« NSPR API Reference « I/O Functions
This is the declaration for the enumeration PRAccessHow, used in the how parameter of PR_Access:
#include <prio.h>
typedef enum PRAccessHow {
  PR_ACCESS_EXISTS = 1,
  PR_ACCESS_WRITE_OK = 2,
  PR_ACCESS_READ_OK = 3
} PRAccessHow;
See PR_Access for what each of these values mean.