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18/ds/18js/lib/text_decoder_index.js

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+import { end_of_stream } from './text_decoder_utils.js'
+import { label_to_encoding } from './table.js'
+
+export default class Stream {
+  /**
+   * A stream represents an ordered sequence of tokens.
+   * @param {!(Array.<number>|Uint8Array)} tokens Array of tokens that provide
+   * the stream.
+   */
+  constructor(tokens) {
+    this.tokens = [...tokens]
+    // Reversed as push/pop is more efficient than shift/unshift.
+    this.tokens.reverse()
+  }
+  /**
+   * @returns True if end-of-stream has been hit.
+   */
+  endOfStream() {
+    return !this.tokens.length
+  }
+  /**
+   * When a token is read from a stream, the first token in the
+   * stream must be returned and subsequently removed, and
+   * end-of-stream must be returned otherwise.
+   *
+   * @return Get the next token from the stream, or end_of_stream.
+   */
+  read() {
+    if (!this.tokens.length)
+      return end_of_stream
+    return this.tokens.pop()
+  }
+  /**
+   * When one or more tokens are prepended to a stream, those tokens
+   * must be inserted, in given order, before the first token in the
+   * stream.
+   *
+   * @param {(number|!Array.<number>)} token The token(s) to prepend to the
+   * stream.
+   */
+  prepend(token) {
+    if (Array.isArray(token)) {
+      var tokens = /**@type {!Array.<number>}*/(token)
+      while (tokens.length)
+        this.tokens.push(tokens.pop())
+    } else {
+      this.tokens.push(token)
+    }
+  }
+  /**
+   * When one or more tokens are pushed to a stream, those tokens
+   * must be inserted, in given order, after the last token in the
+   * stream.
+   *
+   * @param {(number|!Array.<number>)} token The tokens(s) to push to the
+   * stream.
+   */
+  push(token) {
+    if (Array.isArray(token)) {
+      const tokens = /**@type {!Array.<number>}*/(token)
+      while (tokens.length)
+        this.tokens.unshift(tokens.shift())
+    } else {
+      this.tokens.unshift(token)
+    }
+  }
+}
+
+export const DEFAULT_ENCODING = 'utf-8'
+
+
+/**
+ * Returns the encoding for the label.
+ * @param {string} label The encoding label.
+ */
+export function getEncoding(label) {
+  // 1. Remove any leading and trailing ASCII whitespace from label.
+  label = String(label).trim().toLowerCase()
+
+  // 2. If label is an ASCII case-insensitive match for any of the
+  // labels listed in the table below, return the corresponding
+  // encoding, and failure otherwise.
+  if (Object.prototype.hasOwnProperty.call(label_to_encoding, label)) {
+    return label_to_encoding[label]
+  }
+  return null
+}
+
+
+//
+// 5. Encodings
+//
+
+// 5.1 Encoders and decoders
+
+// /** @interface */
+// function Decoder() {}
+// Decoder.prototype = {
+//   /**
+//    * @param {Stream} stream The stream of bytes being decoded.
+//    * @param {number} bite The next byte read from the stream.
+//    * @return {?(number|!Array.<number>)} The next code point(s)
+//    *     decoded, or null if not enough data exists in the input
+//    *     stream to decode a complete code point, or |finished|.
+//    */
+//   handler: function(stream, bite) {},
+// }
+
+// /** @interface */
+// function Encoder() {}
+// Encoder.prototype = {
+//   /**
+//    * @param {Stream} stream The stream of code points being encoded.
+//    * @param {number} code_point Next code point read from the stream.
+//    * @return {(number|!Array.<number>)} Byte(s) to emit, or |finished|.
+//    */
+//   handler: function(stream, code_point) {},
+// }