Add full replacement for Lua's "io" module

To install, run `require('lib.stream.compat').install()`.

src/lib/stream/compat.lua

@@ -0,0 +1,125 @@
+-- Use of this source code is governed by the Apache 2.0 license; see COPYING.
+
+-- Shim to replace Lua's built-in IO module with streams.
+
+module(..., package.seeall)
+
+local stream = require('lib.stream')
+local file = require('lib.stream.file')
+local S = require('syscall')
+
+local io = {}
+
+function io.close(file)
+   if file == nil then file = io.current_output end
+   file:close()
+end
+
+function io.flush()
+   io.current_output:flush()
+end
+
+function io.input(new)
+   if new == nil then return io.current_input end
+   if type(new) == string then new = io.open(new, 'r') end
+   io.current_input = new
+end
+
+function io.lines(filename, ...)
+   if filename == nil then return io.current_input:lines() end
+   local stream = io.open(filename, 'r')
+   local iter = stream:lines(...)
+   return function ()
+      local line = { iter() }
+      if line[1] == nil then
+         stream:close()
+         return nil
+      end
+      return unpack(line)
+   end
+end
+
+local modes = {
+   r='rdonly',
+   w='wronly,creat,trunc',
+   a='wronly,creat,append',
+   ['r+']='rdwr',
+   ['w+']='rdwr,creat,trunc',
+   ['a+']='rdwr,creat,append'
+}
+do
+   local binary_modes = {}
+   for k,v in pairs(modes) do binary_modes[k..'b'] = v end
+   for k,v in pairs(binary_modes) do modes[k] = v end
+end
+
+function io.open(filename, mode)
+   if mode == nil then mode = 'r' end
+   local flags = modes[mode]
+   if flags == nil then return nil, 'invalid mode: '..tostring(mode) end
+   -- This set of permissions is what fopen() uses.  Note that these
+   -- permissions will be modulated by the umask.
+   local fd, err = S.open(filename, flags, "rusr,wusr,rgrp,wgrp,roth,woth")
+   if fd == nil then return nil, err end
+   return file.fdopen(fd, flags)
+end
+
+function io.output(new)
+   if new == nil then return io.current_output end
+   if type(new) == string then new = io.open(new, 'w') end
+   io.current_output = new
+end
+
+function io.popen(prog, mode)
+   return file.popen(prog, mode)
+end
+
+function io.read(...)
+   return io.current_input:read(...)
+end
+
+function io.tmpfile()
+   local name = os.tmpname()
+   local f = io.open(name, 'w+')
+   local close = f.io.close
+   -- FIXME: Doesn't arrange to ensure the file is removed in all cases;
+   -- calling close is required.
+   function f.io:close()
+      close()
+      S.unlink(name)
+   end
+   return f
+end
+
+function io.type(x)
+   if not stream.is_stream(x) then return nil end
+   if not x.io then return 'closed file' end
+   return 'file'
+end
+
+function io.write(...)
+   return io.current_output:write(...)
+end
+
+function install()
+   if _G.io == io then return end
+   _G.io = io
+   io.stdin = file.fdopen(S.t.fd(0), 'rdonly')
+   io.stdout = file.fdopen(S.t.fd(1), 'wronly')
+   io.stderr = file.fdopen(S.t.fd(2), 'wronly')
+   if io.stdout.io.fd:isatty() then io.stdout:setvbuf('line') end
+   io.stderr:setvbuf('no')
+   io.input(io.stdin)
+   io.output(io.stdout)
+end
+
+function selftest()
+   print('selftest: lib.stream.compat')
+
+   _G.io.write('before\n')
+   install()
+   _G.io.write('after\n')
+   assert(_G.io == io)
+
+   print('selftest: ok')
+end