--- -- String buffer facilities. -- -- Lua's string operations are very flexible and offer an easy-to-use way to -- manipulate strings. Concatenation using the .. operator is such -- an operation. The drawback of the built-in API however is the way it handles -- concatenation of many string values. Since strings in Lua are immutable -- values, each time you concatenate two strings both get copied into the -- result string. -- -- The strbuf module offers a workaround for this problem, while -- maintaining the nice syntax. This is accomplished by overloading the -- concatenation operator (..), the equality operator (==) and the tostring -- operator. A string buffer is created by passing a string to -- strbuf.new. Afterwards you can append to the string buffer, -- or compare two string buffers for equality just as you would do with normal -- strings. -- -- When looking at the details there are some more restrictions/oddities: The -- concatenation operator requires its left-hand value to be a string buffer. -- Therefore, if you want to prepend a string to a given string buffer you have -- to create a new string buffer out of the string you want to prepend. The -- string buffer's tostring operator concatenates the strings -- inside the buffer using newlines by default, since this appears to be the -- separator used most often. -- -- Example usage: -- -- local buf = strbuf.new() -- local buf2 = strbuf.new('hello') -- buf = buf .. 'string' -- buf = buf .. 'data' -- print(buf) -- default separator is a newline -- print(strbuf.dump(buf)) -- no separator -- print(strbuf.dump(buf, ' ')) -- separated by spaces -- strbuf.clear(buf) -- -- @copyright Same as Nmap--See https://nmap.org/book/man-legal.html -- DEPENDENCIES -- local stdnse = require "stdnse" local table = require "table" local getmetatable = getmetatable; local setmetatable = setmetatable; local type = type; local error = error; local ipairs = ipairs; local pairs = pairs; local concat = table.concat; _ENV = stdnse.module("strbuf", stdnse.seeall) -- String buffer functions. Concatenation is not efficient in -- lua as strings are immutable. If a large amount of '..' sequential -- operations are needed a string buffer should be used instead -- e.g. for i = 1, 10 do s = s..i end --- Dumps the string buffer as a string. -- -- The second parameter is used as a delimiter between the strings stored inside -- the string buffer. -- @name dump -- @class function -- @param sbuf String buffer to dump. -- @param delimiter String to separate the buffer's contents. -- @return Concatenated string result. dump = concat; --- Appends a string to a string buffer. -- @param sbuf String buffer. -- @param s String to append. -- @return sbuf. function concatbuf(sbuf, s) if type(s) == "string" then sbuf[#sbuf+1] = s; elseif getmetatable(s) == getmetatable(sbuf) then for _,v in ipairs(s) do sbuf[#sbuf+1] = v; end else error("bad #2 operand to strbuf concat operation", 2); end return sbuf; end --- Determines if the two string buffers are equal. Two buffers are equal -- if they are the same or if they have equivalent contents. -- @param sbuf1 String buffer one. -- @param sbuf2 String buffer two. -- @return True if equal, false otherwise. function eqbuf(sbuf1, sbuf2) if getmetatable(sbuf1) ~= getmetatable(sbuf2) then error("one or more operands is not a string buffer", 2); elseif #sbuf1 ~= #sbuf2 then return false; else for i = 1, #sbuf1 do if sbuf1[i] ~= sbuf2[i] then return false; end end return true; end end --- Clears a string buffer. -- @param sbuf String buffer. function clear(sbuf) for k in pairs(sbuf) do sbuf[k] = nil; end end --- Returns the string buffer as a string. The delimiter used is a newline. -- @param sbuf String buffer. -- @return String made from concatenating the buffer. function tostring(sbuf) return concat(sbuf, "\n"); end local mt = { __concat = concatbuf, __tostring = tostring, __eq = eqbuf, __index = _M, }; --- Create a new string buffer. -- -- The optional arguments are added to the string buffer. The result of adding -- non-strings is undefined. The equals and tostring -- operators for string buffers are overloaded to be eqbuf and -- tostring respectively. -- @param ... Strings to add to the buffer initially. -- @return String buffer. function new(...) return setmetatable({...}, mt); end return _ENV;