Merge pull request #2914 from dunhamsteve/enableRawMode

[ base ] Support unbuffered reading of stdin

CHANGELOG.md

@@ -122,6 +122,8 @@
 * Adds `Vect.allFins` for generating all the `Fin` elements as a `Vect` with
   matching length to the number of elements.
 
+* Add `withRawMode`, `enableRawMode`, `resetRawMode` for character at a time input on stdin.
+
 #### System
 
 * Changes `getNProcessors` to return the number of online processors rather than

libs/base/System.idr

@@ -98,6 +98,47 @@ prim__setEnv : String -> String -> Int -> PrimIO Int
          supportNode "unsetEnv"
 prim__unsetEnv : String -> PrimIO Int
 
+%foreign "C:idris2_enableRawMode, libidris2_support, idris_support.h"
+prim__enableRawMode : (1 x : %World) -> IORes Int
+
+%foreign "C:idris2_resetRawMode, libidris2_support, idris_support.h"
+prim__resetRawMode : (1 x : %World) -> IORes ()
+
+||| `enableRawMode` enables raw mode for stdin, allowing characters
+||| to be read one at a time, without buffering or echoing.
+||| If `enableRawMode` is used, the program should call `resetRawMode` before
+||| exiting. Consider using `withRawMode` instead to ensure the tty is reset.
+|||
+||| This is not supported on windows.
+export
+enableRawMode : HasIO io => io (Either FileError ())
+enableRawMode =
+  case !(primIO prim__enableRawMode) of
+    0 => pure $ Right ()
+    _ => returnError
+
+||| `resetRawMode` resets stdin raw mode to original state if
+||| `enableRawMode` had been previously called.
+export
+resetRawMode : HasIO io => io ()
+resetRawMode = primIO prim__resetRawMode
+
+||| `withRawMode` performs a given operation after setting stdin to raw mode
+||| and ensure that stdin is reset to its original state afterwards.
+|||
+||| This is not supported on windows.
+export
+withRawMode : HasIO io =>
+              (onError   : FileError -> io a) ->
+              (onSuccess : () -> io a) ->
+              io a
+withRawMode onError onSuccess = do
+  Right () <- enableRawMode
+    | Left err => onError err
+  result <- onSuccess ()
+  resetRawMode
+  pure result
+
 ||| Retrieve the specified environment variable's value string, or `Nothing` if
 ||| there is no such environment variable.
 |||

support/c/idris_support.c

@@ -5,6 +5,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#ifndef _WIN32
+#include <termios.h>
+#endif
 #include <time.h>
 #include <unistd.h>
 
@@ -98,6 +101,36 @@ int idris2_setenv(const char *name, const char *value, int overwrite) {
 #endif
 }
 
+#ifndef _WIN32
+// The initial state of stdin is stored here if enableRawMode is called.
+struct termios *initial_termios = NULL;
+#endif
+
+int idris2_enableRawMode() {
+#ifndef _WIN32
+  struct termios ti;
+  int rval = tcgetattr(STDIN_FILENO, &ti);
+  if (rval != 0)
+    return rval;
+  if (!initial_termios) {
+    initial_termios = malloc(sizeof(struct termios));
+    *initial_termios = ti;
+  }
+  ti.c_lflag &= ~(ECHO | ICANON);
+  return tcsetattr(STDIN_FILENO, TCSAFLUSH, &ti);
+#else
+  return -1;
+#endif
+}
+
+void idris2_resetRawMode() {
+#ifndef _WIN32
+  if (initial_termios != NULL) {
+    tcsetattr(STDIN_FILENO, TCSAFLUSH, initial_termios);
+  }
+#endif
+}
+
 int idris2_unsetenv(const char *name) {
 #ifdef _WIN32
   return win32_modenv(name, "", 1);