memarray: add fixed-size memory block allocator

sys/include/memarray.h

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+/*
+ * Copyright (C) 2018 Tobias Heider <heidert@nm.ifi.lmu.de>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+/**
+ * @defgroup    sys_memarray memory array allocator
+ * @ingroup     sys
+ * @brief       memory array allocator
+ * @{
+ *
+ * @brief       pseudo dynamic allocation in static memory arrays
+ * @author      Tobias Heider <heidert@nm.ifi.lmu.de>
+ */
+
+#ifndef MEMARRAY_H
+#define MEMARRAY_H
+
+#include <stdint.h>
+#include <stdlib.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief Memory pool
+ */
+typedef struct {
+    void *free_data;    /**< memory pool data / head of the free list */
+    size_t size;        /**< size of single list element */
+    size_t num;         /**< max number of elements in list */
+} memarray_t;
+
+/**
+ * @brief Initialize memarray pool with free list
+ *
+ * @pre `mem != NULL`
+ * @pre `data != NULL`
+ * @pre `size >= sizeof(void*)`
+ * @pre `num != 0`
+ *
+ * @param[in,out] mem    memarray pool to initialize
+ * @param[in]     data   pointer to user-allocated data
+ * @param[in]     size   size of a single element in data
+ * @param[in]     num    number of elements in data
+ */
+void memarray_init(memarray_t *mem, void *data, size_t size, size_t num);
+
+/**
+ * @brief Allocate memory chunk in memarray pool
+ *
+ * @pre `mem != NULL`
+ *
+ * @param[in,out] mem   memarray pool to allocate block in
+ *
+ * @return pointer to allocated structure, if enough memory was available
+ * @return NULL, on failure
+ */
+void *memarray_alloc(memarray_t *mem);
+
+/**
+ * @brief Free memory chunk in memarray pool
+ *
+ * @pre `mem != NULL`
+ * @pre `ptr != NULL`
+ *
+ * @param[in,out] mem   memarray pool to free block in
+ * @param[in]     ptr   pointer to memarray chunk
+ */
+void memarray_free(memarray_t *mem, void *ptr);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* MEMARRAY_H */
+
+/**
+ * @}
+ */

sys/memarray/Makefile

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+include $(RIOTBASE)/Makefile.base

sys/memarray/memarray.c

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+/*
+ * Copyright (C) 2018 Tobias Heider <heidert@nm.ifi.lmu.de>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+#include <string.h>
+#include "memarray.h"
+
+#define ENABLE_DEBUG    (0)
+#include "debug.h"
+
+void memarray_init(memarray_t *mem, void *data, size_t size, size_t num)
+{
+    assert((mem != NULL) && (data != NULL) && (size >= sizeof(void *)) &&
+           (num != 0));
+
+    DEBUG("memarray: Initialize memarray of %u times %u Bytes at %p\n",
+          (unsigned)num, (unsigned)size, data);
+
+    mem->free_data = data;
+    mem->size = size;
+    mem->num = num;
+
+    for (size_t i = 0; i < (mem->num - 1); i++) {
+        void *next = ((char *)mem->free_data) + ((i + 1) * mem->size);
+        memcpy(((char *)mem->free_data) + (i * mem->size), &next, sizeof(void *));
+    }
+}
+
+void *memarray_alloc(memarray_t *mem)
+{
+    assert(mem != NULL);
+
+    if (mem->free_data == NULL) {
+        return NULL;
+    }
+    void *free = mem->free_data;
+    mem->free_data = *((void **)mem->free_data);
+    DEBUG("memarray: Allocate %u Bytes at %p\n", (unsigned)mem->size, free);
+    return free;
+}
+
+void memarray_free(memarray_t *mem, void *ptr)
+{
+    assert((mem != NULL) && (ptr != NULL));
+
+    memcpy(ptr, &mem->free_data, sizeof(void *));
+    mem->free_data = ptr;
+    DEBUG("memarray: Free %u Bytes at %p\n", (unsigned)mem->size, ptr);
+}