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/* -*- 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
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