ESP32纯Cj简单实现图片上传阿里云OSS

对于嵌入式设备资源较少或者运行环境较简单的环境下，如果只是简单上传一张图片到阿里云OSS服务器的话，移植阿里云OSS的SDK就是一件性价比很低而且不一定能实现的事情了。那就得考虑自己实现一套简单的、最基础的图片上传功能。阿里云OSS提供了REST API方式的图片上传接口，即通过HTTP方式将图片PUT到OSS服务器。API接口接口可参考：https://help.aliyun.com/zh/oss/developer-reference/api-reference/?spm=a2c4g.11186623.0.0.1e436d4fztnTzz
上传一张图片到阿里云OSS服务器主要分为如下几个步骤：
1. 连接aliyun OSS服务器；
2. 生成PUT语句并发送；
3. 发送图片；
4. 接收服务器返回的操作结果，判定是否需要重传。

以下具体贴一下代码实现。

一、连接阿里云OSS服务器
`int app_oss_connect_server(void)
{
    int iFd = -1;
    struct hostent *pHostEnt = NULL;
    struct sockaddr_in struServAddr;

    pHostEnt = gethostbyname(APP_OSS_DOMAIN_NAME);
    if (NULL == pHostEnt)
    {
        ESP_LOGE(TAG, "DNS lookup failed");
        return ESP_FAIL;
    }

    iFd = socket(AF_INET, SOCK_STREAM, 0);
    if (-1 == iFd)
    {
        ESP_LOGE(TAG, "Socket create error!");
        return ESP_FAIL;
    }
    
    memset(&struServAddr, 0, sizeof(struServAddr));
    struServAddr.sin_family = AF_INET;
    struServAddr.sin_port = htons(APP_OSS_CONN_PORT);
    struServAddr.sin_addr = *((struct in_addr*)pHostEnt->h_addr);
    //ESP_LOGI(TAG, "Connect to ali-oss server: %s.", inet_ntoa(struServAddr.sin_addr));

    if (0 != connect(iFd, (struct sockaddr *)&struServAddr, sizeof(struct sockaddr)))
    {
        ESP_LOGE(TAG, "Connect to ali-oss server error!");
        close(iFd);
        iFd = ESP_FAIL;
    }

    return iFd;
}`
APP_OSS_DOMAIN_NAME就是购买OSS服务分配的域名，形式如：xxxx.oss-cn-hangzhou.aliyuncs.com 

二、生成PUT语句并发送+发送图片+接收服务器答复
`int app_oss_picture_upload(int iFd)
{
    camera_fb_t *pPicFB = NULL;
    char szPicName[APP_OSS_PIC_NAME_LEN] = {0};
    char szDateTime[32] = {0};
    char szAuthStr[128] = {0};
    char szOssHeader[512] = {0};
    struct tm *pTm = NULL;

    int b64Len = 0;
    unsigned char hmac[20] = {0};
    char b64[((20 + 1) * 4) / 3] = {0};
    char b64Str[((20 + 1) * 4) / 3+1] = {0};

    int wrRet = 0;
    int wrCnt = 0;
    fd_set struFdSet;
    struct timeval struTV;
    int iRet = -1;

    pPicFB = esp_camera_fb_get();
    if (!pPicFB) {
        ESP_LOGE(TAG, "Camera capture failed");
        goto errExit;
    }

