80 lines
2.2 KiB
JavaScript
80 lines
2.2 KiB
JavaScript
/* Copyright 2012 Mozilla Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import { DecodeStream } from "./decode_stream.js";
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class AsciiHexStream extends DecodeStream {
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constructor(str, maybeLength) {
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// Most streams increase in size when decoded, but AsciiHex streams shrink
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// by 50%.
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if (maybeLength) {
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maybeLength = 0.5 * maybeLength;
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}
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super(maybeLength);
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this.str = str;
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this.dict = str.dict;
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this.firstDigit = -1;
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}
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readBlock() {
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const UPSTREAM_BLOCK_SIZE = 8000;
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const bytes = this.str.getBytes(UPSTREAM_BLOCK_SIZE);
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if (!bytes.length) {
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this.eof = true;
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return;
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}
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const maxDecodeLength = (bytes.length + 1) >> 1;
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const buffer = this.ensureBuffer(this.bufferLength + maxDecodeLength);
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let bufferLength = this.bufferLength;
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let firstDigit = this.firstDigit;
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for (const ch of bytes) {
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let digit;
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if (ch >= /* '0' = */ 0x30 && ch <= /* '9' = */ 0x39) {
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digit = ch & 0x0f;
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} else if (
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(ch >= /* 'A' = */ 0x41 && ch <= /* 'Z' = */ 0x46) ||
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(ch >= /* 'a' = */ 0x61 && ch <= /* 'z' = */ 0x66)
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) {
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digit = (ch & 0x0f) + 9;
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} else if (ch === /* '>' = */ 0x3e) {
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this.eof = true;
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break;
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} else {
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// Probably whitespace, ignoring.
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continue;
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}
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if (firstDigit < 0) {
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firstDigit = digit;
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} else {
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buffer[bufferLength++] = (firstDigit << 4) | digit;
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firstDigit = -1;
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}
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}
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if (firstDigit >= 0 && this.eof) {
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// incomplete byte
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buffer[bufferLength++] = firstDigit << 4;
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firstDigit = -1;
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}
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this.firstDigit = firstDigit;
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this.bufferLength = bufferLength;
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}
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}
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export { AsciiHexStream };
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