gdb/ui-file.h

   1 /* UI_FILE - a generic STDIO like output stream.
   2    Copyright (C) 1999-2019 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef UI_FILE_H
  20 #define UI_FILE_H
  21
  22 #include <string>
  23 #include "ui-style.h"
  24
  25 /* The abstract ui_file base class.  */
  26
  27 class ui_file
  28 {
  29 public:
  30   ui_file ();
  31   virtual ~ui_file () = 0;
  32
  33   /* Public non-virtual API.  */
  34
  35   void printf (const char *, ...) ATTRIBUTE_PRINTF (2, 3);
  36
  37   /* Print a string whose delimiter is QUOTER.  Note that these
  38      routines should only be called for printing things which are
  39      independent of the language of the program being debugged.  */
  40   void putstr (const char *str, int quoter);
  41
  42   void putstrn (const char *str, int n, int quoter);
  43
  44   int putc (int c);
  45
  46   void vprintf (const char *, va_list) ATTRIBUTE_PRINTF (2, 0);
  47
  48   /* Methods below are both public, and overridable by ui_file
  49      subclasses.  */
  50
  51   virtual void write (const char *buf, long length_buf) = 0;
  52
  53   /* This version of "write" is safe for use in signal handlers.  It's
  54      not guaranteed that all existing output will have been flushed
  55      first.  Implementations are also free to ignore some or all of
  56      the request.  puts_async is not provided as the async versions
  57      are rarely used, no point in having both for a rarely used
  58      interface.  */
  59   virtual void write_async_safe (const char *buf, long length_buf)
  60   { gdb_assert_not_reached ("write_async_safe"); }
  61
  62   /* Some ui_files override this to provide a efficient implementation
  63      that avoids a strlen.  */
  64   virtual void puts (const char *str)
  65   { this->write (str, strlen (str)); }
  66
  67   virtual long read (char *buf, long length_buf)
  68   { gdb_assert_not_reached ("can't read from this file type"); }
  69
  70   virtual bool isatty ()
  71   { return false; }
  72
  73   /* true indicates terminal output behaviour such as cli_styling.
  74      This default implementation indicates to do terminal output
  75      behaviour if the UI_FILE is a tty.  A derived class can override
  76      TERM_OUT to have cli_styling behaviour without being a tty.  */
  77   virtual bool term_out ()
  78   { return isatty (); }
  79
  80   /* true if ANSI escapes can be used on STREAM.  */
  81   virtual bool can_emit_style_escape ()
  82   { return false; }
  83
  84   virtual void flush ()
  85   {}
  86 };
  87
  88 typedef std::unique_ptr<ui_file> ui_file_up;
  89
  90 /* A ui_file that writes to nowhere.  */
  91
  92 class null_file : public ui_file
  93 {
  94 public:
  95   void write (const char *buf, long length_buf) override;
  96   void write_async_safe (const char *buf, long sizeof_buf) override;
  97   void puts (const char *str) override;
  98 };
  99
 100 /* A preallocated null_file stream.  */
 101 extern null_file null_stream;
 102
 103 extern void gdb_flush (ui_file *);
 104
 105 extern int ui_file_isatty (struct ui_file *);
 106
 107 extern void ui_file_write (struct ui_file *file, const char *buf,
 108                            long length_buf);
 109
 110 extern void ui_file_write_async_safe (struct ui_file *file, const char *buf,
 111                                       long length_buf);
 112
 113 extern long ui_file_read (struct ui_file *file, char *buf, long length_buf);
 114
 115 extern int gdb_console_fputs (const char *, FILE *);
 116
 117 /* A std::string-based ui_file.  Can be used as a scratch buffer for
 118    collecting output.  */
 119
 120 class string_file : public ui_file
 121 {
 122 public:
 123   /* Construct a string_file to collect 'raw' output, i.e. without
 124      'terminal' behaviour such as cli_styling.  */
 125   string_file () : m_term_out (false) {};
 126   /* If TERM_OUT, construct a string_file with terminal output behaviour
 127      such as cli_styling)
 128      else collect 'raw' output like the previous constructor.  */
 129   explicit string_file (bool term_out) : m_term_out (term_out) {};
 130   ~string_file () override;
 131
 132   /* Override ui_file methods.  */
 133
 134   void write (const char *buf, long length_buf) override;
 135
 136   long read (char *buf, long length_buf) override
 137   { gdb_assert_not_reached ("a string_file is not readable"); }
 138
 139   bool term_out () override;
 140   bool can_emit_style_escape () override;
 141
 142   /* string_file-specific public API.  */
 143
 144   /* Accesses the std::string containing the entire output collected
 145      so far.
