void PtexReader::readFaceData(FilePos pos, FaceDataHeader fdh, Res res, int levelid,
FaceData*& face)
{
// keep new face local until fully initialized
FaceData* volatile newface = 0;
seek(pos);
switch (fdh.encoding()) {
case enc_constant:
{
ConstantFace* pf = new ConstantFace((void**)&face, _cache, _pixelsize);
readBlock(pf->data(), _pixelsize);
if (levelid==0 && _premultiply && _header.hasAlpha())
PtexUtils::multalpha(pf->data(), 1, _header.datatype,
_header.nchannels, _header.alphachan);
newface = pf;
}
break;
case enc_tiled:
{
Res tileres;
readBlock(&tileres, sizeof(tileres));
uint32_t tileheadersize;
readBlock(&tileheadersize, sizeof(tileheadersize));
TiledFace* tf = new TiledFace((void**)&face, _cache, res, tileres, levelid, this);
readZipBlock(&tf->_fdh[0], tileheadersize, FaceDataHeaderSize * tf->_ntiles);
computeOffsets(tell(), tf->_ntiles, &tf->_fdh[0], &tf->_offsets[0]);
newface = tf;
}
break;
case enc_zipped:
case enc_diffzipped:
{
int uw = res.u(), vw = res.v();
int npixels = uw * vw;
int unpackedSize = _pixelsize * npixels;
PackedFace* pf = new PackedFace((void**)&face, _cache,
res, _pixelsize, unpackedSize);
bool useMalloc = unpackedSize > AllocaMax;
void* tmp = useMalloc ? malloc(unpackedSize) : alloca(unpackedSize);
readZipBlock(tmp, fdh.blocksize(), unpackedSize);
if (fdh.encoding() == enc_diffzipped)
PtexUtils::decodeDifference(tmp, unpackedSize, _header.datatype);
PtexUtils::interleave(tmp, uw * DataSize(_header.datatype), uw, vw,
pf->data(), uw * _pixelsize,
_header.datatype, _header.nchannels);
if (levelid==0 && _premultiply && _header.hasAlpha())
PtexUtils::multalpha(pf->data(), npixels, _header.datatype,
_header.nchannels, _header.alphachan);
newface = pf;
if (useMalloc) free(tmp);
}
break;
}
face = newface;
}
void PtexReader::readFace(int levelid, Level* level, int faceid)
{
// temporarily release cache lock so other threads can proceed
_cache->cachelock.unlock();
// get read lock and make sure we still need to read
FaceData*& face = level->faces[faceid];
AutoMutex locker(readlock);
if (face) {
// another thread must have read it while we were waiting
_cache->cachelock.lock();
// make sure it's still there now that we have the lock
if (face) {
face->ref();
return;
}
_cache->cachelock.unlock();
}
// Go ahead and read the face, and read nearby faces if
// possible. The goal is to coalesce small faces into single
// runs of consecutive reads to minimize seeking and take
// advantage of read-ahead buffering.
// Try to read as many faces as will fit in BlockSize. Use the
// in-memory size rather than the on-disk size to prevent flooding
// the memory cache. And don't coalesce w/ tiled faces as these
// are meant to be read individually.
// scan both backwards and forwards looking for unread faces
int first = faceid, last = faceid;
int totalsize = 0;
FaceDataHeader fdh = level->fdh[faceid];
if (fdh.encoding() != enc_tiled) {
totalsize += unpackedSize(fdh, levelid, faceid);
int nfaces = int(level->fdh.size());
while (1) {
int f = first-1;
if (f < 0 || level->faces[f]) break;
fdh = level->fdh[f];
if (fdh.encoding() == enc_tiled) break;
int size = totalsize + unpackedSize(fdh, levelid, f);
if (size > BlockSize) break;
first = f;
totalsize = size;
}
while (1) {
int f = last+1;
if (f >= nfaces || level->faces[f]) break;
fdh = level->fdh[f];
if (fdh.encoding() == enc_tiled) break;
int size = totalsize + unpackedSize(fdh, levelid, f);
if (size > BlockSize) break;
last = f;
totalsize = size;
}
}
// read all faces in range
// keep track of extra faces we read so we can add them to the cache later
std::vector<FaceData*> extraFaces;
extraFaces.reserve(last-first);
for (int i = first; i <= last; i++) {
fdh = level->fdh[i];
// skip faces with zero size (which is true for level-0 constant faces)
if (fdh.blocksize()) {
FaceData*& face = level->faces[i];
readFaceData(level->offsets[i], fdh, getRes(levelid, i), levelid, face);
if (i != faceid) extraFaces.push_back(face);
}
}
// reacquire cache lock, then unref extra faces to add them to the cache
_cache->cachelock.lock();
for (size_t i = 0, size = extraFaces.size(); i < size; i++)
extraFaces[i]->unref();
}