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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 {
// read() reads up to p.byteLength bytes into p. It returns 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 == nil. 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 nil error, except when p.byteLength == 0. Callers should treat a
// return of 0 and nil 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 {
// write() writes p.byteLength bytes from p to the underlying data stream. It
// returns 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-nil 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 {}
// copy() 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(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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