Introduce ui_file_style

This introduces the new ui_file_style class and various helpers.  This
class represents a terminal style and provides methods for parsing and
emitting the corresponding ANSI terminal escape sequences.

gdb/ChangeLog
2018-12-28  Tom Tromey  <tom@tromey.com>

	* unittests/style-selftests.c: New file.
	* ui-style.c: New file.
	* ui-style.h: New file.
	* ui-file.h: Include ui-style.h.
	* Makefile.in (COMMON_SFILES): Add ui-style.c.
	(HFILES_NO_SRCDIR): Add ui-style.h.
	(SUBDIR_UNITTESTS_SRCS): Add style-selftests.c.

1 files changed, 413 insertions, 0 deletions

diff --git a/gdb/ui-style.c b/gdb/ui-style.c
new file mode 100644
index 0000000..059824f
--- /dev/null
+++ b/gdb/ui-style.c
@@ -0,0 +1,413 @@
+/* Styling for ui_file
+   Copyright (C) 2018 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "ui-style.h"
+
+/* A regular expression that is used for matching ANSI terminal escape
+   sequences.  */
+
+static const char *ansi_regex_text =
+  /* Introduction.  */
+  "^\033\\["
+#define DATA_SUBEXP 1
+  /* Capture parameter and intermediate bytes.  */
+  "("
+  /* Parameter bytes.  */
+  "[\x30-\x3f]*"
+  /* Intermediate bytes.  */
+  "[\x20-\x2f]*"
+  /* End the first capture.  */
+  ")"
+  /* The final byte.  */
+#define FINAL_SUBEXP 2
+  "([\x40-\x7e])";
+
+/* The number of subexpressions to allocate space for, including the
+   "0th" whole match subexpression.  */
+#define NUM_SUBEXPRESSIONS 3
+
+/* The compiled form of ansi_regex_text.  */
+
+static regex_t ansi_regex;
+
+/* This maps bright colors to RGB triples.  The index is the bright
+   color index, starting with bright black.  The values come from
+   xterm.  */
+
+static const uint8_t bright_colors[][3] = {
+  { 127, 127, 127 },		/* Black.  */
+  { 255, 0, 0 },		/* Red.  */
+  { 0, 255, 0 },		/* Green.  */
+  { 255, 255, 0 },		/* Yellow.  */
+  { 92, 92, 255 },		/* Blue.  */
+  { 255, 0, 255 },		/* Magenta.  */
+  { 0, 255, 255 },		/* Cyan.  */
+  { 255, 255, 255 }		/* White.  */
+};
+
+/* See ui-style.h.  */
+
+bool
+ui_file_style::color::append_ansi (bool is_fg, std::string *str) const
+{
+  if (m_simple)
+    {
+      if (m_value >= BLACK && m_value <= WHITE)
+	str->append (std::to_string (m_value + (is_fg ? 30 : 40)));
+      else if (m_value > WHITE && m_value <= WHITE + 8)
+	str->append (std::to_string (m_value - WHITE + (is_fg ? 90 : 100)));
+      else if (m_value != -1)
+	{
+	  str->append (is_fg ? "38;5;" : "48;5;");
+	  str->append (std::to_string (m_value));
+	}
+      else
+	return false;
+    }
+  else
+    {
+      str->append (is_fg ? "38;2;" : "48;2;");
+      str->append (std::to_string (m_red)
+		   + ";" + std::to_string (m_green)
+		   + ";" + std::to_string (m_blue));
+    }
+  return true;
+}
+
+/* See ui-style.h.  */
+
+void
+ui_file_style::color::get_rgb (uint8_t *rgb) const
+{
+  if (m_simple)
+    {
+      /* Can't call this for a basic color or NONE -- those will end
+	 up in the assert below.  */
+      if (m_value >= 8 && m_value <= 15)
+	memcpy (rgb, bright_colors[m_value - 8], 3 * sizeof (uint8_t));
+      else if (m_value >= 16 && m_value <= 231)
+	{
+	  int value = m_value;
+	  value -= 16;
+	  /* This obscure formula seems to be what terminals actually
+	     do.  */
+	  int component = value / 36;
+	  rgb[0] = component == 0 ? 0 : (55 + component * 40);
