用C写 76byte以太网数据转换CAN报文

在C语言中，将Ethernet（以太网）数据转换成CAN（控制器局域网络）报文通常涉及到几个步骤，因为它们的数据结构和协议差异很大。由于你提到的是76字节的数据长度，这里是一个简化的示例，假设你已经有了一个以太网数据包头和有效负载，并且需要提取前部分用于CAN报文：

#include <stdio.h>
#include <stdint.h>

// Ethernet header (20 bytes)
struct EthernetHeader {
    uint8_t dstMAC[ETH_ALEN];
    uint8_t srcMAC[ETH_ALEN];
    uint16_t ethType;
};

// CAN data structure (8 bytes for ID + payload)
struct CANData {
    uint32_t canID; // CAN identifier
    uint8_t payload[6]; // Up to 6 bytes of useful data from Ethernet
};

void ethToCan(const struct EthernetHeader *eth, struct CANData *can) {
    // Assuming eth->ethType is the start of the useful data in the Ethernet packet
    uint8_t useful_data[7] = {eth->ethType, /* Followed by additional 5 bytes from Ethernet*/ };

    // Copy the first 6 bytes to CAN payload
    memcpy(can->payload, useful_data, sizeof(can->payload));

    // Set CAN ID, assuming it's a fixed offset from the Ethernet packet
    can->canID = *(uint32_t*)(eth + 1); // Assuming the ID starts at the next byte after MAC addresses

    printf("Converted CAN message:\n");
    printf("ID: %08X\n", can->canID);
    printf("Payload: ");
    for (int i = 0; i < 6; i++) {
        printf("%02X ", can->payload[i]);
    }
}

int main() {
    // Replace with actual Ethernet data here
    struct EthernetHeader eth;
    // ... fill in the Ethernet header fields ...

    struct CANData can;
    ethToCan(&eth, &can);

    return 0;
}

这个示例仅适用于简化场景，实际应用中可能需要处理更复杂的帧结构、错误检测以及填充等。记住，在真实环境中，你需要根据网络协议规范来设计和处理数据。