HTML parser in Lua

bastya_elvtars · 20 June, 2007, 15:58:15

Suggestions, fixes, additions and any other types of feedback are welcome. :-)

--[[
HTML Parser in Lua
Inspired by this C# code:
http://www.codeproject.com/useritems/HTML_to_Plain_Text.asp

It does exactly the same as described there.
Only converts offline files.

Distributed under a modified BSD license, see at the end of the file
]]

-- What is the desired newline?
nl = "\n"

filename = "Y:/news.html"

function HTML_ToText (file)
  -- Declare variables, load the file. Make tags lowercase.
  local text
  local f=io.open (file)
  if f then
    text = f:read ("*a")
    f:close()
  end
  text = string.gsub (text,"(%b<>)",
  function (tag)
    return tag:lower()
  end)
  --[[ 
  First we kill the developer formatting (tabs, CR, LF)
  and produce a long string with no newlines and tabs.
  We also kill repeated spaces as browsers ignore them anyway.
  ]]
  local devkill=
    {
      ["("..string.char(10)..")"] = " ",
      ["("..string.char(13)..")"] = " ",
      ["("..string.char(15)..")"] = "",
      ["(%s%s+)"]=" ",
    }
  for pat, res in pairs (devkill) do
    text = string.gsub (text, pat, res)
  end
  -- Then we remove the header. We do this by stripping it first.
  text = string.gsub (text, "(<%s*head[^>]*>)", "<head>")
  text = string.gsub (text, "(<%s*%/%s*head%s*>)", "</head>")
  text = string.gsub (text, "(<head>,*<%/head>)", "")
  -- Kill all scripts. First we nuke their attribs.
  text = string.gsub (text, "(<%s*script[^>]*>)", "<script>")
  text = string.gsub (text, "(<%s*%/%s*script%s*>)", "</script>")
  text = string.gsub (text, "(<script>,*<%/script>)", "")
  -- Ok, same for styles.
  text = string.gsub (text, "(<%s*style[^>]*>)", "<style>")
  text = string.gsub (text, "(<%s*%/%s*style%s*>)", "</style>")
  text = string.gsub (text, "(<style>.*<%/style>)", "")
  
  -- Replace <td> with tabulators.
  text = string.gsub (text, "(<%s*td[^>]*>)","\t")
  
  -- Replace <br> with linebreaks.
  text = string.gsub (text, "(<%s*br%s*%/%s*>)",nl)
  
  -- Replace <li> with an asterisk surrounded by 2 spaces.
  -- Replace </li> with a newline.
  text = string.gsub (text, "(<%s*li%s*%s*>)"," *  ")
  text = string.gsub (text, "(<%s*/%s*li%s*%s*>)",nl)
  
  -- <p>, <div>, <tr>, <ul> will be replaced to a double newline.
    text = string.gsub (text, "(<%s*div[^>]*>)", nl..nl)
    text = string.gsub (text, "(<%s*p[^>]*>)", nl..nl)
    text = string.gsub (text, "(<%s*tr[^>]*>)", nl..nl)
    text = string.gsub (text, "(<%s*%/*%s*ul[^>]*>)", nl..nl)
  -- 
  
  -- Nuke all other tags now.
  text = string.gsub (text, "(%b<>)","")
  
  -- Replace entities to their correspondant stuff where applicable.
  -- C# is owned badly here by using a table. :-P
  -- A metatable secures entities, so you can add them natively as keys.
  -- Enclosing brackets also get added automatically (capture!)
  local entities = {}
  setmetatable (entities,
  {
    __newindex = function (tbl, key, value)
      key = string.gsub (key, "(%#)" , "%%#")
      key = string.gsub (key, "(%&)" , "%%&")
      key = string.gsub (key, "(%;)" , "%%;")
      key = string.gsub (key, "(.+)" , "("..key..")")
      rawset (tbl, key, value)
    end
  })
  entities = 
  {
    ["&nbsp;"] = " ",
    ["&bull;"] = " *  ",
    ["&lsaquo;"] = "<",
    ["&rsaquo;"] = ">",
    ["&trade;"] = "(tm)",
    ["&frasl;"] = "/",
    ["&lt;"] = "<",
    ["&gt;"] = ">",
    ["&copy;"] = "(c)",
    ["&reg;"] = "(r)",
    -- Then kill all others.
    -- You can customize this table if you would like to, 
    -- I just got bored of copypasting. :-)
    -- http://hotwired.lycos.com/webmonkey/reference/special_characters/
    ["%&.+%;"] = "",
  }
  for entity, repl in pairs (entities) do
    text = string.gsub (text, entity, repl)
  end
  
