Major change to try to make performance (and semantics) match the vxWorks

implementation.  The previous implementation would not perform partial copies.
The vxWorks implementation would copy as much as possible.

src/libCom/osi/os/default/osdRing.c

@@ -19,20 +19,20 @@ of this distribution.
 #include "osiInterrupt.h"
 #include "osiRing.h"
 
-
 typedef struct ringPvt {
-    int size;
-    int nextGet;
     int nextPut;
-    int isFull;
+    int nextGet;
+    int size;
     char *buffer;
 }ringPvt;
+
 
 epicsShareFunc ringId  epicsShareAPI ringCreate(int size)
 {
-    ringPvt *pring = callocMustSucceed(1,sizeof(ringPvt),"ringCreate");
-    pring->size = size;
-    pring->buffer = callocMustSucceed(size,sizeof(char),"ringCreate");
+    ringPvt *pring = mallocMustSucceed(sizeof(ringPvt),"ringCreate");
+    pring->size = size + 1;
+    pring->buffer = mallocMustSucceed(pring->size,"ringCreate");
+    pring->nextGet = pring->nextPut = 0;
     return((void *)pring);
 }
 
@@ -46,145 +46,126 @@ epicsShareFunc void epicsShareAPI ringDelete(ringId id)
 epicsShareFunc int epicsShareAPI ringGet(ringId id, char *value,int nbytes)
 {
     ringPvt *pring = (ringPvt *)id;
-    int nextGet = pring->nextGet;
-    int nextPut = pring->nextPut;
-    int size = pring->size;
-    int nToGet;
-    int lockKey;
+    int count;
 
-    if(nextGet < nextPut) {
-        if(nbytes > (nextPut - nextGet)) return(0);
-        memcpy(value,&pring->buffer[nextGet],nbytes);
-        nextGet += nbytes;
-        if(nextGet>=size) nextGet = 0;
-        lockKey = interruptLock();
-        pring->nextGet = nextGet;
-        pring->isFull = 0;
-        interruptUnlock(lockKey);
-        return(nbytes);
+    if (pring->nextGet <= pring->nextPut) {
+        count = pring->nextPut - pring->nextGet;
+        if (count < nbytes)
+            nbytes = count;
+        memcpy (value, &pring->buffer[pring->nextGet], nbytes);
+        pring->nextGet += nbytes;
     }
-    if(nextGet==nextPut && !pring->isFull ) return(0);
-    if(nbytes > (nextPut + (size - nextGet))) return(0);
-    nToGet = size - nextGet;
-    if(nToGet>nbytes) nToGet = nbytes;
-    memcpy(value,&pring->buffer[nextGet],nToGet);
-    value += nToGet;
-    nextGet += nToGet;
-    nToGet = nbytes - nToGet;
-    if(nToGet>0) {
-        nextGet = 0;
-        memcpy(value,&pring->buffer[0],nToGet);
-        nextGet += nToGet;
-    } 
-    if(nextGet>=size) nextGet = 0;
-    lockKey = interruptLock();
-    pring->nextGet = nextGet;
-    pring->isFull = 0;
-    interruptUnlock(lockKey);
-    return(nbytes);
+    else {
+        int nextGet;
+        count = pring->size - pring->nextGet;
+        if (count > nbytes)
+            count = nbytes;
+        memcpy (value, &pring->buffer[pring->nextGet], count);
+        if ((nextGet = pring->nextGet + count) == pring->size) {
+            int nLeft = nbytes - count;
+            if (nLeft > pring->nextPut)
+                nLeft = pring->nextPut;
+            memcpy (value+count, &pring->buffer[0], nLeft);
+            pring->nextGet = nLeft;
+            nbytes = count + nLeft;
+        }
+        else {
+            nbytes = count;
+            pring->nextGet = nextGet;
+        }
+    }
+    return nbytes;
 }
 
 epicsShareFunc int epicsShareAPI ringPut(ringId id, char *value,int nbytes)
 {
     ringPvt *pring = (ringPvt *)id;
-    int nextGet = pring->nextGet;
-    int nextPut = pring->nextPut;
-    int size = pring->size;
-    int nToPut;
-    int lockKey;
+    int count;
 
