uint_to_char.h

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#pragma once

namespace quda {

  /*
    Fast 32-bit and 64-bit conversion to strings.  Slightly modified
    from the original taken from https://github.com/miloyip/itoa-benchmark.

    Copyright (C) 2014 Milo Yip

    Permission is hereby granted, free of charge, to any person
    obtaining a copy of this software and associated documentation
    files (the "Software"), to deal in the Software without
    restriction, including without limitation the rights to use, copy,
    modify, merge, publish, distribute, sublicense, and/or sell copies
    of the Software, and to permit persons to whom the Software is
    furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be
    included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
    HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
    WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
   */

  static const char gDigitsLut[200] = {
    '0','0','0','1','0','2','0','3','0','4','0','5','0','6','0','7','0','8','0','9',
    '1','0','1','1','1','2','1','3','1','4','1','5','1','6','1','7','1','8','1','9',
    '2','0','2','1','2','2','2','3','2','4','2','5','2','6','2','7','2','8','2','9',
    '3','0','3','1','3','2','3','3','3','4','3','5','3','6','3','7','3','8','3','9',
    '4','0','4','1','4','2','4','3','4','4','4','5','4','6','4','7','4','8','4','9',
    '5','0','5','1','5','2','5','3','5','4','5','5','5','6','5','7','5','8','5','9',
    '6','0','6','1','6','2','6','3','6','4','6','5','6','6','6','7','6','8','6','9',
    '7','0','7','1','7','2','7','3','7','4','7','5','7','6','7','7','7','8','7','9',
    '8','0','8','1','8','2','8','3','8','4','8','5','8','6','8','7','8','8','8','9',
    '9','0','9','1','9','2','9','3','9','4','9','5','9','6','9','7','9','8','9','9'
  };

  inline void u32toa(char* buffer, uint32_t value) {
    if (value < 10000) {
      const uint32_t d1 = (value / 100) << 1;
      const uint32_t d2 = (value % 100) << 1;

      if (value >= 1000)
  *buffer++ = gDigitsLut[d1];
      if (value >= 100)
  *buffer++ = gDigitsLut[d1 + 1];
      if (value >= 10)
  *buffer++ = gDigitsLut[d2];
      *buffer++ = gDigitsLut[d2 + 1];
    }
    else if (value < 100000000) {
      // value = bbbbcccc
      const uint32_t b = value / 10000;
      const uint32_t c = value % 10000;

      const uint32_t d1 = (b / 100) << 1;
      const uint32_t d2 = (b % 100) << 1;

      const uint32_t d3 = (c / 100) << 1;
      const uint32_t d4 = (c % 100) << 1;

      if (value >= 10000000)
  *buffer++ = gDigitsLut[d1];
      if (value >= 1000000)
  *buffer++ = gDigitsLut[d1 + 1];
      if (value >= 100000)
  *buffer++ = gDigitsLut[d2];
      *buffer++ = gDigitsLut[d2 + 1];

      *buffer++ = gDigitsLut[d3];
      *buffer++ = gDigitsLut[d3 + 1];
      *buffer++ = gDigitsLut[d4];
      *buffer++ = gDigitsLut[d4 + 1];
    }
    else {
      // value = aabbbbcccc in decimal

      const uint32_t a = value / 100000000; // 1 to 42
      value %= 100000000;

      if (a >= 10) {
  const unsigned i = a << 1;
  *buffer++ = gDigitsLut[i];
  *buffer++ = gDigitsLut[i + 1];
      }
      else
  *buffer++ = '0' + static_cast<char>(a);

      const uint32_t b = value / 10000; // 0 to 9999
      const uint32_t c = value % 10000; // 0 to 9999

      const uint32_t d1 = (b / 100) << 1;
      const uint32_t d2 = (b % 100) << 1;

      const uint32_t d3 = (c / 100) << 1;
      const uint32_t d4 = (c % 100) << 1;

      *buffer++ = gDigitsLut[d1];
      *buffer++ = gDigitsLut[d1 + 1];
      *buffer++ = gDigitsLut[d2];
      *buffer++ = gDigitsLut[d2 + 1];
      *buffer++ = gDigitsLut[d3];
      *buffer++ = gDigitsLut[d3 + 1];
      *buffer++ = gDigitsLut[d4];
      *buffer++ = gDigitsLut[d4 + 1];
    }
    *buffer++ = '\0';
  }

  inline void i32toa(char* buffer, int32_t value) {
    uint32_t u = static_cast<uint32_t>(value);
    if (value < 0) {
      *buffer++ = '-';
      u = ~u + 1;
    }

    u32toa(buffer, u);
  }

  inline void u64toa(char* buffer, uint64_t value) {
    if (value < 100000000) {
      uint32_t v = static_cast<uint32_t>(value);
      if (v < 10000) {
  const uint32_t d1 = (v / 100) << 1;
  const uint32_t d2 = (v % 100) << 1;

  if (v >= 1000)
    *buffer++ = gDigitsLut[d1];
  if (v >= 100)
    *buffer++ = gDigitsLut[d1 + 1];
  if (v >= 10)
    *buffer++ = gDigitsLut[d2];
  *buffer++ = gDigitsLut[d2 + 1];
      }
      else {
  // value = bbbbcccc
  const uint32_t b = v / 10000;
  const uint32_t c = v % 10000;

  const uint32_t d1 = (b / 100) << 1;
  const uint32_t d2 = (b % 100) << 1;

  const uint32_t d3 = (c / 100) << 1;
  const uint32_t d4 = (c % 100) << 1;

  if (value >= 10000000)
    *buffer++ = gDigitsLut[d1];
  if (value >= 1000000)
    *buffer++ = gDigitsLut[d1 + 1];
  if (value >= 100000)
    *buffer++ = gDigitsLut[d2];
  *buffer++ = gDigitsLut[d2 + 1];

