【VxWorks5(2)，干货满满

:						\
(					\
	(toP == (ringId)->bufSize - 1) ?	\
    (					\
    ((ringId)->pFromBuf == 0) ?		\
	0				\
    :					\
	(				\
	(ringId)->buf[toP] = ch,	\
	(ringId)->pToBuf = 0,		\
	1				\
	)				\
    )					\
:					\
    (					\
    (ringId)->buf[toP] = ch,		\
    (ringId)->pToBuf++,			\
    1					\
    )					\
)					\
)

/* function declarations */

#if defined(STDC) || defined(__cplusplus)

extern BOOL rngIsEmpty (RING_ID ringId); extern BOOL rngIsFull (RING_ID ringId); extern RING_ID rngCreate (int nbytes); extern int rngBufGet (RING_ID rngId, char *buffer, int maxbytes); extern int rngBufPut (RING_ID rngId, char *buffer, int nbytes); extern int rngFreeBytes (RING_ID ringId); extern int rngNBytes (RING_ID ringId); extern void rngDelete (RING_ID ringId); extern void rngFlush (RING_ID ringId); extern void rngMoveAhead (RING_ID ringId, int n); extern void rngPutAhead (RING_ID ringId, char byte, int offset);

#else /* STDC */

extern BOOL rngIsEmpty (); extern BOOL rngIsFull (); extern RING_ID rngCreate (); extern int rngBufGet (); extern int rngBufPut (); extern int rngFreeBytes (); extern int rngNBytes (); extern void rngDelete (); extern void rngFlush (); extern void rngMoveAhead (); extern void rngPutAhead ();

#endif /* STDC */

#ifdef __cplusplus } #endif

#endif /* __INCrngLibh */

继续看rngLib.c

/* rngLib.c - ring buffer subroutine library */

/* Copyright 1984-1995 Wind River Systems, Inc. */ #include "copyright_wrs.h"

/* modification history

01x,13feb95,jdi doc tweaks. 01w,20jan93,jdi documentation cleanup for 5.1. 01v,26may92,rrr the tree shuffle 01u,11jan92,wmd fix bug spr #1210, race condition based on updates of buf pointers in more than 1 place in rngBufPut() and rngBufGet(). 01t,13dec91,gae ANSI cleanup. 01s,04oct91,rrr passed through the ansification filter -changed functions to ansi style -changed VOID to void -changed copyright notice 01r,05apr91,jdi documentation -- removed header parens and x-ref numbers; doc review by dnw. 01q,11mar91,jaa documentation cleanup. 01p,11may90,yao added missing modification history (01o) for the last checkin. 01o,09may90,yao typecasted malloc to (char *). 01n,22mar89,dab changed shorts to ints in rngBufGet, rngBufPut. 01m,03feb89,dab added rngDelete to delete a ring buffer. 01l,20aug88,gae documentation. 01k,07jul88,jcf fixed malloc to match new declaration. 01j,30may88,dnw changed to v4 names. 01i,03nov87,ecs documentation. 01h,20oct87,gae documentation. 01g,23mar87,jlf documentation. 01f,21dec86,dnw changed to not get include files from default directories. 01e,14apr86,rdc changed memAllocates to mallocs. 01d,20jul85,jlf documentation. 01c,09sep84,jlf added comments and copyright. 01b,15aug84,dnw changed rngBufCreate to allocate ring buffer one byte larger than requested, because ring buffer algorithm always leaves at least one empty byte in buffer. added rngEmpty, rngFull, rngFreeBytes, rngNBytes, rngFlush, rngPutAhead, rngMoveAhead, some of which used to be macros in rngLib.h. changed rngBufGet,rngBufPut to rngGetBuf,rngPutBuf. changed rngBufCreate to rngCreate. 01a,06jun84,dnw culled from old drvLib.c */

/* This library provides routines for creating and using ring buffers, which are first-in-first-out circular buffers. The routines simply manipulate the ring buffer data structure; no kernel functions are invoked. In particular, ring buffers by themselves provide no task synchronization or mutual exclusion.

However, the ring buffer pointers are manipulated in such a way that a reader task (invoking rngBufGet()) and a writer task (invoking rngBufPut()) can access a ring simultaneously without requiring mutual exclusion. This is because readers only affect a \f2read\f1 pointer and writers only affect a \f2write\f1 pointer in a ring buffer data structure. However, access by multiple readers or writers \f2must\fP be interlocked through a mutual exclusion mechanism (i.e., a mutual-exclusion semaphore guarding a ring buffer).

