【主线待合】尝试解决ringbuffer的memcpy传参为负问题

library/ringbuffer/ringbuffer.c

@@ -120,23 +120,31 @@ int rd_RingbufferPut(rd_ringbuf_t *rb, const char *ptr, int length)
 {
     if (!rb || !ptr || length <= 0) return RD_INVALUE;
 
-    int space = rd_RingbufferSpaceLen(rb);
-    if (space == 0) return 0;
-    if (space < length) length = space;
-
     unsigned short wi = ATOMIC_LOAD(&rb->m_sWriteIndex, unsigned short, ATOMIC_ORDER_RELAXED);
+    unsigned short ri = ATOMIC_LOAD(&rb->m_sReadIndex, unsigned short, ATOMIC_ORDER_RELAXED);
     unsigned char wb = ATOMIC_LOAD(&rb->m_bWriteMirror, unsigned char, ATOMIC_ORDER_RELAXED);
+    unsigned char rb_m = ATOMIC_LOAD(&rb->m_bReadMirror, unsigned char, ATOMIC_ORDER_RELAXED);
+
+    int space;
+    if (wb == rb_m) {
+        space = rb->m_iBufsize - (int)(unsigned short)(wi - ri);
+    } else {
+        space = (int)(unsigned short)(ri - wi);
+    }
+
+    if (space <= 0) return 0;
+    if (space < length) length = space;
 
     /* 写入不跨越尾部 */
-    if (rb->m_iBufsize - wi > length) {
+    int tail = rb->m_iBufsize - wi;
+    if (tail > length) {
         RD_MEMCPY(&rb->m_pcBufPtr[wi], ptr, length);
         wi += length;
     } else {
-        int first = rb->m_iBufsize - wi;
-        RD_MEMCPY(&rb->m_pcBufPtr[wi], ptr, first);
-        RD_MEMCPY(&rb->m_pcBufPtr[0], ptr + first, length - first);
+        RD_MEMCPY(&rb->m_pcBufPtr[wi], ptr, tail);
+        RD_MEMCPY(&rb->m_pcBufPtr[0], ptr + tail, length - tail);
         wb ^= 1;                     /* 翻转镜像位 */
-        wi = length - first;
+        wi = length - tail;
     }
 
     ATOMIC_STORE(&rb->m_sWriteIndex, wi, unsigned short, ATOMIC_ORDER_RELEASE);