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 <CkRest.h>
#include <CkUrl.h>
#include <CkStream.h>
#include <CkTask.h>
#include <CkStringBuilder.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    CkRest rest;

    // 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:
    CkUrl url;
    url.ParseUrl("http://www.nytimes.com/pages/business/index.html");

    bool bAutoReconnect = true;
    success = rest.Connect(url.host(),url.get_Port(),url.get_Ssl(),bAutoReconnect);

    // Send the GET request (This sends the GET request, but does not read the response.)
    success = rest.SendReqNoBody("GET",url.path());
    if (success != true) {
        std::cout << rest.lastErrorText() << "\r\n";
        return;
    }

    // Read the response header.
    int responseStatusCode = rest.ReadResponseHeader();
    if (responseStatusCode < 0) {
        std::cout << rest.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Response status code = " << responseStatusCode << "\r\n";

    // 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
        const char *errResponse = rest.readRespBodyString();
        if (rest.get_LastMethodSuccess() != true) {
            std::cout << rest.lastErrorText() << "\r\n";
        }
        else {
            std::cout << errResponse << "\r\n";
        }

        return;
    }

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

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

    // Start the task. 
    success = readResponseBodyTask->Run();

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

    CkStringBuilder sbBody;
    bool exitLoop = false;
    while (!exitLoop && (bodyStream.get_EndOfStream() != true)) {

        const char *bodyText = bodyStream.readString();
        if (bodyStream.get_LastMethodSuccess() == true) {
            sbBody.Append(bodyText);
            if (sbBody.Contains("</head>",false)) {
                exitLoop = true;
            }

        }
        else {
            exitLoop = true;
        }

    }

    // Cancel the remainder of the task...
    readResponseBodyTask->Cancel();

    delete readResponseBodyTask;

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

    std::cout << "----" << "\r\n";
    std::cout << sbBody.getAsString() << "\r\n";
    std::cout << "----" << "\r\n";
    std::cout << "Successfully received the body up to the desired point." << "\r\n";
    }