Unicode C

HTTP GET -- Read Response from Stream

Demonstrates how to send an HTTP GET for a web page, and then read the response from a Stream. The purpose is to fulfill a situation such as the following: "I have a URL and just want the <head> </head> portion of the HTML. This would avoid having to download a potentially enormous web page just to get at header information, such as the <styles>."

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#include <C_CkRestW.h>
#include <C_CkUrlW.h>
#include <C_CkStreamW.h>
#include <C_CkTaskW.h>
#include <C_CkStringBuilderW.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkRestW rest;
    HCkUrlW url;
    BOOL bAutoReconnect;
    int responseStatusCode;
    const wchar_t *errResponse;
    HCkStreamW bodyStream;
    HCkTaskW readResponseBodyTask;
    HCkStringBuilderW sbBody;
    BOOL exitLoop;
    const wchar_t *bodyText;
    int maxWaitMs;

    success = FALSE;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    rest = CkRestW_Create();

    // In this example, we'll get the web page at http://www.nytimes.com/pages/business/index.html
    // The domain is "www.nytimes.com", and the path is "/pages/business/index.html"

    // If we have only the full URL to begin with, it can be loaded into the Chilkat URL object to
    // access the parts:
    url = CkUrlW_Create();
    CkUrlW_ParseUrl(url,L"http://www.nytimes.com/pages/business/index.html");

    bAutoReconnect = TRUE;
    success = CkRestW_Connect(rest,CkUrlW_host(url),CkUrlW_getPort(url),CkUrlW_getSsl(url),bAutoReconnect);

    // Send the GET request (This sends the GET request, but does not read the response.)
    success = CkRestW_SendReqNoBody(rest,L"GET",CkUrlW_path(url));
    if (success != TRUE) {
        wprintf(L"%s\n",CkRestW_lastErrorText(rest));
        CkRestW_Dispose(rest);
        CkUrlW_Dispose(url);
        return;
    }

    // Read the response header.
    responseStatusCode = CkRestW_ReadResponseHeader(rest);
    if (responseStatusCode < 0) {
        wprintf(L"%s\n",CkRestW_lastErrorText(rest));
        CkRestW_Dispose(rest);
        CkUrlW_Dispose(url);
        return;
    }

    wprintf(L"Response status code = %d\n",responseStatusCode);

    // We expect a 200 response status.
    if (responseStatusCode != 200) {

        // If the response status code is not 200, we could check for a redirect status code and 
        // then follow it, read the entire response (as shown here), or just call rest.Disconnect
        errResponse = CkRestW_readRespBodyString(rest);
        if (CkRestW_getLastMethodSuccess(rest) != TRUE) {
            wprintf(L"%s\n",CkRestW_lastErrorText(rest));
        }
        else {
            wprintf(L"%s\n",errResponse);
        }

        CkRestW_Dispose(rest);
        CkUrlW_Dispose(url);
        return;
    }

    bodyStream = CkStreamW_Create();
    // Set a 10 second read timeout for the stream. 
    // (Give up if no data arrives within 10 seconds after calling a read method.)
    CkStreamW_putReadTimeoutMs(bodyStream,10000);

    // Create a background thread task to read the response body (which feeds
    // it to the bodyStream object.)
    readResponseBodyTask = CkRestW_ReadRespBodyStreamAsync(rest,bodyStream,TRUE);

    // Start the task. 
    success = CkTaskW_Run(readResponseBodyTask);

    // Read the HTTP response body until the "</head>" is seen, or until
    // the end-of-stream is reached.

    sbBody = CkStringBuilderW_Create();
    exitLoop = FALSE;
    while (!exitLoop && (CkStreamW_getEndOfStream(bodyStream) != TRUE)) {

        bodyText = CkStreamW_readString(bodyStream);
        if (CkStreamW_getLastMethodSuccess(bodyStream) == TRUE) {
            CkStringBuilderW_Append(sbBody,bodyText);
            if (CkStringBuilderW_Contains(sbBody,L"</head>",FALSE)) {
                exitLoop = TRUE;
            }

        }
        else {
            exitLoop = TRUE;
        }

    }

    // Cancel the remainder of the task...
    CkTaskW_Cancel(readResponseBodyTask);

    CkTaskW_Dispose(readResponseBodyTask);

    // Ensure we're disconnected from the server.
    maxWaitMs = 50;
    CkRestW_Disconnect(rest,maxWaitMs);

    wprintf(L"----\n");
    wprintf(L"%s\n",CkStringBuilderW_getAsString(sbBody));
    wprintf(L"----\n");
    wprintf(L"Successfully received the body up to the desired point.\n");


    CkRestW_Dispose(rest);
    CkUrlW_Dispose(url);
    CkStreamW_Dispose(bodyStream);
    CkStringBuilderW_Dispose(sbBody);

    }