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Merge pull request #1 from ginkgoch/implementation-and-test
implementation and tests
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‎README.md

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# node-buffer-reader
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# Ginkgoch Buffer Reader for NodeJS
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This is a NodeJS library to help to read [Buffer](https://cn.nodejs.org/api/buffer.html) instance easily.
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## Install
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```terminal
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npm i ginkgoch-buffer-reader --save
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```
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## Example
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**Prepare for data**
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```js
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const buffer = Buffer.alloc(4);
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buffer.writeInt8(8, 0);
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buffer.writeInt16LE(16, 1);
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buffer.writeUInt32LE(32, 3);
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buffer.writeDoubleBE(54.8765, 7);
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```
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**Without `Ginkgoch Buffer Reader`**
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```js
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let i1 = buffer.readInt8(0);
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let i2 = buffer.readInt16LE(1);
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let i3 = buffer.readUInt32LE(3);
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let i4 = buffer.readDoubleBE(7);
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```
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**With `Ginkgoch Buffer Reader`, it automatically manages the read position for you. You don't need to remember the position and the boring type length calculations.**
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```js
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let i1 = br.nextInt8();
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let i2 = br.nextInt16LE();
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let i3 = br.nextUInt32LE();
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let i4 = br.nextDoubleBE();
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```
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## API
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```js
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constructor(buffer: Buffer);
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seek(offset: number, fromBeginning = true);
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nextBuffer(length: number);
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nextString(length: number, encoding = 'utf-8');
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nextIn8();
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nextUInt8();
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nextUInt16LE();
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nextUInt16BE();
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nextInt16LE();
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nextInt16BE();
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nextUInt32LE();
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nextUInt32BE();
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nextInt32LE();
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nextInt32BE();
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nextFloatLE();
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nextFloatBE();
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nextDoubleLE();
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nextDoubleBE();
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```
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## Issues
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Contact [ginkgoch@outlook.com](mailto:ginkgoch@outlook.com) or [sumbit an issue](https://github.com/ginkgoch/node-buffer-reader/issues).

‎index.js

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const assert = require('assert');
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module.exports = class BufferReader {
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constructor(buffer) {
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assert(Buffer.isBuffer(buffer), 'Invalid buffer.');
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this.buffer = buffer;
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this.offset = 0;
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this._makeNextReadFor('Int8', 1);
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this._makeNextReadFor('UInt8', 1);
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this._makeNextReadLEBEFor('UInt16', 2);
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this._makeNextReadLEBEFor('Int16', 2);
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this._makeNextReadLEBEFor('UInt32', 4);
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this._makeNextReadLEBEFor('Int32', 4);
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this._makeNextReadLEBEFor('Float', 4);
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this._makeNextReadLEBEFor('Double', 8);
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}
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seek(offset, fromBeginning = true) {
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if(!fromBeginning) {
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offset += this.offset;
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}
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this._checkOffsetInRange(offset);
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this.offset = offset;
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}
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nextBuffer(length) {
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this._checkPositive(length);
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this._checkOffsetInRange(this.offset + length);
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const buffer = Buffer.alloc(length);
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this.buffer.copy(buffer, 0, this.offset, this.offset + length);
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this.offset += length;
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return buffer;
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}
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nextString(length, encoding = 'utf-8') {
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this._checkPositive(length);
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this._checkOffsetInRange(this.offset + length);
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const str = this.buffer.toString(encoding, this.offset, this.offset + length);
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this.offset += length;
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return str;
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}
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_makeNextReadLEBEFor(method, size) {
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this._makeNextReadFor(method + 'LE', size);
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this._makeNextReadFor(method + 'BE', size);
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}
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_makeNextReadFor(method, size) {
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BufferReader.prototype[`next${method}`] = function() {
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this._checkOffsetInRange(this.offset + size, 'Offset');
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const val = this.buffer[`read${method}`](this.offset);
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this.offset += size;
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return val;
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};
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}
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_checkPositive(number, name = 'Length') {
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assert(number >= 0, `${name} must be positive.`);
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}
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_checkOffsetInRange(offset) {
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assert(offset >= 0 && offset <= this.buffer.length, 'Offset out of range.');
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}
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}

