include swank.R hacks from today

We get far enough to start up a swank server in R and connect to it from
emacs; we get a REPL which formats the R-style results from parsing and
evaluating the input it receives.  Debugging, stepping, documentation,
arglist and so on is basically entirely missing.

swank.R

@@ -0,0 +1,205 @@
+swank <- function(port=4005) {
+  acceptConnections(port, FALSE)
+}
+
+startSwank <- function(portFile) {
+  acceptConnections(FALSE, portFile)
+}
+
+acceptConnections <- function(port, portFile) {
+  s <- socketConnection(host="localhost", server=TRUE, port=port, open="r+b")
+  on.exit(close(s))
+  serve(s)
+}
+
+serve <- function(io) {
+  mainLoop(io)
+}
+
+mainLoop <- function(io) {
+  dispatch <- function(event) {
+    str(event)
+    kind <- event[[1]]
+    if(kind == quote(`:emacs-rex`)) {
+      do.call("emacsRex", event[-1])
+    }
+  }
+  sendToEmacs <- function(obj) {
+    payload <- writeSexpToString(obj)
+    writeChar(sprintf("%06x", nchar(payload)), io, eos=NULL)
+    writeChar(payload, io, eos=NULL)
+    flush(io)
+    cat(sprintf("%06x", nchar(payload)), payload, sep="")
+  }
+  emacsRex <- function(form, pkg, thread, id) {
+    value <- do.call(eval(form[[1]]), form[-1])
+    sendToEmacs(list(quote(`:return`), list(quote(`:ok`), value), id))
+  }
+
+  while(TRUE) {
+    tryCatch(dispatch(readPacket(io)),
+             swankTopLevel=NULL)
+  }
+}
+
+readPacket <- function(io) {
+  header <- readChunk(io, 6)
+  len <- strtoi(header, base=16)
+  payload <- readChunk(io, len)
+  readSexpFromString(payload)
+}
+
+readChunk <- function(io, len) {
+  buffer <- readChar(io, len)
+  if(nchar(buffer) != len) {
+    stop("short read in readChunk")
+  }
+  buffer
+}
+
+readSexpFromString <- function(string) {
+  pos <- 1
+  read <- function() {
+    skipWhitespace()
+    char <- substr(string, pos, pos)
+    switch(char,
+           "("=readList(),
+           "\""=readString(),
+           "'"=readQuote(),
+           {
+             if(pos > nchar(string))
+               stop("EOF during read")
+             obj <- readNumberOrSymbol()
+             if(obj == quote(`.`)) {
+               stop("Consing dot not implemented")
+             }
+             obj
+           })
+  }
+  skipWhitespace <- function() {
+    while(substr(string, pos, pos) %in% c(" ", "\t", "\n")) {
+      pos <<- pos + 1
+    }
+  }
+  readList <- function() {
+    ret <- list()
+    pos <<- pos + 1
+    while(TRUE) {
+      skipWhitespace()
+      char <- substr(string, pos, pos)
+      if(char == ")") {
+        pos <<- pos + 1
+        break
+      } else {
+        obj <- read()
+        if(length(obj) == 1 && obj == quote(`.`)) {
+          stop("Consing dot not implemented")
+        }
+        ret <- c(ret, list(obj))
+      }
+    }
+    ret
+  }
+  readString <- function() {
+    ret <- ""
+    addChar <- function(c) { ret <<- paste(ret, c, sep="") }
+    while(TRUE) {
+      pos <<- pos + 1
+      char <- substr(string, pos, pos)
+      switch(char,
+             "\""={ pos <<- pos + 1; break },
+             "\\"={ pos <<- pos + 1
+                    char2 <- substr(string, pos, pos)
+                    switch(char2,
+                           "\""=addChar(char2),
+                           "\\"=addChar(char2),
+                           stop("Unrecognized escape character")) },
+             addChar(char))
+    }
+    ret
+  }
+  readNumberOrSymbol <- function() {
+    token <- readToken()
+    if(nchar(token)==0) {
+      stop("End of file reading token")
+    } else if(grepl("^[0-9]+$", token)) {
+      strtoi(token)
+    } else if(grepl("^[0-9]+\\.[0-9]+$", token)) {
+      as.double(token)
+    } else {
+      as.name(token)
+    }
+  }
+  readToken <- function() {
+    token <- ""
+    while(TRUE) {
+      char <- substr(string, pos, pos)
+      if(char == "") {
+        break;
+      } else if(char %in% c(" ", "\n", "\t", "(", ")", "\"", "'")) {
+        break;
+      } else {
+        token <- paste(token, char, sep="")
+        pos <<- pos + 1
+      }
+    }
+    token
+  }
+  read()
+}
+
+writeSexpToString <- function(obj) {
+  writeSexpToStringLoop <- function(obj) {
+    switch(typeof(obj),
+           "character"={ string <- paste(string, "\"", gsub("([\"\\])", "\\\\\\1", obj), "\"", sep="") },
+           "list"={ string <- paste(string, "(", sep="")
+                    max <- length(obj)
+                    if(max > 0) {
+                      for(i in 1:max) {
+                        string <- paste(string, writeSexpToString(obj[[i]]), sep="")
+                        if(i != max) {
+                          string <- paste(string, " ", sep="")
+                        }
+                      }
+                    }
+                    string <- paste(string, ")", sep="") },
+           "symbol"={ string <- paste(string, as.character(obj), sep="") },
+           "logical"={ if(obj) { paste(string, "t", sep="") } else { paste(string, "nil", sep="") }},
+           "double"={ string <- paste(string, as.character(obj), sep="") },
+           "integer"={ string <- paste(string, as.character(obj), sep="") },
+           stop(paste("can't write object ", obj, sep="")))
+    string
+  }
+  string <- ""
+  writeSexpToStringLoop(obj)
+}
+
+`swank:connection-info` <- function () {
+  list(quote(`:pid`), Sys.getpid(),
+       quote(`:package`), list(quote(`:name`), "R", quote(`:prompt`), "R> "),
+       quote(`:lisp-implementation`), list(quote(`:type`), "R",
+                                           quote(`:name`), "R",
+                                           quote(`:version`), paste(R.version$major, R.version$minor, sep=".")))
+}
+
+`swank:swank-require` <- function (contribs) {
+  list()
+}
+
+`swank:create-repl` <- function(env, ...) {
+  list("R", "R")
+}
+
+`swank:listener-eval` <- function(string) {
+  val <- eval(parse(text=string))
+  f <- fifo("")
+  sink(f)
+  print(val)
+  sink()
+  lines <- readLines(f)
+  list(quote(`:values`), paste(lines, collapse="\n"))
+}
+
+`swank:autodoc` <- function(rawForm, ...) {
+  "No Arglist Information"
+}