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//------------------------------------------------------------------------------
// GB_bitwise.h: definitions for bitwise operators
//------------------------------------------------------------------------------
// SuiteSparse:GraphBLAS, Timothy A. Davis, (c) 2017-2022, All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0
//------------------------------------------------------------------------------
#ifndef GB_BITWISE_H
#define GB_BITWISE_H
//------------------------------------------------------------------------------
// bitget, bitset, bitclr
//------------------------------------------------------------------------------
// bitget (x,k) returns a single bit from x, as 0 or 1, whose position is given
// by k. k = 1 is the least significant bit, and k = bits (64 for uint64)
// is the most significant bit. If k is outside this range, the result is zero.
#define GB_BITGET(x,k,type,bits) \
( \
(k >= 1 && k <= bits) ? \
( \
/* get the kth bit */ \
((x & (((type) 1) << (k-1))) ? 1 : 0) \
) \
: \
( \
0 \
) \
)
// bitset (x,k) returns x modified by setting a bit from x to 1, whose position
// is given by k. If k is in the range 1 to bits, then k gives the position
// of the bit to set. If k is outside the range 1 to bits, then z = x is
// returned, unmodified.
#define GB_BITSET(x,k,type,bits) \
( \
(k >= 1 && k <= bits) ? \
( \
/* set the kth bit to 1 */ \
(x | (((type) 1) << (k-1))) \
) \
: \
( \
x \
) \
)
// bitclr (x,k) returns x modified by setting a bit from x to 0, whose position
// is given by k. If k is in the range 1 to bits, then k gives the position of
// the bit to clear. If k is outside the range 1 to GB_BITS, then z = x is
// returned, unmodified.
#define GB_BITCLR(x,k,type,bits) \
( \
(k >= 1 && k <= bits) ? \
( \
/* set the kth bit to 0 */ \
(x & ~(((type) 1) << (k-1))) \
) \
: \
( \
x \
) \
)
//------------------------------------------------------------------------------
// z = bitshift (x,y) when x and z are unsigned
//------------------------------------------------------------------------------
inline uint8_t GB_bitshift_uint8 (uint8_t x, int8_t k)
{
if (k == 0)
{
// no shift to do at all
return (x) ;
}
else if (k >= 8 || k <= -8)
{
// ANSI C11 states that the result of x << k is undefined if k is
// negative or if k is greater than the # of bits in x. Here, the
// result is defined to be zero (the same as if shifting left
// or right by 8).
return (0) ;
}
else if (k > 0)
{
// left shift x by k bits. z is defined by ANSI C11 as
// (x * (2^k)) mod (uintmax + 1).
return (x << k) ;
}
else
{
k = -k ;
// right shift x by k bits. z is defined by ANSI C11 as the
// integral part of the quotient of x / (2^k).
return (x >> k) ;
}
}
inline uint16_t GB_bitshift_uint16 (uint16_t x, int8_t k)
{
if (k == 0)
{
// no shift
return (x) ;
}
else if (k >= 16 || k <= -16)
{
return (0) ;
}
else if (k > 0)
{
// left shift
return (x << k) ;
}
else
{
// right shift
return (x >> (-k)) ;
}
}
inline uint32_t GB_bitshift_uint32 (uint32_t x, int8_t k)
{
if (k == 0)
{
// no shift
return (x) ;
}
else if (k >= 32 || k <= -32)
{
return (0) ;
}
else if (k > 0)
{
// left shift
return (x << k) ;
}
else
{
// right shift
return (x >> (-k)) ;
}
}
inline uint64_t GB_bitshift_uint64 (uint64_t x, int8_t k)
{
if (k == 0)
{
// no shift
return (x) ;
}
else if (k >= 64 || k <= -64)
{
return (0) ;
}
else if (k > 0)
{
// left shift
return (x << k) ;
}
else
{
// right shift
return (x >> (-k)) ;
}
}
//------------------------------------------------------------------------------
// z = bitshift (x,y) when x and z are signed
//------------------------------------------------------------------------------
inline int8_t GB_bitshift_int8 (int8_t x, int8_t k)
{
if (k == 0)
{
// no shift to do at all
return (x) ;
}
else if (k >= 8)
{
// ANSI C11 states that z = x << k is undefined if k is greater
// than the # of bits in x. Here, the result is defined to be zero.
return (0) ;
}
else if (k <= -8)
{
// ANSI C11 states that z = x >> (-k) is undefined if (-k) is
// greater than the # of bits in x. Here, the result is defined to
// be the sign of x (z = 0 if x >= 0 and z = -1 if x is negative).
return ((x >= 0) ? 0 : -1) ;
}
else if (k > 0)
{
// left shift x by k bits (where k is in range 1 to #bits - 1).
// ANSI C11 states that z is defined only if x is non-negative and
// x * (2^k) is representable. This computation assumes x and z
// are represented in 2's complement. The result depends on the
// underlying machine architecture and the compiler.
return (x << k) ;
}
else
{
k = -k ;
// right shift x by k bits (where k is in range 1 to 8)
if (x >= 0)
{
// ANSI C11 defines z as the integral part of the quotient
// of x / (2^k).
return (x >> k) ;
}
else
{
// ANSI C11 states that the result is implementation-defined if
// x is negative. This computation assumes x and z are in 2's
// complement, so 1-bits are shifted in on the left, and thus
// the sign bit is always preserved. The result depends on the
// underlying machine architecture and the compiler.
return ((x >> k) | (~(UINT8_MAX >> k))) ;
}
}
}
inline int16_t GB_bitshift_int16 (int16_t x, int8_t k)
{
if (k == 0)
{
// no shift
return (x) ;
}
else if (k >= 16)
{
return (0) ;
}
else if (k <= -16)
{
return ((x >= 0) ? 0 : -1) ;
}
else if (k > 0)
{
// left shift
return (x << k) ;
}
else
{
// right shift
k = -k ;
if (x >= 0)
{
return (x >> k) ;
}
else
{
return ((x >> k) | (~(UINT16_MAX >> k))) ;
}
}
}
inline int32_t GB_bitshift_int32 (int32_t x, int8_t k)
{
if (k == 0)
{
// no shift
return (x) ;
}
else if (k >= 32)
{
return (0) ;
}
else if (k <= -32)
{
return ((x >= 0) ? 0 : -1) ;
}
else if (k > 0)
{
// left shift
return (x << k) ;
}
else
{
// right shift
k = -k ;
if (x >= 0)
{
return (x >> k) ;
}
else
{
return ((x >> k) | (~(UINT32_MAX >> k))) ;
}
}
}
inline int64_t GB_bitshift_int64 (int64_t x, int8_t k)
{
if (k == 0)
{
// no shift
return (x) ;
}
else if (k >= 64)
{
return (0) ;
}
else if (k <= -64)
{
return ((x >= 0) ? 0 : -1) ;
}
else if (k > 0)
{
// left shift
return (x << k) ;
}
else
{
// right shift
k = -k ;
if (x >= 0)
{
return (x >> k) ;
}
else
{
return ((x >> k) | (~(UINT64_MAX >> k))) ;
}
}
}
#endif
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