Handle an _IO_CHMOD message
#include <sys/iofunc.h>
int iofunc_chmod ( resmgr_context_t *ctp,
io_chmod_t *msg,
iofunc_ocb_t *ocb,
iofunc_attr_t *attr );
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
The iofunc_chmod() helper function implements POSIX semantics for the client's chmod() call, which is received as an _IO_CHMOD message by the resource manager.
The iofunc_chmod() function calls iofunc_check_access() to verify that the client has the necessary permissions to effect a chmod() on the attribute. If so, the chmod() is performed, modifying elements of the ocb->attr structure. This function takes care of updating the IOFUNC_ATTR_CTIME, IOFUNC_ATTR_DIRTY_TIME, and IOFUNC_ATTR_DIRTY_MODE bits in ocb->attr->flags. You can use iofunc_time_update(), to update the appropriate time fields in ocb->attr.
You can use iofunc_chmod(), for example, in a filesystem manager, where an _IO_CHMOD message was received, and the filesystem code must now write the values to the medium. The filesystem code may wish to block the client thread until the data was actually written to the medium. Contrast this scenario to the behavior of iofunc_chmod_default(), which calls this routine, and replies to the client thread.
io_chmod_t structure
The io_chmod_t structure holds the _IO_CHMOD message received by the resource manager:
struct _io_chmod {
uint16_t type;
uint16_t combine_len;
mode_t mode;
};
typedef union {
struct _io_chmod i;
} io_chmod_t;
The I/O message structures are unions of an input message (coming to the resource manager) and an output or reply message (going back to the client). In this case, there's only an input message, i.
The i member is a structure of type _io_chmod that contains the following members:
| Safety: | |
|---|---|
| Cancellation point | No |
| Interrupt handler | No |
| Signal handler | Yes |
| Thread | Yes |