forked from denoland/deno
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buffer.ts
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/
buffer.ts
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// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
// This code has been ported almost directly from Go's src/bytes/buffer.go
// Copyright 2009 The Go Authors. All rights reserved. BSD license.
// https://github.com/golang/go/blob/master/LICENSE
import * as eof from "./eof";
import { Reader, Writer, SyncReader, SyncWriter } from "./io";
import { assert } from "./util";
import { TextDecoder } from "./text_encoding";
import { DenoError, ErrorKind } from "./errors";
// MIN_READ is the minimum ArrayBuffer size passed to a read call by
// buffer.ReadFrom. As long as the Buffer has at least MIN_READ bytes beyond
// what is required to hold the contents of r, readFrom() will not grow the
// underlying buffer.
const MIN_READ = 512;
const MAX_SIZE = 2 ** 32 - 2;
// `off` is the offset into `dst` where it will at which to begin writing values
// from `src`.
// Returns the number of bytes copied.
function copyBytes(dst: Uint8Array, src: Uint8Array, off = 0): number {
const r = dst.byteLength - off;
if (src.byteLength > r) {
src = src.subarray(0, r);
}
dst.set(src, off);
return src.byteLength;
}
/** A Buffer is a variable-sized buffer of bytes with read() and write()
* methods. Based on https://golang.org/pkg/bytes/#Buffer
*/
export class Buffer implements Reader, SyncReader, Writer, SyncWriter {
private buf: Uint8Array; // contents are the bytes buf[off : len(buf)]
private off = 0; // read at buf[off], write at buf[buf.byteLength]
constructor(ab?: ArrayBuffer) {
if (ab == null) {
this.buf = new Uint8Array(0);
return;
}
this.buf = new Uint8Array(ab);
}
/** bytes() 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()). 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.
*/
bytes(): Uint8Array {
return this.buf.subarray(this.off);
}
/** toString() returns the contents of the unread portion of the buffer
* as a string. Warning - if multibyte characters are present when data is
* flowing through the buffer, this method may result in incorrect strings
* due to a character being split.
*/
toString(): string {
const decoder = new TextDecoder();
return decoder.decode(this.buf.subarray(this.off));
}
/** empty() returns whether the unread portion of the buffer is empty. */
empty(): boolean {
return this.buf.byteLength <= this.off;
}
/** length is a getter that returns the number of bytes of the unread
* portion of the buffer
*/
get length(): number {
return this.buf.byteLength - this.off;
}
/** Returns the capacity of the buffer's underlying byte slice, that is,
* the total space allocated for the buffer's data.
*/
get capacity(): number {
return this.buf.buffer.byteLength;
}
/** truncate() 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.
*/
truncate(n: number): void {
if (n === 0) {
this.reset();
return;
}
if (n < 0 || n > this.length) {
throw Error("bytes.Buffer: truncation out of range");
}
this._reslice(this.off + n);
}
/** reset() resets the buffer to be empty, but it retains the underlying
* storage for use by future writes. reset() is the same as truncate(0)
*/
reset(): void {
this._reslice(0);
this.off = 0;
}
/** _tryGrowByReslice() is a version of grow for the fast-case
* where the internal buffer only needs to be resliced. It returns the index
* where bytes should be written and whether it succeeded.
* It returns -1 if a reslice was not needed.
*/
private _tryGrowByReslice(n: number): number {
const l = this.buf.byteLength;
if (n <= this.capacity - l) {
this._reslice(l + n);
return l;
}
return -1;
}
private _reslice(len: number): void {
assert(len <= this.buf.buffer.byteLength);
this.buf = new Uint8Array(this.buf.buffer, 0, len);
}
/** readSync() reads the next len(p) bytes from the buffer or until the buffer
* is drained. The return value n is the number of bytes read. If the
* buffer has no data to return, eof in the response will be true.
