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-rw-r--r--dom/media/XiphExtradata.cpp80
1 files changed, 80 insertions, 0 deletions
diff --git a/dom/media/XiphExtradata.cpp b/dom/media/XiphExtradata.cpp
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+++ b/dom/media/XiphExtradata.cpp
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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