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