text: /* ---------------------------------------------------------------------------------------
   * 
   * 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
   * 
   * 
   * 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
  }
  
  /*
   * 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
  }
  
  /*
   * 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
  }
  
  #endif /* COMMON_INT_H */
  
  