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