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Many thanks for detail explanation and proper code.
Finally I need to go for LPeg approach. Now I am just about to prove that with Lua, I will be able to simulate a sip call flow.
Thanks
Austin
It was thus said that the Great Austin Einter once stated:
> Hi AllIn my opinion, use LPeg for parsing. Yes, there is some learning curve,
> I can have an input string with any one of below formats
>
> \r\nContent-Length: 100 \r\n
> \r\nContent-Length : 100 \r\n
> \r\nContent-Length:100 \r\n
>
> Input string can be of any one value from above examples
>
> My aim is to extract 100 as an integer.
>
> What is the best way to do it.
but for what you are trying to do, there isn't anything better than LPeg. I
use it at work all the time for parsing issues.
Here's an example that applies to your case:
local lpeg = require "lpeg"
local P = lpeg.P
local S = lpeg.S
local C = lpeg.C
local crlf = P"\r"^-1 * P"\n"
local lwsp = S" \t"
local eoh = (crlf * #crlf) + (crlf - (crlf^-1 * lwsp))
local lws = (crlf^-1 * lwsp)^0
local value = (P(1) - eoh)^0
/ function(v)
return v:gsub("[%s%c]+"," ")
end
local name = C((P(1) - (P":" + crlf + lwsp))^1)
local header = name * lws * ":" * lws * value * eoh
hdr,val = header:match "Content-Length: 100 \r\n" print(hdr,val)
hdr,val = header:match "Content-Length : 100 \r\n" print(hdr,val)
hdr,val = header:match "Content-Length:100 \r\n" print(hdr,val)
hdr,val = header:match "X-some-made-up-header: foobar bazx\r\n" print(hdr,val)
hdr,val = header:match [[
X-Some-crazy-header :
some
value here
]] print(hdr,val)
You might also want to look at RFC-5322 as that describes the general
format for Internet message formats (which is what you're parsing) as that
covers the general format for headers.
-spc