Question

我遇到以下代码的问题。我已经看到大量使用InternetReadFile保存到文件的示例。但我找不到一个，或让它为char []工作。我想添加szBuffer以获取holdBuff，然后将内容设置为holdBuff。

#include <stdio.h>
#include <tchar.h>
#include <string.h>
#include <windows.h>
#include <WinInet.h>

HINTERNET hSession;
void urlToChar(char* url, char** content);

int main()
{
    hSession = InternetOpen("Mozilla/4.0 (compatible) Poison", INTERNET_OPEN_TYPE_PRECONFIG, NULL, NULL, 0);
    char* content;
    urlToChar("http://google.com/", &content);
    printf("%s",content);
    return 0;
}

void urlToChar(char* url, char** content)
{
    HINTERNET hConnect = InternetConnect(hSession, _T(""),INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1);
    HINTERNET hRequest = InternetOpenUrl(hSession, url, NULL, 0, 0, 0);
    if (hRequest)
    {
        char holdBuff[] = "";
        char szBuff[1025];
        memset(szBuff, 0x00, sizeof(szBuff));
        DWORD bytesRead;
        while (InternetReadFile(hRequest, szBuff, 1024, &bytesRead) == TRUE && bytesRead > 0)
        {
            // Cat szBuff to holdBuff
            memset(szBuff, 0x00, sizeof(szBuff));
        }
        *content = holdBuff;
        // memset(holdBuff, 0x00, sizeof(holdBuff));  <-- Need this?
    }
    InternetCloseHandle(hRequest);
    InternetCloseHandle(hConnect);
}

Answer 1

变量声明

char xyz[] = "Hello World!";

将告诉编译器将字符串的内容放在堆栈上。当然，当你的函数返回时，堆栈会消失。

所以在你的情况下：

char holdBuff[] = "";
...
*content = holdBuff;

这告诉编译器创建一个长度为1的字符串（NULL终止符）作为局部变量。仅仅因为您将content的值设置为holdBuff并不意味着holdBuff指向的内容不再存在。

你必须纠正两件事。首先，您必须使用strcpy()或类似功能。其次，您必须为holdBuff分配足够的空间。

示例：

char holdBuff[4096];    // or some other sufficiently large size
...
*content = malloc (strlen(holdBuff) + 1);
strcpy (*content, holdBuff);

完成后，您需要free(content) main()。

现在，关于如何实际连接：如果您忘记使用szBuff并直接写入holdBuff，您的表现会好得多。

char* temp = holdBuff;
while (InternetReadFile(hRequest, temp, 1024, &bytesRead) == TRUE && bytesRead > 0)
{
    temp += bytesRead;
}
*temp = '\0';    // manually append NULL terminator

现在holdBuff将拥有您想要的数据而无需中间连接。

Answer 2

void urlToChar(char* url, char** content)
{
    HINTERNET hConnect = InternetConnect(hSession, _T(""),INTERNET_DEFAULT_HTTP_PORT, NULL, NULL, INTERNET_SERVICE_HTTP, 0, 1);
    HINTERNET hRequest = InternetOpenUrl(hSession, url, NULL, 0, 0, 0);
    if (hRequest)
    {
        char holdBuff[] = "";   //do not use fixed size char array and allocate buffer in stack,you can allocate large enough buffer in heap,but recommend you can use string or CString
        char szBuff[1025];
        memset(szBuff, 0x00, sizeof(szBuff));
        DWORD bytesRead;
        while (InternetReadFile(hRequest, szBuff, 1024, &bytesRead) == TRUE && bytesRead > 0)
        {
            // Cat szBuff to holdBuff
            //strcat when using char array
            // operator+ when using stl string
            // [stl string][1]
            memset(szBuff, 0x00, sizeof(szBuff));
        }
        *content = holdBuff;
        // memset(holdBuff, 0x00, sizeof(holdBuff));  <-- Need this?
    }
    InternetCloseHandle(hRequest);
    InternetCloseHandle(hConnect);
}

C中的InternetReadFile到Char *

2 个答案: