@msgpack/msgpack/dist/CachedKeyDecoder.js

MessagePack for JavaScript/ECMA-262

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.CachedKeyDecoder = void 0;
const utf8_1 = require("./utils/utf8");
const DEFAULT_MAX_KEY_LENGTH = 16;
const DEFAULT_MAX_LENGTH_PER_KEY = 16;
class CachedKeyDecoder {
    constructor(maxKeyLength = DEFAULT_MAX_KEY_LENGTH, maxLengthPerKey = DEFAULT_MAX_LENGTH_PER_KEY) {
        this.maxKeyLength = maxKeyLength;
        this.maxLengthPerKey = maxLengthPerKey;
        this.hit = 0;
        this.miss = 0;
        // avoid `new Array(N)` to create a non-sparse array for performance.
        this.caches = [];
        for (let i = 0; i < this.maxKeyLength; i++) {
            this.caches.push([]);
        }
    }
    canBeCached(byteLength) {
        return byteLength > 0 && byteLength <= this.maxKeyLength;
    }
    get(bytes, inputOffset, byteLength) {
        const records = this.caches[byteLength - 1];
        FIND_CHUNK: for (const record of records) {
            const recordBytes = record.bytes;
            for (let j = 0; j < byteLength; j++) {
                if (recordBytes[j] !== bytes[inputOffset + j]) {
                    continue FIND_CHUNK;
                }
            }
            return record.value;
        }
        return null;
    }
    store(bytes, value) {
        const records = this.caches[bytes.length - 1];
        const record = { bytes, value };
        if (records.length >= this.maxLengthPerKey) {
            // `records` are full!
            // Set `record` to a randomized position.
            records[(Math.random() * records.length) | 0] = record;
        }
        else {
            records.push(record);
        }
    }
    decode(bytes, inputOffset, byteLength) {
        const cachedValue = this.get(bytes, inputOffset, byteLength);
        if (cachedValue != null) {
            this.hit++;
            return cachedValue;
        }
        this.miss++;
        const value = utf8_1.utf8DecodeJs(bytes, inputOffset, byteLength);
        // Ensure to copy a slice of bytes because the byte may be NodeJS Buffer and Buffer#slice() returns a reference to its internal ArrayBuffer.
        const slicedCopyOfBytes = Uint8Array.prototype.slice.call(bytes, inputOffset, inputOffset + byteLength);
        this.store(slicedCopyOfBytes, value);
        return value;
    }
}
exports.CachedKeyDecoder = CachedKeyDecoder;
//# sourceMappingURL=CachedKeyDecoder.js.map