test_common.h

#pragma once

#include <unistd.h>
#include <stdint.h>
#include <sys/time.h>

#define CREATE_MODE_RW (S_IWUSR | S_IRUSR)

#ifdef CZL_DEBUG
#define CZL_PRINT(format, a...) printf("DEBUG: %-30s %3d:"#format"\n", __FUNCTION__, __LINE__, ##a)
#else 
#define CZL_PRINT(format, a...)
#endif

static inline int file_exists(char const *file)
{
    return access(file, F_OK);
}

/*
 * find_last_set_64 -- returns last set bit position or -1 if set bit not found
 */
static inline int
find_last_set_64(uint64_t val)
{
    return 64 - __builtin_clzll(val) - 1;
}

// inline uint64_t get_now_micros(){
//         struct timeval tv;
//         gettimeofday(&tv, NULL);
//         return (tv.tv_sec) * 1000000 + tv.tv_usec;
// }

namespace rocksdb {

// A very simple random number generator.  Not especially good at
// generating truly random bits, but good enough for our needs in this
// package.
class Random {
 private:
  enum : uint32_t {
    M = 2147483647L  // 2^31-1
  };
  enum : uint64_t {
    A = 16807  // bits 14, 8, 7, 5, 2, 1, 0
  };

  uint32_t seed_;

  static uint32_t GoodSeed(uint32_t s) { return (s & M) != 0 ? (s & M) : 1; }

 public:
  // This is the largest value that can be returned from Next()
  enum : uint32_t { kMaxNext = M };

  explicit Random(uint32_t s) : seed_(GoodSeed(s)) {}

  void Reset(uint32_t s) { seed_ = GoodSeed(s); }

  uint32_t Next() {
    // We are computing
    //       seed_ = (seed_ * A) % M,    where M = 2^31-1
    //
    // seed_ must not be zero or M, or else all subsequent computed values
    // will be zero or M respectively.  For all other values, seed_ will end
    // up cycling through every number in [1,M-1]
    uint64_t product = seed_ * A;

    // Compute (product % M) using the fact that ((x << 31) % M) == x.
    seed_ = static_cast<uint32_t>((product >> 31) + (product & M));
    // The first reduction may overflow by 1 bit, so we may need to
    // repeat.  mod == M is not possible; using > allows the faster
    // sign-bit-based test.
    if (seed_ > M) {
      seed_ -= M;
    }
    return seed_;
  }

  // Returns a uniformly distributed value in the range [0..n-1]
  // REQUIRES: n > 0
  uint32_t Uniform(int n) { return Next() % n; }

  // Randomly returns true ~"1/n" of the time, and false otherwise.
  // REQUIRES: n > 0
  bool OneIn(int n) { return (Next() % n) == 0; }

  // Skewed: pick "base" uniformly from range [0,max_log] and then
  // return "base" random bits.  The effect is to pick a number in the
  // range [0,2^max_log-1] with exponential bias towards smaller numbers.
  uint32_t Skewed(int max_log) {
    return Uniform(1 << Uniform(max_log + 1));
  }

  // Returns a Random instance for use by the current thread without
  // additional locking
  static Random* GetTLSInstance();
};

// A simple 64bit random number generator based on std::mt19937_64
class Random64 {
 private:
  std::mt19937_64 generator_;

 public:
  explicit Random64(uint64_t s) : generator_(s) { }

  // Generates the next random number
  uint64_t Next() { return generator_(); }

  // Returns a uniformly distributed value in the range [0..n-1]
  // REQUIRES: n > 0
  uint64_t Uniform(uint64_t n) {
    return std::uniform_int_distribution<uint64_t>(0, n - 1)(generator_);
  }

  // Randomly returns true ~"1/n" of the time, and false otherwise.
  // REQUIRES: n > 0
  bool OneIn(uint64_t n) { return Uniform(n) == 0; }

  // Skewed: pick "base" uniformly from range [0,max_log] and then
  // return "base" random bits.  The effect is to pick a number in the
  // range [0,2^max_log-1] with exponential bias towards smaller numbers.
  uint64_t Skewed(int max_log) {
    return Uniform(uint64_t(1) << Uniform(max_log + 1));
  }
};

}  // namespace rocksdb