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--- Reading and writing strings using file-like objects. <br>
--
-- f = stringio.open(text)
-- l1 = f:read() -- read first line
-- n,m = f:read ('*n','*n') -- read two numbers
-- for line in f:lines() do print(line) end -- iterate over all lines
-- f = stringio.create()
-- f:write('hello')
-- f:write('dolly')
-- assert(f:value(),'hellodolly')
--
-- See @{03-strings.md.File_style_I_O_on_Strings|the Guide}.
-- @module pl.stringio
local unpack = rawget(_G,'unpack') or rawget(table,'unpack')
local tonumber = tonumber
local concat,append = table.concat,table.insert
local stringio = {}
-- Writer class
local SW = {}
SW.__index = SW
local function xwrite(self,...)
local args = {...} --arguments may not be nil!
for i = 1, #args do
append(self.tbl,args[i])
end
end
function SW:write(arg1,arg2,...)
if arg2 then
xwrite(self,arg1,arg2,...)
else
append(self.tbl,arg1)
end
end
function SW:writef(fmt,...)
self:write(fmt:format(...))
end
function SW:value()
return concat(self.tbl)
end
function SW:__tostring()
return self:value()
end
function SW:close() -- for compatibility only
end
function SW:seek()
end
-- Reader class
local SR = {}
SR.__index = SR
function SR:_read(fmt)
local i,str = self.i,self.str
local sz = #str
if i > sz then return nil end
local res
if fmt == '*l' or fmt == '*L' then
local idx = str:find('\n',i) or (sz+1)
res = str:sub(i,fmt == '*l' and idx-1 or idx)
self.i = idx+1
elseif fmt == '*a' then
res = str:sub(i)
self.i = sz
elseif fmt == '*n' then
local _,i2,idx
_,idx = str:find ('%s*%d+',i)
_,i2 = str:find ('^%.%d+',idx+1)
if i2 then idx = i2 end
_,i2 = str:find ('^[eE][%+%-]*%d+',idx+1)
if i2 then idx = i2 end
local val = str:sub(i,idx)
res = tonumber(val)
self.i = idx+1
elseif type(fmt) == 'number' then
res = str:sub(i,i+fmt-1)
self.i = i + fmt
else
error("bad read format",2)
end
return res
end
function SR:read(...)
if select('#',...) == 0 then
return self:_read('*l')
else
local res, fmts = {},{...}
for i = 1, #fmts do
res[i] = self:_read(fmts[i])
end
return unpack(res)
end
end
function SR:seek(whence,offset)
local base
whence = whence or 'cur'
offset = offset or 0
if whence == 'set' then
base = 1
elseif whence == 'cur' then
base = self.i
elseif whence == 'end' then
base = #self.str
end
self.i = base + offset
return self.i
end
function SR:lines(...)
local n, args = select('#',...)
if n > 0 then
args = {...}
end
return function()
if n == 0 then
return self:_read '*l'
else
return self:read(unpack(args))
end
end
end
function SR:close() -- for compatibility only
end
--- create a file-like object which can be used to construct a string.
-- The resulting object has an extra `value()` method for
-- retrieving the string value. Implements `file:write`, `file:seek`, `file:lines`,
-- plus an extra `writef` method which works like `utils.printf`.
-- @usage f = create(); f:write('hello, dolly\n'); print(f:value())
function stringio.create()
return setmetatable({tbl={}},SW)
end
--- create a file-like object for reading from a given string.
-- Implements `file:read`.
-- @string s The input string.
-- @usage fs = open '20 10'; x,y = f:read ('*n','*n'); assert(x == 20 and y == 10)
function stringio.open(s)
return setmetatable({str=s,i=1},SR)
end
function stringio.lines(s,...)
return stringio.open(s):lines(...)
end
return stringio
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