This library also supplies two macros, RNG_ELEM_PUT and RNG_ELEM_GET, for putting and getting single bytes from a ring buffer. They are defined in rngLib.h. .CS int RNG_ELEM_GET (ringId, pch, fromP) int RNG_ELEM_PUT (ringId, ch, toP) .CE Both macros require a temporary variable or , which should be declared as `register int' for maximum efficiency. RNG_ELEM_GET returns 1 if there was a character available in the buffer; it returns 0 otherwise. RNG_ELEM_PUT returns 1 if there was room in the buffer; it returns 0 otherwise. These are somewhat faster than rngBufPut() and rngBufGet(), which can put and get multi-byte buffers.

INCLUDE FILES: rngLib.h */

/* LINTLIBRARY */

#include "vxWorks.h" #include "memLib.h" #include "rngLib.h" #include "stdlib.h" #include "string.h"

/******************************************************************************* *

• rngCreate - create an empty ring buffer
• This routine creates a ring buffer of size , and initializes
• it. Memory for the buffer is allocated from the system memory partition.
• RETURNS
• The ID of the ring buffer, or NULL if memory cannot be allocated. */

RING_ID rngCreate ( int nbytes /* number of bytes in ring buffer */ ) { char *buffer; RING_ID ringId = (RING_ID) malloc (sizeof (RING));

if (ringId == NULL)
return (NULL);

/* bump number of bytes requested because ring buffer algorithm
 * always leaves at least one empty byte in buffer */

buffer = (char *) malloc ((unsigned) ++nbytes);

if (buffer == NULL)
{
free ((char *)ringId);
return (NULL);
}

ringId->bufSize = nbytes;
ringId->buf	    = buffer;

rngFlush (ringId);

return (ringId);
}

/******************************************************************************* *

• rngDelete - delete a ring buffer
• This routine deletes a specified ring buffer.
• Any data currently in the buffer will be lost.
• RETURNS: N/A */

void rngDelete ( FAST RING_ID ringId /* ring buffer to delete / ) { free (ringId->buf); free ((char )ringId); } /***************************************************************************** *

• rngFlush - make a ring buffer empty
• This routine initializes a specified ring buffer to be empty.
• Any data currently in the buffer will be lost.
• RETURNS: N/A */

void rngFlush ( FAST RING_ID ringId /* ring buffer to initialize / ) { ringId->pToBuf = 0; ringId->pFromBuf = 0; } /****************************************************************************** *

• rngBufGet - get characters from a ring buffer
• This routine copies bytes from the ring buffer into .
• It copies as many bytes as are available in the ring, up to .
• The bytes copied will be removed from the ring.
• RETURNS:
• The number of bytes actually received from the ring buffer;
• it may be zero if the ring buffer is empty at the time of the call. */

int rngBufGet ( FAST RING_ID rngId, /* ring buffer to get data from */ char buffer, / pointer to buffer to receive data / int maxbytes / maximum number of bytes to get */ ) { FAST int bytesgot = 0; int pToBuf = rngId->pToBuf; int bytes2; int pRngTmp = 0;

if (pToBuf >= rngId->pFromBuf)
{
/* pToBuf has not wrapped around */

bytesgot = min (maxbytes, pToBuf - rngId->pFromBuf);
bcopy (&rngId->buf [rngId->pFromBuf], buffer, bytesgot);
rngId->pFromBuf += bytesgot;
}
else
{
/* pToBuf has wrapped around.  Grab chars up to the end of the
 * buffer, then wrap around if we need to. */

bytesgot = min (maxbytes, rngId->bufSize - rngId->pFromBuf);
bcopy (&rngId->buf [rngId->pFromBuf], buffer, bytesgot);
pRngTmp = rngId->pFromBuf + bytesgot;

/* If pFromBuf is equal to bufSize, we've read the entire buffer,
 * and need to wrap now.  If bytesgot < maxbytes, copy some more chars
 * in now. */

if (pRngTmp == rngId->bufSize)
    {
    bytes2 = min (maxbytes - bytesgot, pToBuf);
    bcopy (rngId->buf, buffer + bytesgot, bytes2);
    rngId->pFromBuf = bytes2;
    bytesgot += bytes2;
    }
else
    rngId->pFromBuf = pRngTmp;
}
return (bytesgot);
}

