Buffer | /io/mod.ts | std@0.220.0

class Buffer

implements Writer, WriterSync, Reader, ReaderSync

Re-export

import { Buffer } from "https://deno.land/std@0.220.0/io/mod.ts";

A variable-sized buffer of bytes with read() and write() methods.

Buffer is almost always used with some I/O like files and sockets. It allows one to buffer up a download from a socket. Buffer grows and shrinks as necessary.

Buffer is NOT the same thing as Node's Buffer. Node's Buffer was created in 2009 before JavaScript had the concept of ArrayBuffers. It's simply a non-standard ArrayBuffer.

ArrayBuffer is a fixed memory allocation. Buffer is implemented on top of ArrayBuffer.

Based on Go Buffer.

Constructors

new

Buffer(ab?: ArrayBufferLike | ArrayLike<number>)

Properties

readonly

capacity: number

The read only capacity of the buffer's underlying byte slice, that is, the total space allocated for the buffer's data.

readonly

length: number

A read only number of bytes of the unread portion of the buffer.

Methods

bytes(options?): Uint8Array

Returns a slice holding the unread portion of the buffer.

The slice is valid for use only until the next buffer modification (that is, only until the next call to a method like read(), write(), reset(), or truncate()). If options.copy is false the slice aliases the buffer content at least until the next buffer modification, so immediate changes to the slice will affect the result of future reads.

empty(): boolean

Returns whether the unread portion of the buffer is empty.

grow(n: number)

Grows the buffer's capacity, if necessary, to guarantee space for another n bytes. After .grow(n), at least n bytes can be written to the buffer without another allocation. If n is negative, .grow() will throw. If the buffer can't grow it will throw an error.

Based on Go Lang's Buffer.Grow.

read(p: Uint8Array): Promise<number | null>

Reads the next p.length bytes from the buffer or until the buffer is drained. Resolves to the number of bytes read. If the buffer has no data to return, resolves to EOF (null).

NOTE: This methods reads bytes synchronously; it's provided for compatibility with Reader interfaces.

readFrom(r: Reader): Promise<number>

Reads data from r until EOF (null) and appends it to the buffer, growing the buffer as needed. It resolves to the number of bytes read. If the buffer becomes too large, .readFrom() will reject with an error.

Based on Go Lang's Buffer.ReadFrom.

readFromSync(r: ReaderSync): number

Reads data from r until EOF (null) and appends it to the buffer, growing the buffer as needed. It returns the number of bytes read. If the buffer becomes too large, .readFromSync() will throw an error.

Based on Go Lang's Buffer.ReadFrom.

readSync(p: Uint8Array): number | null

Reads the next p.length bytes from the buffer or until the buffer is drained. Returns the number of bytes read. If the buffer has no data to return, the return is EOF (null).

reset()

truncate(n: number)

Discards all but the first n unread bytes from the buffer but continues to use the same allocated storage. It throws if n is negative or greater than the length of the buffer.

write(p: Uint8Array): Promise<number>

NOTE: This methods writes bytes synchronously; it's provided for compatibility with Writer interface.

writeSync(p: Uint8Array): number