gecko/toolkit/components/mediasniffer/nsMediaSniffer.cpp

108 lines
3.5 KiB
C++

/* -*- 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 "nsMemory.h"
#include "nsIHttpChannel.h"
#include "nsAString.h"
#include "nsMimeTypes.h"
#include "mozilla/ModuleUtils.h"
#include "nsIClassInfoImpl.h"
// 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 PRUint32 MAX_BYTES_SNIFFED = 512;
NS_IMPL_CLASSINFO(nsMediaSniffer, NULL, 0, NS_MEDIA_SNIFFER_CID)
NS_IMPL_ISUPPORTS1(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),
// WebM
PATTERN_ENTRY("\xFF\xFF\xFF\xFF", "\x1A\x45\xDF\xA3", VIDEO_WEBM),
// mp3 without ID3 tags.
PATTERN_ENTRY("\xFF\xFB", "\xFF\xFA", AUDIO_MP3),
// 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 PRUint8* aData, const PRUint32 aLength)
{
if (aLength <= MP4_MIN_BYTES_COUNT) {
return false;
}
// Conversion from big endian to host byte order.
PRUint32 boxSize = (PRUint32)(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 (PRUint32 i = 2; i <= boxSize / 4 - 1 ; i++) {
if (i == 3) {
continue;
}
// The string "mp4".
if (aData[4*i] == 0x6D &&
aData[4*i+1] == 0x70 &&
aData[4*i+2] == 0x34) {
return true;
}
}
return false;
}
NS_IMETHODIMP
nsMediaSniffer::GetMIMETypeFromContent(nsIRequest* aRequest,
const PRUint8* aData,
const PRUint32 aLength,
nsACString& aSniffedType)
{
const PRUint32 clampedLength = NS_MIN(aLength, MAX_BYTES_SNIFFED);
for (PRUint32 i = 0; i < NS_ARRAY_LENGTH(sSnifferEntries); ++i) {
const nsMediaSnifferEntry& currentEntry = sSnifferEntries[i];
if (clampedLength < currentEntry.mLength || currentEntry.mLength == 0) {
continue;
}
bool matched = true;
for (PRUint32 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;
}
// 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;
}