+	  value %= 36;
+	  component = value / 6;
+	  rgb[1] = component == 0 ? 0 : (55 + component * 40);
+	  value %= 6;
+	  rgb[2] = value == 0 ? 0 : (55 + value * 40);
+	}
+      else if (m_value >= 232)
+	{
+	  uint8_t v = (m_value - 232) * 10 + 8;
+	  rgb[0] = v;
+	  rgb[1] = v;
+	  rgb[2] = v;
+	}
+      else
+	gdb_assert_not_reached ("get_rgb called on invalid color");
+    }
+  else
+    {
+      rgb[0] = m_red;
+      rgb[1] = m_green;
+      rgb[2] = m_blue;
+    }
+}
+
+/* See ui-style.h.  */
+
+std::string
+ui_file_style::to_ansi () const
+{
+  std::string result ("\033[");
+  bool need_semi = m_foreground.append_ansi (true, &result);
+  if (!m_background.is_none ())
+    {
+      if (need_semi)
+	result.push_back (';');
+      m_background.append_ansi (false, &result);
+      need_semi = true;
+    }
+  if (m_intensity != NORMAL)
+    {
+      if (need_semi)
+	result.push_back (';');
+      result.append (std::to_string (m_intensity));
+      need_semi = true;
+    }
+  if (m_reverse)
+    {
+      if (need_semi)
+	result.push_back (';');
+      result.push_back ('7');
+    }
+  result.push_back ('m');
+  return result;
+}
+
+/* Read a ";" and a number from STRING.  Return the number of
+   characters read and put the number into *NUM.  */
+
+static bool
+read_semi_number (const char *string, int *idx, long *num)
+{
+  if (string[*idx] != ';')
+    return false;
+  ++*idx;
+  if (string[*idx] < '0' || string[*idx] > '9')
+    return false;
+  char *tail;
+  *num = strtol (string + *idx, &tail, 10);
+  *idx = tail - string;
+  return true;
+}
+
+/* A helper for ui_file_style::parse that reads an extended color
+   sequence; that is, and 8- or 24- bit color.  */
+
+static bool
+extended_color (const char *str, int *idx, ui_file_style::color *color)
+{
+  long value;
+
+  if (!read_semi_number (str, idx, &value))
+    return false;
+
+  if (value == 5)
+    {
+      /* 8-bit color.  */
+      if (!read_semi_number (str, idx, &value))
+	return false;
+
+      if (value >= 0 && value <= 255)
+	*color = ui_file_style::color (value);
+      else
+	return false;
+    }
+  else if (value == 2)
+    {
+      /* 24-bit color.  */
+      long r, g, b;
+      if (!read_semi_number (str, idx, &r)
+	  || r > 255
+	  || !read_semi_number (str, idx, &g)
+	  || g > 255
+	  || !read_semi_number (str, idx, &b)
+	  || b > 255)
+	return false;
+      *color = ui_file_style::color (r, g, b);
+    }
+  else
+    {
+      /* Unrecognized sequence.  */
+      return false;
+    }
+
+  return true;
+}
+
+/* See ui-style.h.  */
+
+bool
+ui_file_style::parse (const char *buf, size_t *n_read)
+{
+  regmatch_t subexps[NUM_SUBEXPRESSIONS];
+
+  int match = regexec (&ansi_regex, buf, ARRAY_SIZE (subexps), subexps, 0);
+  if (match == REG_NOMATCH)
+    {
+      *n_read = 0;
+      return false;
+    }
+  /* Other failures mean the regexp is broken.  */
+  gdb_assert (match == 0);
+  /* The regexp is anchored.  */
+  gdb_assert (subexps[0].rm_so == 0);
+  /* The final character exists.  */
+  gdb_assert (subexps[FINAL_SUBEXP].rm_eo - subexps[FINAL_SUBEXP].rm_so == 1);
+
+  if (buf[subexps[FINAL_SUBEXP].rm_so] != 'm')
+    {
+      /* We don't handle this sequence, so just drop it.  */
+      *n_read = subexps[0].rm_eo;
+      return false;
+    }
+
+  /* Examine each setting in the match and apply it to the result.
