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lib/bt/common/osi/buffer.c

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+/******************************************************************************
+ *
+ *  Copyright (C) 2014 Google, Inc.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at:
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ ******************************************************************************/
+#include <stdint.h>
+#include "bt_common.h"
+#include "osi/allocator.h"
+#include "osi/buffer.h"
+
+struct buffer_t {
+    buffer_t *root;
+    size_t refcount;
+    size_t length;
+    uint8_t data[];
+};
+
+buffer_t *buffer_new(size_t size)
+{
+    assert(size > 0);
+
+    buffer_t *buffer = osi_malloc(sizeof(buffer_t) + size);
+    if (!buffer) {
+        OSI_TRACE_ERROR("%s unable to allocate buffer of %zu bytes.", __func__, size);
+        return NULL;
+    }
+
+    buffer->root = buffer;
+    buffer->refcount = 1;
+    buffer->length = size;
+
+    return buffer;
+}
+
+buffer_t *buffer_new_ref(const buffer_t *buf)
+{
+    assert(buf != NULL);
+    return buffer_new_slice(buf, buf->length);
+}
+
+buffer_t *buffer_new_slice(const buffer_t *buf, size_t slice_size)
+{
+    assert(buf != NULL);
+    assert(slice_size > 0);
+    assert(slice_size <= buf->length);
+
+    buffer_t *ret = osi_calloc(sizeof(buffer_t));
+    if (!ret) {
+        OSI_TRACE_ERROR("%s unable to allocate new buffer for slice of length %zu.", __func__, slice_size);
+        return NULL;
+    }
+
+    ret->root = buf->root;
+    ret->refcount = SIZE_MAX;
+    ret->length = slice_size;
+
+    ++buf->root->refcount;
+
+    return ret;
+}
+
+void buffer_free(buffer_t *buffer)
+{
+    if (!buffer) {
+        return;
+    }
+
+    if (buffer->root != buffer) {
+        // We're a leaf node. Delete the root node if we're the last referent.
+        if (--buffer->root->refcount == 0) {
+            osi_free(buffer->root);
+        }
+        osi_free(buffer);
+    } else if (--buffer->refcount == 0) {
+        // We're a root node. Roots are only deleted when their refcount goes to 0.
+        osi_free(buffer);
+    }
+}
+
+void *buffer_ptr(const buffer_t *buf)
+{
+    assert(buf != NULL);
+    return buf->root->data + buf->root->length - buf->length;
+}
+
+size_t buffer_length(const buffer_t *buf)
+{
+    assert(buf != NULL);
+    return buf->length;
+}