  return text
  
end

--[[
Copyright (c) 2007, bastya_elvtars

All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice, this
      list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright notice,
      this list of conditions and the following disclaimer in the documentation
      and/or other materials provided with the distribution.
    * Neither the name of the author nor the names of contributors may be used
      to endorse or promote products derived from this code without specific
      prior written permission.

THIS CODE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
CODE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
]][/code ]

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achiever · 20 June, 2007, 20:43:41

bastya where does the text file of this gets stored? or does it stores it at all?
i couldnt find how it work, so i asked.

bastya_elvtars · 20 June, 2007, 20:54:19

This does not work with PtokaX. This is just code for incorporation into a proper script.

achiever · 20 June, 2007, 21:11:02

ok

Yahoo · 29 June, 2007, 06:40:40

hello, how to use this script??

bastya_elvtars · 27 July, 2007, 03:21:46

Quote from: bastya_elvtars on 20 June, 2007, 20:54:19
This does not work with PtokaX. This is just code for incorporation into a proper script.

Hi all, here comes an updated version. It parses a tags as well, and collects links as endnotes. It parses http://www.lua.org/ in the following way:

  The Programming Language Lua        

 	 	  	 ? about[1] ? news[2] ? download[3] ? documentation[4] ? community[5] ? site map[6] ? portuguęs[7] ? contact[8] ? rss[9] 

 	  

  

  

  	     Lua 5.1.2[10] released, fixing all known bugs in Lua 5.1[11]. 

   Korean translation[12] of Programming in Lua published. 

   

--

[1]http://www.lua.org/about.html
[2]http://www.lua.org/news.html
[3]http://www.lua.org/download.html
[4]http://www.lua.org/docs.html
[5]http://www.lua.org/community.html
[6]http://www.lua.org/map.html
[7]http://www.lua.org/portugues.html
[8]http://www.lua.org/contact.html
[9]http://www.lua.org/rss.html
[10]http://www.lua.org/ftp/lua-5.1.2.tar.gz
[11]http://www.lua.org/bugs.html#5.1.1
[12]http://insightbook.springnote.com/pages/253177

Here is the updated snippet:

Code: lua

--[[
HTML Parser in Lua
Inspired by this C# code:
http://www.codeproject.com/useritems/HTML_to_Plain_Text.asp

It does exactly the same as described there.
Only converts offline files.

Distributed under a modified BSD license, see at the end of the file]]

-- What is the desired newline?
nl = "\n"

filename = "E:/luaorg.htm"

function HTML_ToText (file)
  -- Declare variables, load the file. Make tags lowercase.
  local text
  local f=io.open (file)
  if f then
    if f:seek("end") <= 0 then return end
    f:seek("set")
    text = f:read ("*a")
    f:close()
  end
  text = string.gsub (text,"(<([^>]-)>)",function (str) return str:lower() end)
  --[[ 
  First we kill the developer formatting (tabs, CR, LF)
  and produce a long string with no newlines and tabs.
  We also kill repeated spaces as browsers ignore them anyway.
  ]]
  local devkill=
    {
      ["("..string.char(10)..")"] = " ",
      ["("..string.char(13)..")"] = " ",
      ["("..string.char(15)..")"] = "",
      ["(%s%s+)"]=" ",
    }
  for pat, res in pairs (devkill) do
    text = string.gsub (text, pat, res)
  end
  -- Then we remove the header. We do this by stripping it first.
  text = string.gsub (text, "(<%s*head[^>]*>)", "<head>")
  text = string.gsub (text, "(<%s*%/%s*head%s*>)", "</head>")
  text = string.gsub (text, "(<head>,*<%/head>)", "")
  -- Kill all scripts. First we nuke their attribs.
  text = string.gsub (text, "(<%s*script[^>]*>)", "<script>")
  text = string.gsub (text, "(<%s*%/%s*script%s*>)", "</script>")
  text = string.gsub (text, "(<script>,*<%/script>)", "")
  -- Ok, same for styles.
  text = string.gsub (text, "(<%s*style[^>]*>)", "<style>")
  text = string.gsub (text, "(<%s*%/%s*style%s*>)", "</style>")
  text = string.gsub (text, "(<style>.*<%/style>)", "")
  
