# PR_GetUniqueIdentity

Asks the runtime to allocate a unique identity for a layer identified by
the layer's name.

## Syntax

```{code}
#include <prio.h>

PRDescIdentity PR_GetUniqueIdentity(const char *layer_name);
```

### Parameter

The function has the following parameter:

`layer_name`

: The string associated with the creation of a layer's identity.

### Returns

The function returns one of the following values:

- If successful, the {ref}`PRDescIdentity` for the layer associated with
  the string specified in the layer named `layer_name`.
- If the function cannot allocate enough dynamic memory, it fails and
  returns the value `PR_INVALID_IO_LAYER` with the error code
  `PR_OUT_OF_MEMORY_ERROR`.

## Description

A string may be associated with a layer when the layer is created.
{ref}`PR_GetUniqueIdentity` allocates a unique layer identity and
associates it with the string. The string can be subsequently passed to
{ref}`PR_CreateIOLayerStub` to create a new file descriptor of that layer.

Call {ref}`PR_GetUniqueIdentity` only once for any particular layer name.
If you're creating a custom I/O layer, cache the result, and then use
that cached result every time you call {ref}`PR_CreateIOLayerStub`.