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[Libevent-users] Re: parse query string

Awesome! Thank you


On Saturday, 11 August 2012, Nir Soffer <nirsof@xxxxxxxxx> wrote:
>
> On Aug 11, 2012, at 6:30 PM, Riccardo Tacconi wrote:
>
>> Hi,
>>
>> I have the following code called from libevent's http-server.c demo:
>>
>> #include "servlet.h"
>>
>> void servlet(struct evhttp_request *req, struct evbuffer *evb) {
>>     size_t len = evbuffer_get_length(evhttp_request_get_input_buffer(req));
>>     struct evbuffer *in_evb = evhttp_request_get_input_buffer(req);
>>     char *data = "">>>     evbuffer_copyout(in_evb, data, len);
>>     evhttp_parse_query_str(data, evhttp_request_get_input_headers(req));
>>
>>     time_t now;
>>     time(&now);
>>
>>     evbuffer_add_printf(evb, "<html>\n <head>\n"
>>             "  <title>%s</title>\n"
>>             " </head>\n"
>>             " <body>\n"
>>             "  <h1>%s</h1>\n"
>>             " <p>Current time is: %s</p>"
>>             " <p>received data size: %d</p>\n"
>>             " <p>received data: %s</p></body></html>",
>>             "C servlet title",
>>             "C servlet",
>>             ctime(&now),
>>             (int)len,
>>             data);
>>     evhttp_add_header(evhttp_request_get_output_headers(req),
>>             "Content-Type", "text/html");
>>         evhttp_send_reply(req, 200, "OK", evb);
>>     free(data);
>> }
>>
>> in data I have this string "param1=value1&param2=value2". I would like to use the in-build parser and I added:
>>
>> evhttp_parse_query_str(data, evhttp_request_get_input_headers(req));
>>
>> but I am not sure how I can access the parsed key/values and if I am using the right function.
>
> You can url encoded data from the input buffer like this:
>
> // Include the keyvalq_struct header, for creating evkeyvalq struct and accessing keys and values
> #include <event2/keyvalq_struct.h>
>
> // Create a evkeyvalq to keep parsed parameters
> struct evkeyvalq params;
>
> // Ensure that data is null terminated - evhttp_parse_query_str() expects a null terminated string, but the input buffer may contain non-terminated data.
> char *data = "" + 1);
> evbuffer_copyout(in_evb, data, len);
> data[len] = '\0';
>
> // Parse the query string
> evhttp_parse_query_str(data, &params);
>
> // Now you can access the parameters using
> const char *value = evhttp_find_header(params, "name");
>
> // If you want to iterate over all values, you can do
> struct evkeyval *param;
>
> TAILQ_FOREACH(param, &params, next) {
>         // Do something with param->key and param->value
> }
>
> // Finally, you have to free the memory allocated for the parameters
> evhttp_clear_headers(&params);
>
>
>
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--
Riccardo Tacconi
Ruby on Rails and PHP development - System Administration
VIRTUELOGIC LIMITED

http://github.com/rtacconi
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