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/*
pack.c: bit-packing/unpacking for Kronecker substitution routines
Copyright (C) 2007, 2008, David Harvey
This file is part of the zn_poly library (version 0.8).
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 2 of the License, or
(at your option) version 3 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "zn_poly_internal.h"
/*
Same as zn_array_pack(), but requires bits <= ULONG_BITS.
*/
#define zn_array_pack1 \
ZNP_zn_array_pack1
void zn_array_pack1(mp_limb_t* res, const ulong* op, size_t len,
ptrdiff_t skip, unsigned bits, unsigned lead,
size_t requested)
{
ZNP_ASSERT(bits > 0 && bits <= ULONG_BITS);
#if GMP_NAIL_BITS == 0 && ULONG_BITS == GMP_NUMB_BITS
// where to write the next limb
mp_limb_t* dest = res;
// write leading zero-padding
while (lead >= ULONG_BITS)
{
*dest++ = 0;
lead -= ULONG_BITS;
}
// limb currently being filled
mp_limb_t buf = 0;
// number of bits used in buf; always in [0, ULONG_BITS)
unsigned buf_bits = lead;
unsigned old_buf_bits;
for (; len > 0; len--, op += skip)
{
ZNP_ASSERT(bits >= ULONG_BITS || *op < (1UL << bits));
// put low bits of current input into buffer
buf += *op << buf_bits;
old_buf_bits = buf_bits;
buf_bits += bits;
if (buf_bits >= ULONG_BITS)
{
// buffer is full; flush it
*dest++ = buf;
buf_bits -= ULONG_BITS;
// put remaining bits of current input into buffer
buf = old_buf_bits ? (*op >> (ULONG_BITS - old_buf_bits)) : 0;
}
}
// write last limb if it's non-empty
if (buf_bits)
*dest++ = buf;
// zero-pad up to requested length
if (requested)
{
size_t written = dest - res;
ZNP_ASSERT(written <= requested);
for (; written < requested; written++)
*dest++ = 0;
}
#else
#error Not nails-safe yet
#endif
}
void zn_array_pack(mp_limb_t* res, const ulong* op, size_t len,
ptrdiff_t skip, unsigned bits, unsigned lead,
size_t requested)
{
ZNP_ASSERT(bits > 0 && bits < 3*ULONG_BITS);
if (bits <= ULONG_BITS)
{
// use specialised version if bits is small enough
zn_array_pack1(res, op, len, skip, bits, lead, requested);
return;
}
#if GMP_NAIL_BITS == 0 && ULONG_BITS == GMP_NUMB_BITS
// where to write the next limb
mp_limb_t* dest = res;
// write leading zero-padding
while (lead >= ULONG_BITS)
{
*dest++ = 0;
lead -= ULONG_BITS;
}
// limb currently being filled
mp_limb_t buf = 0;
// number of bits used in buf; always in [0, ULONG_BITS)
unsigned buf_bits = lead;
unsigned old_buf_bits;
for (; len > 0; len--, op += skip)
{
ZNP_ASSERT(bits >= ULONG_BITS || *op < (1UL << bits));
// put low bits of current input into buffer
buf += *op << buf_bits;
old_buf_bits = buf_bits;
buf_bits += bits;
if (buf_bits >= ULONG_BITS)
{
// buffer is full; flush it
*dest++ = buf;
buf_bits -= ULONG_BITS;
// put remaining bits of current input into buffer
buf = old_buf_bits ? (*op >> (ULONG_BITS - old_buf_bits)) : 0;
// write as many extra zeroes as necessary
if (buf_bits >= ULONG_BITS)
{
*dest++ = buf;
buf = 0;
buf_bits -= ULONG_BITS;
if (buf_bits >= ULONG_BITS)
{
*dest++ = 0;
buf_bits -= ULONG_BITS;
ZNP_ASSERT(buf_bits < ULONG_BITS);
}
}
}
}
// write last limb if it's non-empty
if (buf_bits)
*dest++ = buf;
// zero-pad up to requested length
if (requested)
{
size_t written = dest - res;
ZNP_ASSERT(written <= requested);
for (; written < requested; written++)
*dest++ = 0;
}
#else
#error Not nails-safe yet
#endif
}
/*
Same as zn_array_unpack(), but requires bits <= ULONG_BITS
(i.e. writes one word per coefficient)
*/
#define zn_array_unpack1 \
ZNP_zn_array_unpack1
void zn_array_unpack1(ulong* res, const mp_limb_t* op, size_t len,
unsigned bits, unsigned lead)
{
ZNP_ASSERT(bits <= ULONG_BITS);
#if GMP_NAIL_BITS == 0 && ULONG_BITS == GMP_NUMB_BITS
// limb we're currently extracting bits from
mp_limb_t buf = 0;
// number of bits currently in buf; always in [0, ULONG_BITS)
unsigned buf_bits = 0;
// skip over _lead_ leading bits
while (lead >= GMP_NUMB_BITS)
{
lead -= GMP_NUMB_BITS;
op++;
}
if (lead)
{
buf = *op++;
buf >>= lead;
buf_bits = ULONG_BITS - lead;
}
if (bits == ULONG_BITS)
{
// various special cases
if (buf_bits)
{
for (; len > 0; len--)
{
// we need bits from both sides of a limb boundary
ulong temp = buf;
