Bare metal VGA: implement "status report" escape codes (#613)

* Bare metal VGA: implement "status report" escape codes
* Minor fix to pseudoteletypewriter code

Co-authored-by: tkchia <tkchia-cosmo@gmx.com>

examples/hello4.c

@@ -8,13 +8,30 @@
 ╚─────────────────────────────────────────────────────────────────*/
 #endif
 #include "libc/math.h"
+#include "libc/calls/termios.h"
+#include "libc/isystem/unistd.h"
+#include "libc/str/str.h"
 #include "libc/stdio/stdio.h"
+#include "libc/sysv/consts/termios.h"
 
 STATIC_YOINK("vga_console");
 
 int main(int argc, char *argv[]) {
   volatile long double x = -.5;
   volatile long double y = 1.5;
+  struct termios tio;
+  char buf[4];
+  ssize_t res;
+  if (tcgetattr(0, &tio) != -1) {
+    tio.c_lflag &= ~(ECHO | ICANON);
+    tcsetattr(0, TCSANOW, &tio);
+  }
+  write(1, "\e[5n", 4);
+  res = read(0, buf, 4);
+  if (res != 4 || memcmp(buf, "\e[0n", 4) != 0) {
+    printf("res = %d?\n", res);
+    return -1;
+  }
   printf("Hello World! %.19Lg\n", atan2l(x, y));
   return 0;
 }

libc/calls/readv-metal.c

@@ -20,15 +20,29 @@
 #include "libc/calls/struct/fd.internal.h"
 #include "libc/calls/struct/iovec.h"
 #include "libc/calls/struct/iovec.internal.h"
+#include "libc/intrin/weaken.h"
 #include "libc/macros.internal.h"
 #include "libc/str/str.h"
 #include "libc/sysv/errfuns.h"
+#include "libc/vga/vga.internal.h"
 
 ssize_t sys_readv_metal(struct Fd *fd, const struct iovec *iov, int iovlen) {
   int i;
   size_t got, toto;
   struct MetalFile *file;
   switch (fd->kind) {
+    case kFdConsole:
+      /*
+       * The VGA teletypewriter code may wish to send out "status report"
+       * escape sequences, in response to requests sent to it via write().
+       * Read & return these if they are available.
+       */
+      if (weaken(sys_readv_vga)) {
+        ssize_t res = weaken(sys_readv_vga)(fd, iov, iovlen);
+        if (res > 0)
+          return res;
+      }
+      /* fall through */
     case kFdSerial:
       return sys_readv_serial(fd, iov, iovlen);
     case kFdFile:

libc/vga/readv-vga.c

@@ -0,0 +1,49 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ This is free and unencumbered software released into the public domain.      │
+│                                                                              │
+│ Anyone is free to copy, modify, publish, use, compile, sell, or              │
+│ distribute this software, either in source code form or as a compiled        │
+│ binary, for any purpose, commercial or non-commercial, and by any            │
+│ means.                                                                       │
+│                                                                              │
+│ In jurisdictions that recognize copyright laws, the author or authors        │
+│ of this software dedicate any and all copyright interest in the              │
+│ software to the public domain. We make this dedication for the benefit       │
+│ of the public at large and to the detriment of our heirs and                 │
+│ successors. We intend this dedication to be an overt act of                  │
+│ relinquishment in perpetuity of all present and future rights to this        │
+│ software under copyright law.                                                │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,              │
+│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF           │
+│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.       │
+│ IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR            │
+│ OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,        │
+│ ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR        │
+│ OTHER DEALINGS IN THE SOFTWARE.                                              │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/struct/fd.internal.h"
+#include "libc/calls/struct/iovec.h"
+#include "libc/calls/struct/iovec.internal.h"
+#include "libc/vga/vga.internal.h"
+
+ssize_t sys_readv_vga(struct Fd *fd, const struct iovec *iov, int iovlen) {
+  /* NOTE: this routine is always non-blocking. */
+  size_t i, redd = 0;
+  ssize_t res = 0;
+  for (i = 0; i < iovlen; ++i) {
+    void *input = iov[i].iov_base;
+    size_t len = iov[i].iov_len;
+    res = _TtyRead(&_vga_tty, input, len);
+    if (res < 0)
+      break;
+    redd += res;
+    if (redd != len)
+      return redd;
+  }
+  if (!redd)
+    return res;
+  return redd;
+}

libc/vga/tty.c

@@ -536,15 +536,18 @@ static void TtyDeleteLines(struct Tty *tty) {
 }
 
 static void TtyReportDeviceStatus(struct Tty *tty) {
-  _TtyWriteInput(tty, "\e[0n", 4);
+  static const char report[] = "\e[0n";
+  _TtyWriteInput(tty, report, strlen(report));
 }
 
 static void TtyReportPreferredVtType(struct Tty *tty) {
-  _TtyWriteInput(tty, "\e[?1;0c", 4);
+  static const char report[] = "\e[?1;0c";
+  _TtyWriteInput(tty, report, strlen(report));
 }
 
 static void TtyReportPreferredVtIdentity(struct Tty *tty) {
-  _TtyWriteInput(tty, "\e/Z", 4);
+  static const char report[] = "\e/Z";
+  _TtyWriteInput(tty, report, strlen(report));
 }
 
