diff -r 000000000000 -r 6474c204b198 toolkit/components/mediasniffer/nsMediaSniffer.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolkit/components/mediasniffer/nsMediaSniffer.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,159 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 tw=80 et cindent: */
+/* 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 "nsMediaSniffer.h"
+#include "nsIHttpChannel.h"
+#include "nsString.h"
+#include "nsMimeTypes.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/ModuleUtils.h"
+#include "mp3sniff.h"
+#ifdef MOZ_WEBM
+#include "nestegg/nestegg.h"
+#endif
+
+#include "nsIClassInfoImpl.h"
+#include <algorithm>
+
+// The minimum number of bytes that are needed to attempt to sniff an mp4 file.
+static const unsigned MP4_MIN_BYTES_COUNT = 12;
+// The maximum number of bytes to consider when attempting to sniff a file.
+static const uint32_t MAX_BYTES_SNIFFED = 512;
+// The maximum number of bytes to consider when attempting to sniff for a mp3
+// bitstream.
+// This is 320kbps * 144 / 32kHz + 1 padding byte + 4 bytes of capture pattern.
+static const uint32_t MAX_BYTES_SNIFFED_MP3 = 320 * 144 / 32 + 1 + 4;
+
+NS_IMPL_ISUPPORTS(nsMediaSniffer, nsIContentSniffer)
+
+nsMediaSniffer::nsMediaSnifferEntry nsMediaSniffer::sSnifferEntries[] = {
+  // The string OggS, followed by the null byte.
+  PATTERN_ENTRY("\xFF\xFF\xFF\xFF\xFF", "OggS", APPLICATION_OGG),
+  // The string RIFF, followed by four bytes, followed by the string WAVE
+  PATTERN_ENTRY("\xFF\xFF\xFF\xFF\x00\x00\x00\x00\xFF\xFF\xFF\xFF", "RIFF\x00\x00\x00\x00WAVE", AUDIO_WAV),
+  // mp3 with ID3 tags, the string "ID3".
+  PATTERN_ENTRY("\xFF\xFF\xFF", "ID3", AUDIO_MP3)
+};
+
+// This function implements mp4 sniffing algorithm, described at
+// http://mimesniff.spec.whatwg.org/#signature-for-mp4
+static bool MatchesMP4(const uint8_t* aData, const uint32_t aLength)
+{
+  if (aLength <= MP4_MIN_BYTES_COUNT) {
+    return false;
+  }
+  // Conversion from big endian to host byte order.
+  uint32_t boxSize = (uint32_t)(aData[3] | aData[2] << 8 | aData[1] << 16 | aData[0] << 24);
+
+  // Boxsize should be evenly divisible by 4.
+  if (boxSize % 4 || aLength < boxSize) {
+    return false;
+  }
+  // The string "ftyp".
+  if (aData[4] != 0x66 ||
+      aData[5] != 0x74 ||
+      aData[6] != 0x79 ||
+      aData[7] != 0x70) {
+    return false;
+  }
+  for (uint32_t i = 2; i <= boxSize / 4 - 1 ; i++) {
+    if (i == 3) {
+      continue;
+    }
+    // The string "mp42" or "mp41".
+    if (aData[4*i]   == 0x6D &&
+        aData[4*i+1] == 0x70 &&
+        aData[4*i+2] == 0x34) {
+      return true;
+    }
+    // The string "isom" or "iso2".
+    if (aData[4*i]   == 0x69 &&
+        aData[4*i+1] == 0x73 &&
+        aData[4*i+2] == 0x6F &&
+        (aData[4*i+3] == 0x6D || aData[4*i+3] == 0x32)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+static bool MatchesWebM(const uint8_t* aData, const uint32_t aLength)
+{
+#ifdef MOZ_WEBM
+  return nestegg_sniff((uint8_t*)aData, aLength) ? true : false;
+#else
+  return false;
+#endif
+}
+
+// This function implements mp3 sniffing based on parsing
+// packet headers and looking for expected boundaries.
+static bool MatchesMP3(const uint8_t* aData, const uint32_t aLength)
+{
+  return mp3_sniff(aData, (long)aLength);
+}
+
+NS_IMETHODIMP
+nsMediaSniffer::GetMIMETypeFromContent(nsIRequest* aRequest,
+                                       const uint8_t* aData,
+                                       const uint32_t aLength,
+                                       nsACString& aSniffedType)
+{
+  // For media, we want to sniff only if the Content-Type is unknown, or if it
+  // is application/octet-stream.
+  nsCOMPtr<nsIChannel> channel = do_QueryInterface(aRequest);
+  if (channel) {
+    nsAutoCString contentType;
+    nsresult rv = channel->GetContentType(contentType);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (!contentType.IsEmpty() &&
+        !contentType.EqualsLiteral(APPLICATION_OCTET_STREAM) &&
+        !contentType.EqualsLiteral(UNKNOWN_CONTENT_TYPE)) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+  }
+
+  const uint32_t clampedLength = std::min(aLength, MAX_BYTES_SNIFFED);
+
+  for (uint32_t i = 0; i < mozilla::ArrayLength(sSnifferEntries); ++i) {
+    const nsMediaSnifferEntry& currentEntry = sSnifferEntries[i];
+    if (clampedLength < currentEntry.mLength || currentEntry.mLength == 0) {
+      continue;
+    }
+    bool matched = true;
+    for (uint32_t j = 0; j < currentEntry.mLength; ++j) {
+      if ((currentEntry.mMask[j] & aData[j]) != currentEntry.mPattern[j]) {
+        matched = false;
+        break;
+      }
+    }
+    if (matched) {
+      aSniffedType.AssignASCII(currentEntry.mContentType);
+      return NS_OK;
+    }
+  }
+
+  if (MatchesMP4(aData, clampedLength)) {
+    aSniffedType.AssignLiteral(VIDEO_MP4);
+    return NS_OK;
+  }
+
+  if (MatchesWebM(aData, clampedLength)) {
+    aSniffedType.AssignLiteral(VIDEO_WEBM);
+    return NS_OK;
+  }
+
+  // Bug 950023: 512 bytes are often not enough to sniff for mp3.
+  if (MatchesMP3(aData, std::min(aLength, MAX_BYTES_SNIFFED_MP3))) {
+    aSniffedType.AssignLiteral(AUDIO_MP3);
+    return NS_OK;
+  }
+
+  // Could not sniff the media type, we are required to set it to
+  // application/octet-stream.
+  aSniffedType.AssignLiteral(APPLICATION_OCTET_STREAM);
+  return NS_ERROR_NOT_AVAILABLE;
+}