return s;
}
+static void _udiv64(uint64_t dividend, uint64_t divisor, uint64_t* quotient, uint64_t* remainder) {
+ uint64_t _quotient = 0;
+ uint64_t _remainder = 0;
+
+ // 整体算法类似10进的除法，只不过换成二进制的数来算
+ // 10进制需要猜能乘几，而二进制不用猜，只有0和1，所以直接比较大小即可
+ for (int i = 63; i >= 0; i--) {
+ // 以下两行可以看成类似10进制除法的被除数从高往低试除数时，被除数被逐渐试的高位数
+ _remainder <<= 1;
+ _remainder |= (dividend >> i) & 1;
+
+ // 如果这部分高位数能比被除数大，则商的对应位为1，否则为0
+ if (_remainder >= divisor) {
+ _remainder -= divisor;
+ _quotient |= (1ULL << i);
+ } else {
+ // 商为0的比特位其实什么都不用做
+ }
+ }
+
+ if (quotient) {
+ *quotient = _quotient;
+ }
+
+ if (remainder) {
+ *remainder = _remainder;
+ }
+}
+
char* i64tou(char* s, uint64_t n) {
- itou(s, n >> 32);
- int i = 0;
- if ((n >> 32) > 0) {
- i = strlen(s);
+ char* p = s;
+ char* h = s;
+
+ do {
+ uint64_t remainder = 0;
+ _udiv64(n, 10, &n, &remainder);
+ *p++ = remainder + '0';
+ } while (n > 0);
+
+ *p = 0;
+ p--;
+
+ while (h < p) {
+ swap_char(h, p);
+ h++;
+ p--;
}
- itou(s + i, n & 0xFFFFFFFF);
return s;
}