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Code Issues Releases Wiki Activity

io: Add skip() method to BitStream and beef up unit tests

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This commit is contained in:
Jeff Schiller 2024-01-20 17:30:42 -08:00
parent 45fdedd663
commit c07aa83e12
3 changed files with 160 additions and 58 deletions
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32
io/bitstream.js
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@ -1,7 +1,7 @@
/*
* bitstream.js
*
* Provides readers for bitstreams.
* A pull stream for binary bits.
*
* Licensed under the MIT License
*
@ -118,6 +118,8 @@ export class BitStream {
peekBits_ltm(n, opt_movePointers) {
const NUM = parseInt(n, 10);
let num = NUM;
// TODO: Handle this consistently between ByteStream and BitStream. ByteStream throws an error.
if (n !== num || num <= 0) {
return 0;
}
@ -176,6 +178,8 @@ export class BitStream {
peekBits_mtl(n, opt_movePointers) {
const NUM = parseInt(n, 10);
let num = NUM;
// TODO: Handle this consistently between ByteStream and BitStream. ByteStream throws an error.
if (n !== num || num <= 0) {
return 0;
}
@ -305,4 +309,30 @@ export class BitStream {
readBytes(n) {
return this.peekBytes(n, true);
}
/**
* Skips n bits in the stream. Will throw an error if n is < 0 or greater than the number of
* bits left in the stream.
* @param {number} n The number of bits to skip. Must be a positive integer.
* @returns {BitStream} Returns this BitStream for chaining.
*/
skip(n) {
const num = parseInt(n, 10);
if (n !== num || num < 0) throw `Error! Called skip(${n})`;
else if (num === 0) return this;
const totalBitsLeft = this.getNumBitsLeft();
if (n > totalBitsLeft) {
throw `Error! Overflowed the bit stream for skip(${n}), ptrs=${this.bytePtr}/${this.bitPtr}`;
}
this.bitsRead_ += num;
this.bitPtr += num;
if (this.bitPtr >= 8) {
this.bytePtr += Math.floor(this.bitPtr / 8);
this.bitPtr %= 8;
}
return this;
}
}