Module

std/io/buffer.ts

Deno standard library
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class BufReader
implements Reader
import { BufReader } from "https://deno.land/std@0.145.0/io/buffer.ts";

BufReader implements buffering for a Reader object.

Constructors

new
BufReader(rd: Reader, size?: number)

Methods

buffered(): number
peek(n: number): Promise<Uint8Array | null>

peek() returns the next n bytes without advancing the reader. The bytes stop being valid at the next read call.

When the end of the underlying stream is reached, but there are unread bytes left in the buffer, those bytes are returned. If there are no bytes left in the buffer, it returns null.

If an error is encountered before n bytes are available, peek() throws an error with the partial property set to a slice of the buffer that contains the bytes that were available before the error occurred.

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

reads data into p. It returns the number of bytes read into p. The bytes are taken from at most one Read on the underlying Reader, hence n may be less than len(p). To read exactly len(p) bytes, use io.ReadFull(b, p).

readByte(): Promise<number | null>

Returns the next byte [0, 255] or null.

readFull(p: Uint8Array): Promise<Uint8Array | null>

reads exactly p.length bytes into p.

If successful, p is returned.

If the end of the underlying stream has been reached, and there are no more bytes available in the buffer, readFull() returns null instead.

An error is thrown if some bytes could be read, but not enough to fill p entirely before the underlying stream reported an error or EOF. Any error thrown will have a partial property that indicates the slice of the buffer that has been successfully filled with data.

Ported from https://golang.org/pkg/io/#ReadFull

readLine(): Promise<ReadLineResult | null>

readLine() is a low-level line-reading primitive. Most callers should use readString('\n') instead or use a Scanner.

readLine() tries to return a single line, not including the end-of-line bytes. If the line was too long for the buffer then more is set and the beginning of the line is returned. The rest of the line will be returned from future calls. more will be false when returning the last fragment of the line. The returned buffer is only valid until the next call to readLine().

The text returned from ReadLine does not include the line end ("\r\n" or "\n").

When the end of the underlying stream is reached, the final bytes in the stream are returned. No indication or error is given if the input ends without a final line end. When there are no more trailing bytes to read, readLine() returns null.

Calling unreadByte() after readLine() will always unread the last byte read (possibly a character belonging to the line end) even if that byte is not part of the line returned by readLine().

readSlice(delim: number): Promise<Uint8Array | null>

readSlice() reads until the first occurrence of delim in the input, returning a slice pointing at the bytes in the buffer. The bytes stop being valid at the next read.

If readSlice() encounters an error before finding a delimiter, or the buffer fills without finding a delimiter, it throws an error with a partial property that contains the entire buffer.

If readSlice() encounters the end of the underlying stream and there are any bytes left in the buffer, the rest of the buffer is returned. In other words, EOF is always treated as a delimiter. Once the buffer is empty, it returns null.

Because the data returned from readSlice() will be overwritten by the next I/O operation, most clients should use readString() instead.

readString(delim: string): Promise<string | null>

readString() reads until the first occurrence of delim in the input, returning a string containing the data up to and including the delimiter. If ReadString encounters an error before finding a delimiter, it returns the data read before the error and the error itself (often null). ReadString returns err != nil if and only if the returned data does not end in delim. For simple uses, a Scanner may be more convenient.

reset(r: Reader): void

Discards any buffered data, resets all state, and switches the buffered reader to read from r.

size(): number

Returns the size of the underlying buffer in bytes.

Static Methods

create(r: Reader, size?: number): BufReader

return new BufReader unless r is BufReader