//_____________________________________________________________________________
void WordLoc::Load( const THaEvData& evdata )
{
// Load data at header/notoskip position from crate data buffer
typedef const UInt_t rawdata_t;
Int_t roclen = evdata.GetRocLength(crate);
if( roclen < ntoskip+1 ) return;
rawdata_t* cratebuf = evdata.GetRawDataBuffer(crate), *endp = cratebuf+roclen;
assert(cratebuf); // Must exist if roclen > 0
// Accelerated search for the header word. Coded explicitly because there
// is no "memstr" in the standard library.
//FIXME: Can this be made faster because each header is followed by the offset
// to the next header?
// Get the first byte of the header, regardless of byte order
int h = ((UChar_t*)&header)[0];
rawdata_t* p = cratebuf;
while( (p = (rawdata_t*)memchr(p,h,sizeof(rawdata_t)*(endp-p-1)+1)) &&
p <= endp-ntoskip-1 ) {
// The header must be aligned at a word boundary
int off = (p-cratebuf) & (sizeof(rawdata_t)-1); // same as % sizeof()
if( off != 0 ) {
p += sizeof(rawdata_t)-off;
continue;
}
// Compare all 4 bytes of the header word
if( memcmp(p,&header,sizeof(rawdata_t)) == 0 ) {
// Fetch the requested word (as UInt_t, i.e. 4 bytes)
// BTW, notoskip == 0 makes no sense since it would fetch the header itself
data = *(p+ntoskip);
break;
}
p += sizeof(rawdata_t);
}
}