 static void TtyBell(struct Tty *tty) {
@@ -1148,9 +1151,11 @@ ssize_t _TtyWriteInput(struct Tty *tty, const void *data, size_t n) {
   if (cr && i < sizeof tty->input.p) {
     p[i++] = '\n';
   }
+#ifdef VGA_PERSNICKETY_STATUS
   if (!(tty->conf & kTtyNoecho)) {
     _TtyWrite(tty, p + tty->input.i, i - tty->input.i);
   }
+#endif
   tty->input.i = i;
   return n;
 }
@@ -1159,6 +1164,7 @@ ssize_t _TtyRead(struct Tty *tty, void *buf, size_t size) {
   char *p;
   size_t n;
   n = MIN(size, tty->input.i);
+#ifdef VGA_PERSNICKETY_STATUS
   if (!(tty->conf & kTtyNocanon)) {
     if ((p = memchr(tty->input.p, '\n', n))) {
       n = MIN(n, tty->input.p - p + 1);
@@ -1166,6 +1172,7 @@ ssize_t _TtyRead(struct Tty *tty, void *buf, size_t size) {
       n = 0;
     }
   }
+#endif
   memcpy(buf, tty->input.p, n);
   memcpy(tty->input.p, tty->input.p + n, tty->input.i - n);
   tty->input.i -= n;

libc/vga/vga-init.S

@@ -72,3 +72,4 @@ vga_console:
 	.endobj	vga_console,globl,hidden
 	.previous
 	.yoink	sys_writev_vga
+	.yoink	sys_readv_vga

libc/vga/vga.internal.h

@@ -60,6 +60,14 @@
  *      (https://www.delorie.com/djgpp/doc/rbinter/id/22/1.html)
  */
 #undef VGA_USE_BLINK
+/**
+ * If VGA_PERSNICKETY_STATUS is defined, then when deciding how to return
+ * status response codes (e.g. "\e[0n"), the tty code will pay attention to
+ * the terminal's termios mode (TODO).  If undefined, the tty code will
+ * simply return any response strings immediately, & will not echo them —
+ * per the common use case.
+ */
+#undef VGA_PERSNICKETY_STATUS
 
 #define kTtyFg      0x0001
 #define kTtyBg      0x0002
@@ -146,6 +154,9 @@ void _TtyErase(struct Tty *, size_t, size_t);
 void _TtySetY(struct Tty *, unsigned short);
 void _TtySetX(struct Tty *, unsigned short);
 
+extern struct Tty _vga_tty;
+
+ssize_t sys_readv_vga(struct Fd *, const struct iovec *, int);
 ssize_t sys_writev_vga(struct Fd *, const struct iovec *, int);
 
 COSMOPOLITAN_C_END_

libc/vga/writev-vga.c

@@ -31,20 +31,21 @@
 #include "libc/runtime/pc.internal.h"
 #include "libc/str/str.h"
 
-static struct Tty vga_tty;
 #ifdef VGA_USE_WCS
 static wchar_t vga_wcs[VGA_TTY_HEIGHT * VGA_TTY_WIDTH];
 #else
 static wchar_t * const vga_wcs = NULL;
 #endif
 
+struct Tty _vga_tty;
+
 ssize_t sys_writev_vga(struct Fd *fd, const struct iovec *iov, int iovlen) {
   size_t i, wrote = 0;
   ssize_t res = 0;
   for (i = 0; i < iovlen; ++i) {
-    void *input = iov[i].iov_base;
+    void *output = iov[i].iov_base;
     size_t len = iov[i].iov_len;
-    res = _TtyWrite(&vga_tty, input, len);
+    res = _TtyWrite(&_vga_tty, output, len);
     if (res < 0)
       break;
     wrote += res;
@@ -75,6 +76,6 @@ __attribute__((__constructor__)) static textstartup void _vga_init(void) {
    * Initialize our tty structure from the current screen contents, current
    * cursor position, & character height.
    */
-  _StartTty(&vga_tty, VGA_TTY_HEIGHT, VGA_TTY_WIDTH, pos.row, pos.col,
+  _StartTty(&_vga_tty, VGA_TTY_HEIGHT, VGA_TTY_WIDTH, pos.row, pos.col,
             chr_ht, vid_buf, vga_wcs);
 }

tool/build/lib/pty.c

@@ -641,15 +641,18 @@ static void PtyDeleteLines(struct Pty *pty) {
 }
 
 static void PtyReportDeviceStatus(struct Pty *pty) {
-  PtyWriteInput(pty, "\e[0n", 4);
+  static const char report[] = "\e[0n";
+  PtyWriteInput(pty, report, strlen(report));
 }
 
 static void PtyReportPreferredVtType(struct Pty *pty) {
-  PtyWriteInput(pty, "\e[?1;0c", 4);
+  static const char report[] = "\e[?1;0c";
+  PtyWriteInput(pty, report, strlen(report));
 }
 
 static void PtyReportPreferredVtIdentity(struct Pty *pty) {
-  PtyWriteInput(pty, "\e/Z", 4);
+  static const char report[] = "\e/Z";
+  PtyWriteInput(pty, report, strlen(report));
 }
 
 static void PtyBell(struct Pty *pty) {