reader) {}
+  async read(p: Uint8Array): Promise<Deno.ReadResult> {
+    // Fill internal buffer with sufficient bytes to decode
+    if (this.in.length < 2 && !this.err) {
+      let numCopy = 0;
+      let numRead = 0;
+
+      numCopy = copyBytes(this.arr.slice(), this.in);
+      const { nread, eof } = await this.r.read(this.arr.slice(numCopy));
+      numRead = nread;
+      this.in = this.arr.slice(0, numCopy + numRead);
+
+      if (eof && this.in.length % 2 != 0) {
+        const [, ok] = fromHexChar(this.in[this.in.length - 1]);
+        if (!ok) {
+          this.err = errInvalidByte(this.in[this.in.length - 1]);
+        } else {
+          this.err = new Error("unexpected EOF");
+        }
+      }
+    }
+
+    // Decode internal buffer into output buffer
+    const numAvail = this.in.length / 2;
+    if (numAvail && p.length > numAvail) {
+      p = p.slice(0, numAvail);
+    }
+
+    const [numDec, err] = decode(p, this.in.slice(0, p.length * 2));
+
+    this.in = this.in.slice(2 * numDec);
+
+    if (err) {
+      // Decode error; discard input remainder
+      throw err;
+    }
+
+    if (this.in.length < 2) {
+      // Only throw errors when buffer fully consumed
+      if (this.err) {
+        throw err;
+      }
+      return {
+        nread: numDec,
+        eof: true
+      };
+    }
+
+    return {
+      nread: numDec,
+      eof: false
+    };
+  }
+}