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/*

 *   xfermem.h

 *

 *   Oliver Fromme  <oliver.fromme@heim3.tu-clausthal.de>

 *   Sat Mar 29 04:41:34 MET 1997

 *

 *   This is a stand-alone module which implements a unidirectional,

 *   fast pipe using mmap().  Its primary use is to transfer large

 *   amounts of data from a parent process to its child process,

 *   with a buffer in between which decouples blocking conditions

 *   on both sides.  Control information is transferred between the

 *   processes through a socketpair.  See xftest.c for an example on

 *   how to use this module.

 */

#ifndef TRUE

#define FALSE 0

#define TRUE  1

#endif

typedef unsigned char byte;

typedef struct {

        int freeindex;  /* [W] next free index */

        int readindex;  /* [R] next index to read */

        int fd[2];

        int wakeme[2];

        byte *data;

        byte *metadata;

        int size;

        int metasize;

} txfermem;

/*

 *   [W] -- May be written to by the writing process only!

 *   [R] -- May be written to by the reading process only!

 *   All other entries are initialized once.

 */

void xfermem_init (txfermem **xf, int bufsize, int msize);

void xfermem_init_writer (txfermem *xf);

void xfermem_init_reader (txfermem *xf);

int  xfermem_write (txfermem *xf, byte *data, int count);

int  xfermem_read  (txfermem *xf, byte *data, int count);

int xfermem_get_freespace (txfermem *xf);

int xfermem_get_usedspace (txfermem *xf);

#define XF_CMD_WAKEUP    0x02

#define XF_CMD_TERMINATE 0x03

#define XF_WRITER 0

#define XF_READER 1

int xfermem_getcmd (int fd, int block);

int xfermem_putcmd (int fd, byte cmd);

int xfermem_block (int fd, txfermem *xf);

void xfermem_done (txfermem *xf);

#define xfermem_done_writer xfermem_init_reader

#define xfermem_done_reader xfermem_init_writer

/* EOF */