测试100M(1亿)个元素的初始化时间长度作为效率对比参考值。CPU: Intel i5@2.90GHZ
最后封装一个优化后的自定义双字节memset函数。
typedef unsigned char uint8_t;
typedef unsigned short uint16_t;
typedef unsigned int uint32_t;
typedef unsigned long long uint64_t;#define MAX_SIZE (1024*1024*100) //100MiByte
uint8_t pBuff[MAX_SIZE] = { 0 };uint64_t len = MAX_SIZE;uint16_t value = 0x1234; uint8_t ch_High = value >> 8;uint8_t ch_Low = value&0xFF;//测试1：传统for运行耗时47ms for (uint64_t i = 0; i < len/2; i++){pBuff[i] = ch_High;pBuff[i+1] = ch_Low;}//测试2：指针for运行耗时31ms uint8_t* pt = pBuff;for (uint64_t i = 0; i < len/2; i ++ ){*(uint16_t*)pt = value;pt += 2;}//通过以上测试可以看出用指针赋值比传统数组赋值快51%
//故有优化后的my_memset函数，用于初始化双字节函数。void my_memset(uint8_t *buf,uint16_t value,uint64_t len)
{for (uint64_t i = 0; i < len/2; i ++){*(uint16_t*)buf = value;//关键：指针类型的转换buf += 2;}
}//整体测试使用
void main()
{uint8_t testData[10] = { 0 };my_memset(testData, 0x1234, sizeof(testData));for (size_t i = 0; i < sizeof(testData); i++){printf("%02x ",testData[i]);}
}//最终输出：34 12 34 12 34 12 34 12 34 12
