@gmod/cram/dist/cramFile/codecs/getBits.js

read CRAM files with pure Javascript

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.CramBufferOverrunError = void 0;
exports.getBits = getBits;
class CramBufferOverrunError extends Error {
}
exports.CramBufferOverrunError = CramBufferOverrunError;
function getBits(data, cursor, numBits) {
    let val = 0;
    if (cursor.bytePosition + (7 - cursor.bitPosition + numBits) / 8 >
        data.length) {
        throw new CramBufferOverrunError('read error during decoding. the file seems to be truncated.');
    }
    for (let dlen = numBits; dlen; dlen--) {
        // get the next `dlen` bits in the input, put them in val
        val <<= 1;
        val |= (data[cursor.bytePosition] >> cursor.bitPosition) & 1;
        cursor.bitPosition -= 1;
        if (cursor.bitPosition < 0) {
            cursor.bytePosition += 1;
        }
        cursor.bitPosition &= 7;
    }
    return val;
}
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