  *buffer++ = gDigitsLut[d3];
  *buffer++ = gDigitsLut[d3 + 1];
  *buffer++ = gDigitsLut[d4];
  *buffer++ = gDigitsLut[d4 + 1];
      }
    }
    else if (value < 10000000000000000) {
      const uint32_t v0 = static_cast<uint32_t>(value / 100000000);
      const uint32_t v1 = static_cast<uint32_t>(value % 100000000);

      const uint32_t b0 = v0 / 10000;
      const uint32_t c0 = v0 % 10000;

      const uint32_t d1 = (b0 / 100) << 1;
      const uint32_t d2 = (b0 % 100) << 1;

      const uint32_t d3 = (c0 / 100) << 1;
      const uint32_t d4 = (c0 % 100) << 1;

      const uint32_t b1 = v1 / 10000;
      const uint32_t c1 = v1 % 10000;

      const uint32_t d5 = (b1 / 100) << 1;
      const uint32_t d6 = (b1 % 100) << 1;

      const uint32_t d7 = (c1 / 100) << 1;
      const uint32_t d8 = (c1 % 100) << 1;

      if (value >= 1000000000000000)
  *buffer++ = gDigitsLut[d1];
      if (value >= 100000000000000)
  *buffer++ = gDigitsLut[d1 + 1];
      if (value >= 10000000000000)
  *buffer++ = gDigitsLut[d2];
      if (value >= 1000000000000)
  *buffer++ = gDigitsLut[d2 + 1];
      if (value >= 100000000000)
  *buffer++ = gDigitsLut[d3];
      if (value >= 10000000000)
  *buffer++ = gDigitsLut[d3 + 1];
      if (value >= 1000000000)
  *buffer++ = gDigitsLut[d4];
      if (value >= 100000000)
  *buffer++ = gDigitsLut[d4 + 1];

      *buffer++ = gDigitsLut[d5];
      *buffer++ = gDigitsLut[d5 + 1];
      *buffer++ = gDigitsLut[d6];
      *buffer++ = gDigitsLut[d6 + 1];
      *buffer++ = gDigitsLut[d7];
      *buffer++ = gDigitsLut[d7 + 1];
      *buffer++ = gDigitsLut[d8];
      *buffer++ = gDigitsLut[d8 + 1];
    }
    else {
      const uint32_t a = static_cast<uint32_t>(value / 10000000000000000); // 1 to 1844
      value %= 10000000000000000;

      if (a < 10)
  *buffer++ = '0' + static_cast<char>(a);
      else if (a < 100) {
  const uint32_t i = a << 1;
  *buffer++ = gDigitsLut[i];
  *buffer++ = gDigitsLut[i + 1];
      }
      else if (a < 1000) {
  *buffer++ = '0' + static_cast<char>(a / 100);

  const uint32_t i = (a % 100) << 1;
  *buffer++ = gDigitsLut[i];
  *buffer++ = gDigitsLut[i + 1];
      }
      else {
  const uint32_t i = (a / 100) << 1;
  const uint32_t j = (a % 100) << 1;
  *buffer++ = gDigitsLut[i];
  *buffer++ = gDigitsLut[i + 1];
  *buffer++ = gDigitsLut[j];
  *buffer++ = gDigitsLut[j + 1];
      }

      const uint32_t v0 = static_cast<uint32_t>(value / 100000000);
      const uint32_t v1 = static_cast<uint32_t>(value % 100000000);

      const uint32_t b0 = v0 / 10000;
      const uint32_t c0 = v0 % 10000;

      const uint32_t d1 = (b0 / 100) << 1;
      const uint32_t d2 = (b0 % 100) << 1;

      const uint32_t d3 = (c0 / 100) << 1;
      const uint32_t d4 = (c0 % 100) << 1;

      const uint32_t b1 = v1 / 10000;
      const uint32_t c1 = v1 % 10000;

      const uint32_t d5 = (b1 / 100) << 1;
      const uint32_t d6 = (b1 % 100) << 1;

      const uint32_t d7 = (c1 / 100) << 1;
      const uint32_t d8 = (c1 % 100) << 1;

      *buffer++ = gDigitsLut[d1];
      *buffer++ = gDigitsLut[d1 + 1];
      *buffer++ = gDigitsLut[d2];
      *buffer++ = gDigitsLut[d2 + 1];
      *buffer++ = gDigitsLut[d3];
      *buffer++ = gDigitsLut[d3 + 1];
      *buffer++ = gDigitsLut[d4];
      *buffer++ = gDigitsLut[d4 + 1];
      *buffer++ = gDigitsLut[d5];
      *buffer++ = gDigitsLut[d5 + 1];
      *buffer++ = gDigitsLut[d6];
      *buffer++ = gDigitsLut[d6 + 1];
      *buffer++ = gDigitsLut[d7];
      *buffer++ = gDigitsLut[d7 + 1];
      *buffer++ = gDigitsLut[d8];
      *buffer++ = gDigitsLut[d8 + 1];
    }

    *buffer = '\0';
  }

  inline void i64toa(char* buffer, int64_t value) {
    uint64_t u = static_cast<uint64_t>(value);
    if (value < 0) {
      *buffer++ = '-';
      u = ~u + 1;
    }

    u64toa(buffer, u);
  }

}