HTTP parser for Lua -


i'm trying parse http post requests in lua. implementation works, eats hell lot of cpu load. critical, hence on embedded platform.

i've looked on other implementations, can't fit, because image hardly fit in memory, wouldn't use library. rolled own parser, uses of system resource. question how optimize have lower cpu load.

this openwrt based system, have lua 5.1. core function looks boundary (in str variable). reads input block block, , seeks it.

the other solution use luci libraries heavy lifting, don't want code integrated in luci.

--look pattern (str) , copy input until found output. local function writeuntil(in_fp, str, out_fp)      local buff = ""     local ret = false     local bs = 4096 --block size. amount of data read @ once      local c = in_fp:read(bs)     local strstartpos = 1      while c         local blocklen = string.len(c) --not sure whole block read, size of actual block.         local found = string.find(c, str, 1, true) --try locate str, don't have work.         if (found ~= nil)             if found > 2                 out_fp:write(string.sub(c, 1, found - 1))             end             ret = true             break --we done         else --try mach str till end of block             local strpos = string.find(c, string.sub(str, strstartpos, strstartpos), 1, true) --try locate first character             if strpos --there starting character in block                 if (strpos > 1)                         out_fp:write(string.sub(c, 1, strpos - 1))                 end                 = strpos, blocklen --iterate through block                     local ch = string.sub(c, i, i)                     if ch == string.sub(str, strstartpos, strstartpos)                         buff = buff .. ch                         if string.len(buff) == string.len(str)                             ret = true                             break --we're done                         end                         strstartpos = strstartpos + 1                     else --lost track. output.                         if string.len(buff) > 0                             out_fp:write(buff)                             buff = ""                         end                         out_fp:write(ch)                         strstartpos = 1                     end                 end             else                 out_fp:write(c)             end         end         if ret             break         end         c = in_fp:read(bs) --read next block     end     return ret end

egor, right, ended solution. uses less cpu. not perfect hence scp faster (although implemented in c).

--look pattern (str) , copy input until found output. local function writeuntil(in_fp, str, out_fp)      local buff = ""     local ret = false     local bs = 4096 --block size. amount of data read @ once      local c = in_fp:read(bs)     local strstartpos = 1     local laststrpos = 1     local needdata = true      while c         local blocklen = string.len(c) --not sure whole block read, size of actual block.         local found = string.find(c, str, 1, true) --try locate str, don't have work.         if (found ~= nil)             if found > 1                 if #buff > 0                     out_fp:write(buff)                 end                 out_fp:write(string.sub(c, 1, found - 1))             end             ret = true             break --we done         else --try mach str till end of block             local strpos = string.find(c, string.sub(str, strstartpos, strstartpos), laststrpos, true) --try locate first character             if strpos --there starting character in block                 out_fp:write(string.sub(c, laststrpos, strpos - 1))                 = strpos, blocklen --iterate through block                     local ch = string.sub(c, i, i)                     if ch == string.sub(str, strstartpos, strstartpos)                         buff = buff .. ch                         if string.len(buff) == string.len(str)                             ret = true                             break --we're done                         end                         strstartpos = strstartpos + 1                         laststrpos = + 1                     else --lost track. output.                         if string.len(buff) > 0                             out_fp:write(buff)                             buff = ""                         end                         out_fp:write(ch)                         strstartpos = 1                         if == blocklen                             needdata = true                         else                             laststrpos = + 1                             needdata = false                         end                         break                     end                 end             else                 if ret == false                     if string.len(buff) > 0                         out_fp:write(buff)                         buff = ""                     end                     out_fp:write(string.sub(c, laststrpos))                     laststrpos = 1                     needdata = true                 else                     break                 end             end         end         if ret             break         end         if needdata             c = in_fp:read(bs) --read next block             laststrpos = 1         end     end     return ret end

Comments

Post a Comment

Popular posts from this blog

Sort a complex associative array in PHP -

this question has answer here: php sort array subarray value 5 answers i have associative array in php like: $newarray1 = array ( [producta] => array ( [link] => http://sanjosespartan.com/blog/products/agile-java-development/ [visitcount] => 4 ) [productd] => array ( [link] => http://sanjosespartan.com/blog/products/intro-to-go/ [visitcount] => 1 ) [productg] => array ( [link] => http://sanjosespartan.com/blog/products/node-js-for-developers/ [visitcount] => 1 ) [productb] => array ( [link] => http://sanjosespartan.com/blog/products/beginning-mysql/ [visitcount] => 1 ) [productc] => array ( [link] => http://sanjosespartan.com/blog/products/computer-networks/ [visitcount] => 1 ) ...
Read more

vb.net - How to ignore if a cell is empty nothing -

how use roscolor() ignore value (like empty cell) ? color row if value upper 5 when there nothing in cell, want ignore roscolor() apply, how? public sub roscolor() integer = 0 quotedatagridview1.rows.count() - 1 step +1 dim val integer val = quotedatagridview1.rows(i).cells(3).value if val = vbempty quotedatagridview1.rows(i).defaultcellstyle.backcolor = color.white elseif val < 5 quotedatagridview1.rows(i).defaultcellstyle.backcolor = color.red elseif val > 5 , val < 10 quotedatagridview1.rows(i).defaultcellstyle.backcolor = color.lightyellow end if next end sub you can check empty value following public sub roscolor() integer = 0 quotedatagridview1.rows.count() - 1 step +1 dim val = quotedatagridview1.rows(i).cells(3).value if isdbnull(val) or val nothing quotedatagridview1.rows(i).defaultcellstyle.backcolor = color.white ...
Read more

recursion - Can every recursive algorithm be improved with dynamic programming? -

i first year undergraduate csc student looking competitive programming. recursion involves defining , solving sub problems. understand, top down dynamic programming (dp) involves memoizing solutions sub problems reduce time complexity of algorithm. can top down dp used improve efficiency of every recursive algorithm overlapping sub problems? dp fail work , how can identify this? the short answer is: yes. however, there constraints. obvious 1 recursive calls must overlap. i.e. during execution of algorithm, recursive function must called multiple times same parameters. lets truncate recursion tree memoization. can use memoization reduce number of calls. however, reduction of calls comes price. need store results somewhere. next obvious constraint need have enough memory. comes not-so obvious constraint. memory access requires time. first need find result stored , maybe copy location. in cases, might faster let recursion calculate result instead of loading somewher...
Read more