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esballoc(9r)
NAME
  esballoc - STREAMS: Allocates a message block with a shared buffer

SYNOPSIS
  #include <sys/stream.h>

  mblk_t * esballoc(
	  unsigned char *base,
	  int size,
	  int pri,
	  frtn_t *free_rtnp );

ARGUMENTS
  base
      Specifies the address of the user-supplied data buffer.

  size
      Specifies the number of bytes in the data buffer.

  pri Specifies the priority of the allocation request (to be used by the
      allocb interface, which esballoc calls).

  free_rtnp
      Specifies the free interface (routine) data structure.

DESCRIPTION
  The esballoc interface creates a STREAMS message and attaches a user-
  supplied data buffer in place of a STREAMS data buffer.  The interface
  calls allocb to obtain a message and data block header. The user-supplied
  data buffer, pointed to by the base argument, is used as the data buffer
  for the message.

  The free_rtn structure is referenced by the dp_freep member of the datab
  structure.  When the freeb interface is called to free the message, the
  driver's message free interface (referenced through the free_rtn structure)
  is called, with arguments, to free the data buffer.

  The free_rtn structure is defined as follows:

       /* Free return structure for esballoc */
       typedef struct free_rtn {
	 void	 (*free_func)(char *, char *); /* Interface to free buffer */
	 char *	 free_arg;		       /* Parameter to free_func */
       } frtn_t;

  Instead of requiring a specific number of arguments, the free_arg member is
  of type char *. This way, the driver can pass a pointer to a structure if
  more than one argument is needed.

NOTES
  The free_func interface must be defined in kernel space and should be
  declared void. It has no user context and must not sleep.

RETURN VALUES
  Upon successful completion, the esballoc interface returns a pointer to the
  newly 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.

  On failure, esballoc returns a NULL pointer.

SEE ALSO
  Kernel Interfaces: allocb(9r), freeb(9r)

  Programmer's Guide: STREAMS

Index for Section 9r

Alphabetical listing for E

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