106 lines
3.1 KiB
TypeScript
106 lines
3.1 KiB
TypeScript
// src/index-file/protocol.ts
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import {
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INDEX_MAGIC,
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INDEX_VERSION,
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INDEX_HEADER_SIZE,
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INDEX_ENTRY_SIZE,
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FLAG_VALID,
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} from './constants.js';
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import type { IndexHeader, IndexEntry } from './types.js';
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const CRC_TABLE = new Uint32Array(256);
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for (let i = 0; i < 256; i++) {
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let c = i;
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for (let j = 0; j < 8; j++) {
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c = (c & 1) ? (0xEDB88320 ^ (c >>> 1)) : (c >>> 1);
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}
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CRC_TABLE[i] = c >>> 0;
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}
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export function crc32(buf: Buffer, start = 0, end?: number): number {
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let crc = 0xFFFFFFFF;
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const len = end ?? buf.length;
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for (let i = start; i < len; i++) {
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crc = CRC_TABLE[(crc ^ buf[i]) & 0xFF] ^ (crc >>> 8);
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}
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return (~crc) >>> 0;
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}
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export class IndexProtocol {
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static createHeader(entryCount: number, magic = INDEX_MAGIC): Buffer {
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const buf = Buffer.alloc(INDEX_HEADER_SIZE);
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buf.write(magic, 0, 4, 'ascii');
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buf.writeUInt32LE(INDEX_VERSION, 4);
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buf.writeBigUInt64LE(BigInt(Date.now()) * 1000000n, 8);
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buf.writeUInt32LE(INDEX_ENTRY_SIZE, 16);
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buf.writeUInt32LE(entryCount, 20);
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buf.writeUInt32LE(0, 24);
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buf.writeBigUInt64LE(0n, 28);
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buf.writeUInt32LE(0, 36);
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return buf;
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}
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static readHeader(buf: Buffer): IndexHeader {
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return {
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magic: buf.toString('ascii', 0, 4),
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version: buf.readUInt32LE(4),
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createdAt: buf.readBigUInt64LE(8),
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entrySize: buf.readUInt32LE(16),
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entryCount: buf.readUInt32LE(20),
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validCount: buf.readUInt32LE(24),
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dataFileSize: buf.readBigUInt64LE(28),
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lastSequence: buf.readUInt32LE(36),
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reserved: buf.subarray(40, 64),
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};
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}
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static updateHeaderCounts(
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buf: Buffer,
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validCount: number,
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dataFileSize: bigint,
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lastSequence: number
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): void {
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buf.writeUInt32LE(validCount, 24);
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buf.writeBigUInt64LE(dataFileSize, 28);
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buf.writeUInt32LE(lastSequence, 36);
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}
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static writeEntry(buf: Buffer, index: number, entry: Omit<IndexEntry, 'checksum'>): void {
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const off = INDEX_HEADER_SIZE + index * INDEX_ENTRY_SIZE;
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buf.writeUInt32LE(entry.sequence, off);
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buf.writeBigUInt64LE(entry.timestamp, off + 4);
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buf.writeBigUInt64LE(entry.offset, off + 12);
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buf.writeUInt32LE(entry.length, off + 20);
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buf.writeUInt32LE(entry.flags | FLAG_VALID, off + 24);
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const checksum = crc32(buf, off, off + 28);
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buf.writeUInt32LE(checksum, off + 28);
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}
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static readEntry(buf: Buffer, index: number): IndexEntry | null {
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const off = INDEX_HEADER_SIZE + index * INDEX_ENTRY_SIZE;
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const flags = buf.readUInt32LE(off + 24);
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if (!(flags & FLAG_VALID)) return null;
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return {
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sequence: buf.readUInt32LE(off),
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timestamp: buf.readBigUInt64LE(off + 4),
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offset: buf.readBigUInt64LE(off + 12),
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length: buf.readUInt32LE(off + 20),
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flags,
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checksum: buf.readUInt32LE(off + 28),
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};
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}
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static isValidEntry(buf: Buffer, index: number): boolean {
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const off = INDEX_HEADER_SIZE + index * INDEX_ENTRY_SIZE;
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const flags = buf.readUInt32LE(off + 24);
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return (flags & FLAG_VALID) !== 0;
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}
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static calcFileSize(entryCount: number): number {
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return INDEX_HEADER_SIZE + INDEX_ENTRY_SIZE * entryCount;
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}
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} |