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273 lines
6.9 KiB
273 lines
6.9 KiB
/*-------------------------------------------------------------------------
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*
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* int.h
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* Routines to perform integer math, while checking for overflows.
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*
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* The routines in this file are intended to be well defined C, without
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* relying on compiler flags like -fwrapv.
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*
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* To reduce the overhead of these routines try to use compiler intrinsics
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* where available. That's not that important for the 16, 32 bit cases, but
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* the 64 bit cases can be considerably faster with intrinsics. In case no
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* intrinsics are available 128 bit math is used where available.
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*
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* Copyright (c) 2017-2019, PostgreSQL Global Development Group
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*
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* src/include/common/int.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef COMMON_INT_H
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#define COMMON_INT_H
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/*
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* If a + b overflows, return true, otherwise store the result of a + b into
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* *result. The content of *result is implementation defined in case of
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* overflow.
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*/
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static inline bool
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pg_add_s16_overflow(int16 a, int16 b, int16 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_add_overflow(a, b, result);
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#else
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int32 res = (int32) a + (int32) b;
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if (res > PG_INT16_MAX || res < PG_INT16_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int16) res;
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return false;
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#endif
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}
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/*
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* If a - b overflows, return true, otherwise store the result of a - b into
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* *result. The content of *result is implementation defined in case of
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* overflow.
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*/
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static inline bool
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pg_sub_s16_overflow(int16 a, int16 b, int16 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_sub_overflow(a, b, result);
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#else
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int32 res = (int32) a - (int32) b;
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if (res > PG_INT16_MAX || res < PG_INT16_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int16) res;
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return false;
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#endif
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}
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/*
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* If a * b overflows, return true, otherwise store the result of a * b into
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* *result. The content of *result is implementation defined in case of
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* overflow.
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*/
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static inline bool
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pg_mul_s16_overflow(int16 a, int16 b, int16 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_mul_overflow(a, b, result);
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#else
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int32 res = (int32) a * (int32) b;
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if (res > PG_INT16_MAX || res < PG_INT16_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int16) res;
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return false;
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#endif
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}
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/*
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* If a + b overflows, return true, otherwise store the result of a + b into
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* *result. The content of *result is implementation defined in case of
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* overflow.
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*/
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static inline bool
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pg_add_s32_overflow(int32 a, int32 b, int32 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_add_overflow(a, b, result);
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#else
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int64 res = (int64) a + (int64) b;
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if (res > PG_INT32_MAX || res < PG_INT32_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int32) res;
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return false;
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#endif
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}
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/*
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* If a - b overflows, return true, otherwise store the result of a - b into
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* *result. The content of *result is implementation defined in case of
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* overflow.
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*/
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static inline bool
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pg_sub_s32_overflow(int32 a, int32 b, int32 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_sub_overflow(a, b, result);
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#else
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int64 res = (int64) a - (int64) b;
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if (res > PG_INT32_MAX || res < PG_INT32_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int32) res;
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return false;
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#endif
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}
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/*
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* If a * b overflows, return true, otherwise store the result of a * b into
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* *result. The content of *result is implementation defined in case of
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* overflow.
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*/
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static inline bool
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pg_mul_s32_overflow(int32 a, int32 b, int32 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_mul_overflow(a, b, result);
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#else
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int64 res = (int64) a * (int64) b;
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if (res > PG_INT32_MAX || res < PG_INT32_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int32) res;
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return false;
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#endif
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}
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/*
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* If a + b overflows, return true, otherwise store the result of a + b into
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* *result. The content of *result is implementation defined in case of
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* overflow.
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*/
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static inline bool
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pg_add_s64_overflow(int64 a, int64 b, int64 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_add_overflow(a, b, result);
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#elif defined(HAVE_INT128)
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int128 res = (int128) a + (int128) b;
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if (res > PG_INT64_MAX || res < PG_INT64_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int64) res;
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return false;
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#else
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if ((a > 0 && b > 0 && a > PG_INT64_MAX - b) ||
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(a < 0 && b < 0 && a < PG_INT64_MIN - b))
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = a + b;
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return false;
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#endif
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}
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/*
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* If a - b overflows, return true, otherwise store the result of a - b into
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* *result. The content of *result is implementation defined in case of
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* overflow.
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*/
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static inline bool
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pg_sub_s64_overflow(int64 a, int64 b, int64 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_sub_overflow(a, b, result);
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#elif defined(HAVE_INT128)
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int128 res = (int128) a - (int128) b;
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if (res > PG_INT64_MAX || res < PG_INT64_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int64) res;
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return false;
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#else
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if ((a < 0 && b > 0 && a < PG_INT64_MIN + b) ||
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(a > 0 && b < 0 && a > PG_INT64_MAX + b))
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = a - b;
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return false;
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#endif
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}
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/*
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* If a * b overflows, return true, otherwise store the result of a * b into
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* *result. The content of *result is implementation defined in case of
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* overflow.
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*/
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static inline bool
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pg_mul_s64_overflow(int64 a, int64 b, int64 *result)
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{
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#if defined(HAVE__BUILTIN_OP_OVERFLOW)
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return __builtin_mul_overflow(a, b, result);
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#elif defined(HAVE_INT128)
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int128 res = (int128) a * (int128) b;
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if (res > PG_INT64_MAX || res < PG_INT64_MIN)
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = (int64) res;
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return false;
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#else
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/*
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* Overflow can only happen if at least one value is outside the range
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* sqrt(min)..sqrt(max) so check that first as the division can be quite a
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* bit more expensive than the multiplication.
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*
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* Multiplying by 0 or 1 can't overflow of course and checking for 0
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* separately avoids any risk of dividing by 0. Be careful about dividing
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* INT_MIN by -1 also, note reversing the a and b to ensure we're always
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* dividing it by a positive value.
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*
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*/
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if ((a > PG_INT32_MAX || a < PG_INT32_MIN ||
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b > PG_INT32_MAX || b < PG_INT32_MIN) &&
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a != 0 && a != 1 && b != 0 && b != 1 &&
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((a > 0 && b > 0 && a > PG_INT64_MAX / b) ||
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(a > 0 && b < 0 && b < PG_INT64_MIN / a) ||
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(a < 0 && b > 0 && a < PG_INT64_MIN / b) ||
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(a < 0 && b < 0 && a < PG_INT64_MAX / b)))
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{
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*result = 0x5EED; /* to avoid spurious warnings */
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return true;
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}
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*result = a * b;
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return false;
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#endif
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}
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#endif /* COMMON_INT_H */
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