*/
readSync(p: Uint8Array): number | eof.EOF {
if (this.empty()) {
// Buffer is empty, reset to recover space.
this.reset();
if (p.byteLength === 0) {
// this edge case is tested in 'bufferReadEmptyAtEOF' test
return 0;
}
return eof.EOF;
}
const nread = copyBytes(p, this.buf.subarray(this.off));
this.off += nread;
return nread;
}
async read(p: Uint8Array): Promise<number | eof.EOF> {
const rr = this.readSync(p);
return Promise.resolve(rr);
}
writeSync(p: Uint8Array): number {
const m = this._grow(p.byteLength);
return copyBytes(this.buf, p, m);
}
async write(p: Uint8Array): Promise<number> {
const n = this.writeSync(p);
return Promise.resolve(n);
}
/** _grow() grows the buffer to guarantee space for n more bytes.
* It returns the index where bytes should be written.
* If the buffer can't grow it will throw with ErrTooLarge.
*/
private _grow(n: number): number {
const m = this.length;
// If buffer is empty, reset to recover space.
if (m === 0 && this.off !== 0) {
this.reset();
}
// Fast: Try to grow by means of a reslice.
const i = this._tryGrowByReslice(n);
if (i >= 0) {
return i;
}
const c = this.capacity;
if (n <= Math.floor(c / 2) - m) {
// We can slide things down instead of allocating a new
// ArrayBuffer. We only need m+n <= c to slide, but
// we instead let capacity get twice as large so we
// don't spend all our time copying.
copyBytes(this.buf, this.buf.subarray(this.off));
} else if (c > MAX_SIZE - c - n) {
throw new DenoError(
ErrorKind.TooLarge,
"The buffer cannot be grown beyond the maximum size."
);
} else {
// Not enough space anywhere, we need to allocate.
const buf = new Uint8Array(2 * c + n);
copyBytes(buf, this.buf.subarray(this.off));
this.buf = buf;
}
// Restore this.off and len(this.buf).
this.off = 0;
this._reslice(m + n);
return m;
}
/** grow() 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 panic. If
* the buffer can't grow it will throw ErrTooLarge.
* Based on https://golang.org/pkg/bytes/#Buffer.Grow
*/
grow(n: number): void {
if (n < 0) {
throw Error("Buffer.grow: negative count");
}
const m = this._grow(n);
this._reslice(m);
}
/** readFrom() reads data from r until EOF and appends it to the buffer,
* growing the buffer as needed. It returns the number of bytes read. If the
* buffer becomes too large, readFrom will panic with ErrTooLarge.
* Based on https://golang.org/pkg/bytes/#Buffer.ReadFrom
*/
async readFrom(r: Reader): Promise<number> {
let n = 0;
while (true) {
try {
const i = this._grow(MIN_READ);
this._reslice(i);
const fub = new Uint8Array(this.buf.buffer, i);
const nread = await r.read(fub);
if (nread === eof.EOF) {
return n;
}
this._reslice(i + nread);
n += nread;
} catch (e) {
return n;
}
}
}
/** Sync version of `readFrom`
*/
readFromSync(r: SyncReader): number {
let n = 0;
while (true) {
try {
const i = this._grow(MIN_READ);
this._reslice(i);
const fub = new Uint8Array(this.buf.buffer, i);
const nread = r.readSync(fub);
if (nread === eof.EOF) {
return n;
}
this._reslice(i + nread);
n += nread;
} catch (e) {
return n;
}
}
}
}
/** Read `r` until EOF and return the content as `Uint8Array`.
*/
export async function readAll(r: Reader): Promise<Uint8Array> {
const buf = new Buffer();
await buf.readFrom(r);
return buf.bytes();
}
/** Read synchronously `r` until EOF and return the content as `Uint8Array`.
*/
export function readAllSync(r: SyncReader): Uint8Array {
const buf = new Buffer();
buf.readFromSync(r);
return buf.bytes();
}