openGauss-server/src/include/common/int.h

/* ---------------------------------------------------------------------------------------
 * 
 * int.h
 *    Routines to perform integer math, while checking for overflows.
 *
 * 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) 2017-2019, PostgreSQL Global Development Group
 * Portions Copyright (c) 2021, openGauss Contributors
 * 
 * 
 * IDENTIFICATION
 *        src/include/common/int.h
 *
 * ---------------------------------------------------------------------------------------
 */
#ifndef COMMON_INT_H
#define COMMON_INT_H

/*
 * 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.
 */
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
}

/*
 * 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.
 */
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
}

/*
 * 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.
 */
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
}

/*
 * 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.
 */
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
}

/*
 * 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.
 */
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
}

/*
 * 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.
 */
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
}

/*
 * 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.
 */
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_add_s128_overflow(int128 a, int128 b, int128* result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
    return __builtin_add_overflow(a, b, result);
#else
    if ((a > 0 && b > 0 && a > PG_INT128_MAX - b) || (a < 0 && b < 0 && a < PG_INT128_MIN - b)) {
        *result = 0x5EED; /* to avoid spurious warnings */
        return true;
    }
    *result = a + b;
    return false;
#endif
}

/*
 * 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.
 */
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
    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_sub_s128_overflow(int128 a, int128 b, int128* result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
    return __builtin_sub_overflow(a, b, result);
#else
    if ((a < 0 && b > 0 && a < PG_INT128_MIN + b) || (a > 0 && b < 0 && a > PG_INT128_MAX + b)) {
        *result = 0x5EED; /* to avoid spurious warnings */
        return true;
    }
    *result = a - b;
    return false;
#endif
}

/*
 * 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.
 */
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
}

static inline bool check_sqrroot_overflow(int128 a, int128 b)
{
    return a > PG_INT64_MAX || a < PG_INT64_MIN || b > PG_INT64_MAX || b < PG_INT64_MIN;
}

static inline bool pg_mul_s128_overflow(int128 a, int128 b, int128* result)
{
#if defined(HAVE__BUILTIN_OP_OVERFLOW)
    return __builtin_mul_overflow(a, b, result);
#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 (check_sqrroot_overflow(a, b) && a != 0 && a != 1 && b != 0 && b != 1 &&
        ((a > 0 && b > 0 && a > PG_INT128_MAX / b) || (a > 0 && b < 0 && b < PG_INT128_MIN / a) ||
            (a < 0 && b > 0 && a < PG_INT128_MIN / b) || (a < 0 && b < 0 && a < PG_INT128_MAX / b))) {
        *result = 0x5EED; /* to avoid spurious warnings */
        return true;
    }
    *result = a * b;
    return false;
#endif
}



#endif /* COMMON_INT_H */