key-value-compress/lib/_util.js

Key-Value interface to deflate, split, concatenate and inflate storage.

"use strict";
/**
 * _util.ts
 */
Object.defineProperty(exports, "__esModule", { value: true });
exports.base64KVS = exports.concatBuffer = exports.splitBuffer = exports.digestBuffer = void 0;
const crypto = require("crypto");
const _transform_1 = require("./_transform");
/**
 * generate digest hash string for Buffer
 */
function digestBuffer(algorithm, chunk) {
    return crypto.createHash(algorithm).update(chunk).digest("hex");
}
exports.digestBuffer = digestBuffer;
/**
 * split a large Buffer to smaller chunks
 */
function splitBuffer(buffer, chunkSize) {
    const chunks = [];
    let start = 0;
    const total = buffer.length;
    if (total < chunkSize)
        return [buffer];
    while (start < total) {
        const end = Math.min(start + chunkSize, total);
        const chunk = buffer.slice(start, end);
        chunks.push(chunk);
        start = end;
    }
    return chunks;
}
exports.splitBuffer = splitBuffer;
/**
 * concatenate Buffer chunks to a single Buffer
 */
function concatBuffer(chunks) {
    if (!chunks)
        return;
    if (chunks.length === 1) {
        return chunks[0]; // single chunk
    }
    else {
        return Buffer.concat(chunks); // multiple chunks
    }
}
exports.concatBuffer = concatBuffer;
/**
 * transform key-value storage to encode Buffer to base64 string, and vice versa
 */
function base64KVS(storage, encoding) {
    if (!encoding)
        encoding = "base64";
    return (0, _transform_1.encodeKVS)(storage, {
        // Buffer to base64
        encode: buf => buf.toString(encoding),
        // base64 to Buffer
        decode: str => Buffer.from(str || "", encoding),
    });
}
exports.base64KVS = base64KVS;