Lucene 源码分析集------- Random

生成伪随机数的接口

Random::Random() { this->seed = (int64_t)MiscUtils::currentTimeMillis(); } Random::Random(int64_t seed) { this->seed = seed; } Random::~Random() { } void Random::setSeed(int64_t seed) { this->seed = (seed ^ 0x5deece66dLL) & (((int64_t)1 << 48) - 1); } int32_t Random::nextInt(int32_t limit) { if ((limit & -limit) == limit) { return (int32_t)((limit * (int64_t)next(31)) >> 31); } int32_t bits = 0; int32_t val = 0; do { bits = next(31); val = bits % limit; } while (bits - val + (limit - 1) < 0); return val; } double Random::nextDouble() { return ((double)(((int64_t)next(26) << 27) + next(27)) / (double)((int64_t)1 << 53)); } int32_t Random::next(int32_t bits) { seed = (seed * 0x5deece66dLL + 0xb) & (((int64_t)1 << 48) - 1); return (int32_t)(seed >> (48 - bits)); }