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// Interfaces 100% copied from Go.
// Documentation liberally lifted from them too.
// Thank you! We love Go!
// The bytes read during an I/O call and a boolean indicating EOF.
export interface ReadResult {
nread: number;
eof: boolean;
}
// Reader is the interface that wraps the basic read() method.
// https://golang.org/pkg/io/#Reader
export interface Reader {
/** Reads up to p.byteLength bytes into `p`. It resolves to the number
* of bytes read (`0` <= `n` <= `p.byteLength`) and any error encountered.
* Even if `read()` returns `n` < `p.byteLength`, it may use all of `p` as
* scratch space during the call. If some data is available but not
* `p.byteLength` bytes, `read()` conventionally returns what is available
* instead of waiting for more.
*
* When `read()` encounters an error or end-of-file condition after
* successfully reading `n` > `0` bytes, it returns the number of bytes read.
* It may return the (non-nil) error from the same call or return the error
* (and `n` == `0`) from a subsequent call. An instance of this general case
* is that a `Reader` returning a non-zero number of bytes at the end of the
* input stream may return either `err` == `EOF` or `err` == `null`. The next
* `read()` should return `0`, `EOF`.
*
* Callers should always process the `n` > `0` bytes returned before
* considering the `EOF`. Doing so correctly handles I/O errors that happen
* after reading some bytes and also both of the allowed `EOF` behaviors.
*
* Implementations of `read()` are discouraged from returning a zero byte
* count with a `null` error, except when `p.byteLength` == `0`. Callers
* should treat a return of `0` and `null` as indicating that nothing
* happened; in particular it does not indicate `EOF`.
*
* Implementations must not retain `p`.
*/
read(p: ArrayBufferView): Promise<ReadResult>;
}
// Writer is the interface that wraps the basic write() method.
// https://golang.org/pkg/io/#Writer
export interface Writer {
/** Writes `p.byteLength` bytes from `p` to the underlying data
* stream. It resolves to the number of bytes written from `p` (`0` <= `n` <=
* `p.byteLength`) and any error encountered that caused the write to stop
* early. `write()` must return a non-null error if it returns `n` <
* `p.byteLength`. write() must not modify the slice data, even temporarily.
*
* Implementations must not retain `p`.
*/
write(p: ArrayBufferView): Promise<number>;
}
// https://golang.org/pkg/io/#Closer
export interface Closer {
// The behavior of Close after the first call is undefined. Specific
// implementations may document their own behavior.
close(): void;
}
// https://golang.org/pkg/io/#Seeker
export interface Seeker {
/** Seek sets the offset for the next `read()` or `write()` to offset,
* interpreted according to `whence`: `SeekStart` means relative to the start
* of the file, `SeekCurrent` means relative to the current offset, and
* `SeekEnd` means relative to the end. Seek returns the new offset relative
* to the start of the file and an error, if any.
*
* Seeking to an offset before the start of the file is an error. Seeking to
* any positive offset is legal, but the behavior of subsequent I/O operations
* on the underlying object is implementation-dependent.
*/
seek(offset: number, whence: number): Promise<void>;
}
// https://golang.org/pkg/io/#ReadCloser
export interface ReaderCloser extends Reader, Closer {}
// https://golang.org/pkg/io/#WriteCloser
export interface WriteCloser extends Writer, Closer {}
// https://golang.org/pkg/io/#ReadSeeker
export interface ReadSeeker extends Reader, Seeker {}
// https://golang.org/pkg/io/#WriteSeeker
export interface WriteSeeker extends Writer, Seeker {}
// https://golang.org/pkg/io/#ReadWriteCloser
export interface ReadWriteCloser extends Reader, Writer, Closer {}
// https://golang.org/pkg/io/#ReadWriteSeeker
export interface ReadWriteSeeker extends Reader, Writer, Seeker {}
/** Copies from `src` to `dst` until either `EOF` is reached on `src`
* or an error occurs. It returns the number of bytes copied and the first
* error encountered while copying, if any.
*
* Because `copy()` is defined to read from `src` until `EOF`, it does not
* treat an `EOF` from `read()` as an error to be reported.
*/
// https://golang.org/pkg/io/#Copy
export async function copy(dst: Writer, src: Reader): Promise<number> {
let n = 0;
const b = new Uint8Array(32 * 1024);
let gotEOF = false;
while (gotEOF === false) {
const result = await src.read(b);
if (result.eof) {
gotEOF = true;
}
n += await dst.write(b.subarray(0, result.nread));
}
return n;
}
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