-    if(nextPut < nextGet) {
-        if(nbytes > (nextGet - nextPut)) return(0);
-        memcpy(&pring->buffer[nextPut],value,nbytes);
-        nextPut += nbytes;
-        if(nextPut>=size) nextPut = 0;
-        lockKey = interruptLock();
-        pring->nextPut = nextPut;
-        if(nextPut==nextGet) pring->isFull = 1;
-        interruptUnlock(lockKey);
-        return(nbytes);
+    if (pring->nextPut < pring->nextGet) {
+        count = pring->nextGet - pring->nextPut - 1;
+        if (nbytes > count)
+            nbytes = count;
+        memcpy (&pring->buffer[pring->nextPut], value, nbytes);
+        pring->nextPut += nbytes;
     }
-    if(nextGet==nextPut && pring->isFull ) return(0);
-    if(nbytes > (nextGet + (size - nextPut))) return(0);
-    nToPut = size - nextPut;
-    if(nToPut>nbytes) nToPut = nbytes;
-    memcpy(&pring->buffer[nextPut],value,nToPut);
-    value += nToPut;
-    nextPut += nToPut;
-    nToPut = nbytes - nToPut;
-    if(nToPut>0) {
-        nextPut = 0;
-        memcpy(&pring->buffer[0],value,nToPut);
-        nextPut += nToPut;
+    else if (pring->nextGet == 0) {
+        count = pring->size - pring->nextPut - 1;
+        if (nbytes > count)
+            nbytes = count;
+        memcpy (&pring->buffer[pring->nextPut], value, nbytes);
+        pring->nextPut += nbytes;
     }
-    if(nextPut>=size) nextPut = 0;
-    lockKey = interruptLock();
-    pring->nextPut = nextPut;
-    if(nextPut==nextGet) pring->isFull = 1;
-    interruptUnlock(lockKey);
-    return(nbytes);
+    else {
+        int nextPut;
+        count = pring->size - pring->nextPut;
+        if (count > nbytes)
+            count = nbytes;
+        memcpy (&pring->buffer[pring->nextPut], value, count);
+        if ((nextPut = pring->nextPut + count) == pring->size) {
+            int nLeft = nbytes - count;
+            if (nLeft > (pring->nextGet - 1))
+                nLeft = pring->nextGet - 1;
+            memcpy (&pring->buffer[0], value+count, nLeft);
+            pring->nextPut = nLeft;
+            nbytes = count + nLeft;
+        }
+        else {
+            nbytes = count;
+            pring->nextPut = nextPut;
+        }
+    }
+    return nbytes;
 }
 
 epicsShareFunc void epicsShareAPI ringFlush(ringId id)
 {
     ringPvt *pring = (ringPvt *)id;
-    int lockKey;
 
-    lockKey = interruptLock();
     pring->nextGet = pring->nextPut = 0;
-    pring->isFull = 0;
-    interruptUnlock(lockKey);
 }
 
 epicsShareFunc int epicsShareAPI ringFreeBytes(ringId id)
 {
     ringPvt *pring = (ringPvt *)id;
     int n;
-    int lockKey;
 
-    lockKey = interruptLock();
-    n = pring->nextGet - pring->nextPut;
-    if(n<=0) n += pring->size;
-    if(pring->isFull) n = 0;
-    interruptUnlock(lockKey);
-    return(n);
+    n = pring->nextGet - pring->nextPut - 1;
+    if (n < 0)
+    	n += pring->size;
+    return n;
 }
 
 epicsShareFunc int epicsShareAPI ringUsedBytes(ringId id)
 {
     ringPvt *pring = (ringPvt *)id;
     int n;
-    int lockKey;
 
-    lockKey = interruptLock();
     n = pring->nextPut - pring->nextGet;
-    if(n<0) n += pring->size;
-    if(pring->isFull) n = pring->size;
-    interruptUnlock(lockKey);
-    return(n);
+    if (n < 0)
+    	n += pring->size;
+    return n;
 }
 
 epicsShareFunc int epicsShareAPI ringSize(ringId id)
 {
     ringPvt *pring = (ringPvt *)id;
-    return(pring->size);
+
+    return pring->size - 1;
 }
 
 epicsShareFunc int epicsShareAPI ringIsEmpty(ringId id)
 {
     ringPvt *pring = (ringPvt *)id;
-    int lockKey;
-    int result;
 
-    lockKey = interruptLock();
-    result = (pring->nextGet==pring->nextPut && !pring->isFull) ? TRUE : FALSE;
-    interruptUnlock(lockKey);
-    return(result);
+    return (pring->nextPut == pring->nextGet);
 }
 
 epicsShareFunc int epicsShareAPI ringIsFull(ringId id)
 {
     ringPvt *pring = (ringPvt *)id;
+    int count;
 
-    return(pring->isFull);
+    count = (pring->nextPut - pring->nextGet) + 1;
+    return ((count == 0) || (count == pring->size));
 }