Tested each sample.

gem/ex1.lua

@@ -0,0 +1,4 @@
+local CRLF = "\013\010"
+local input = source.chain(source.file(io.stdin), normalize(CRLF))
+local output = sink.file(io.stdout)
+pump.all(input, output)

gem/ex10.lua

@@ -0,0 +1,17 @@
+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
+
+function pump.all(src, snk, step)
+    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

gem/ex11.lua

@@ -0,0 +1,7 @@
+local input = source.chain(
+  source.file(io.open("input.bin", "rb")), 
+  encode("base64"))
+local output = sink.chain(
+  wrap(76), 
+  sink.file(io.open("output.b64", "w")))
+pump.all(input, output)

gem/ex12.lua

@@ -0,0 +1,34 @@
+local smtp = require"socket.smtp"
+local mime = require"mime"
+local ltn12 = require"ltn12"
+
+CRLF = "\013\010"
+
+local message = smtp.message{
+  headers = {
+    from = "Sicrano <sicrano@example.com>",
+    to = "Fulano <fulano@example.com>",
+    subject = "A message with an attachment"},
+  body = {
+    preamble = "Hope you can see the attachment" .. CRLF,
+    [1] = {
+      body = "Here is our logo" .. CRLF},
+    [2] = {
+      headers = {
+        ["content-type"] = 'image/png; name="luasocket.png"',
+        ["content-disposition"] =
+          'attachment; filename="luasocket.png"',
+        ["content-description"] = 'LuaSocket logo',
+        ["content-transfer-encoding"] = "BASE64"},
+      body = ltn12.source.chain(
+        ltn12.source.file(io.open("luasocket.png", "rb")),
+        ltn12.filter.chain(
+          mime.encode("base64"),
+          mime.wrap()))}}}
+
+assert(smtp.send{
+  rcpt = "<diego@cs.princeton.edu>",
+  from = "<diego@cs.princeton.edu>",
+  server = "localhost",
+  port = 2525,
+  source = message})

gem/ex2.lua

@@ -0,0 +1,11 @@
+function filter.cycle(lowlevel, context, extra)
+  return function(chunk)
+    local ret
+    ret, context = lowlevel(context, chunk, extra)
+    return ret
+  end
+end
+
+function normalize(marker)
+  return filter.cycle(eol, 0, marker)
+end

gem/ex3.lua

@@ -0,0 +1,15 @@
+local function chainpair(f1, f2)
+  return function(chunk)
+    local ret = f2(f1(chunk))
+    if chunk then return ret
+    else return (ret or "") .. (f2() or "") end
+  end
+end
+
+function filter.chain(...)
+  local f = select(1, ...) 
+  for i = 2, select('#', ...) do
+    f = chainpair(f, select(i, ...))
+  end
+  return f
+end

gem/ex4.lua

@@ -0,0 +1,5 @@
+local qp = filter.chain(normalize(CRLF), encode("quoted-printable"), 
+  wrap("quoted-printable"))
+local input = source.chain(source.file(io.stdin), qp)
+local output = sink.file(io.stdout)
+pump.all(input, output)

gem/ex5.lua

@@ -0,0 +1,15 @@
+function source.empty(err)
+  return function()
+    return nil, err
+  end
+end
+
+function source.file(handle, io_err)
+  if handle then
+    return function()
+      local chunk = handle:read(20)
+      if not chunk then handle:close() end
+      return chunk
+    end
+  else return source.empty(io_err or "unable to open file") end
+end

gem/ex6.lua

@@ -0,0 +1,14 @@
+function source.chain(src, f)
+  return function()
+    if not src then
+      return nil
+    end
+    local chunk, err = src()
+    if not chunk then
+      src = nil
+      return f(nil)
+    else
+      return f(chunk)
+    end
+  end
+end

gem/ex7.lua

@@ -0,0 +1,16 @@
+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
+
+local function null()
+  return 1
+end
+
+function sink.null()
+  return null
+end

gem/ex8.lua

@@ -0,0 +1,5 @@
+local input = source.file(io.stdin)
+local output, t = sink.table()
+output = sink.chain(normalize(CRLF), output)
+pump.all(input, output)
+io.write(table.concat(t))

gem/ex9.lua

@@ -0,0 +1,3 @@
+for chunk in source.file(io.stdin) do
+  io.write(chunk)
+end

gem/gem.c

@@ -0,0 +1,54 @@
+#include "lua.h"
+#include "lauxlib.h"
+
+#define CR '\xD'
+#define LF '\xA'
+#define CRLF "\xD\xA"
+
+#define candidate(c) (c == CR || c == LF)
+static int pushchar(int c, int last, const char *marker, 
+    luaL_Buffer *buffer) {
+  if (candidate(c)) {
+    if (candidate(last)) {
+      if (c == last) 
+        luaL_addstring(buffer, marker);
+      return 0;
+    } else {
+      luaL_addstring(buffer, marker);
+      return c;
+    }
+  } else {
+    luaL_putchar(buffer, c);
+    return 0;
+  }
+}
+
+static int eol(lua_State *L) {
+  int context = luaL_checkint(L, 1);
+  size_t isize = 0;
+  const char *input = luaL_optlstring(L, 2, NULL, &isize);
+  const char *last = input + isize;
+  const char *marker = luaL_optstring(L, 3, CRLF);
+  luaL_Buffer buffer;
+  luaL_buffinit(L, &buffer);
+  if (!input) {
+    lua_pushnil(L);
+    lua_pushnumber(L, 0);
+    return 2;
+  }
+  while (input < last)
+    context = pushchar(*input++, context, marker, &buffer);
+  luaL_pushresult(&buffer);
+  lua_pushnumber(L, context);
+  return 2;
+}
+
+static luaL_reg func[] = {
+    { "eol", eol },
+    { NULL, NULL }
+};
+
+int luaopen_gem(lua_State *L) {
+    luaL_openlib(L, "gem", func, 0);
+	return 0;
+}