Function ReadFile [src]

If buffer's length exceeds what a Windows DWORD integer can hold, it will be broken into multiple non-atomic reads.

Prototype

pub fn ReadFile(in_hFile: HANDLE, buffer: []u8, offset: ?u64) ReadFileError!usize

Parameters

in_hFile: HANDLEbuffer: []u8offset: ?u64

Possible Errors

AccessDenied

Known to be possible when:

Unable to read from disconnected virtual com port (Windows)

BrokenPipe

ConnectionResetByPeer

The specified network name is no longer available.

LockViolation

Unable to read file due to lock.

NotOpenForReading

OperationAborted

Unexpected

Source

  pub fn ReadFile(in_hFile: HANDLE, buffer: []u8, offset: ?u64) ReadFileError!usize {
    while (true) {
        const want_read_count: DWORD = @min(@as(DWORD, maxInt(DWORD)), buffer.len);
        var amt_read: DWORD = undefined;
        var overlapped_data: OVERLAPPED = undefined;
        const overlapped: ?*OVERLAPPED = if (offset) |off| blk: {
            overlapped_data = .{
                .Internal = 0,
                .InternalHigh = 0,
                .DUMMYUNIONNAME = .{
                    .DUMMYSTRUCTNAME = .{
                        .Offset = @as(u32, @truncate(off)),
                        .OffsetHigh = @as(u32, @truncate(off >> 32)),
                    },
                },
                .hEvent = null,
            };
            break :blk &overlapped_data;
        } else null;
        if (kernel32.ReadFile(in_hFile, buffer.ptr, want_read_count, &amt_read, overlapped) == 0) {
            switch (GetLastError()) {
                .IO_PENDING => unreachable,
                .OPERATION_ABORTED => continue,
                .BROKEN_PIPE => return 0,
                .HANDLE_EOF => return 0,
                .NETNAME_DELETED => return error.ConnectionResetByPeer,
                .LOCK_VIOLATION => return error.LockViolation,
                .ACCESS_DENIED => return error.AccessDenied,
                .INVALID_HANDLE => return error.NotOpenForReading,
                else => |err| return unexpectedError(err),
            }
        }
        return amt_read;
    }
}  