char buf[1024]; memset(buf, 0, sizeof(buf)); memcpy(buf, &msg, sizeof(msg)); 什么意思

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; }

这段代码是一个函数，用于构建一个自定义协议的数据包。函数接收参数pkt，是一个指向Packet结构体的指针，包含了构建数据包所需的信息。函数的作用是将数据包的第1和第2个字节设定为0x5A和0xA5，以此标识数据包的起始，并将pkt->ofs设置为6（2个字节的起始标识符、2个字节的数据长度和2个字节的CRC校验值），表示下一个数据项要添加到数据包的第6个字节之后。接着，使用memcpy()函数将数据项buf中的len个字节添加到数据包的buf缓冲区中，同时更新pkt->ofs的值，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。这些操作都是为了构建一个自定义协议的数据包，以便进行数据通信。