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Tcp4u - HTTP related functions

• Http4uErrorString
• Http4uSetBufferSize
• Http4uSetTimeout
• HttpGetFile
• HttpGetFileEx

Http4uErrorString

This function translates integer error codes into constants strings.

Syntax:   const char *Http4uErrorString (int msg_code);

Arguments:

Return:

Http4uSetBufferSize

This functions changes the internal buffer size. By default, Http4u uses 4k buffers. If a value attempts to reduce the internal buffer below 256 bytes, a buffer of 256 is used.

Syntax:   void Http4uSetBufferSize (unsigned uBufferSize);

Arguments:

Http4uSetTimeout

This functions changes the internal timeout. The new value is given in seconds. By default, Http4u uses a 60 seconds timeout.
Note: If used in a multi-thread environment or in a shared library (DLL or .so files), this value is changed for all threads or processes. However, it will not change the behavior of a waiting call.

Syntax:   Http4uSetTimeout (unsigned uTimeout);

Arguments:

HttpGetFile

This function retrieves a file using the HTTP protocol and copy it into a local file. It can be used through a firewall.
The remote file name, its location, the server name and the port to be used are packed into the URL string. The URL format is specified in the RFC1738.
Since HttpGetFile accepts only the HTTP protocol, the "http:" specifications in the URL can be shortened. Thus the URL has the following form:
[http://]host[:port][/directory][file]
The URL of the proxy server (firewall) should have the same format.
Notes:

• Since this function is fully reentrant, it can be safely called simultaneously from different threads or processes.
  
• This function enables itself to retrieve any file type. Thus it can download HTML files, images, sounds, executables or any other files.
  
• If the function fails to retrieve the specified file, the local file is removed unless a timeout error is returned.
  
• The application must have successfully called Tcp4uInit, before calling any Http4u functions.
  

Syntax:   HttpGetFile (const char *szURL, 
                       const char *szProxyURL,
                       const char *szFile);

Arguments:

Returns:

Exemple: 
  HttpGetFile ("http://www.magic.fr/~jounin-ph",  /* URL to be retrieved */
               "my_fw.fr:8080",    /* Use firewall my_fw.fr on port 8080 */
               "welcome.html"           /* save location in welcome.html */
              );

HttpGetFileEx

This function retrieves a file using the HTTP protocol and copy it into a local file.
A proxy server can be specified in order to reach a site through a firewall.
HTTP4U waits for a 3 parts response sent by the remote server (See RFC1945 for more information) :

• Status Code and Reason Phrase
  
• Response Header Fields
  
• Entity (The file to be received).
  

The first time this function is called, lBytesTransferred and nRcvd are set to 0. This call tells the application that the file is to be retrieved.
If this callback function returns FALSE, the transfer is stopped and the value HTTP4U_CANCELLED is returned to the application.
Notes :

• If the parameters szLocalFile and CbkTransmit are both set to NULL, HttpGetFileEx sends a HEAD request instead of the usual GET. Thus the Entity field is not sent by the server.
  
• The application must have successfully called Tcp4uInit, before calling any Http4u functions.
  
• Since this function is fully reentrant, it can be safely called simultaneously from different threads or processes.
  
• This function enables itself to retrieve any file type. Thus it can download HTML files, images, sounds, executables or any other files.
  
• The buffers szResponse and szHeaders can be safely read from the application once the callback function is called.
  

Syntax:   HttpGetFileEx (const char *szURL, 
                         const char *szProxyURL,
                         const char *szFile,
                         const char *szHeaderFile,
                         BOOL CALLBACK (*CbkTransmit)(),
                         long  lUserValue,
                         char *szResponse, 
                         int   nResponseSize,
                         char *szHeaders,
                         int   nHeadersSize);

Arguments:

Returns:

Exemple: 
HttpGetFileEx ("http://www.magic.fr/~jounin-ph",  /* URL to be retrieved */
               "my_fw.fr:8080/",   /* Use firewall my_fw.fr on port 8080 */
               NULL,                 /* do not save location into a File */
               NULL,                  /* do not save headers into a file */
              (HTTP4U_CALLBACK) DataAvailable, /* function in which the  */
                                               /* data are processed     */
               12345,                   /* to be tested in DataAvailable */
               szStatus, sizeof szStatus,/* on error display this string */
               szHeaders, sizeof szHeaders     /* save headers in memory */
              );
/* The HttpGetFile function */
return HttpGetFileEx (szURL, szProxyURL, szLocalFile,
                      NULL,           /* do not save headers into a file */
                      NULL,                               /* no callback */
                      0,                      /* and no associated value */
                      NULL, 0,                         /* no status code */
                      NULL, 0,                         /* and no headers */
                     );