vrb_new_opt(3)						      VRB Programmer's Manual						    vrb_new_opt(3)

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.   Other-
       wise  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)

vrb								    2002-09-30							    vrb_new_opt(3)