1 files changed, 77 insertions, 0 deletions
diff --git a/dom/media/XiphExtradata.cpp b/dom/media/XiphExtradata.cpp
new file mode 100644
index 0000000000..ff8ea1901d
--- /dev/null
+++ b/dom/media/XiphExtradata.cpp
@@ -0,0 +1,77 @@
+/* -*- 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