1  // Copyright 2018 Ulf Adams
       2  //
       3  // The contents of this file may be used under the terms of the Apache License,
       4  // Version 2.0.
       5  //
       6  //    (See accompanying file LICENSE-Apache or copy at
       7  //     http://www.apache.org/licenses/LICENSE-2.0)
       8  //
       9  // Alternatively, the contents of this file may be used under the terms of
      10  // the Boost Software License, Version 1.0.
      11  //    (See accompanying file LICENSE-Boost or copy at
      12  //     https://www.boost.org/LICENSE_1_0.txt)
      13  //
      14  // Unless required by applicable law or agreed to in writing, this software
      15  // is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
      16  // KIND, either express or implied.
      17  #ifndef RYU_COMMON_H
      18  #define RYU_COMMON_H
      19  
      20  
      21  #if defined(_M_IX86) || defined(_M_ARM)
      22  #define RYU_32_BIT_PLATFORM
      23  #endif
      24  
      25  // Returns the number of decimal digits in v, which must not contain more than 9 digits.
      26  static inline uint32_t decimalLength9(const uint32_t v) {
      27    // Function precondition: v is not a 10-digit number.
      28    // (f2s: 9 digits are sufficient for round-tripping.)
      29    // (d2fixed: We print 9-digit blocks.)
      30    assert(v < 1000000000);
      31    if (v >= 100000000) { return 9; }
      32    if (v >= 10000000) { return 8; }
      33    if (v >= 1000000) { return 7; }
      34    if (v >= 100000) { return 6; }
      35    if (v >= 10000) { return 5; }
      36    if (v >= 1000) { return 4; }
      37    if (v >= 100) { return 3; }
      38    if (v >= 10) { return 2; }
      39    return 1;
      40  }
      41  
      42  // Returns e == 0 ? 1 : [log_2(5^e)]; requires 0 <= e <= 3528.
      43  static inline int32_t log2pow5(const int32_t e) {
      44    // This approximation works up to the point that the multiplication overflows at e = 3529.
      45    // If the multiplication were done in 64 bits, it would fail at 5^4004 which is just greater
      46    // than 2^9297.
      47    assert(e >= 0);
      48    assert(e <= 3528);
      49    return (int32_t) ((((uint32_t) e) * 1217359) >> 19);
      50  }
      51  
      52  // Returns e == 0 ? 1 : ceil(log_2(5^e)); requires 0 <= e <= 3528.
      53  static inline int32_t pow5bits(const int32_t e) {
      54    // This approximation works up to the point that the multiplication overflows at e = 3529.
      55    // If the multiplication were done in 64 bits, it would fail at 5^4004 which is just greater
      56    // than 2^9297.
      57    assert(e >= 0);
      58    assert(e <= 3528);
      59    return (int32_t) (((((uint32_t) e) * 1217359) >> 19) + 1);
      60  }
      61  
      62  // Returns e == 0 ? 1 : ceil(log_2(5^e)); requires 0 <= e <= 3528.
      63  static inline int32_t ceil_log2pow5(const int32_t e) {
      64    return log2pow5(e) + 1;
      65  }
      66  
      67  // Returns floor(log_10(2^e)); requires 0 <= e <= 1650.
      68  static inline uint32_t log10Pow2(const int32_t e) {
      69    // The first value this approximation fails for is 2^1651 which is just greater than 10^297.
      70    assert(e >= 0);
      71    assert(e <= 1650);
      72    return (((uint32_t) e) * 78913) >> 18;
      73  }
      74  
      75  // Returns floor(log_10(5^e)); requires 0 <= e <= 2620.
      76  static inline uint32_t log10Pow5(const int32_t e) {
      77    // The first value this approximation fails for is 5^2621 which is just greater than 10^1832.
      78    assert(e >= 0);
      79    assert(e <= 2620);
      80    return (((uint32_t) e) * 732923) >> 20;
      81  }
      82  
      83  static inline uint32_t float_to_bits(const float f) {
      84    uint32_t bits = 0;
      85    memcpy(&bits, &f, sizeof(float));
      86    return bits;
      87  }
      88  
      89  static inline uint64_t double_to_bits(const double d) {
      90    uint64_t bits = 0;
      91    memcpy(&bits, &d, sizeof(double));
      92    return bits;
      93  }
      94  
      95  #endif // RYU_COMMON_H