zx_counter_add

Summary

Add a value to a counter.

Declaration

#include <zircon/syscalls.h>

zx_status_t zx_counter_add(zx_handle_t handle, int64_t value);

Description

zx_counter_add() adds value to the counter referenced by handle.

After the result of the addition, if the counter's value is:

  • less than or equal to zero - ZX_COUNTER_NON_POSITIVE will be asserted and ZX_COUNTER_POSITIVE will be deasserted.

  • greater than zero - ZX_COUNTER_POSITIVE will be asserted and ZX_COUNTER_NON_POSITIVE will be deasserted.

Rights

handle must have both ZX_RIGHT_READ and ZX_RIGHT_WRITE. Because a counter's value could be determined by checking for ZX_ERR_OUT_OF_RANGE on a series of carefully crafted zx_counter_add() calls, there is no way to create a counter that cannot be read, but which can be added.

Return value

zx_counter_add() returns ZX_OK on success.

On failure, an error value is returned.

Errors

ZX_ERR_WRONG_TYPE if handle is not a counter handle.

ZX_ERR_ACCESS_DENIED if handle does not have ZX_RIGHT_WRITE.

ZX_ERR_OUT_OF_RANGE if the result of the addition would overflow or underflow.

See also