Improve Windows Console I/O

- Blocking read operations on the Windows Console can now EINTR
- Blocking read operations on Windows pipes now EINTR more reliably
- setitimer() will no longer be inherited across fork() on Windows
- It's now possible to use ECHO when the console is in raw mode
- The ECHOCTL flag now works correctly on the Windows Console
- The ICRNL flag now works correctly on the Windows Console
- pread() and pwrite() will now raise ESPIPE on Windows
- Opening /dev/tty on Windows is improved (untested)
- Overlapped I/O is now implemented in a better way

libc/calls/tcsetattr-nt.c

@@ -29,57 +29,86 @@
 #include "libc/sysv/consts/termios.h"
 #include "libc/sysv/errfuns.h"
 
-textwindows int tcsetattr_nt(int ignored, int opt, const struct termios *tio) {
-  int64_t in, out;
-  bool32 ok, inok, outok;
+textwindows int tcsetattr_nt(int fd, int opt, const struct termios *tio) {
+  bool32 ok;
+  int ttymagic;
+  int64_t hInput, hOutput;
   uint32_t inmode, outmode;
-  inok = GetConsoleMode((in = __getfdhandleactual(0)), &inmode);
-  outok = GetConsoleMode((out = __getfdhandleactual(1)), &outmode);
-  if (inok | outok) {
+  if (__isfdkind(fd, kFdConsole)) {
+    // program manually opened /dev/tty in O_RDWR mode for cmd.exe
+    hInput = g_fds.p[fd].handle;
+    hOutput = g_fds.p[fd].extra;
+  } else if (fd == 0 || fd == 1) {
+    // otherwise just assume cmd.exe console stdio
+    // there's no serial port support yet
+    hInput = g_fds.p[0].handle;
+    hOutput = g_fds.p[1].handle;
+    fd = 0;
+  } else {
+    STRACE("tcsetattr(fd) must be 0, 1, or open'd /dev/tty");
+    return enotty();
+  }
+  if (GetConsoleMode(hInput, &inmode) && GetConsoleMode(hOutput, &outmode)) {
 
-    if (inok) {
-      if (opt == TCSAFLUSH) {
-        FlushConsoleInputBuffer(in);
+    if (opt == TCSAFLUSH) {
+      FlushConsoleInputBuffer(hInput);
+    }
+    inmode &=
+        ~(kNtEnableLineInput | kNtEnableEchoInput | kNtEnableProcessedInput);
+    inmode |= kNtEnableWindowInput;
+    ttymagic = 0;
+    if (tio->c_lflag & ICANON) {
+      inmode |= kNtEnableLineInput;
+    } else {
+      ttymagic |= kFdTtyMunging;
+      if (tio->c_cc[VMIN] != 1) {
+        STRACE("tcsetattr c_cc[VMIN] must be 1 on Windows");
+        return einval();
       }
-      inmode &=
-          ~(kNtEnableLineInput | kNtEnableEchoInput | kNtEnableProcessedInput);
-      inmode |= kNtEnableWindowInput;
+    }
+    if (!(tio->c_iflag & ICRNL)) {
+      ttymagic |= kFdTtyNoCr2Nl;
+    }
+    if (!(tio->c_lflag & ECHOCTL)) {
+      ttymagic |= kFdTtyEchoRaw;
+    }
+    if (tio->c_lflag & ECHO) {
+      // "kNtEnableEchoInput can be used only if the
+      //  kNtEnableLineInput mode is also enabled." -MSDN
       if (tio->c_lflag & ICANON) {
-        inmode |= kNtEnableLineInput;
+        inmode |= kNtEnableEchoInput;
+      } else {
+        // If ECHO is enabled in raw mode, then read(0) needs to
+        // magically write(1) to simulate echoing. This normally
+        // visualizes control codes, e.g. \r → ^M unless ECHOCTL
+        // hasn't been specified.
+        ttymagic |= kFdTtyEchoing;
       }
-      if (tio->c_lflag & ECHO) {
-        /*
-         * kNtEnableEchoInput can be used only if the ENABLE_LINE_INPUT mode
-         * is also enabled. --Quoth MSDN
-         */
-        inmode |= kNtEnableEchoInput | kNtEnableLineInput;
-      }
-      if (tio->c_lflag & (IEXTEN | ISIG)) {
-        inmode |= kNtEnableProcessedInput;
-      }
-      if (IsAtLeastWindows10()) {
-        inmode |= kNtEnableVirtualTerminalInput;
-      }
-      ok = SetConsoleMode(in, inmode);
-      (void)ok;
-      NTTRACE("SetConsoleMode(%p, %s) → %hhhd", in,
-              DescribeNtConsoleInFlags(inmode), ok);
     }
+    if (tio->c_lflag & (IEXTEN | ISIG)) {
+      inmode |= kNtEnableProcessedInput;
+    }
+    if (IsAtLeastWindows10()) {
+      inmode |= kNtEnableVirtualTerminalInput;
+    }
+    g_fds.p[fd].ttymagic = ttymagic;
+    ok = SetConsoleMode(hInput, inmode);
+    (void)ok;
+    NTTRACE("SetConsoleMode(%p, %s) → %hhhd", hInput,
+            DescribeNtConsoleInFlags(inmode), ok);
 
-    if (outok) {
-      outmode &= ~(kNtDisableNewlineAutoReturn);
-      outmode |= kNtEnableProcessedOutput;
-      if (!(tio->c_oflag & ONLCR)) {
-        outmode |= kNtDisableNewlineAutoReturn;
-      }
-      if (IsAtLeastWindows10()) {
-        outmode |= kNtEnableVirtualTerminalProcessing;
-      }
-      ok = SetConsoleMode(out, outmode);
-      (void)ok;
-      NTTRACE("SetConsoleMode(%p, %s) → %hhhd", out,
-              DescribeNtConsoleOutFlags(outmode), ok);
+    outmode &= ~kNtDisableNewlineAutoReturn;
+    outmode |= kNtEnableProcessedOutput;
+    if (!(tio->c_oflag & ONLCR)) {
+      outmode |= kNtDisableNewlineAutoReturn;
     }
+    if (IsAtLeastWindows10()) {
+      outmode |= kNtEnableVirtualTerminalProcessing;
+    }
+    ok = SetConsoleMode(hOutput, outmode);
+    (void)ok;
+    NTTRACE("SetConsoleMode(%p, %s) → %hhhd", hOutput,
+            DescribeNtConsoleOutFlags(outmode), ok);
 
     return 0;
   } else {