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#include "sdsl/coder_elias_gamma.hpp"
namespace sdsl
{
namespace coder
{
elias_gamma::impl elias_gamma::data;
uint64_t elias_gamma::decode_prefix_sum(const uint64_t* d, const size_type start_idx, const size_type end_idx, size_type n)
{
if (n==0)
return 0;
const uint64_t* lastdata = d + ((end_idx+63) >> 6);
d += (start_idx >> 6);
uint64_t w = 0, value = 0;
int16_t buffered = 0, read = start_idx & 0x3F;
size_type i = 0;
if (n + read <= 64) {
if (((*d >> read)&bits::lo_set[n]) == bits::lo_set[n])
return n;
} else { // n+read > 64
if ((*d >> read) == bits::lo_set[64-read]) {// all bits are set to 1
value = 64-read;
++d;
n -= (64-read);
read = 0;
while (n >= 64) {
if (*d == 0xFFFFFFFFFFFFFFFFULL) {
value += 64;
++d;
n -= 64;
} else
goto start_decoding;
}
// 0 <= n <= 64
if ((*d&bits::lo_set[n]) == bits::lo_set[n])
return value + n;
}
}
start_decoding:
while (i<n) {
while (buffered < 64 and d < lastdata) {
fill_buffer:
w |= (((*d)>>read)<<buffered);
if (read >= buffered) {
++d;
buffered += 64-read;
read = 0;
} else { // read buffered
read += 64-buffered;
buffered = 64;
}
}
uint32_t rbp = bits::lo(~w);
if (rbp > 0) {
i += rbp;
value += rbp;
if (i >= n) { // decoded too much
return value - (i-n); // return corrected value
}
assert(buffered >= rbp);
buffered -= rbp;
w >>= rbp;
if (buffered<16)
goto fill_buffer;
}
{
// i < n
begin_decode:
uint32_t psum = elias_gamma::data.prefixsum[w&0x0000FFFF];
if (!psum or i+((psum>>16)&0x00FF) > n) {
if (w==0) {// buffer is not full
w |= (((*d)>>read)<<buffered);
if (read >= buffered) {
++d;
buffered += 64-read;
read = 0;
} else {
read += 64-buffered;
buffered = 64;
};
if (!w) {
w |= (((*d)>>read)<<buffered);
if (read >= buffered) {
++d;
buffered += 64-read;
read = 0;
} else {
read += 64-buffered;
buffered = 64;
};
}
}
// assert(w>0);
uint16_t len_1 = bits::lo(w); // read length of length
buffered -= (len_1+1);
w >>= (len_1+1);
if (len_1 > buffered) {// buffer is not full
w |= (((*d)>>read)<<buffered);
if (read >= buffered) {
++d;
buffered += 64-read;
read = 0;
} else {
read += 64-buffered;
buffered = 64;
};
if (len_1 > buffered) {
w |= (((*d)>>read)<<buffered);
if (read >= buffered) {
++d;
buffered += 64-read;
read = 0;
} else {
read += 64-buffered;
buffered = 64;
};
}
}
value += (w&bits::lo_set[len_1]) + (len_1<64) * (1ULL << len_1);
buffered -= len_1;
if (len_1 < 64) {
w >>= len_1;
} else {
w = 0;
}
++i;
if (i==n)
return value;
if (buffered>=16)
goto begin_decode;
} else {
value += (psum&0x0000FFFF);
i += ((psum>>16)&0x00FF);
if (i==n)
return value;
buffered -= (psum>>24);
w >>= (psum>>24);
if (buffered>=16)
goto begin_decode;
}
}
};
return value;
}
uint64_t elias_gamma::decode_prefix_sum(const uint64_t* d, const size_type start_idx, size_type n)
{
if (n==0)
return 0;
d += (start_idx >> 6);
uint64_t value = 0;
size_type i = 0;
uint8_t offset = start_idx & 0x3F;
if (n < 24) {
if (n + offset <= 64) {
if (((*d >> offset)&bits::lo_set[n]) == bits::lo_set[n])
return n;
} else { // n+offset > 64
if ((*d >> offset) == bits::lo_set[64-offset]) {// all bits are set to 1
value = 64-offset;
++d;
n -= (64-offset);
offset = 0;
while (n >= 64) {
if (*d == 0xFFFFFFFFFFFFFFFFULL) {
value += 64;
++d;
n -= 64;
} else {
uint8_t temp = bits::lo(~(*d));
value += temp;
n -= temp;
offset = temp;
goto start_decoding;
}
}
// 0 <= n <= 64
if ((*d&bits::lo_set[n]) == bits::lo_set[n])
return value + n;
}
}
}
start_decoding:
while (i < n) {// while not all values are decoded
// n-i values to decode
if (((*d>>offset)&0xF)==0xF) {
uint8_t maxdecode = n-i > 63 ? 63 : n-i;
uint8_t rbp = bits::lo(~bits::read_int(d, offset,maxdecode));
i += rbp;
value += rbp;
if (rbp+offset>=64) {
++d;
offset = (rbp+offset)&0x3F;
} else {
offset += rbp;
}
if (rbp == maxdecode)
continue;
}
while (i < n) {
uint32_t psum = elias_gamma::data.prefixsum[bits::read_int(d, offset, 16)];
if (psum == 0) { // value does not fit in 16 bits
goto decode_single;
} else if (i+((psum>>16)&0x00FF) > n) { // decoded too much
if (n-i <= 8) {
psum = elias_gamma::data.prefixsum_8bit[bits::read_int(d, offset, 8) | ((n-i-1)<<8)];
if (psum > 0) {
value += (psum&0xFF);
i += ((psum>>8)&0xF);
offset += (psum>>12);
if (offset>=64) {
offset&=0x3F;
++d;
}
}
}
break;
} else {
value += (psum&0x0000FFFF);
i += ((psum>>16)&0x00FF);
offset += (psum>>24);
if (offset>=64) {
offset&=0x3F;
++d;
}
}
}
if (i<n) {
decode_single:
i++;
uint16_t len_1 = bits::read_unary_and_move(d, offset); // read length of length of x
value += bits::read_int_and_move(d, offset, len_1) + (len_1<64) * (1ULL << len_1);
}
}
return value;
}
} // end namespace sdsl
} // end namespace coder
|
