char buf[1024]; memset(buf, 0, sizeof(buf)); memcpy(buf, &msg, sizeof(msg)); 什么意思
时间: 2024-05-19 15:11:06 浏览: 11
src, strlen(src));
This code initializes a character array called buf with a size of 1024 and sets all its elements to 0 using memset. Then, it copies the content of a string called src into buf using memcpy. The length of src is obtained using strlen, which returns the number of characters in the string excluding the null terminator. The content of src is copied into buf starting from the first element of buf. If the length of src is greater than the size of buf, memcpy will copy only up to the size of buf.
相关问题
char buf[1024]; memset(buf, 0, sizeof(buf)); memcpy(buf, &msg, sizeof(msg));
void* src, size_t count);
This function copies a block of memory from a source address to a destination address. It takes three arguments: the destination buffer (buf), the source buffer (src), and the number of bytes to copy (count). It returns a pointer to the destination buffer.
In this specific example, the function is being used to clear the contents of the buf array by setting all its elements to zero. The memset function is called with buf as its first argument, 0 as its second argument (which represents the value to set each byte to), and sizeof(buf) as its third argument (which specifies the number of bytes to set). Then, the memcpy function is called to copy the contents of the src buffer (which is not defined in the provided code) into buf.
uint32_t Packet_Begin(Packet_t *pkt) { pkt->ofs = 6; /* sof(2) len(2) + crc(2) */ memset(&pkt->buf[0], 0, sizeof(pkt->buf)); pkt->buf[0] = 0x5A; /* header */ pkt->buf[1] = 0xA5; /* data packet */ return CH_OK; } uint32_t Packet_AddData(Packet_t *pkt, uint8_t *buf, uint16_t len) { /* add item content into buffer */ memcpy((pkt->buf + pkt->ofs), buf, len); pkt->ofs += len; return CH_OK; }
这两个函数都是用于构建自定义协议数据包的函数,Packet_Begin()函数用于初始化数据包的开始部分,Packet_AddData()函数用于将数据项添加到数据包缓冲区中。
Packet_Begin()函数中,首先将pkt->ofs的值设置为6,表示数据包的前6个字节是协议的起始标识符、长度和CRC校验位。然后使用memset()函数将pkt->buf缓冲区的前sizeof(pkt->buf)个字节都设为0,以便清除缓冲区中的旧数据。接着,将pkt->buf的前两个字节分别设为0x5A和0xA5,用于标识协议的起始部分。最后,返回CH_OK表示初始化数据包成功。
Packet_AddData()函数中,首先使用memcpy()函数将数据项buf中的len个字节添加到pkt->buf缓冲区中,从pkt->buf的第pkt->ofs个字节开始存储。然后将pkt->ofs的值加上len,以便指向下一个数据项应该添加到的位置。最后,返回CH_OK表示添加数据项成功。
这两个函数的作用是构建自定义协议数据包,以便进行数据通信。其中Packet_Begin()函数用于初始化数据包的起始部分,Packet_AddData()函数用于添加数据项到数据包缓冲区中。
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