ReadFile

Reads bytes from a file or device.

Module: MacOS

Signature

func ReadFile(
    file: *opaque,
    buffer: *opaque,
    bytesToRead: uint32,
    bytesRead: *uint32,
    overlapped: *opaque
) -> bool32;

Parameters

Name	Type	Description
file	*opaque	BSD file descriptor encoded as a pointer.
buffer	*opaque	Writable buffer for up to bytesToRead bytes.
bytesToRead	uint32	Maximum number of bytes to read.
bytesRead	*uint32	Receives the number of bytes actually read.
overlapped	*opaque	Compatibility parameter; pass null.

Returns

bool32 — nonzero when the underlying read succeeds, including an end-of-file result of zero bytes; zero when it fails.

Description

The operation is synchronous and may return fewer than bytesToRead bytes. The caller must provide a writable buffer large enough for the requested count and a valid bytesRead pointer.

WARNING

This binding does not expose the underlying macOS error number. It also does not automatically retry a read interrupted by a signal.

Example

import MacOS::{ GetStdHandle, ReadFile, StdHandle };

var buffer: char8[256];
var count: uint32 = 0;
let input = GetStdHandle(StdHandle::Input);
if ReadFile(input, buffer.data, 256u32, &count, null) == 0 {
    return 1i32;
}

See also

• Console and I/O — I/O overview
• WriteFile — write bytes