用WinHttp 写一个POST访问https://sellercentral.amazon.com.au/ap/signin 自定义函数。参数有提交数据和访问头，并且返回响应内容和响应头，代码使用 Unicode 字符集

好的，以下是使用WinHttp发送POST请求的示例代码：

#include <windows.h>
#include <winhttp.h>
#include <string>

#pragma comment(lib, "winhttp.lib")

std::string UnicodeToUtf8(const wchar_t* unicode_str) {
    int len = WideCharToMultiByte(CP_UTF8, 0, unicode_str, -1, nullptr, 0, nullptr, nullptr);
    std::string utf8_str(len - 1, '\0');
    WideCharToMultiByte(CP_UTF8, 0, unicode_str, -1, &utf8_str[0], len, nullptr, nullptr);
    return utf8_str;
}

std::wstring Utf8ToUnicode(const char* utf8_str) {
    int len = MultiByteToWideChar(CP_UTF8, 0, utf8_str, -1, nullptr, 0);
    std::wstring unicode_str(len - 1, '\0');
    MultiByteToWideChar(CP_UTF8, 0, utf8_str, -1, &unicode_str[0], len);
    return unicode_str;
}

bool SendHttpPostRequest(const wchar_t* url, const std::string& data, const std::wstring& headers, std::string& response_data, std::wstring& response_headers) {
    HINTERNET hSession = nullptr;
    HINTERNET hConnect = nullptr;
    HINTERNET hRequest = nullptr;

    bool result = false;

    DWORD dwSize = 0;
    DWORD dwDownloaded = 0;
    LPSTR pszOutBuffer = nullptr;

    // Use WinHttpOpen to obtain a session handle.
    hSession = WinHttpOpen(L"WinHTTP Example/1.0", WINHTTP_ACCESS_TYPE_DEFAULT_PROXY, WINHTTP_NO_PROXY_NAME, WINHTTP_NO_PROXY_BYPASS, 0);

    // Specify an HTTP server.
    if (hSession)
        hConnect = WinHttpConnect(hSession, url, INTERNET_DEFAULT_HTTPS_PORT, 0);

    // Create an HTTP request handle.
    if (hConnect)
        hRequest = WinHttpOpenRequest(hConnect, L"POST", nullptr, nullptr, WINHTTP_NO_REFERER, WINHTTP_DEFAULT_ACCEPT_TYPES, WINHTTP_FLAG_SECURE);

    // Add headers to the request.
    if (hRequest)
        WinHttpAddRequestHeaders(hRequest, headers.c_str(), (DWORD)-1L, WINHTTP_ADDREQ_FLAG_ADD);

    // Send a request.
    if (hRequest)
        result = WinHttpSendRequest(hRequest, WINHTTP_NO_ADDITIONAL_HEADERS, 0, (LPVOID)data.c_str(), (DWORD)data.length(), (DWORD)data.length(), 0);

    // End the request.
    if (result)
        result = WinHttpReceiveResponse(hRequest, nullptr);

    // Get the status code.
    DWORD statusCode = 0;
    DWORD statusCodeSize = sizeof(statusCode);
    if (result)
        result = WinHttpQueryHeaders(hRequest, WINHTTP_QUERY_STATUS_CODE | WINHTTP_QUERY_FLAG_NUMBER, nullptr, &statusCode, &statusCodeSize, nullptr);

    // Get the response headers.
    std::wstring responseHeaders;
    DWORD headersSize = 0;
    if (result) {
        result = WinHttpQueryHeaders(hRequest, WINHTTP_QUERY_RAW_HEADERS_CRLF, WINHTTP_HEADER_NAME_BY_INDEX, nullptr, &headersSize, WINHTTP_NO_HEADER_INDEX);
        if (GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
            std::vector<wchar_t> headersBuffer(headersSize / sizeof(wchar_t) + 1);
            if (WinHttpQueryHeaders(hRequest, WINHTTP_QUERY_RAW_HEADERS_CRLF, WINHTTP_HEADER_NAME_BY_INDEX, &headersBuffer[0], &headersSize, WINHTTP_NO_HEADER_INDEX)) {
                responseHeaders = &headersBuffer[0];
            }
        }
    }

    // Get the response data.
    if (result) {
        do {
            // Check for available data.
            dwSize = 0;
            if (!WinHttpQueryDataAvailable(hRequest, &dwSize))
                break;

            // Allocate space for the buffer.
            pszOutBuffer = new char[dwSize + 1];
            if (!pszOutBuffer)
                break;

            // Read the data.
            ZeroMemory(pszOutBuffer, dwSize + 1);
            if (!WinHttpReadData(hRequest, (LPVOID)pszOutBuffer, dwSize, &dwDownloaded))
                break;

            // Append the data to the response.
            response_data.append(pszOutBuffer, dwDownloaded);

            // Free the memory allocated to the buffer.
            delete[] pszOutBuffer;
            pszOutBuffer = nullptr;

        } while (dwSize > 0);
    }

    // Close any open handles.
    if (hRequest)
        WinHttpCloseHandle(hRequest);

    if (hConnect)
        WinHttpCloseHandle(hConnect);

    if (hSession)
        WinHttpCloseHandle(hSession);

    response_headers = responseHeaders;
    return result;
}

int wmain(int argc, wchar_t* argv[]) {
    // 提交数据
    std::string data = "username=test&password=test123";
    // 访问头
    std::wstring headers = L"Content-Type: application/x-www-form-urlencoded\r\n";
    headers += L"User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36\r\n";
    headers += L"Accept: */*\r\n";

    // 发送POST请求
    std::string response_data;
    std::wstring response_headers;
    if (SendHttpPostRequest(L"sellercentral.amazon.com.au", data, headers, response_data, response_headers)) {
        std::wprintf(L"Response headers: %s\n", response_headers.c_str());
        std::printf("Response data: %s\n", response_data.c_str());
    }
    else {
        DWORD error = GetLastError();
        std::printf("Failed to send HTTP request. Error code: %u\n", error);
    }

    return 0;
}

在上面的示例代码中，我们使用了`WinHttpOpen`、`WinHttpConnect`、`WinHttpOpenRequest`、`WinHttpAddRequestHeaders`、`WinHttpSendRequest`、`WinHttpReceiveResponse`、`WinHttpQueryHeaders`和`WinHttpReadData`这些WinHttp的API来发送POST请求，并获取响应内容和响应头。其中，`UnicodeToUtf8`和`Utf8ToUnicode`是用来在Unicode和UTF-8之间进行转换的辅助函数。