Imported ring buffer allocator from node CRT (#527)

* Imported ring buffer allocator from node, fixed bugs, added unit test

* Implemented realloc as an assert to prevent use

include/aws/common/ring_buffer.h

@@ -101,6 +101,17 @@ AWS_COMMON_API bool aws_ring_buffer_buf_belongs_to_pool(
     const struct aws_ring_buffer *ring_buffer,
     const struct aws_byte_buf *buf);
 
+/**
+ * Initializes the supplied allocator to be based on the provided ring buffer. Allocations must be allocated
+ * and freed in the same order, or the ring buffer will assert.
+ */
+AWS_COMMON_API int aws_ring_buffer_allocator_init(struct aws_allocator *allocator, struct aws_ring_buffer *ring_buffer);
+
+/**
+ * Cleans up a ring buffer allocator instance. Does not clean up the ring buffer.
+ */
+AWS_COMMON_API void aws_ring_buffer_allocator_clean_up(struct aws_allocator *allocator);
+
 #ifndef AWS_NO_STATIC_IMPL
 #    include <aws/common/ring_buffer.inl>
 #endif /* AWS_NO_STATIC_IMPL */

source/ring_buffer.c

@@ -268,3 +268,64 @@ bool aws_ring_buffer_buf_belongs_to_pool(const struct aws_ring_buffer *ring_buff
     AWS_POSTCONDITION(aws_byte_buf_is_valid(buf));
     return rval;
 }
+
+/* Ring buffer allocator implementation */
+static void *s_ring_buffer_mem_acquire(struct aws_allocator *allocator, size_t size) {
+    struct aws_ring_buffer *buffer = allocator->impl;
+    struct aws_byte_buf buf;
+    AWS_ZERO_STRUCT(buf);
+    /* allocate extra space for the size */
+    if (aws_ring_buffer_acquire(buffer, size + sizeof(size_t), &buf)) {
+        return NULL;
+    }
+    /* store the size ahead of the allocation */
+    *((size_t *)buf.buffer) = buf.capacity;
+    return buf.buffer + sizeof(size_t);
+}
+
+static void s_ring_buffer_mem_release(struct aws_allocator *allocator, void *ptr) {
+    /* back up to where the size is stored */
+    const void *addr = ((uint8_t *)ptr - sizeof(size_t));
+    const size_t size = *((size_t *)addr);
+
+    struct aws_byte_buf buf = aws_byte_buf_from_array(addr, size);
+    buf.allocator = allocator;
+
+    struct aws_ring_buffer *buffer = allocator->impl;
+    aws_ring_buffer_release(buffer, &buf);
+}
+
+static void *s_ring_buffer_mem_calloc(struct aws_allocator *allocator, size_t num, size_t size) {
+    void *mem = s_ring_buffer_mem_acquire(allocator, num * size);
+    if (!mem) {
+        return NULL;
+    }
+    memset(mem, 0, num * size);
+    return mem;
+}
+
+static void *s_ring_buffer_mem_realloc(struct aws_allocator *allocator, void *ptr, size_t old_size, size_t new_size) {
+    (void)allocator;
+    (void)ptr;
+    (void)old_size;
+    (void)new_size;
+    AWS_FATAL_ASSERT(!"ring_buffer_allocator does not support realloc, as it breaks allocation ordering");
+    return NULL;
+}
+
+int aws_ring_buffer_allocator_init(struct aws_allocator *allocator, struct aws_ring_buffer *ring_buffer) {
+    if (allocator == NULL || ring_buffer == NULL) {
+        return aws_raise_error(AWS_ERROR_INVALID_ARGUMENT);
+    }
+
+    allocator->impl = ring_buffer;
+    allocator->mem_acquire = s_ring_buffer_mem_acquire;
+    allocator->mem_release = s_ring_buffer_mem_release;
+    allocator->mem_calloc = s_ring_buffer_mem_calloc;
+    allocator->mem_realloc = s_ring_buffer_mem_realloc;
+    return AWS_OP_SUCCESS;
+}
+
+void aws_ring_buffer_allocator_clean_up(struct aws_allocator *allocator) {
+    AWS_ZERO_STRUCT(*allocator);
+}

tests/CMakeLists.txt

@@ -335,6 +335,7 @@ add_test_case(ring_buffer_acquire_up_to_test)
 add_test_case(ring_buffer_acquire_tail_always_chases_head_test)
 add_test_case(ring_buffer_acquire_multi_threaded_test)
 add_test_case(ring_buffer_acquire_up_to_multi_threaded_test)
+add_test_case(ring_buffer_allocator_test)
 
 add_test_case(test_logging_filter_at_AWS_LL_NONE_s_logf_all_levels)
 add_test_case(test_logging_filter_at_AWS_LL_FATAL_s_logf_all_levels)

tests/ring_buffer_test.c

@@ -398,3 +398,40 @@ static int s_test_acquire_up_to_multi_threaded(struct aws_allocator *allocator,
 }
 
 AWS_TEST_CASE(ring_buffer_acquire_up_to_multi_threaded_test, s_test_acquire_up_to_multi_threaded)
+
+#define RING_BUFFER_ALLOCATOR_CAPACITY (16 * 1024)
+
+static int s_test_ring_buffer_allocator(struct aws_allocator *allocator, void *ctx) {
+    (void)ctx;
+    struct aws_ring_buffer ring_buffer;
+    struct aws_allocator rb_allocator;
+    ASSERT_SUCCESS(aws_ring_buffer_init(&ring_buffer, allocator, RING_BUFFER_ALLOCATOR_CAPACITY));
+    ASSERT_SUCCESS(aws_ring_buffer_allocator_init(&rb_allocator, &ring_buffer));
+
+    for (int cycles = 0; cycles < 10; ++cycles) {
+        size_t total_size = 0;
+        const size_t chunk_size = (cycles + 1) * 16;
+        int chunk_count = 0;
+        AWS_VARIABLE_LENGTH_ARRAY(void *, chunks, RING_BUFFER_ALLOCATOR_CAPACITY / (16 + sizeof(size_t)));
+        while ((total_size + chunk_size) <= RING_BUFFER_ALLOCATOR_CAPACITY) {
+            void *chunk = aws_mem_calloc(&rb_allocator, 1, chunk_size);
+            if (chunk == NULL) {
+                ASSERT_TRUE(chunk_count > 0);
+                break;
+            }
+            chunks[chunk_count++] = chunk;
+            total_size += chunk_size;
+        }
+
+        for (int idx = 0; idx < chunk_count; ++idx) {
+            aws_mem_release(&rb_allocator, chunks[idx]);
+        }
+    }
+
+    aws_ring_buffer_allocator_clean_up(&rb_allocator);
+    aws_ring_buffer_clean_up(&ring_buffer);
+
+    return AWS_OP_SUCCESS;
+}
+
+AWS_TEST_CASE(ring_buffer_allocator_test, s_test_ring_buffer_allocator);