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MJPEGServerImpl: Refactor NeedsDHT.

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This commit is contained in:
Peter Johnson
2016-11-12 21:57:25 -08:00
parent 7e0e8286eb
commit 0bcafedebf
1 changed files with 18 additions and 15 deletions
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33
src/MJPEGServerImpl.cpp
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@@ -432,6 +432,23 @@ void MJPEGServerImpl::Stop() {
source->Wakeup();
}
static bool NeedsDHT(const char* data, std::size_t* size, std::size_t* locSOF) {
// Search first 2048 bytes (or until SOS) for DHT tag
for (llvm::StringRef::size_type i = 0; i < 2048 && i < *size; ++i) {
if (static_cast<unsigned char>(data[i]) != 0xff) continue; // not a tag
unsigned char tag = static_cast<unsigned char>(data[i + 1]);
if (tag == 0xda) break; // SOS
if (tag == 0xc4) return false; // DHT
if (tag == 0xc0) *locSOF = i; // SOF
}
// Only add DHT if we also found SOF (insertion point)
if (*locSOF != *size) {
*size += sizeof(dhtData);
return true;
}
return false;
}
// Send HTTP response and a stream of JPG-frames
void MJPEGServerImpl::ConnThread::SendStream(wpi::raw_socket_ostream& os) {
os.SetUnbuffered();
@@ -470,21 +487,7 @@ void MJPEGServerImpl::ConnThread::SendStream(wpi::raw_socket_ostream& os) {
case VideoMode::kMJPEG:
// Determine if we need to add DHT to it, and allocate enough space
// for adding it if required.
// Search first 2048 bytes (or until SOS) for DHT tag
for (llvm::StringRef::size_type i = 0; i < 2048 && i < size; ++i) {
if (static_cast<unsigned char>(data[i]) != 0xff)
continue; // not a tag
unsigned char tag = static_cast<unsigned char>(data[i + 1]);
if (tag == 0xda) break; // SOS
if (tag == 0xc4) goto done; // DHT
if (tag == 0xc0) locSOF = i; // SOF
}
// Only add DHT if we also found SOF (insertion point)
if (locSOF != size) {
addDHT = true;
size += sizeof(dhtData);
}
done:
addDHT = NeedsDHT(data, &size, &locSOF);
break;
case VideoMode::kYUYV:
case VideoMode::kRGB565: