1 files changed, 119 insertions, 0 deletions

diff --git a/examples/read.lua b/examples/read.lua
new file mode 100644
index 0000000..7a1c747
--- /dev/null
+++ b/examples/read.lua
@@ -0,0 +1,119 @@
+local sys = require "system"
+
+print [[
+
+This example shows how to do a non-blocking read from the cli.
+
+]]
+
+-- setup Windows console to handle ANSI processing
+local of_in = sys.getconsoleflags(io.stdin)
+local of_out = sys.getconsoleflags(io.stdout)
+sys.setconsoleflags(io.stdout, sys.getconsoleflags(io.stdout) + sys.COF_VIRTUAL_TERMINAL_PROCESSING)
+sys.setconsoleflags(io.stdin, sys.getconsoleflags(io.stdin) + sys.CIF_VIRTUAL_TERMINAL_INPUT)
+
+-- setup Posix terminal to use non-blocking mode, and disable line-mode
+local of_attr = sys.tcgetattr(io.stdin)
+local of_block = sys.getnonblock(io.stdin)
+sys.setnonblock(io.stdin, true)
+sys.tcsetattr(io.stdin, sys.TCSANOW, {
+  lflag = of_attr.lflag - sys.L_ICANON - sys.L_ECHO, -- disable canonical mode and echo
+})
+
+-- cursor sequences
+local get_cursor_pos = "\27[6n"
+
+
+
+local read_input do
+  local left_over_key
+
+  -- Reads a single key, if it is a 27 (start of ansi escape sequence) then it reads
+  -- the rest of the sequence.
+  -- This function is non-blocking, and will return nil if no key is available.
+  -- In case of an ANSI sequence, it will return the full sequence as a string.
+  -- @return nil|string the key read, or nil if no key is available
+  function read_input()
+    if left_over_key then
+      -- we still have a cached key, return it
+      local key = left_over_key
+      left_over_key = nil
+      return string.char(key)
+    end
+
+    local key = sys.readkey()
+    if key == nil then
+      return nil
+    end
+
+    if key ~= 27 then
+      return string.char(key)
+    end
+
+    -- looks like an ansi escape sequence, immediately read next char
+    -- as an heuristic against manually typing escape sequences
+    local brack = sys.readkey()
+    if brack ~= 91 then
+      -- not the expected [ character, so we return the key as is
+      -- and store the extra key read for the next call
+      left_over_key = brack
+      return string.char(key)
+    end
+
+    -- escape sequence detected, read the rest of the sequence
+    local seq = { key, brack }
+    while true do
+      key = sys.readkey()
+      table.insert(seq, key)
+      if (key >= 65 and key <= 90) or (key >= 97 and key <= 126) then
+        -- end of sequence, return the full sequence
+        return string.char((unpack or table.unpack)(seq))
+      end
+    end
+    -- unreachable
+  end
+end
+
+
+
+print("Press a key, or 'A' to get cursor position, 'ESC' to exit")
+while true do
+  local key
+
+  -- wait for a key, and sleep a bit to not do a busy-wait
+  while not key do
+    key = read_input()
+    if not key then sys.sleep(0.1) end
+  end
+
+  if key == "A" then io.write(get_cursor_pos); io.flush() end
+
+  -- check if we got a key or ANSI sequence
+  if #key == 1 then
+    -- just a key
+    local b = key:byte()
+    if b < 32 then
+      key = "." -- replace control characters with a simple "." to not mess up the screen
+    end
+
+    print("you pressed: " .. key .. " (" .. b .. ")")
+    if b == 27 then
+      print("Escape pressed, exiting")
+      break
+    end
+
+  else
+    -- we got an ANSI sequence
+    local seq = { key:byte(1, #key) }
+    print("ANSI sequence received: " .. key:sub(2,-1), "(bytes: " .. table.concat(seq, ", ")..")")
+  end
+end
+
+
+
+-- Clean up afterwards
+sys.setnonblock(io.stdin, false)
+sys.setconsoleflags(io.stdout, of_out)
+sys.setconsoleflags(io.stdin, of_in)
+sys.tcsetattr(io.stdin, sys.TCSANOW, of_attr)
+sys.setnonblock(io.stdin, of_block)