  -- Replace <td> and <th> with tabulators.
  text = string.gsub (text, "(<%s*td[^>]*>)","\t")
  text = string.gsub (text, "(<%s*th[^>]*>)","\t")
  
  -- Replace <br> with linebreaks.
  text = string.gsub (text, "(<%s*br%s*%/%s*>)",nl)
  
  -- Replace <li> with an asterisk surrounded by spaces.
  -- Replace </li> with a newline.
  text = string.gsub (text, "(<%s*li%s*%s*>)"," *  ")
  text = string.gsub (text, "(<%s*/%s*li%s*%s*>)",nl)
  
  -- <p>, <div>, <tr>, <ul> will be replaced to a double newline.
  text = string.gsub (text, "(<%s*div[^>]*>)", nl..nl)
  text = string.gsub (text, "(<%s*p[^>]*>)", nl..nl)
  text = string.gsub (text, "(<%s*tr[^>]*>)", nl..nl)
  text = string.gsub (text, "(<%s*%/*%s*ul[^>]*>)", nl..nl)
    
  -- Some petting with the <a> tags. :-P
  local addresses,c = {},0
  text=string.gsub(text,"<%s*a.-href=[\'\"](%S+)[\'\"][^>]*>(.-)<%s*%/*%s*a[^>]->", -- gets URL from a tag, and the enclosed name
  function (url,name)
    c = c + 1
    name = string.gsub (name, "<([^>]-)>","") -- strip name from tags (e. g. images as links)
    
    -- We only consider the URL valid if the name contains alphanumeric characters.
    if name:find("%w") then print(url, name, c) table.insert (addresses, {url, name}) return name.."["..#addresses.."]" else return "" end    
  end)

  -- Nuke all other tags now.
  text = string.gsub (text, "(%b<>)","")
  
  -- Replace entities to their correspondant stuff where applicable.
  -- C# is owned badly here by using a table. :-P
  -- A metatable secures entities, so you can add them natively as keys.
  -- Enclosing brackets also get added automatically (capture!)
  local entities = {}
  setmetatable (entities,
  {
    __newindex = function (tbl, key, value)
      key = string.gsub (key, "(%#)" , "%%#")
      key = string.gsub (key, "(%&)" , "%%&")
      key = string.gsub (key, "(%;)" , "%%;")
      key = string.gsub (key, "(.+)" , "("..key..")")
      rawset (tbl, key, value)
    end
  })
  entities = 
  {
    ["&nbsp;"] = " ",
    ["&bull;"] = " *  ",
    ["&lsaquo;"] = "<",
    ["&rsaquo;"] = ">",
    ["&trade;"] = "(tm)",
    ["&frasl;"] = "/",
    ["&lt;"] = "<",
    ["&gt;"] = ">",
    ["&copy;"] = "(c)",
    ["&reg;"] = "(r)",
    -- Then kill all others.
    -- You can customize this table if you would like to, 
    -- I just got bored of copypasting. :-)
    -- http://hotwired.lycos.com/webmonkey/reference/special_characters/
    ["%&.+%;"] = "",
  }
  for entity, repl in pairs (entities) do
    text = string.gsub (text, entity, repl)
  end
--   text = text..nl..nl..("-"):rep(27)..nl..nl
--   
--   for k,v in ipairs (addresses) do
--     text = text.."["..k.."] "..v[1]..nl
--   end
  if #addresses > 0 then
    text=text..nl:rep(2)..("-"):rep(2)..nl
    for key, tbl in ipairs(addresses) do
      text = text..nl.."["..key.."]"..tbl[1]
    end
  end
  
  return text
  
end

local f=io.open(filename..".txt", "w")
f:write(HTML_ToText (filename))
f:close()
--[[
Copyright (c) 2007, bastya_elvtars

All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice, this
      list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright notice,
      this list of conditions and the following disclaimer in the documentation
      and/or other materials provided with the distribution.
    * Neither the name of the author nor the names of contributors may be used
      to endorse or promote products derived from this code without specific
      prior written permission.

THIS CODE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
CODE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
]]

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HTML parser in Lua

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