DataView

Вид DataView предоставляет низко-уровневый интерфейс для чтения и записи многочисленных числовых типов в бинарном ArrayBuffer, независимо от порядка байтов платформы.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

Синтаксис

new DataView(buffer [, byteOffset [, byteLength]])

Параметры

buffer

Существующий ArrayBuffer или SharedArrayBuffer для использования как хранилище для нового объекта DataView.

byteOffset Необязательный

Смещение в байтах к первому байту в заданном буфере. Если не определён, то вид буфера будет начинаться с первого байта.

byteLength Необязательный

Количество элементов в массиве байтов. Если не определён, то длина вида будет соответствовать длине буфера.

Возвращаемое значение

Новый объект DataView представляющий определённый буфер данных.

Исключения

RangeError

Выкидывается если byteOffset  и byteLength заходит за пределы буфера.

Описание

Порядок байтов

Многобайтовые числовые форматы представлены в памяти по разному в зависимости от архитектуры машины, см Endianness для объяснения. Аксессоры DataView предоставляют явный контроль над обращением к данным вне зависимости от порядка байтов архитектуры платформы.

var littleEndian = (function() {
  var buffer = new ArrayBuffer(2);
  new DataView(buffer).setInt16(0, 256, true /* littleEndian */);
  // Int16Array uses the platform's endianness.
  return new Int16Array(buffer)[0] === 256;
})();
console.log(littleEndian); // true or false

Свойства

All DataView instances inherit from DataView.prototype and allows the addition of properties to all DataView objects.

DataView.prototype.constructor

Specifies the function that creates an object's prototype. The initial value is the standard built-in DataView constructor.

DataView.prototype.buffer Read only

The ArrayBuffer referenced by this view. Fixed at construction time and thus read only.

DataView.prototype.byteLength Read only

The length (in bytes) of this view from the start of its ArrayBuffer. Fixed at construction time and thus read only.

DataView.prototype.byteOffset Read only

The offset (in bytes) of this view from the start of its ArrayBuffer. Fixed at construction time and thus read only.

Методы

Read

DataView.prototype.getInt8()

Gets a signed 8-bit integer (byte) at the specified byte offset from the start of the view.

DataView.prototype.getUint8()

Gets an unsigned 8-bit integer (unsigned byte) at the specified byte offset from the start of the view.

DataView.prototype.getInt16()

Gets a signed 16-bit integer (short) at the specified byte offset from the start of the view.

DataView.prototype.getUint16()

Gets an unsigned 16-bit integer (unsigned short) at the specified byte offset from the start of the view.

DataView.prototype.getInt32()

Gets a signed 32-bit integer (long) at the specified byte offset from the start of the view.

DataView.prototype.getUint32()

Gets an unsigned 32-bit integer (unsigned long) at the specified byte offset from the start of the view.

DataView.prototype.getFloat32()

Gets a signed 32-bit float (float) at the specified byte offset from the start of the view.

DataView.prototype.getFloat64()

Gets a signed 64-bit float (double) at the specified byte offset from the start of the view.

DataView.prototype.getBigInt64()

Gets a signed 64-bit integer (long long) at the specified byte offset from the start of the view.

DataView.prototype.getBigUint64()

Gets an unsigned 64-bit integer (unsigned long long) at the specified byte offset from the start of the view.

Write

DataView.prototype.setInt8()

Stores a signed 8-bit integer (byte) value at the specified byte offset from the start of the view.

DataView.prototype.setUint8()

Stores an unsigned 8-bit integer (unsigned byte) value at the specified byte offset from the start of the view.

DataView.prototype.setInt16()

Stores a signed 16-bit integer (short) value at the specified byte offset from the start of the view.

DataView.prototype.setUint16()

Stores an unsigned 16-bit integer (unsigned short) value at the specified byte offset from the start of the view.

DataView.prototype.setInt32()

Stores a signed 32-bit integer (long) value at the specified byte offset from the start of the view.

DataView.prototype.setUint32()

Stores an unsigned 32-bit integer (unsigned long) value at the specified byte offset from the start of the view.

DataView.prototype.setFloat32()

Stores a signed 32-bit float (float) value at the specified byte offset from the start of the view.

DataView.prototype.setFloat64()

Stores a signed 64-bit float (double) value at the specified byte offset from the start of the view.

DataView.prototype.setBigInt64()

Stores a signed 64-bit integer (long long) value at the specified byte offset from the start of the view.

DataView.prototype.setBigUint64()

Stores an unsigned 64-bit integer (unsigned long long) value at the specified byte offset from the start of the view.

Пример

var buffer = new ArrayBuffer(16);
var dv = new DataView(buffer, 0);

dv.setInt16(1, 42);
dv.getInt16(1); //42

Спецификация

Таблица совместимости

Замечания совместимости

Starting with Firefox 40, DataView requires to be constructed with a new operator. Calling DataView() as a function without new, will throw a TypeError from now on.

var dv = DataView(buffer, 0); 
// TypeError: calling a builtin DataView constructor without new is forbidden

var dv = new DataView(buffer, 0);

Также

• jDataView: JavaScript library that polyfills and extends the DataView API to all browsers and Node.js.
• ArrayBuffer
• SharedArrayBuffer