/*
 *
 * Copyright 2015, Google Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */

#import "NSData+GRPC.h"

#include <grpc/byte_buffer.h>
#include <string.h>

// TODO(jcanizales): Move these two incantations to the C library.

static void CopyByteBufferToCharArray(grpc_byte_buffer *buffer, char *array) {
  size_t offset = 0;
  grpc_byte_buffer_reader *reader = grpc_byte_buffer_reader_create(buffer);
  gpr_slice next;
  while (grpc_byte_buffer_reader_next(reader, &next) != 0){
    memcpy(array + offset, GPR_SLICE_START_PTR(next), (size_t) GPR_SLICE_LENGTH(next));
    offset += GPR_SLICE_LENGTH(next);
    gpr_slice_unref(next);
  }
  grpc_byte_buffer_reader_destroy(reader);
}

static grpc_byte_buffer *CopyCharArrayToNewByteBuffer(const char *array, size_t length) {
  gpr_slice slice = gpr_slice_from_copied_buffer(array, length);
  grpc_byte_buffer *buffer = grpc_byte_buffer_create(&slice, 1);
  gpr_slice_unref(slice);
  return buffer;
}

@implementation NSData (GRPC)
+ (instancetype)grpc_dataWithByteBuffer:(grpc_byte_buffer *)buffer {
  if (buffer == NULL) {
    return nil;
  }
  NSUInteger length = grpc_byte_buffer_length(buffer);
  char *array = malloc(length * sizeof(*array));
  if (!array) {
    // TODO(jcanizales): grpc_byte_buffer is reference-counted, so we can
    // prevent this memory problem by implementing a subclass of NSData
    // that wraps the grpc_byte_buffer. Then enumerateByteRangesUsingBlock:
    // can be implemented using a grpc_byte_buffer_reader.
    return nil;
  }
  CopyByteBufferToCharArray(buffer, array);
  return [self dataWithBytesNoCopy:array length:length freeWhenDone:YES];
}

- (grpc_byte_buffer *)grpc_byteBuffer {
  // Some implementations of NSData, as well as grpc_byte_buffer, support O(1)
  // appending of byte arrays by not using internally a single contiguous memory
  // block for representation.
  // The following implementation is thus not optimal, sometimes requiring two
  // copies (one by self.bytes and another by gpr_slice_from_copied_buffer).
  // If it turns out to be an issue, we can use enumerateByteRangesUsingblock:
  // to create an array of gpr_slice objects to pass to grpc_byte_buffer_create.
  // That would make it do exactly one copy, always.
  return CopyCharArrayToNewByteBuffer((const char *)self.bytes, (size_t)self.length);
}
@end