buf = *op++;
*res++ = temp + (buf << buf_bits);
buf >>= (ULONG_BITS - buf_bits);
}
}
else
{
for (; len > 0; len--)
*res++ = *op++;
}
}
else
{
ulong mask = (1UL << bits) - 1;
for (; len > 0; len--)
{
if (bits <= buf_bits)
{
// buf contains all the bits we need
*res++ = buf & mask;
buf >>= bits;
buf_bits -= bits;
}
else
{
// we need bits from both sides of a limb boundary
ulong temp = buf;
buf = *op++;
*res++ = temp + ((buf << buf_bits) & mask);
buf >>= (bits - buf_bits);
buf_bits = ULONG_BITS - (bits - buf_bits);
}
}
}
#else
#error Not nails-safe yet
#endif
}
/*
Same as zn_array_unpack(), but requires ULONG_BITS < bits <= 2*ULONG_BITS
(i.e. writes two words per coefficient)
*/
#define zn_array_unpack2 \
ZNP_zn_array_unpack2
void zn_array_unpack2(ulong* res, const mp_limb_t* op, size_t len,
unsigned bits, unsigned lead)
{
ZNP_ASSERT(bits > ULONG_BITS && bits <= 2*ULONG_BITS);
#if GMP_NAIL_BITS == 0 && ULONG_BITS == GMP_NUMB_BITS
// limb we're currently extracting bits from
mp_limb_t buf = 0;
// number of bits currently in buf; always in [0, ULONG_BITS)
unsigned buf_bits = 0;
// skip over _lead_ leading bits
while (lead >= GMP_NUMB_BITS)
{
lead -= GMP_NUMB_BITS;
op++;
}
if (lead)
{
buf = *op++;
buf >>= lead;
buf_bits = ULONG_BITS - lead;
}
if (bits == 2*ULONG_BITS)
{
len = 2*len;
// various special cases
if (buf_bits)
{
for (; len > 0; len--)
{
// we need bits from both sides of a limb boundary
ulong temp = buf;
buf = *op++;
*res++ = temp + (buf << buf_bits);
buf >>= (ULONG_BITS - buf_bits);
}
}
else
{
for (; len > 0; len--)
*res++ = *op++;
}
}
else
{
bits -= ULONG_BITS;
ulong mask = (1UL << bits) - 1;
for (; len > 0; len--)
{
// shunt one whole limb through first
if (buf_bits)
{
ulong temp = buf;
buf = *op++;
*res++ = temp + (buf << buf_bits);
buf >>= (ULONG_BITS - buf_bits);
}
else
*res++ = *op++;
// now handle the fractional limb
if (bits <= buf_bits)
{
// buf contains all the bits we need
*res++ = buf & mask;
buf >>= bits;
buf_bits -= bits;
}
else
{
// we need bits from both sides of a limb boundary
ulong temp = buf;
buf = *op++;
*res++ = temp + ((buf << buf_bits) & mask);
buf >>= (bits - buf_bits);
buf_bits = ULONG_BITS - (bits - buf_bits);
}
}
}
#else
#error Not nails-safe yet
#endif
}
/*
Same as zn_array_unpack(), but requires 2*ULONG_BITS < bits < 3*ULONG_BITS
(i.e. writes three words per coefficient)
*/
#define zn_array_unpack3 \
ZNP_zn_array_unpack3
void zn_array_unpack3(ulong* res, const mp_limb_t* op, size_t len,
unsigned bits, unsigned lead)
{
ZNP_ASSERT(bits > 2*ULONG_BITS && bits < 3*ULONG_BITS);
#if GMP_NAIL_BITS == 0 && ULONG_BITS == GMP_NUMB_BITS
// limb we're currently extracting bits from
mp_limb_t buf = 0;
// number of bits currently in buf; always in [0, ULONG_BITS)
unsigned buf_bits = 0;
// skip over _lead_ leading bits
while (lead >= GMP_NUMB_BITS)
{
lead -= GMP_NUMB_BITS;
op++;
}
if (lead)
{
buf = *op++;
buf >>= lead;
buf_bits = ULONG_BITS - lead;
}
bits -= 2*ULONG_BITS;
ulong mask = (1UL << bits) - 1;
for (; len > 0; len--)
{
// shunt two whole limbs through first
if (buf_bits)
{
ulong temp = buf;
buf = *op++;
*res++ = temp + (buf << buf_bits);
buf >>= (ULONG_BITS - buf_bits);
temp = buf;
buf = *op++;
*res++ = temp + (buf << buf_bits);
buf >>= (ULONG_BITS - buf_bits);
}
else
{
*res++ = *op++;
*res++ = *op++;
}
// now handle the fractional limb
if (bits <= buf_bits)
{
// buf contains all the bits we need
*res++ = buf & mask;
buf >>= bits;
buf_bits -= bits;
}
else
{
// we need bits from both sides of a limb boundary
ulong temp = buf;
buf = *op++;
*res++ = temp + ((buf << buf_bits) & mask);
buf >>= (bits - buf_bits);
buf_bits = ULONG_BITS - (bits - buf_bits);
}
}
#else
#error Not nails-safe yet
#endif
}
void zn_array_unpack(ulong* res, const mp_limb_t* op, size_t len,
unsigned bits, unsigned lead)
{
ZNP_ASSERT(bits >= 1 && bits <= 3 * ULONG_BITS);
if (bits <= ULONG_BITS)
zn_array_unpack1(res, op, len, bits, lead);
else if (bits <= 2 * ULONG_BITS)
zn_array_unpack2(res, op, len, bits, lead);
else // bits < 3 * ULONG_BITS
zn_array_unpack3(res, op, len, bits, lead);
}
// end of file ****************************************************************
|
