Bare metal VGA: support some VT100 escape sequences & UTF-8

The code is based on a pared-down version of the pty code
in tool/build/lib/pty.c.

It currently adds about 12 KiB to the size of the final
executable (compared to the earlier (simplistic) teletype
implementation).

Some terminal features, such as kTtyBell & kTtyNocursor,
are not yet implemented.

libc/vga/vga.internal.h

@@ -1,6 +1,58 @@
 #ifndef COSMOPOLITAN_LIBC_VGA_VGA_INTERNAL_H_
 #define COSMOPOLITAN_LIBC_VGA_VGA_INTERNAL_H_
 
+/*
+ * VGA_TTY_HEIGHT, VGA_TTY_WIDTH, & VGA_USE_WCS are configuration knobs
+ * which can potentially be used to tweak the features to be compiled into
+ * our VGA teletypewriter support.
+ */
+
+/**
+ * Height of the video screen, in character units.  Undefine if the height
+ * may vary at runtime.
+ */
+#define VGA_TTY_HEIGHT 25
+/**
+ * Width of the video screen, in character units.  Undefine if the width may
+ * vary at runtime.
+ */
+#define VGA_TTY_WIDTH 80
+/**
+ * If VGA_USE_WCS is defined, the tty code can maintain an array of the
+ * Unicode characters "underlying" the 8-bit (or 9-bit) characters that are
+ * actually displayed on the text screen.  This can be used to implement
+ * something similar to Linux's /dev/vcsu* facility.
+ *
+ * @see lkml.kernel.org/lkml/204888.1529277815@turing-police.cc.vt.edu/T/
+ */
+#undef VGA_USE_WCS
+
+#define kTtyFg      0x0001
+#define kTtyBg      0x0002
+#define kTtyBold    0x0004
+#define kTtyFlip    0x0008
+#define kTtyFaint   0x0010
+#define kTtyUnder   0x0020
+#define kTtyDunder  0x0040
+#define kTtyTrue    0x0080
+#define kTtyBlink   0x0100
+#define kTtyItalic  0x0200
+#define kTtyFraktur 0x0400
+#define kTtyStrike  0x0800
+#define kTtyConceal 0x1000
+
+#define kTtyBell        0x001
+#define kTtyRedzone     0x002
+#define kTtyNocursor    0x004
+#define kTtyBlinkcursor 0x008
+#define kTtyNocanon     0x010
+#define kTtyNoecho      0x020
+#define kTtyNoopost     0x040
+#define kTtyLed1        0x080
+#define kTtyLed2        0x100
+#define kTtyLed3        0x200
+#define kTtyLed4        0x400
+
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 #include "libc/calls/struct/fd.internal.h"
 #include "libc/calls/struct/iovec.h"
@@ -8,8 +60,59 @@
 
 COSMOPOLITAN_C_START_
 
+struct VgaTextCharCell {
+  uint8_t ch, attr;
+};
+
+struct Tty {
+  unsigned short y, x;
+#ifndef VGA_TTY_HEIGHT
+  unsigned short yn;
+#endif
+#ifndef VGA_TTY_WIDTH
+  unsigned short xn;
+#endif
+  uint32_t u8;
+  uint32_t n8;
+  uint32_t pr;
+  uint8_t fg, bg;
+  uint32_t conf;
+  unsigned short savey, savex;
+  struct VgaTextCharCell *ccs;
+#ifdef VGA_USE_WCS
+  wchar_t *wcs;
+#endif
+  wchar_t *xlat;
+  enum TtyState {
+    kTtyAscii,
+    kTtyUtf8,
+    kTtyEsc,
+    kTtyCsi,
+  } state;
+  struct TtyEsc {
+    unsigned i;
+    char s[64];
+  } esc;
+  struct TtyInput {
+    size_t i;
+    char p[256];
+  } input;
+};
+
+void _StartTty(struct Tty *, unsigned short, unsigned short,
+               unsigned short, unsigned short, void *, wchar_t *);
+ssize_t _TtyRead(struct Tty *, void *, size_t);
+ssize_t _TtyWrite(struct Tty *, const void *, size_t);
+ssize_t _TtyWriteInput(struct Tty *, const void *, size_t);
+void _TtyResetOutputMode(struct Tty *);
+void _TtyFullReset(struct Tty *);
+void _TtyMemmove(struct Tty *, size_t, size_t, size_t);
+void _TtyErase(struct Tty *, size_t, size_t);
+void _TtySetY(struct Tty *, unsigned short);
+void _TtySetX(struct Tty *, unsigned short);
+
 ssize_t sys_writev_vga(struct Fd *, const struct iovec *, int);
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
-#endif /* COSMOPOLITAN_LIBC_VGA_VGA_H_ */
+#endif /* COSMOPOLITAN_LIBC_VGA_VGA_INTERNAL_H_ */

libc/vga/writev-vga.c

@@ -31,105 +31,42 @@
 #include "libc/runtime/pc.internal.h"
 #include "libc/str/str.h"
 
