/* -*- 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