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postgresql/src/include/common/int.h

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/*-------------------------------------------------------------------------
*
* int.h
* Overflow-aware integer math and integer comparison routines.
*
* The routines in this file are intended to be well defined C, without
* relying on compiler flags like -fwrapv.
*
* To reduce the overhead of these routines try to use compiler intrinsics
* where available. That's not that important for the 16, 32 bit cases, but
* the 64 bit cases can be considerably faster with intrinsics. In case no
* intrinsics are available 128 bit math is used where available.
*
* Copyright (c) 2017-2024, PostgreSQL Global Development Group
*
* src/include/common/int.h
*
*-------------------------------------------------------------------------
*/
#ifndef COMMON_INT_H
#define COMMON_INT_H
/*---------
* The following guidelines apply to all the overflow routines:
* - If a + b overflows, return true, otherwise store the result of a + b
* into *result. The content of *result is implementation defined in case of
* overflow.
* - If a - b overflows, return true, otherwise store the result of a - b
* into *result. The content of *result is implementation defined in case of
* overflow.
* - If a * b overflows, return true, otherwise store the result of a * b
* into *result. The content of *result is implementation defined in case of
* overflow.
*---------
*/
/*------------------------------------------------------------------------
* Overflow routines for signed integers
*------------------------------------------------------------------------
*/
/*
* INT16
*/
static inline bool
pg_add_s16_overflow(int16 a, int16 b, int16 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_add_overflow(a, b, result);
#else
int32 res = (int32) a + (int32) b;
if (res > PG_INT16_MAX || res < PG_INT16_MIN)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (int16) res;
return false;
#endif
}
static inline bool
pg_sub_s16_overflow(int16 a, int16 b, int16 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_sub_overflow(a, b, result);
#else
int32 res = (int32) a - (int32) b;
if (res > PG_INT16_MAX || res < PG_INT16_MIN)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (int16) res;
return false;
#endif
}
static inline bool
pg_mul_s16_overflow(int16 a, int16 b, int16 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_mul_overflow(a, b, result);
#else
int32 res = (int32) a * (int32) b;
if (res > PG_INT16_MAX || res < PG_INT16_MIN)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (int16) res;
return false;
#endif
}
/*
* INT32
*/
static inline bool
pg_add_s32_overflow(int32 a, int32 b, int32 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_add_overflow(a, b, result);
#else
int64 res = (int64) a + (int64) b;
if (res > PG_INT32_MAX || res < PG_INT32_MIN)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (int32) res;
return false;
#endif
}
static inline bool
pg_sub_s32_overflow(int32 a, int32 b, int32 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_sub_overflow(a, b, result);
#else
int64 res = (int64) a - (int64) b;
if (res > PG_INT32_MAX || res < PG_INT32_MIN)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (int32) res;
return false;
#endif
}
static inline bool
pg_mul_s32_overflow(int32 a, int32 b, int32 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_mul_overflow(a, b, result);
#else
int64 res = (int64) a * (int64) b;
if (res > PG_INT32_MAX || res < PG_INT32_MIN)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (int32) res;
return false;
#endif
}
/*
* INT64
*/
static inline bool
pg_add_s64_overflow(int64 a, int64 b, int64 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_add_overflow(a, b, result);
#elif defined(HAVE_INT128)
int128 res = (int128) a + (int128) b;
if (res > PG_INT64_MAX || res < PG_INT64_MIN)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (int64) res;
return false;
#else
if ((a > 0 && b > 0 && a > PG_INT64_MAX - b) ||
(a < 0 && b < 0 && a < PG_INT64_MIN - b))
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = a + b;
return false;
#endif
}
static inline bool
pg_sub_s64_overflow(int64 a, int64 b, int64 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_sub_overflow(a, b, result);
#elif defined(HAVE_INT128)
int128 res = (int128) a - (int128) b;
if (res > PG_INT64_MAX || res < PG_INT64_MIN)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (int64) res;
return false;
#else
/*
* Note: overflow is also possible when a == 0 and b < 0 (specifically,
* when b == PG_INT64_MIN).
*/
if ((a < 0 && b > 0 && a < PG_INT64_MIN + b) ||
(a >= 0 && b < 0 && a > PG_INT64_MAX + b))
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = a - b;
return false;
#endif
}
static inline bool
pg_mul_s64_overflow(int64 a, int64 b, int64 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_mul_overflow(a, b, result);
#elif defined(HAVE_INT128)
int128 res = (int128) a * (int128) b;
if (res > PG_INT64_MAX || res < PG_INT64_MIN)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (int64) res;
return false;
#else
/*
* Overflow can only happen if at least one value is outside the range
* sqrt(min)..sqrt(max) so check that first as the division can be quite a
* bit more expensive than the multiplication.
