core
/
eccodes
mirror of https://github.com/ecmwf/eccodes.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

ECC-386: Slow-down of read routine. Fixed decoding

This commit is contained in:
Shahram Najm 2016-12-05 14:51:30 +00:00
parent 09a4f88014
commit 3dd428aa4f
1 changed files with 57 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

89
src/grib_bits_any_endian_simple.c
View File

@ -94,42 +94,67 @@ int grib_decode_double_array(const unsigned char* p, long *bitp, long bitsPerVal
val[i] = (double)x;
}
#endif
unsigned long mask = BIT_MASK(bitsPerValue);
if (bitsPerValue%8 == 0)
{
/* See ECC-386 */
int bc;
int l = bitsPerValue/8;
size_t o = 0;
/* pi: position of bitp in p[]. >>3 == /8 */
long pi = *bitp / 8;
/* some bits might of the current byte at pi might be used */
/* by the previous number usefulBitsInByte gives remaining unused bits */
/* number of useful bits in current byte */
int usefulBitsInByte = 8-(*bitp & 7);
for(i=0;i < n_vals;i++) {
/* value read as long */
long bitsToRead = 0;
lvalue = 0;
bitsToRead = bitsPerValue;
/* read one byte after the other to lvalue until >= bitsPerValue are read */
while (bitsToRead > 0) {
for(i=0;i < n_vals;i++)
{
lvalue = 0;
lvalue <<= 8;
lvalue += p[pi];
pi++;
bitsToRead -= usefulBitsInByte;
usefulBitsInByte = 8;
}
*bitp += bitsPerValue;
/* bitsToRead is now <= 0, remove the last bits */
lvalue >>= -1*bitsToRead;
/* set leading bits to 0 - removing bits used for previous number */
lvalue &= mask;
lvalue |= p[o++] ;
usefulBitsInByte = -1*bitsToRead; /* prepare for next round */
if (usefulBitsInByte > 0) {
pi--; /* reread the current byte */
} else {
usefulBitsInByte = 8; /* start with next full byte */
for ( bc=1; bc<l; bc++ )
{
lvalue <<= 8;
lvalue |= p[o++] ;
}
x=((lvalue*s)+reference_value)*d;
val[i] = (double)x;
}
}
else
{
unsigned long mask = BIT_MASK(bitsPerValue);
/* pi: position of bitp in p[]. >>3 == /8 */
long pi = *bitp / 8;
/* some bits might of the current byte at pi might be used */
/* by the previous number usefulBitsInByte gives remaining unused bits */
/* number of useful bits in current byte */
int usefulBitsInByte = 8-(*bitp & 7);
for(i=0;i < n_vals;i++) {
/* value read as long */
long bitsToRead = 0;
lvalue = 0;
bitsToRead = bitsPerValue;
/* read one byte after the other to lvalue until >= bitsPerValue are read */
while (bitsToRead > 0) {
lvalue <<= 8;
lvalue += p[pi];
pi++;
bitsToRead -= usefulBitsInByte;
usefulBitsInByte = 8;
}
*bitp += bitsPerValue;
/* bitsToRead is now <= 0, remove the last bits */
lvalue >>= -1*bitsToRead;
/* set leading bits to 0 - removing bits used for previous number */
lvalue &= mask;
usefulBitsInByte = -1*bitsToRead; /* prepare for next round */
if (usefulBitsInByte > 0) {
pi--; /* reread the current byte */
} else {
usefulBitsInByte = 8; /* start with next full byte */
}
/* scaling and move value to output */
x=((lvalue*s)+reference_value)*d;
val[i] = (double)x;
}
/* scaling and move value to output */
x=((lvalue*s)+reference_value)*d;
val[i] = (double)x;
}
return 0;
}