immutablejs源碼中這個計算數(shù)字哈希的函數(shù)的怎么理解？function hashNum(o) {var type = typeof o;  if (type === 'number') {    if (o !== o || o === Infinity) {      return 0;    }    var h = o | 0;    if (h !== o) {      h ^= o * 0xFFFFFFFF;    }    while (o > 0xFFFFFFFF) {      o /= 0xFFFFFFFF;      h ^= o;    }    return smi(h);  }}// v8 has an optimization（優(yōu)化組合） for storing 31-bit signed numbers（有正負符號數(shù)）.// Values which have either 00 or 11 as the high order bits（高字節(jié)位） qualify（限定）.// This function drops the highest order bit in a signed number（有正負符號數(shù)）, maintaining（堅持，保衛(wèi)）// the sign bit（符號位）.function smi(i32) {  return ((i32 >>> 1) & 0x40000000) | (i32 & 0xBFFFFFFF);}