/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

/* vim: set ts=8 sts=2 et sw=2 tw=80: */

/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "XiphExtradata.h"

namespace mozilla {

bool XiphHeadersToExtradata(MediaByteBuffer* aCodecSpecificConfig,

                            const nsTArray<const unsigned char*>& aHeaders,

                            const nsTArray<size_t>& aHeaderLens)

{

  size_t nheaders = aHeaders.Length();

  if (!nheaders || nheaders > 255) return false;

  aCodecSpecificConfig->AppendElement(nheaders - 1);

  for (size_t i = 0; i < nheaders - 1; i++) {

    size_t headerLen;

    for (headerLen = aHeaderLens[i]; headerLen >= 255; headerLen -= 255) {

      aCodecSpecificConfig->AppendElement(255);

    }

    aCodecSpecificConfig->AppendElement(headerLen);

  }

  for (size_t i = 0; i < nheaders; i++) {

    aCodecSpecificConfig->AppendElements(aHeaders[i], aHeaderLens[i]);

  }

  return true;

}

bool XiphExtradataToHeaders(nsTArray<unsigned char*>& aHeaders,

                            nsTArray<size_t>& aHeaderLens,

                            unsigned char* aData,

                            size_t aAvailable)

{

  size_t total = 0;

  if (aAvailable < 1) {

    return false;

  }

  aAvailable--;

  int nHeaders = *aData++ + 1;

  for (int i = 0; i < nHeaders - 1; i++) {

    size_t headerLen = 0;

    for (;;) {

      // After this test, we know that (aAvailable - total > headerLen) and

      // (headerLen >= 0) so (aAvailable - total > 0). The loop decrements

      // aAvailable by 1 and total remains fixed, so we know that in the next

      // iteration (aAvailable - total >= 0). Thus (aAvailable - total) can

      // never underflow.

      if (aAvailable - total <= headerLen) {

        return false;

      }

      // Since we know (aAvailable > total + headerLen), this can't overflow

      // unless total is near 0 and both aAvailable and headerLen are within

      // 255 bytes of the maximum representable size. However, that is

      // impossible, since we would have had to have gone through this loop

      // more than 255 times to make headerLen that large, and thus decremented

      // aAvailable more than 255 times.

      headerLen += *aData;

      aAvailable--;

      if (*aData++ != 255) break;

    }

    // And this check ensures updating total won't cause (aAvailable - total)

    // to underflow.

    if (aAvailable - total < headerLen) {

      return false;

    }

    aHeaderLens.AppendElement(headerLen);

    // Since we know aAvailable >= total + headerLen, this can't overflow.

    total += headerLen;

  }

  aHeaderLens.AppendElement(aAvailable - total);

  for (int i = 0; i < nHeaders; i++) {

    aHeaders.AppendElement(aData);

    aData += aHeaderLens[i];

  }

  return true;

}

} // namespace mozilla