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.\" Copyright © 2002 - Philip Howard - All rights reserved
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.TH vrb_new_opt 3 2002-09-30 vrb "VRB Programmer's Manual"
.SH NAME
vrb_new_opt - create a new virtual ring buffer
.SH LIBRARY
.B -lvrb
.SH SYNOPSIS
.B #include <vrb.h>
.sp
.IB "vrb_p " "vrb_new_opt" "(size_t " "size" ", const char *" "name" ", int " "options" ");"
.SH DESCRIPTION
.B vrb_new_opt
creates a new instance of a virtual ring buffer.
.sp
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.
.SH ARGUMENTS
.IB "size_t " size
.br
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.
.sp
.IB "const char *" name
.br
specifies an optional temporary name pattern or an actual name
of a file to be used as backing store via
.B mmap(2)
in a mounted filesystem in which the process has write permission.
If the name string ends in "XXXXXX" then
.B 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
.B NULL
is given, swap space will be used as backing store via
.B shmat(2).
.sp
.IB "int options"
.br
specifies option flags that may be given to alter the behaviour of the
virtual ring buffer.
The implemented options are:
.TP
.B VRB_NOGUARD
Do not include guard pages that would protect against buffer overflow
errors.
.TP
.B VRB_ENVGUARD
Override VRB_NOGUARD if the environment variable VRBGUARD is defined
with a value other than the string "0".
.SH "RETURN VALUE"
.I vrb_p
.br
On success, a handle (pointer) to the newly created virtual ring buffer
is returned.
On error,
.B NULL
is returned.
.SH ERRORS
If an error is returned, then
.I errno
will have one of the following values:
.TP
.B EINVAL
A buffer size was requested which is too large for address space
allocation arithmetic.
.TP
.B ENOMEM
Out of memory allocating the virtual ring buffer structure.
.TP
-
An
.I errno
value set by a failing system call.
.SH "SEE ALSO"
.BR vrb (3),
.BR vrb_capacity (3),
.BR vrb_data_len (3),
.BR vrb_data_ptr (3),
.BR vrb_destroy (3),
.BR vrb_get (3),
.BR vrb_get_min (3),
.BR vrb_give (3),
.BR vrb_init (3),
.BR vrb_init_opt (3),
.BR vrb_is_empty (3),
.BR vrb_is_full (3),
.BR vrb_is_not_empty (3),
.BR vrb_is_not_full (3),
.BR vrb_move (3),
.BR vrb_new (3),
.BR vrb_put (3),
.BR vrb_put_all (3),
.BR vrb_read (3),
.BR vrb_read_min (3),
.BR vrb_resize (3),
.BR vrb_space_len (3),
.BR vrb_space_ptr (3),
.BR vrb_take (3),
.BR vrb_uninit (3),
.BR vrb_write (3),
.BR vrb_write_min (3)