*
* Multiplying by 0 or 1 can't overflow of course and checking for 0
* separately avoids any risk of dividing by 0. Be careful about dividing
* INT_MIN by -1 also, note reversing the a and b to ensure we're always
* dividing it by a positive value.
*
*/
if ((a > PG_INT32_MAX || a < PG_INT32_MIN ||
b > PG_INT32_MAX || b < PG_INT32_MIN) &&
a != 0 && a != 1 && b != 0 && b != 1 &&
((a > 0 && b > 0 && a > PG_INT64_MAX / b) ||
(a > 0 && b < 0 && b < PG_INT64_MIN / a) ||
(a < 0 && b > 0 && a < PG_INT64_MIN / b) ||
(a < 0 && b < 0 && a < PG_INT64_MAX / b)))
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = a * b;
return false;
#endif
}
/*------------------------------------------------------------------------
* Overflow routines for unsigned integers
*------------------------------------------------------------------------
*/
/*
* UINT16
*/
static inline bool
pg_add_u16_overflow(uint16 a, uint16 b, uint16 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_add_overflow(a, b, result);
#else
uint16 res = a + b;
if (res < a)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = res;
return false;
#endif
}
static inline bool
pg_sub_u16_overflow(uint16 a, uint16 b, uint16 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_sub_overflow(a, b, result);
#else
if (b > a)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = a - b;
return false;
#endif
}
static inline bool
pg_mul_u16_overflow(uint16 a, uint16 b, uint16 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_mul_overflow(a, b, result);
#else
uint32 res = (uint32) a * (uint32) b;
if (res > PG_UINT16_MAX)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (uint16) res;
return false;
#endif
}
/*
* INT32
*/
static inline bool
pg_add_u32_overflow(uint32 a, uint32 b, uint32 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_add_overflow(a, b, result);
#else
uint32 res = a + b;
if (res < a)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = res;
return false;
#endif
}
static inline bool
pg_sub_u32_overflow(uint32 a, uint32 b, uint32 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_sub_overflow(a, b, result);
#else
if (b > a)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = a - b;
return false;
#endif
}
static inline bool
pg_mul_u32_overflow(uint32 a, uint32 b, uint32 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_mul_overflow(a, b, result);
#else
uint64 res = (uint64) a * (uint64) b;
if (res > PG_UINT32_MAX)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (uint32) res;
return false;
#endif
}
/*
* UINT64
*/
static inline bool
pg_add_u64_overflow(uint64 a, uint64 b, uint64 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_add_overflow(a, b, result);
#else
uint64 res = a + b;
if (res < a)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = res;
return false;
#endif
}
static inline bool
pg_sub_u64_overflow(uint64 a, uint64 b, uint64 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_sub_overflow(a, b, result);
#else
if (b > a)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = a - b;
return false;
#endif
}
static inline bool
pg_mul_u64_overflow(uint64 a, uint64 b, uint64 *result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
return __builtin_mul_overflow(a, b, result);
#elif defined(HAVE_INT128)
uint128 res = (uint128) a * (uint128) b;
if (res > PG_UINT64_MAX)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = (uint64) res;
return false;
#else
uint64 res = a * b;
if (a != 0 && b != res / a)
{
*result = 0x5EED; /* to avoid spurious warnings */
return true;
}
*result = res;
return false;
#endif
}
/*------------------------------------------------------------------------
*
* Comparison routines for integer types.
*
* These routines are primarily intended for use in qsort() comparator
* functions and therefore return a positive integer, 0, or a negative
* integer depending on whether "a" is greater than, equal to, or less
* than "b", respectively. These functions are written to be as efficient
* as possible without introducing overflow risks, thereby helping ensure
* the comparators that use them are transitive.
*
* Types with fewer than 32 bits are cast to signed integers and
* subtracted. Other types are compared using > and <, and the results of
* those comparisons (which are either (int) 0 or (int) 1 per the C
* standard) are subtracted.
*
* NB: If the comparator function is inlined, some compilers may produce
* worse code with these helper functions than with code with the
* following form:
*
* if (a < b)
* return -1;
* if (a > b)
* return 1;
* return 0;
*
*------------------------------------------------------------------------
*/
static inline int
pg_cmp_s16(int16 a, int16 b)
{
return (int32) a - (int32) b;
}
static inline int
pg_cmp_u16(uint16 a, uint16 b)
{
return (int32) a - (int32) b;
}
static inline int
pg_cmp_s32(int32 a, int32 b)
{
return (a > b) - (a < b);
}
static inline int
pg_cmp_u32(uint32 a, uint32 b)
{
return (a > b) - (a < b);
}
static inline int
pg_cmp_s64(int64 a, int64 b)
{
return (a > b) - (a < b);
}
static inline int
pg_cmp_u64(uint64 a, uint64 b)
{
return (a > b) - (a < b);
}
static inline int
pg_cmp_size(size_t a, size_t b)
{
return (a > b) - (a < b);
}
#endif /* COMMON_INT_H */
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