Mail Box Parsing

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Parsing Mail box files

Say you save the source code in the current directory (or elsewhere in your PackagePath) as mboxparser.lua. In your code, put:

parse = require "mboxparser" 

The main function, parse.mbox, receives the mailbox file contents as a string and returns a table with one entry per message. Each entry has the following structure:

message = {
    headers = {
        [["name_1"]] = "value_1",
        [["name_2"]] = "value_2",
        ...           ...
        [["name_n"]] = "value_n",
    },
    body = "message body"
}
	

Therefore, if a mailbox has the following contents:

From  whoever@tecgraf.puc-rio.br  Thu Nov 22 13:59:05 2001
Date: Thu, 22 Nov 2001 13:59:04 -0200 (EDT)
From: Whoever Smith <whoever@tecgraf.puc-rio.br>
To: Other Smith <other@tecgraf.puc-rio.br>
Subject: This is a test message
Content-Type: TEXT/PLAIN; charset=US-ASCII

Hi, This is the message body.  Regards, Diego.
	

Calling parse.mbox on it would return the following table:

messages = {
  { 
    headers = {
      from = "Whoever Smith <whoever@tecgraf.puc-rio.br>", 
      subject = "This is a test message", 
      to = "Other Smith <other@tecgraf.puc-rio.br>", 
      date = "Thu, 22 Nov 2001 13:59:04 -0200 (EDT)", 
      ["content-type"] = "TEXT/PLAIN; charset=US-ASCII", 
    }, 
    body = "Hi, This is the message body.  Regards, Diego.",
  }
}
	

Source Code

local Public = {}
local strfind, strlower, gsub = string.find, string.lower, string.gsub
local strsub, tinsert = string.sub, table.insert

function Public.headers(headers_s)
    local headers = {}
    headers_s = "\n" .. headers_s .. "$$$:\n"
    local i, j = 1, 1
    local name, value, _
    while 1 do
        j = strfind(headers_s, "\n%S-:", i+1)
        if not j then break end
        _, _, name, value = strfind(strsub(headers_s, i+1, j-1), "(%S-):(.*)")
        value = gsub(value or "", "\r\n", "\n")
        value = gsub(value, "\n%s*", " ")
        name = strlower(name)
        if headers[name] then headers[name] = headers[name] .. ", " ..  value
        else headers[name] = value end
        i, j = j, i
    end
    headers["$$$"] = nil
    return headers
end

function Public.message(message_s)
    message_s = gsub(message_s, "^.-\n", "")
    local _, headers_s, body
    _, _, headers_s, body = strfind(message_s, "^(.-\n)\n(.*)")
    headers_s = headers_s or ""
    body = body or ""
    return { headers = Public.headers(headers_s), body = body }
end

function Public.mbox(mbox_s)
    local mbox = {}
    mbox_s = "\n" .. mbox_s .. "\nFrom "
    local i, j = 1, 1
    while 1 do
        j = strfind(mbox_s, "\nFrom ", i + 1)
        if not j then break end
        tinsert(mbox, Public.message(strsub(mbox_s, i + 1, j - 1)))
        i, j = j, i
    end
    return mbox
end

return Public
	

Credits

The original Lua 4 code was created by DiegoNehab, and is used to test the LuaSocket[1] 1.4 SMTP code. The Lua 5 version was made by DirkLaurie.