Decommision src_common prior to reintroducing it for files common between eth and plugins

src/mem.c

@@ -0,0 +1,65 @@
+/**
+ * Dynamic allocator that uses a fixed-length buffer that is hopefully big enough
+ *
+ * The two functions alloc & dealloc use the buffer as a simple stack.
+ * Especially useful when an unpredictable amount of data will be received and have to be stored
+ * during the transaction but discarded right after.
+ */
+
+#ifdef HAVE_DYN_MEM_ALLOC
+
+#include <stdint.h>
+#include "mem.h"
+
+#define SIZE_MEM_BUFFER 8192
+
+static uint8_t mem_buffer[SIZE_MEM_BUFFER];
+static size_t mem_idx;
+
+/**
+ * Initializes the memory buffer index
+ */
+void mem_init(void) {
+    mem_idx = 0;
+}
+
+/**
+ * Resets the memory buffer index
+ */
+void mem_reset(void) {
+    mem_init();
+}
+
+/**
+ * Allocates (push) a chunk of the memory buffer of a given size.
+ *
+ * Checks to see if there are enough space left in the memory buffer, returns
+ * the current location in the memory buffer and moves the index accordingly.
+ *
+ * @param[in] size Requested allocation size in bytes
+ * @return Allocated memory pointer; \ref NULL if not enough space left.
+ */
+void *mem_alloc(size_t size) {
+    if ((mem_idx + size) > SIZE_MEM_BUFFER)  // Buffer exceeded
+    {
+        return NULL;
+    }
+    mem_idx += size;
+    return &mem_buffer[mem_idx - size];
+}
+
+/**
+ * De-allocates (pop) a chunk of memory buffer by a given size.
+ *
+ * @param[in] size Requested deallocation size in bytes
+ */
+void mem_dealloc(size_t size) {
+    if (size > mem_idx)  // More than is already allocated
+    {
+        mem_idx = 0;
+    } else {
+        mem_idx -= size;
+    }
+}
+
+#endif  // HAVE_DYN_MEM_ALLOC