-#define CRTPORT 0x3d4
+static struct Tty vga_tty;
-#define WIDTH 80
+#ifdef VGA_USE_WCS
-
+static wchar_t vga_wcs[VGA_TTY_HEIGHT * VGA_TTY_WIDTH];
-typedef struct {
+#else
-  char ch;
+static wchar_t * const vga_wcs = NULL;
-  uint8_t attr;
+#endif
-} char_cell_t;
-
-typedef char_cell_t char_row_t[WIDTH];
-
-static unsigned short height = 25, curr_row, curr_col;
-static uint8_t curr_attr = 0x07;
-
-static void scroll(void) {
-  unsigned j;
-  uint8_t attr = curr_attr;
-  char_row_t * const vid_buf = (char_row_t *)(BANE + 0xb8000ull);
-  memmove(vid_buf, vid_buf + 1, (height - 1) * sizeof(char_row_t));
-  for (j = 0; j < WIDTH; ++j)
-    vid_buf[height - 1][j] = (char_cell_t){ ' ', attr };
-}
-
-static void may_scroll(void) {
-  if (curr_col >= WIDTH) {
-    curr_col = 0;
-    scroll();
-  }
-}
-
-static void updatexy_vga(void) {
-  unsigned short pos = curr_row * WIDTH + curr_col;
-  outb(CRTPORT, 0x0e);
-  outb(CRTPORT + 1, (unsigned char)(pos >> 8));
-  outb(CRTPORT, 0x0f);
-  outb(CRTPORT + 1, (unsigned char)pos);
-}
-
-static void writec_vga(char c) {
-  /* TODO: handle UTF-8 multi-bytes */
-  /* TODO: handle VT102 escape sequences */
-  /* TODO: maybe make BEL (\a) character code emit an alarm of some sort */
-  char_row_t * const vid_buf = (char_row_t *)(BANE + 0xb8000ull);
-  uint8_t attr = curr_attr;
-  unsigned short col;
-  switch (c) {
-    case '\b':
-      if (curr_col) {
-        col = curr_col - 1;
-        vid_buf[curr_row][col] = (char_cell_t){ ' ', attr };
-        curr_col = col;
-      }
-      break;
-    case '\t':
-      col = curr_col;
-      do {
-        vid_buf[curr_row][col] = (char_cell_t){ ' ', attr };
-        ++col;
-      } while (col % 8 != 0);
-      curr_col = col;
-      may_scroll();
-      break;
-    case '\r':
-      curr_col = 0;
-      break;
-    case '\n':
-      curr_col = 0;
-      if (curr_row < height - 1)
-        ++curr_row;
-      else
-        scroll();
-      break;
-    default:
-      col = curr_col;
-      vid_buf[curr_row][col] = (char_cell_t){ c, attr };
-      curr_col = col + 1;
-      may_scroll();
-  }
-}
 
 ssize_t sys_writev_vga(struct Fd *fd, const struct iovec *iov, int iovlen) {
-  char_row_t * const vid_buf = (char_row_t *)(BANE + 0xb8000ull);
+  size_t i, wrote = 0;
-  size_t i, j, wrote = 0;
+  ssize_t res = 0;
   for (i = 0; i < iovlen; ++i) {
-    const char *input = (const char *)iov[i].iov_base;
+    void *input = iov[i].iov_base;
-    for (j = 0; j < iov[i].iov_len; ++j) {
+    size_t len = iov[i].iov_len;
-      writec_vga(input[j]);
+    res = _TtyWrite(&vga_tty, input, len);
-      ++wrote;
+    if (res < 0)
-    }
+      break;
+    wrote += res;
+    if (res != len)
+      return wrote;
   }
-  updatexy_vga();
+  if (!wrote)
+    return res;
   return wrote;
 }
 
 __attribute__((__constructor__)) static textstartup void _vga_init(void) {
+  void * const vid_buf = (void *)(BANE + 0xb8000ull);
   /* Get the initial cursor position from the BIOS data area. */
   typedef struct {
     unsigned char col, row;
   } bios_curs_pos_t;
   bios_curs_pos_t pos = *(bios_curs_pos_t *)(BANE + 0x0450ull);
-  curr_row = pos.row;
+  /*
-  curr_col = pos.col;
+   * Initialize our tty structure from the current screen contents & current
+   * cursor position.
+   */
+  _StartTty(&vga_tty, VGA_TTY_HEIGHT, VGA_TTY_WIDTH, pos.row, pos.col,
+            vid_buf, vga_wcs);
 }