47 lines
1.3 KiB
JavaScript
47 lines
1.3 KiB
JavaScript
import * as Token from 'token-types';
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export class BitReader {
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constructor(tokenizer) {
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this.pos = 0;
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this.dword = null;
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this.tokenizer = tokenizer;
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}
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/**
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*
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* @param bits 1..30 bits
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*/
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async read(bits) {
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while (this.dword === null) {
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this.dword = await this.tokenizer.readToken(Token.UINT32_LE);
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}
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let out = this.dword;
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this.pos += bits;
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if (this.pos < 32) {
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out >>>= (32 - this.pos);
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return out & ((1 << bits) - 1);
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}
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this.pos -= 32;
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if (this.pos === 0) {
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this.dword = null;
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return out & ((1 << bits) - 1);
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}
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this.dword = await this.tokenizer.readToken(Token.UINT32_LE);
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if (this.pos) {
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out <<= this.pos;
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out |= this.dword >>> (32 - this.pos);
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}
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return out & ((1 << bits) - 1);
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}
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async ignore(bits) {
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if (this.pos > 0) {
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const remaining = 32 - this.pos;
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this.dword = null;
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bits -= remaining;
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this.pos = 0;
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}
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const remainder = bits % 32;
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const numOfWords = (bits - remainder) / 32;
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await this.tokenizer.ignore(numOfWords * 4);
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return this.read(remainder);
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}
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}
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