Init indexed file

lib/dat/binary-helpers.ts

@@ -0,0 +1,92 @@
+export class BinaryWriter {
+  private chunks: Buffer[] = [];
+
+  writeUInt32(value: number): this {
+    const buf = Buffer.alloc(4);
+    buf.writeUInt32LE(value, 0);
+    this.chunks.push(buf);
+    return this;
+  }
+
+  writeDouble(value: number): this {
+    const buf = Buffer.alloc(8);
+    buf.writeDoubleLE(value, 0);
+    this.chunks.push(buf);
+    return this;
+  }
+
+  writeBigUInt64(value: bigint): this {
+    const buf = Buffer.alloc(8);
+    buf.writeBigUInt64LE(value, 0);
+    this.chunks.push(buf);
+    return this;
+  }
+
+  writeString(value: string): this {
+    const strBuf = Buffer.from(value, 'utf8');
+    this.writeUInt32(strBuf.length);
+    this.chunks.push(strBuf);
+    return this;
+  }
+
+  writeNumberArray(values: number[]): this {
+    this.writeUInt32(values.length);
+    for (const v of values) this.writeDouble(v);
+    return this;
+  }
+
+  writeStringArray(values: string[]): this {
+    this.writeUInt32(values.length);
+    for (const v of values) this.writeString(v);
+    return this;
+  }
+
+  toBuffer(): Buffer {
+    return Buffer.concat(this.chunks);
+  }
+}
+
+export class BinaryReader {
+  private offset = 0;
+
+  constructor(private buf: Buffer) {}
+
+  readUInt32(): number {
+    const v = this.buf.readUInt32LE(this.offset);
+    this.offset += 4;
+    return v;
+  }
+
+  readDouble(): number {
+    const v = this.buf.readDoubleLE(this.offset);
+    this.offset += 8;
+    return v;
+  }
+
+  readBigUInt64(): bigint {
+    const v = this.buf.readBigUInt64LE(this.offset);
+    this.offset += 8;
+    return v;
+  }
+
+  readString(): string {
+    const len = this.readUInt32();
+    const v = this.buf.toString('utf8', this.offset, this.offset + len);
+    this.offset += len;
+    return v;
+  }
+
+  readNumberArray(): number[] {
+    const len = this.readUInt32();
+    const arr: number[] = [];
+    for (let i = 0; i < len; i++) arr.push(this.readDouble());
+    return arr;
+  }
+
+  readStringArray(): string[] {
+    const len = this.readUInt32();
+    const arr: string[] = [];
+    for (let i = 0; i < len; i++) arr.push(this.readString());
+    return arr;
+  }
+}