allocb(9r) [osf1 man page]

allocb(9r)																allocb(9r)

NAME

       allocb - STREAMS: Allocates a message block

SYNOPSIS

       #include <sys/stream.h>

       MBLKP allocb(
	       int size,
	       uint pri );

ARGUMENTS

       Specifies the number of bytes in the message block.  Specifies the priority of the request. You use this argument to determine if the allo-
       cation of memory blocks (waits) on the request. If you call the allocb interface at a high priority and it blocks on the request, the  sys-
       tem could deadlock. Typically, you pass the constant BPRI_WAITOK, which signifies that allocb can block. If allocb cannot block, you should
       pass the BPRI_HI constant.

DESCRIPTION

       The allocb interface attempts to allocate a STREAMS message block. Buffer allocation fails only when the system is out of  memory.   If	no
       buffer is available, you can call the bufcall interface, which helps a module recover from a memory allocation failure.

RETURN VALUES

       Upon  successful  completion,  the  allocb interface returns a pointer to the allocated message block. This message block is of type struct
       msgb *. The msgb data structure is defined in the /usr/sys/include/sys/stream.h file.

       If allocb cannot allocate a message block, it returns a NULL pointer.

SEE ALSO

       Kernel Routines: bufcall(9r), esballoc(9r), testb(9r)

       Programmer's Guide: STREAMS

																	allocb(9r)

bufcall(9r)															       bufcall(9r)

NAME

       bufcall - STREAMS: Gets a buffer when allocb fails

SYNOPSIS

       #include <sys/stream.h>

       int bufcall(
	       int size,
	       int pri,
	       int (*function) (),
	       long argument );

ARGUMENTS

       Specifies the number of bytes in the buffer.  Specifies the priority of the allocb allocation request (no longer used).	Specifies a kernel
       or driver interface to be called when a buffer becomes available.  Specifies an argument to be passed to the  kernel  or  driver  interface
       specified in the function argument.

DESCRIPTION

       The  bufcall  interface	serves	as  a timeout call of indeterminate length. When a buffer allocation request fails, you can use bufcall to
       schedule the interface passed to the function argument to be called with the argument passed to argument when a buffer  becomes	available.
       The interface passed to function can be a routine that calls allocb or it can be implemented to perform something else.

NOTES

       Even  when the bufcall interface calls the interface passed to the function argument, the allocb interface can still fail if another module
       or device driver allocated the memory before the interface in function was able to call allocb.

RETURN VALUES

       Upon successful completion, the bufcall interface returns a bufcall id that you can use in a call to the unbufcall interface to cancel  the
       request. If the bufcall scheduling fails (that is, a buffer is not available), the interface passed to function is never called and bufcall
       returns the value zero(0).

SEE ALSO

       Kernel Routines: allocb(9r), esballoc(9r), testb(9r)

       Programmer's Guide: STREAMS

																       bufcall(9r)