/******************************************************************************* *

• rngBufPut - put bytes into a ring buffer
• This routine puts bytes from into ring buffer . The
• specified number of bytes will be put into the ring, up to the number of
• bytes available in the ring.
• INTERNAL
• Always leaves at least one byte empty between pToBuf and pFromBuf, to
• eliminate ambiguities which could otherwise occur when the two pointers
• are equal.
• RETURNS:
• The number of bytes actually put into the ring buffer;
• it may be less than number requested, even zero,
• if there is insufficient room in the ring buffer at the time of the call. */

int rngBufPut ( FAST RING_ID rngId, /* ring buffer to put data into */ char buffer, / buffer to get data from / int nbytes / number of bytes to try to put */ ) { FAST int bytesput = 0; int pFromBuf = rngId->pFromBuf; int bytes2; int pRngTmp = 0;

if (pFromBuf > rngId->pToBuf)
{
/* pFromBuf is ahead of pToBuf.  We can fill up to two bytes
 * before it */

bytesput = min (nbytes, pFromBuf - rngId->pToBuf - 1);
bcopy (buffer, &rngId->buf [rngId->pToBuf], bytesput);
rngId->pToBuf += bytesput;
}
else if (pFromBuf == 0)
{
/* pFromBuf is at the beginning of the buffer.  We can fill till
 * the next-to-last element */

bytesput = min (nbytes, rngId->bufSize - rngId->pToBuf - 1);
bcopy (buffer, &rngId->buf [rngId->pToBuf], bytesput);
rngId->pToBuf += bytesput;
}
else
{
/* pFromBuf has wrapped around, and its not 0, so we can fill
 * at least to the end of the ring buffer.  Do so, then see if
 * we need to wrap and put more at the beginning of the buffer. */

bytesput = min (nbytes, rngId->bufSize - rngId->pToBuf);
bcopy (buffer, &rngId->buf [rngId->pToBuf], bytesput);
pRngTmp = rngId->pToBuf + bytesput;

if (pRngTmp == rngId->bufSize)
    {
    /* We need to wrap, and perhaps put some more chars */

    bytes2 = min (nbytes - bytesput, pFromBuf - 1);
    bcopy (buffer + bytesput, rngId->buf, bytes2);
    rngId->pToBuf = bytes2;
    bytesput += bytes2;
    }
else
    rngId->pToBuf = pRngTmp;
}
return (bytesput);
}

/******************************************************************************* *

• rngIsEmpty - test if a ring buffer is empty
• This routine determines if a specified ring buffer is empty.
• RETURNS:
• TRUE if empty, FALSE if not. */

BOOL rngIsEmpty ( RING_ID ringId /* ring buffer to test / ) { return (ringId->pToBuf == ringId->pFromBuf); } /****************************************************************************** *

• rngIsFull - test if a ring buffer is full (no more room)
• This routine determines if a specified ring buffer is completely full.
• RETURNS:
• TRUE if full, FALSE if not. */

BOOL rngIsFull ( FAST RING_ID ringId /* ring buffer to test */ ) { int n = ringId->pToBuf - ringId->pFromBuf + 1;

return ((n == 0) || (n == ringId->bufSize));
}

/******************************************************************************* *

• rngFreeBytes - determine the number of free bytes in a ring buffer
• This routine determines the number of bytes currently unused in a specified
• ring buffer.
• RETURNS: The number of unused bytes in the ring buffer. */

int rngFreeBytes ( FAST RING_ID ringId /* ring buffer to examine */ ) { FAST int n = ringId->pFromBuf - ringId->pToBuf - 1;

if (n < 0)
n += ringId->bufSize;

return (n);
}

/******************************************************************************* *

• rngNBytes - determine the number of bytes in a ring buffer
• This routine determines the number of bytes currently in a specified
• ring buffer.
• RETURNS: The number of bytes filled in the ring buffer. */

int rngNBytes ( FAST RING_ID ringId /* ring buffer to be enumerated */ ) { FAST int n = ringId->pToBuf - ringId->pFromBuf;

if (n < 0)
n += ringId->bufSize;

return (n);

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