cute HTTP functions.

[Andre Garzia]

Hi Folks,

I built some cute HTTP functions that I think someone here might  
like. They are very handy and are making me more productive so I  
think they are some good candidates for sharing. I'll glue tem here  
and explain below what they do and why should one use it.

---- Start Cute Functions ----

function http.headers pServer, pResource
     put format("HEAD %s HTTP/1.1\nHost: %s\nUser-agent: Revolution",  
pResource, pServer) into tHeaders
     libUrlSetCustomHTTPHeaders tHeaders
     get URL ("http://" & pServer)
     put  libUrlLastRHHeaders() into tResp
     IF "200" is in line 1 of tResp THEN
         replace ": " with numToChar(4) in tResp
         delete line 1 of tResp
         split tResp by  cr AND numToChar(4)
         return tResp
     ELSE
         return "Error" && word 2 to -1 of line 1 of tResp
     END IF
END http.headers

function http.header pServer, pResource, pHeader
     put http.headers(pServer, pResource) into tTempA
     IF the keys of tTempA is empty THEN
         return tTempA
     ELSE
         return tTempA[pHeader]
     END IF
END http.header

function http.lastModificationDate pServer, pResource
     return http.header(pServer, pResource, "Last-Modified")
END http.lastModificationDate

function http.type pServer, pResource
     return http.header(pServer, pResource, "Content-type")
END http.type

function http.length pServer, pResource
     return http.header(pServer, pResource, "Content-length")
END http.length


---- End Cute Functions ----

I am using dot notation on the function names to avoid collisions  
with other people functions. Feel free to remove my dot notations.

The first function http.headers() accept two parameters a server, a  
resource. Why I splited in two params when I could have used an URL,  
well, this way you can use constants, you can declare a constant like  
kServer = "andregarzia.com" and replace the file being asked without  
changing the server. It's easier. This function returns an array with  
the headers returned by the server or an error if the server returned  
an error. This function is called by the ones below.

Function http.header() This function accepts three parameters, the  
first two ones are server and resource and are passed to http.headers 
() then the third one is an specific array element you're looking  
for. This is another example of modular coding making functions that  
build upon previous functions like a onion skin and thus moving the  
functions to higher levels. For example, I want to know the ETag for  
my index  file on my server to check if I need to update my apps  
cache, just call http.header("andregarzia.com", "index.html", "ETag").

There are headers that are always used, the most used headers in my  
humble opinion are: Last-Modified, Type and Length. I use Last- 
Modified to mantain my resources sync'd among different clients and  
thus ensuring everything is always up to date. I use type check what  
the server is sending me and length to see if I should use a chunked  
connection or not.

This functions execute very fast because they are using HEAD method  
instead of GET method, meaning they are not loading the resource they  
are just checking the HTTP Headers the server would send case you  
used GET. Suppose your app is needs to check if it should download  
some file, first it would call http.lastModificationDate() to see if  
it is up to date or not, if it is not, it might call http.length() to  
check the size of the file before download, if the file is to big it  
might download it using som asynchronous call instead of a blocking  
call.

Anyway, I have use for this functions, someone on this list might  
have too, so I decided to share. Those functions are just too simple  
to be shared as a stack right now so I used copy & paste.

Happy HTTP Hacking
Andre Garzia