Is HANDLE similar to file descriptor in Linux?

Question

Is HANDLE similar to file descriptor in Linux? As far as I know, HANDLE is used for handling every resources on Windows, such as font, icons, files, devices..., which in essence is just a void pointer point to a memory block holding data of a specific resource

Answer 1

Yes, Windows handles are very similar to Unix file descriptors (FDs).

Note that a HANDLE is not a pointer to a block of memory. Although HANDLE is typedef'd as void *, that's just to make it more opaque. In practice, a HANDLE is an index that is looked up in a table, just as an FD number is.

This blog post explores some of the similarities and differences: http://lackingrhoticity.blogspot.com/2015/05/passing-fds-handles-between-processes.html

Answer 2

Yes, they are conceptually similar. File descriptors in unix map integers to a per-process table of pointers to other objects (which can be other things than files, too). File descriptors are not as unified though -- some things exist in a separate "namespace" (e.g., process timers). In that respect, Windows is more orthogonal -- CloseHandle will always free a resource regardless of what it is.

Answer 3

Besides the fact that handles refer to a far broader concept on Windows. Even we restrict the discussion to only file handles, there is significant differences. There is a function called _open_osfhandle() as part of C run-time library on Windows. Its purpose is to, quote "Associates a C run-time file descriptor with an existing operating-system file handle." That is, a glue function between the kernel land and the C Run-time land. The function signature is as below:

int _open_osfhandle (
    intptr_t osfhandle,
    int flags
);

File handles Windows is actually more feature rich than file descriptors in C, which can be configured when a file handle is created with CreateFileA (ANSI version) or CreateFile (UTF16 version), reflecting the design difference between *Nix and Windows. And the resulted handle carries all these information around with all its implications.

Answer 4

A HANDLE is a void pointer

typedef PVOID HANDLE;
typedef void *PVOID;

Windows Data Types