‎index.test.js

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const BufferReader = require('./index.js');
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describe('buffer reader tests', () => {
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test('init test - normal', () => {
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const buffer = Buffer.alloc(4);
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const br = new BufferReader(buffer);
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expect(br).not.toBeNull();
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expect(br).not.toBeUndefined();
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});
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test('init test - not buffer', () => {
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const buffer = undefined;
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function init() { const br = new BufferReader(buffer); }
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expect(init).toThrow(/Invalid buffer./);
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});
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test('seek from beginning - normal', () => {
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const buffer = Buffer.from([1, 2, 3, 4]);
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const br = new BufferReader(buffer);
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expect(br.offset).toBe(0);
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expect(br.buffer).not.toBeNull();
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expect(br.buffer).not.toBeUndefined();
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br.seek(2);
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expect(br.offset).toBe(2);
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});
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test('seek from current - normal', () => {
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const buffer = Buffer.from([1, 2, 3, 4]);
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const br = new BufferReader(buffer);
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br.seek(1);
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expect(br.offset).toBe(1);
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br.seek(1, false);
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expect(br.offset).toBe(2);
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br.seek(1, false);
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expect(br.offset).toBe(3);
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br.seek(1);
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expect(br.offset).toBe(1);
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});
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test('seek from beginning - out of range', () => {
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const buffer = Buffer.from([1, 2, 3, 4]);
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const br = new BufferReader(buffer);
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expect(() => br.seek(5)).toThrow(/Offset out of range./);
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});
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test('seek from current - out of range', () => {
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const buffer = Buffer.from([1, 2, 3, 4]);
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const br = new BufferReader(buffer);
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br.seek(2);
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br.seek(3);
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expect(() => br.seek(2, false)).toThrow(/Offset out of range./);
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});
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test('nextBuffer test - positive', () => {
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const buffer = Buffer.from([1, 2, 3, 4]);
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const br = new BufferReader(buffer);
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expect(() => br.nextBuffer(-1)).toThrow(/Length must be positive./);
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});
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test('nextBuffer test - oor', () => {
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const buffer = Buffer.from([1, 2, 3, 4]);
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const br = new BufferReader(buffer);
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expect(() => br.nextBuffer(5)).toThrow(/Offset out of range./);
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});
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test('nextBuffer test - normal', () => {
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const buffer1 = Buffer.from([1, 2, 3, 4]);
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const buffer2 = Buffer.from([4, 5]);
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const br = new BufferReader(Buffer.concat([buffer1, buffer2]));
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const nBuffer1 = br.nextBuffer(4);
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const nBuffer2 = br.nextBuffer(2);
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expect(Buffer.compare(buffer1, nBuffer1, 0));
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expect(Buffer.compare(buffer2, nBuffer2, 0));
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});
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test('nextString test - normal', () => {
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const str = 'hello world 01!';
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const buffer = new Buffer(str, 'utf-8');
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const br = new BufferReader(Buffer.concat([Buffer.from([0, 2]), buffer]));
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br.seek(2);
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const nStr = br.nextString(15, 'utf-8');
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expect(nStr).toEqual(str);
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});
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test('nextString test - positive', () => {
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const br = new BufferReader(new Buffer('hello', 'utf-8'));
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expect(() => br.nextString(-1)).toThrow(/Length must be positive./);
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});
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test('nextString test - oor', () => {
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const br = new BufferReader(new Buffer('hello', 'utf-8'));
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expect(() => br.nextString(6)).toThrow(/Offset out of range./);
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});
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test('nextInt8 test', () => {
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const buffer = Buffer.alloc(4);
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buffer.writeInt8(1, 0);
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buffer.writeInt8(2, 1);
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buffer.writeInt8(3, 2);
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buffer.writeInt8(4, 3);
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const br = new BufferReader(buffer);
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expect(br.nextInt8()).toBe(1);
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expect(br.nextInt8()).toBe(2);
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expect(br.nextInt8()).toBe(3);
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expect(br.nextInt8()).toBe(4);
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expect(() => br.nextInt8()).toThrow(/Offset out of range./);
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});
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test('nextInt16LE test', () => {
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const buffer = Buffer.alloc(4);
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buffer.writeInt16LE(16, 0);
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buffer.writeInt16LE(32, 2);
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const br = new BufferReader(buffer);
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expect(br.nextInt16LE()).toBe(16);
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expect(br.nextInt16LE()).toBe(32);
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expect(() => br.nextInt16LE()).toThrow(/Offset out of range./);
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});
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test('nextInt16BE test', () => {
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const buffer = Buffer.alloc(4);
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buffer.writeInt16BE(16, 0);
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buffer.writeInt16BE(32, 2);
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const br = new BufferReader(buffer);
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expect(br.nextInt16BE()).toBe(16);
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expect(br.nextInt16BE()).toBe(32);
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expect(() => br.nextInt16BE()).toThrow(/Offset out of range./);
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});
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test('nextUInt32LE test', () => {
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const buffer = Buffer.alloc(8);
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buffer.writeUInt32LE(16, 0);
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buffer.writeUInt32LE(32, 4);
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const br = new BufferReader(buffer);
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expect(br.nextUInt32LE()).toBe(16);
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expect(br.nextUInt32LE()).toBe(32);
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expect(() => br.nextUInt32LE()).toThrow(/Offset out of range./);
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});
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test('nextDoubleBE test', () => {
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const buffer = Buffer.alloc(16);
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const d1 = 12.3432;
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const d2 = 32.8976;
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buffer.writeDoubleBE(d1, 0);
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buffer.writeDoubleBE(d2, 8);
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const br = new BufferReader(buffer);
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expect(br.nextDoubleBE()).toBe(d1);
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expect(br.nextDoubleBE()).toBe(d2);
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expect(() => br.nextDoubleBE()).toThrow(/Offset out of range./);
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});
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test('demo test', () => {
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const buffer = Buffer.alloc(15);
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buffer.writeInt8(8, 0);
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buffer.writeInt16LE(16, 1);
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buffer.writeUInt32LE(32, 3);
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buffer.writeDoubleBE(54.8765, 7);
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// original
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expect(buffer.readInt8(0)).toBe(8);
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expect(buffer.readInt16LE(1)).toBe(16);
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expect(buffer.readUInt32LE(3)).toBe(32);
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expect(buffer.readDoubleBE(7)).toBe(54.8765);
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// new
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const br = new BufferReader(buffer);
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expect(br.nextInt8()).toBe(8);
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expect(br.nextInt16LE()).toBe(16);
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expect(br.nextUInt32LE()).toBe(32);
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expect(br.nextDoubleBE()).toBe(54.8765);
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});
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});

‎package.json

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{
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"name": "ginkgoch-buffer-reader",
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"version": "1.0.0",
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"main": "index.js",
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"scripts": {
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"test": "./node_modules/.bin/jest"
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},
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"author": {
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"name": "Ginkgoch",
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"email": "ginkgoch@outlook.com",
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"url": "https://github.com/ginkgoch/node-buffer-reader"
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},
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"keywords": [
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"ginkgoch", "buffer-reader", "bufferreader", "node-buffer-reader"
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],
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"license": "MIT",
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"description": "This is a library to help to easily read Buffer instance.",
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"devDependencies": {
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"jest": "^23.4.1"
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}
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}

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