Reorganization

1 files changed, 103 insertions, 0 deletions

@@ -0,0 +1,103 @@
+--- lam.port --- port objects
+-- because the implementation for ports is fairly involved, they're in their own
+-- file outside of `type'.
+
+local m = {}
+local util = require("util")
+local error = util.error
+local tochars = util.tochars
+
+-- The EOF object is what the reader emits when it hits an end-of-file or use up
+-- a port.
+m.eof = setmetatable({}, {
+                __type = "eof",
+                __tostring = function () return "#<eof>" end,
+})
+
+---[[ INPUT PORTS ]]---
+
+-- return the next token from PORT, given READTABLE
+local function input_port_next_token (port, readtable)
+        repeat
+                if #port.buffer == 0 then
+                        if port.file then
+                                local ln = port.file:read()
+                                if ln == nil then
+                                        return m.eof
+                                end
+                                port.buffer = tochars(ln)
+                        else
+                                return m.eof
+                        end
+                end
+
+                local token, token_type
+                local c = port.buffer[1]
+                if readtable.chars[c] then
+                        token, token_type, port.buffer =
+                                readtable.chars[c](port.buffer)
+                else
+                        for re, fn in pairs(readtable.regex) do
+                                if c:match(re) then
+                                        token, token_type, port.buffer =
+                                                fn(port.buffer)
+                                        break
+                                end
+                        end
+                        if token == nil then
+                                token, token_type, port.buffer =
+                                        readtable.default(port.buffer)
+                        end
+                end
+
+                port.buffer = port.buffer or {}
+                if token then
+                        return token, token_type
+                end
+        until nil
+end
+
+function m.input_port (source, source_type)
+        -- SOURCE is the name of the file/string to read or nil; nil means
+        -- standard input.  SOURCE_TYPE is one of "file", "string"; "file" is
+        -- the default.
+        local f, b
+        source_type = source_type or "file"
+        if source then
+                if source_type == "file" then
+                        f = io.open(source, "r")
+                elseif source_type == "string" then
+                        b = tochars(source)
+                else
+                        error("input-port: bad type", source_type)
+                end
+        else
+                f = io.input() -- ignore SOURCE_TYPE
+        end
+        local t = {
+                file = f,
+                name = f and source or "[string]",
+                type = source_type,
+                buffer = b or {},
+                flush = function (self) self.buffer = {} end,
+                next = input_port_next_token, -- port:next(readtable)
+                close =
+                        function (self)
+                                if self.file then self.file:close() end
+                        end,
+        }
+        local mt = {
+                __type = "input-port",
+                __tostring =
+                        function (self)
+                                return string.format("#<port %s>", self.name)
+                        end,
+        }
+        return setmetatable(t, mt)
+end
+
+---[[ OUTPUT PORTS ]]---
+-- TODO
+
+--------
+return m