/******************************************************************************
 *
 *  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.
 *
 ******************************************************************************/

#define LOG_TAG "bt_osi_buffer"

#include <assert.h>
#include <stdint.h>

#include "osi/include/allocator.h"
#include "osi/include/buffer.h"
#include "osi/include/log.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_calloc(sizeof(buffer_t) + size);
  if (!buffer) {
    LOG_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) {
    LOG_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;
}