    /* Fill the header content */
    memset(&struTV, 0, sizeof(struTV));
    tTime = time(NULL);
    pTm = gmtime(&tTime);
    gettimeofday(&struTV, NULL);
    snprintf(szPicName, sizeof(szPicName), 
        "/DIR/%4d%02d%02d_%02d%02d%02d%03d.jpg", 
        pTm->tm_year+1900, pTm->tm_mon+1, pTm->tm_mday,
        pTm->tm_hour, pTm->tm_min, pTm->tm_sec, (int)((struTV.tv_usec/1000)%1000));
    app_oss_global_pic_name_set(szPicName);
    snprintf(szDateTime, sizeof(szDateTime),
        "%s, %02d %s %04d %02d:%02d:%02d GMT", 
        week[pTm->tm_wday], pTm->tm_mday, months[pTm->tm_mon], 
        pTm->tm_year+1900, pTm->tm_hour, pTm->tm_min, pTm->tm_sec);
    snprintf(szAuthStr, sizeof(szAuthStr),
        "PUT\n\nimage/jpeg\n%s\n%s", szDateTime, szPicName);
    //ESP_LOGI(TAG, "szAuthStr: %s(%d)", szAuthStr, strlen(szAuthStr));

    hmac_sha1((unsigned char*)APP_OSS_ACCESS_KEY_SECRET, 
        strlen(APP_OSS_ACCESS_KEY_SECRET),
        (unsigned char*)szAuthStr, strlen(szAuthStr), hmac);    
    b64Len = oss_base64_encode(hmac, 20, b64);
    memcpy(b64Str, b64, b64Len);

    memset(szOssHeader, 0, APP_OSS_HEADER_BUFSIZE);
    snprintf(szOssHeader, APP_OSS_HEADER_BUFSIZE,
        "PUT %s HTTP/1.1\r\n" \
        "User-Agent: esp-idf/1.0 esp32\r\n" \
        "Host: %s\r\n" \
        "Accept: */*\r\n" \
        "Content-Length: %d\r\n" \
        "Content-Type: image/jpeg\r\n" \
        "Date: %s\r\n" \
        "Authorization: OSS %s:%s\r\n\r\n",
        szPicName, APP_OSS_DOMAIN_NAME, pPicFB->len, szDateTime, 
        APP_OSS_ACCESS_KEY_ID, b64Str);

    wrCnt = write(iFd, szOssHeader, strlen(szOssHeader));
    if (wrCnt <= 0)
    {
        ESP_LOGE(TAG, "OSS send header to server error!");
        goto errExit;
    }

    wrCnt = write(iFd, pPicFB->buf, pPicFB->len);
    if (wrCnt <= 0)
    {
        ESP_LOGE(TAG, "OSS send picture to server error!");
        goto errExit;
    }

    memset(&struTV, 0, sizeof(struTV));
    memset(&struFdSet, 0, sizeof(struFdSet));
    struTV.tv_sec = 5;
    struTV.tv_usec = 0;
    FD_ZERO(&struFdSet);
    FD_CLR(iFd, &struFdSet);
    FD_SET(iFd, &struFdSet);
    wrRet = select(iFd + 1, &struFdSet, 0, 0, &struTV);
    if (wrRet > 0)
    {
        if (FD_ISSET(iFd, &struFdSet))
        {
            memset(szOssHeader, 0, APP_OSS_HEADER_BUFSIZE);
            wrCnt = read(iFd, szOssHeader, APP_OSS_HEADER_BUFSIZE-1);
            if (wrCnt > 0)
            {
                //ESP_LOGI(TAG, "OSS Response: %s", szOssHeader);
                if (NULL != strstr(szOssHeader, "200 OK"))
                {
                    ESP_LOGI(TAG, "APP OSS upload picture ok!");
                    iRet = 0;
                }
                else
                {
                    ESP_LOGE(TAG, "APP OSS upload picture failed!");
                }
            }
            else
            {
                ESP_LOGE(TAG, "OSS read response error!");
            }
        }
    } 
    else
    {
        ESP_LOGE(TAG, "OSS wait for response select error or timeout!");
    }

errExit:

    if (pPicFB)
    {
        esp_camera_fb_return(pPicFB);
        pPicFB = NULL;
    }

    return iRet;
}`
这里最主要就是header的生成，需要注意的时日期时间还得是UTC 0时区的时间，不然服务器会报错误。
base64使用普通的那种就可以了。

对于删除图片等其他操作，流程也类似。有问题欢迎留言讨论。

谢绝转载！