+     See the Select Graphic Rendition section of
+     https://en.wikipedia.org/wiki/ANSI_escape_code.  In essence each
+     code is just a number, separated by ";"; there are some more
+     wrinkles but we don't support them all..  */
+
+  /* "\033[m" means the same thing as "\033[0m", so handle that
+     specially here.  */
+  if (subexps[DATA_SUBEXP].rm_so == subexps[DATA_SUBEXP].rm_eo)
+    *this = ui_file_style ();
+
+  for (regoff_t i = subexps[DATA_SUBEXP].rm_so;
+       i < subexps[DATA_SUBEXP].rm_eo;
+       ++i)
+    {
+      if (buf[i] == ';')
+	{
+	  /* Skip.  */
+	}
+      else if (buf[i] >= '0' && buf[i] <= '9')
+	{
+	  char *tail;
+	  long value = strtol (buf + i, &tail, 10);
+	  i = tail - buf;
+
+	  switch (value)
+	    {
+	    case 0:
+	      /* Reset.  */
+	      *this = ui_file_style ();
+	      break;
+	    case 1:
+	      /* Bold.  */
+	      m_intensity = BOLD;
+	      break;
+	    case 2:
+	      /* Dim.  */
+	      m_intensity = DIM;
+	      break;
+	    case 7:
+	      /* Reverse.  */
+	      m_reverse = true;
+	      break;
+	    case 21:
+	      m_intensity = NORMAL;
+	      break;
+	    case 22:
+	      /* Normal.  */
+	      m_intensity = NORMAL;
+	      break;
+	    case 27:
+	      /* Inverse off.  */
+	      m_reverse = false;
+	      break;
+
+	    case 30:
+	    case 31:
+	    case 32:
+	    case 33:
+	    case 34:
+	    case 35:
+	    case 36:
+	    case 37:
+	      /* Note: not 38.  */
+	    case 39:
+	      m_foreground = color (value - 30);
+	      break;
+
+	    case 40:
+	    case 41:
+	    case 42:
+	    case 43:
+	    case 44:
+	    case 45:
+	    case 46:
+	    case 47:
+	      /* Note: not 48.  */
+	    case 49:
+	      m_background = color (value - 40);
+	      break;
+
+	    case 90:
+	    case 91:
+	    case 92:
+	    case 93:
+	    case 94:
+	    case 95:
+	    case 96:
+	    case 97:
+	      m_foreground = color (value - 90 + 8);
+	      break;
+
+	    case 100:
+	    case 101:
+	    case 102:
+	    case 103:
+	    case 104:
+	    case 105:
+	    case 106:
+	    case 107:
+	      m_background = color (value - 100 + 8);
+	      break;
+
+	    case 38:
+	      /* If we can't parse the extended color, fail.  */
+	      if (!extended_color (buf, &i, &m_foreground))
+		{
+		  *n_read = subexps[0].rm_eo;
+		  return false;
+		}
+	      break;
+
+	    case 48:
+	      /* If we can't parse the extended color, fail.  */
+	      if (!extended_color (buf, &i, &m_background))
+		{
+		  *n_read = subexps[0].rm_eo;
+		  return false;
+		}
+	      break;
+
+	    default:
+	      /* Ignore everything else.  */
+	      break;
+	    }
+	}
+      else
+	{
+	  /* Unknown, let's just ignore.  */
+	}
+    }
+
+  *n_read = subexps[0].rm_eo;
+  return true;
+}
+
+/* See ui-style.h.  */
+
+bool
+skip_ansi_escape (const char *buf, int *n_read)
+{
+  regmatch_t subexps[NUM_SUBEXPRESSIONS];
+
+  int match = regexec (&ansi_regex, buf, ARRAY_SIZE (subexps), subexps, 0);
+  if (match == REG_NOMATCH || buf[subexps[FINAL_SUBEXP].rm_so] != 'm')
+    return false;
+
+  *n_read = subexps[FINAL_SUBEXP].rm_eo;
+  return true;
+}
+
+void
+_initialize_ui_style ()
+{
+  int code = regcomp (&ansi_regex, ansi_regex_text, REG_EXTENDED);
+  /* If the regular expression was incorrect, it was a programming
+     error.  */
+  gdb_assert (code == 0);
+}