April 11, 2007 ATOMIC_SWAP 3

### NAME

atomic_swap, atomic_swap_32, atomic_swap_uint, atomic_swap_ulong, atomic_swap_ptr, atomic_swap_64 - atomic swap operations

### SYNOPSIS

```uint32_t` atomic_swap_32(```volatile uint32_t *ptr``, uint32_t new`)
```unsigned` `int` atomic_swap_uint(```volatile unsigned int *ptr``, unsigned int new`)
```unsigned` `long` atomic_swap_ulong(```volatile unsigned long *ptr``, unsigned long new`)
```void``*` atomic_swap_ptr(```volatile void *ptr``, void *new`)
```uint64_t` atomic_swap_64(```volatile uint64_t *ptr``, uint64_t new`)

### DESCRIPTION

The atomic_swap family of functions perform a swap operation in an atomic fashion. The value of the variable referenced by ```ptr` is replaced by ```new` and the old value returned.

The 64-bit variants of these functions are available only on platforms that can support atomic 64-bit memory access. Applications can check for the availability of 64-bit atomic memory operations by testing if the pre-processor macro ```__HAVE_ATOMIC64_OPS` is defined.

### SEE ALSO

atomic_ops(3)

### HISTORY

The atomic_swap functions first appeared in NetBSD5.0.