NAME¶
vrb_new_opt - create a new virtual ring buffer
LIBRARY¶
-lvrb
SYNOPSIS¶
#include <vrb.h>
vrb_p vrb_new_opt(size_t size, const char
*name, int options);
DESCRIPTION¶
vrb_new_opt creates a new instance of a virtual ring buffer.
A virtual ring buffer is a character FIFO queue with the special property that
any sequence of characters in the buffer may be accessed as a single
contiguous block of memory, eliminating the need to split any sequence to
handle a buffer wraparound.
ARGUMENTS¶
size_t size
specifies the requested minimum buffer size to be allocated. The given value
will be rounded up to the nearest or equal whole multiple of the system page
size. The virtual ring buffer is implemented by mapping two adjacent blocks of
memory to the same memory object. Thus, twice as much virtual address space
will be used and the specified size must be less than half of the available
virtual address space for this process.
const char *name
specifies an optional temporary name pattern or an actual name of a file to be
used as backing store via
mmap(2) in a mounted filesystem in which the
process has write permission. If the name string ends in "XXXXXX"
then
mkstemp(3) will be used to make the file unique. Otherwise it will
be used as is. If the named file already exists or otherwise cannot be opened
for write, an error will occur. If
NULL is given, swap space will be
used as backing store via
shmat(2).
int options
specifies option flags that may be given to alter the behaviour of the virtual
ring buffer. The implemented options are:
- VRB_NOGUARD
- Do not include guard pages that would protect against
buffer overflow errors.
- VRB_ENVGUARD
- Override VRB_NOGUARD if the environment variable VRBGUARD
is defined with a value other than the string "0".
RETURN VALUE¶
vrb_p
On success, a handle (pointer) to the newly created virtual ring buffer is
returned. On error,
NULL is returned.
ERRORS¶
If an error is returned, then
errno will have one of the following
values:
- EINVAL
- A buffer size was requested which is too large for address
space allocation arithmetic.
- ENOMEM
- Out of memory allocating the virtual ring buffer
structure.
- -
- An errno value set by a failing system call.
SEE ALSO¶
vrb(3),
vrb_capacity(3),
vrb_data_len(3),
vrb_data_ptr(3),
vrb_destroy(3),
vrb_get(3),
vrb_get_min(3),
vrb_give(3),
vrb_init(3),
vrb_init_opt(3),
vrb_is_empty(3),
vrb_is_full(3),
vrb_is_not_empty(3),
vrb_is_not_full(3),
vrb_move(3),
vrb_new(3),
vrb_put(3),
vrb_put_all(3),
vrb_read(3),
vrb_read_min(3),
vrb_resize(3),
vrb_space_len(3),
vrb_space_ptr(3),
vrb_take(3),
vrb_uninit(3),
vrb_write(3),
vrb_write_min(3)