nrf5/sdk: Adding macro based ringbuffer written by Philip Thrasher. source: https://github.com/pthrasher/c-generic-ring-buffer/blob/master/ringbuffer.h. Copyright noticed copied into the file, and file reviewed by Philip.

nrf5/sdk/ringbuffer.h

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+/* The MIT License (MIT)
+ *
+ * Copyright (c) 2013 Philip Thrasher
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+ * the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+ * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ * Philip Thrasher's Crazy Awesome Ring Buffer Macros!
+ *
+ * Below you will find some naughty macros for easy owning and manipulating
+ * generic ring buffers. Yes, they are slightly evil in readability, but they
+ * are really fast, and they work great.
+ *
+ * Example usage:
+ *
+ * #include <stdio.h>
+ *
+ * // So we can use this in any method, this gives us a typedef
+ * // named 'intBuffer'.
+ * ringBuffer_typedef(int, intBuffer);
+ *
+ * int main() {
+ *   // Declare vars.
+ *   intBuffer myBuffer;
+ *
+ *   bufferInit(myBuffer,1024,int);
+ *
+ *   // We must have the pointer. All of the macros deal with the pointer.
+ *   // (except for init.)
+ *   intBuffer* myBuffer_ptr;
+ *   myBuffer_ptr = &myBuffer;
+ *
+ *   // Write two values.
+ *   bufferWrite(myBuffer_ptr,37);
+ *   bufferWrite(myBuffer_ptr,72);
+ *
+ *   // Read a value into a local variable.
+ *   int first;
+ *   bufferRead(myBuffer_ptr,first);
+ *   assert(first == 37); // true
+ *
+ *   int second;
+ *   bufferRead(myBuffer_ptr,second);
+ *   assert(second == 72); // true
+ *
+ *   return 0;
+ * }
+ *
+ */
+
+#ifndef _ringbuffer_h
+#define _ringbuffer_h
+
+#define ringBuffer_typedef(T, NAME) \
+  typedef struct { \
+    int size; \
+    int start; \
+    int end; \
+    T* elems; \
+  } NAME
+
+#define bufferInit(BUF, S, T) \
+  BUF.size = S+1; \
+  BUF.start = 0; \
+  BUF.end = 0; \
+  BUF.elems = (T*)calloc(BUF.size, sizeof(T))
+
+
+#define bufferDestroy(BUF) free(BUF->elems)
+#define nextStartIndex(BUF) ((BUF->start + 1) % BUF->size)
+#define nextEndIndex(BUF) ((BUF->end + 1) % BUF->size)
+#define isBufferEmpty(BUF) (BUF->end == BUF->start)
+#define isBufferFull(BUF) (nextEndIndex(BUF) == BUF->start)
+
+#define bufferWrite(BUF, ELEM) \
+  BUF->elems[BUF->end] = ELEM; \
+  BUF->end = (BUF->end + 1) % BUF->size; \
+  if (isBufferEmpty(BUF)) { \
+    BUF->start = nextStartIndex(BUF); \
+  }
+
+#define bufferRead(BUF, ELEM) \
+    ELEM = BUF->elems[BUF->start]; \
+    BUF->start = nextStartIndex(BUF);
+
+#endif