Hi, I just started using HTTrack quite recently. I 
first downloaded 3.06 and (using the provided 
httracklib.* and example.* files in the lib dir) 
created a simple program I could link to HTTrack. 
After downloading 3.07, I noticed the lib dir has 
changed, including the removal of the httracklib.* 
files. These files had a bit of documentation in them 
regarding the callback functions which I found useful.

Anyway, here is a list of the callback functions. I've 
tried to trace them a bit to see what they do. I'm not 
sure about these descriptions, perhaps Xavier Roche or 
someone else more familiar with HTTrack could check 
them when time allows. For what they are worth, here 
they are:


Functions to call at start-up:
------------------------------

   Name:           hts_init
   Purpose:        initialisation function
                   must be called first
   Params:         None
   Return:         int
                   0 = failure
                   1 = success


   Name:           hts_main
   Purpose:        main entry point
   Params:         int argc (number of arguments)
                   char** argv (arguments)
   Return:         int
                   -1 = failure
                   0 = success or user discontinue


   Name:           htswrap_add
   Purpose:        adds a callback (wrapper) function
                   must be called after hts_init() but 
before hts_main
   Params:         char* name (special callback 
identifier, see below)
                   void* fct (address of callback 
function)
   Return:         int
                   0 = failure
                   1 = success


List of callback functions
--------------------------

Their 'name' is the special identifier which must be 
passed to htswrap_add()
-------------------------------------------------------
---------------------


   Name:           "init"
   Purpose:        Called during HTTrack initialization
   Params:         None
   Valid Return:   Nothing


   Name:           "query", "query2", "query3"
   Purpose:        Called to get an answer to a 
question
   Params:         char* question
   Valid Return:   char* response, which can be ""


   Name:           "start"
   Purpose:        Called before HTTrack starts the 
mirror
   Params:         httrackp* opt 
                   (all the options for this session, 
see 'htsopt.h')
   Valid Return:   int
                   0 = HTTrack should end
                   1 = HTTrack should continue 
(default behaviour)


   Name:           "change-options"
   Purpose:        Called when options have been 
changed by HTTrack
   Params:         httrackp* opt 
                   (all the options for this session, 
see 'htsopt.h')
   Valid Return:   int 1 (ignored as far as I can 
tell, but to be safe use 1)


   Name:           "link-detected"
   Purpose:        Called when a link is detected
   Params:         char* link (the text of the 'href=' 
attribute)
                   links are usually relative, so this 
text will likely
                   be something like 'filename.ext' 
or 'subdir/filename.ext'
   Valid Return:   int 
                   0 = process the link
                   1 = ignore the link


   Name:           "check-link"
   Purpose:        Called to test if a link should be 
accepted or refused
   Params:         char* host_name (eg: www.foo.com)
                   char* filename (eg: /index.html)
                   int current_status
                     0 = link should be accepted
                     1 = link should be refused
                    -1 = the engine has no opinion 
                         (by default, the link will be 
refused)
   Valid Return:   int
                   0 = process the link
                   1 = skip the link
                   -1 = no opinion (by default, 
current status will be kept)


   Name:           "check-html"
   Purpose:        Called to check if an HTML file 
                   should be parsed after download
   Params:         char* buffer_html (address of the 
HTML buffer)
                   int buffer_html_size (size of this 
buffer in bytes)
                   char* host_name (eg: www.foo.com)
                   char* filename (eg: /index.html)
   Valid Return:   int
                   0 = do not parse this file
                   1 = parse this file (default 
behaviour)
   Notes:          This function is also called for 
the primary URL,
                   before downloading.
                   In this case, it is passed the URL 
in 'buffer_html'
                   and the word "primary" 
in 'host_name' 
                   and "/primary" in 'filename'.


   Name:           "save-file"
   Purpose:        Called when a file is about to be 
saved
   Params:         char* filename
                   (path to local file, starting with 
the prefix given 
                   with the -O command line option; if 
the given prefix 
                   was relative then this name will be 
relative also
   Valid Return:   int 
                   0 = don't save the file
                   1 = save the file (default behavior)


   Name:           "loop"
   Purpose:        Called during a download loop, 
after every chunk of bytes
   Params:         many, many
   Valid Return:   int
                   0 = HTTrack should end
                   1 = HTTrack should continue


   Name:           "pause"
   Purpose:        Called to wait for the lock file to 
be deleted
   Params:         char* lockfile
   Valid Return:   Nothing


   Name:           "end"
   Purpose:        Called after HTTrack ends the mirror
   Params:         None
   Valid Return:   int 1 (ignored as far as I can 
tell, but to be safe use 1)


   Name:           "free"
   Purpose:        Called during HTTrack termination
   Params:         None
   Valid Return:   Nothing