Custom scheme: how to use request PostDataElement ?

[Mirco]

Dear Reader,

I'm busy programming a scheme handler in CEF rev. 259 (coming from rev. 231 the programming interface is really cleaned up, my compliments on that !).

In my scheme handler I'm implementing the ProcessRequest function:

Code: Select all

ProcessRequest(CefRefPtr<CefRequest> request, CefString& redirectUrl, CefRefPtr<CefResponse> response, int* response_length)

Now I'm stuck on a POST request. I can get the request Content-Type out of the headers, but what I don't understand is how to get the request http-body bytes. I found the request->GetPostData function to retrieve the PostData.

I'm having the following questions:
1) How do I convert CefPostData to request http-body-bytes ?
2) CefPostData is build on a list of elements, which kan be retrieved by CefPostData::GetElements. Each element can be bytes, a filename or empty. Must I concatenate these elements myself into a http-body or is there some helper function ?

Any help or pointers are welcome !

Kind regards,
Mirco Babin (The Netherlands)

[magreenblatt]

Hi Mirco,

If your content type is "application/x-www-form-urlencoded" then you should have a single CefPostDataElement of type PDE_TYPE_BYTES that contains the POST data in URL encoded format. The http://code.google.com/p/chromiumembedd ... g_util.cpp source file provides an example of how to retrieve the CefPostDataElement contents. See http://www.w3.org/TR/html4/interact/for ... -17.13.4.1 for more information on the URL encoded format. CEF does not currently expose a parser for URL encoded data but many already exist on the internet (take a look at http://code.google.com/p/libjingle/sour ... lencode.cc for example).

Regards,
Marshall

[Mirco]

Hi Marshall,

Thanks for the answer. I think I understand the PostData now. PostData::GetElements is already in the format specified by Content-Type.

So to get the http-request-body-bytes you have to iterate through CefPostData::GetElements(), copying bytes or copying the contents of a file. The resulting bytestream is in the Content-Type specified by the request header.

The GET already worked.
The POST with x-www-url-encoded works now.
The POST with multipart/form-data works also (without file upload)
I'm now busy testing the POST with multipart/form-data and fileupload.

I do have one suggestion for the function

virtual size_t CefPostDataElement::GetBytes(size_t size, void* bytes) =0;

Because I'm reading in the http-request-body-bytes in chunks of 4096 bytes, I manually have to keep track at which offset I am. GetBytes can only return bytes from the beginning. It would be convient if there was a:

virtual size_t CefPostDataElement::GetBytes(size_t offset, size_t size, void* bytes) =0;
offset being a byte-offset in the original buffer

Now I'm coding something like

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    unsigned char *mybuffer;
    unsigned int offset = 0;
    unsigned int send;
    unsigned int len = element->GetBytesCount();

    malloc(mybuffer, len);
    element->GetBytes(len, mybuffer);

    while (len>0)
    {
        if (len>4096)
            send = 4096;
        else
            send = len;

        MySendBytes(&mybuffer[offset], send);

        offset += send;
        len -= send;
    }

    free(mybuffer);


With this new suggested function this could be reduced to (no malloc):

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    unsigned char mybuffer[4096]
    unsigned int offset = 0;
    unsigned int send;
    unsigned int len = element->GetBytesCount();

    while (len>0)
    {
        if (len>4096)
            send = 4096;
        else
            send = len;

        element->GetBytes(offset, len, mybuffer);
        MySendBytes(mybuffer, send);

        offset += send;
        len -= send;
    }


Kind Regards,
Mirco

[magreenblatt]

I do have one suggestion for the function

Code: Select all

virtual size_t CefPostDataElement::GetBytes(size_t size, void* bytes) =0;

Because I'm reading in the http-request-body-bytes in chunks of 4096 bytes, I manually have to keep track at which offset I am. GetBytes can only return bytes from the beginning. It would be convient if there was a:

Code: Select all

virtual size_t CefPostDataElement::GetBytes(size_t offset, size_t size, void* bytes) =0;

offset being a byte-offset in the original buffer

I agree that this could be useful. Please create a new issue for this in the CEF issue tracker.

[Mirco]

Hi Marshall,

I created the issue http://code.google.com/p/chromiumembedded/issues/detail?id=308. Well, this actually is the first time ever I entered an issue for an open source project. So it could be the format is not as desired.

The POST multipart/form-data with file upload also works correctly.
Thanks again for pointing out the PostData::GetElements() is already in the x-www-urlencoded or multipart/form-data encoding.

Kind regards,
Mirco

[magreenblatt]

Hi Marshall,

I created the issue http://code.google.com/p/chromiumembedded/issues/detail?id=308. Well, this actually is the first time ever I entered an issue for an open source project. So it could be the format is not as desired.

The POST multipart/form-data with file upload also works correctly.
Thanks again for pointing out the PostData::GetElements() is already in the x-www-urlencoded or multipart/form-data encoding.

Kind regards,
Mirco

The issue looks good, thanks. I'm glad you were able to get everything working.

Regards,
Marshall

[silver]

If your content type is "application/x-www-form-urlencoded" then you should have a single CefPostDataElement of type PDE_TYPE_BYTES that contains the POST data in URL encoded format.

This should be mentioned in the docs.