vrb_init_opt(3) initialize a virtual ring buffer




#include <vrb.h>

vrb_p vrb_init_opt(vrb_p vrb, size_t size, const char *name, int options);


vrb_init_opt Initialize a static or pre-allocated virtual ring buffer structure.

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.


vrb_p vrb
specifies the virtual ring buffer structure to be initialized. The caller must release buffer resources via vrb_uninit(3) when this virtual ring buffer is no longer needed. If NULL is given, a new virtual ring buffer structure is allocated and the caller must release buffer resources via vrb_destroy(3) when an allocated virtual ring buffer is no longer needed.

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:

Do not include guard pages that would protect against buffer overflow errors.
Override VRB_NOGUARD if the environment variable VRBGUARD is defined with a value other than the string "0".


On success, a handle (pointer) to the newly created virtual ring buffer is returned. On error, NULL is returned.


If an error is returned, then errno will have one of the following values:
A buffer size was requested which is too large for address space allocation arithmetic.
Out of memory allocating the virtual ring buffer structure.
An errno value set by a failing system call.