| ----------------------------------------------------------------------------- |
| -- LTN12 - Filters, sources, sinks and pumps. |
| -- LuaSocket toolkit. |
| -- Author: Diego Nehab |
| -- RCS ID: $Id: ltn12.lua,v 1.31 2006/04/03 04:45:42 diego Exp $ |
| ----------------------------------------------------------------------------- |
| |
| ----------------------------------------------------------------------------- |
| -- Declare module |
| ----------------------------------------------------------------------------- |
| local string = require("string") |
| local table = require("table") |
| local base = _G |
| module("ltn12") |
| |
| filter = {} |
| source = {} |
| sink = {} |
| pump = {} |
| |
| -- 2048 seems to be better in windows... |
| BLOCKSIZE = 2048 |
| _VERSION = "LTN12 1.0.1" |
| |
| ----------------------------------------------------------------------------- |
| -- Filter stuff |
| ----------------------------------------------------------------------------- |
| -- returns a high level filter that cycles a low-level filter |
| function filter.cycle(low, ctx, extra) |
| base.assert(low) |
| return function(chunk) |
| local ret |
| ret, ctx = low(ctx, chunk, extra) |
| return ret |
| end |
| end |
| |
| -- chains a bunch of filters together |
| -- (thanks to Wim Couwenberg) |
| function filter.chain(...) |
| local n = table.getn(arg) |
| local top, index = 1, 1 |
| local retry = "" |
| return function(chunk) |
| retry = chunk and retry |
| while true do |
| if index == top then |
| chunk = arg[index](chunk) |
| if chunk == "" or top == n then return chunk |
| elseif chunk then index = index + 1 |
| else |
| top = top+1 |
| index = top |
| end |
| else |
| chunk = arg[index](chunk or "") |
| if chunk == "" then |
| index = index - 1 |
| chunk = retry |
| elseif chunk then |
| if index == n then return chunk |
| else index = index + 1 end |
| else base.error("filter returned inappropriate nil") end |
| end |
| end |
| end |
| end |
| |
| ----------------------------------------------------------------------------- |
| -- Source stuff |
| ----------------------------------------------------------------------------- |
| -- create an empty source |
| local function empty() |
| return nil |
| end |
| |
| function source.empty() |
| return empty |
| end |
| |
| -- returns a source that just outputs an error |
| function source.error(err) |
| return function() |
| return nil, err |
| end |
| end |
| |
| -- creates a file source |
| function source.file(handle, io_err) |
| if handle then |
| return function() |
| local chunk = handle:read(BLOCKSIZE) |
| if not chunk then handle:close() end |
| return chunk |
| end |
| else return source.error(io_err or "unable to open file") end |
| end |
| |
| -- turns a fancy source into a simple source |
| function source.simplify(src) |
| base.assert(src) |
| return function() |
| local chunk, err_or_new = src() |
| src = err_or_new or src |
| if not chunk then return nil, err_or_new |
| else return chunk end |
| end |
| end |
| |
| -- creates string source |
| function source.string(s) |
| if s then |
| local i = 1 |
| return function() |
| local chunk = string.sub(s, i, i+BLOCKSIZE-1) |
| i = i + BLOCKSIZE |
| if chunk ~= "" then return chunk |
| else return nil end |
| end |
| else return source.empty() end |
| end |
| |
| -- creates rewindable source |
| function source.rewind(src) |
| base.assert(src) |
| local t = {} |
| return function(chunk) |
| if not chunk then |
| chunk = table.remove(t) |
| if not chunk then return src() |
| else return chunk end |
| else |
| table.insert(t, chunk) |
| end |
| end |
| end |
| |
| function source.chain(src, f) |
| base.assert(src and f) |
| local last_in, last_out = "", "" |
| local state = "feeding" |
| local err |
| return function() |
| if not last_out then |
| base.error('source is empty!', 2) |
| end |
| while true do |
| if state == "feeding" then |
| last_in, err = src() |
| if err then return nil, err end |
| last_out = f(last_in) |
| if not last_out then |
| if last_in then |
| base.error('filter returned inappropriate nil') |
| else |
| return nil |
| end |
| elseif last_out ~= "" then |
| state = "eating" |
| if last_in then last_in = "" end |
| return last_out |
| end |
| else |
| last_out = f(last_in) |
| if last_out == "" then |
| if last_in == "" then |
| state = "feeding" |
| else |
| base.error('filter returned ""') |
| end |
| elseif not last_out then |
| if last_in then |
| base.error('filter returned inappropriate nil') |
| else |
| return nil |
| end |
| else |
| return last_out |
| end |
| end |
| end |
| end |
| end |
| |
| -- creates a source that produces contents of several sources, one after the |
| -- other, as if they were concatenated |
| -- (thanks to Wim Couwenberg) |
| function source.cat(...) |
| local src = table.remove(arg, 1) |
| return function() |
| while src do |
| local chunk, err = src() |
| if chunk then return chunk end |
| if err then return nil, err end |
| src = table.remove(arg, 1) |
| end |
| end |
| end |
| |
| ----------------------------------------------------------------------------- |
| -- Sink stuff |
| ----------------------------------------------------------------------------- |
| -- creates a sink that stores into a table |
| function sink.table(t) |
| t = t or {} |
| local f = function(chunk, err) |
| if chunk then table.insert(t, chunk) end |
| return 1 |
| end |
| return f, t |
| end |
| |
| -- turns a fancy sink into a simple sink |
| function sink.simplify(snk) |
| base.assert(snk) |
| return function(chunk, err) |
| local ret, err_or_new = snk(chunk, err) |
| if not ret then return nil, err_or_new end |
| snk = err_or_new or snk |
| return 1 |
| end |
| end |
| |
| -- creates a file sink |
| function sink.file(handle, io_err) |
| if handle then |
| return function(chunk, err) |
| if not chunk then |
| handle:close() |
| return 1 |
| else return handle:write(chunk) end |
| end |
| else return sink.error(io_err or "unable to open file") end |
| end |
| |
| -- creates a sink that discards data |
| local function null() |
| return 1 |
| end |
| |
| function sink.null() |
| return null |
| end |
| |
| -- creates a sink that just returns an error |
| function sink.error(err) |
| return function() |
| return nil, err |
| end |
| end |
| |
| -- chains a sink with a filter |
| function sink.chain(f, snk) |
| base.assert(f and snk) |
| return function(chunk, err) |
| if chunk ~= "" then |
| local filtered = f(chunk) |
| local done = chunk and "" |
| while true do |
| local ret, snkerr = snk(filtered, err) |
| if not ret then return nil, snkerr end |
| if filtered == done then return 1 end |
| filtered = f(done) |
| end |
| else return 1 end |
| end |
| end |
| |
| ----------------------------------------------------------------------------- |
| -- Pump stuff |
| ----------------------------------------------------------------------------- |
| -- pumps one chunk from the source to the sink |
| function pump.step(src, snk) |
| local chunk, src_err = src() |
| local ret, snk_err = snk(chunk, src_err) |
| if chunk and ret then return 1 |
| else return nil, src_err or snk_err end |
| end |
| |
| -- pumps all data from a source to a sink, using a step function |
| function pump.all(src, snk, step) |
| base.assert(src and snk) |
| step = step or pump.step |
| while true do |
| local ret, err = step(src, snk) |
| if not ret then |
| if err then return nil, err |
| else return 1 end |
| end |
| end |
| end |
| |