 146
 147      Returns a non-const reference so that it's easy to move the
 148      string contents out of the string_file.  E.g.:
 149
 150       string_file buf;
 151       buf.printf (....);
 152       buf.printf (....);
 153       return std::move (buf.string ());
 154   */
 155   std::string &string () { return m_string; }
 156
 157   /* Provide a few convenience methods with the same API as the
 158      underlying std::string.  */
 159   const char *data () const { return m_string.data (); }
 160   const char *c_str () const { return m_string.c_str (); }
 161   size_t size () const { return m_string.size (); }
 162   bool empty () const { return m_string.empty (); }
 163   void clear () { return m_string.clear (); }
 164
 165 private:
 166   /* The internal buffer.  */
 167   std::string m_string;
 168
 169   bool m_term_out;
 170 };
 171
 172 /* A ui_file implementation that maps directly onto <stdio.h>'s FILE.
 173    A stdio_file can either own its underlying file, or not.  If it
 174    owns the file, then destroying the stdio_file closes the underlying
 175    file, otherwise it is left open.  */
 176
 177 class stdio_file : public ui_file
 178 {
 179 public:
 180   /* Create a ui_file from a previously opened FILE.  CLOSE_P
 181      indicates whether the underlying file should be closed when the
 182      stdio_file is destroyed.  */
 183   explicit stdio_file (FILE *file, bool close_p = false);
 184
 185   /* Create an stdio_file that is not managing any file yet.  Call
 186      open to actually open something.  */
 187   stdio_file ();
 188
 189   ~stdio_file () override;
 190
 191   /* Open NAME in mode MODE, and own the resulting file.  Returns true
 192      on success, false otherwise.  If the stdio_file previously owned
 193      a file, it is closed.  */
 194   bool open (const char *name, const char *mode);
 195
 196   void flush () override;
 197
 198   void write (const char *buf, long length_buf) override;
 199
 200   void write_async_safe (const char *buf, long length_buf) override;
 201
 202   void puts (const char *) override;
 203
 204   long read (char *buf, long length_buf) override;
 205
 206   bool isatty () override;
 207
 208   bool can_emit_style_escape () override;
 209
 210 private:
 211   /* Sets the internal stream to FILE, and saves the FILE's file
 212      descriptor in M_FD.  */
 213   void set_stream (FILE *file);
 214
 215   /* The file.  */
 216   FILE *m_file;
 217
 218   /* The associated file descriptor is extracted ahead of time for
 219      stdio_file::write_async_safe's benefit, in case fileno isn't
 220      async-safe.  */
 221   int m_fd;
 222
 223   /* If true, M_FILE is closed on destruction.  */
 224   bool m_close_p;
 225 };
 226
 227 typedef std::unique_ptr<stdio_file> stdio_file_up;
 228
 229 /* Like stdio_file, but specifically for stderr.
 230
 231    This exists because there is no real line-buffering on Windows, see
 232    <http://msdn.microsoft.com/en-us/library/86cebhfs%28v=vs.71%29.aspx>
 233    so the stdout is either fully-buffered or non-buffered.  We can't
 234    make stdout non-buffered, because of two concerns:
 235
 236     1. Non-buffering hurts performance.
 237     2. Non-buffering may change GDB's behavior when it is interacting
 238        with a front-end, such as Emacs.
 239
 240    We leave stdout as fully buffered, but flush it first when
 241    something is written to stderr.
 242
 243    Note that the 'write_async_safe' method is not overridden, because
 244    there's no way to flush a stream in an async-safe manner.
 245    Fortunately, it doesn't really matter, because:
 246
 247     1. That method is only used for printing internal debug output
 248        from signal handlers.
 249
 250     2. Windows hosts don't have a concept of async-safeness.  Signal
 251        handlers run in a separate thread, so they can call the regular
 252        non-async-safe output routines freely.
 253 */
 254 class stderr_file : public stdio_file
 255 {
 256 public:
 257   explicit stderr_file (FILE *stream);
 258
 259   /* Override the output routines to flush gdb_stdout before deferring
 260      to stdio_file for the actual outputting.  */
 261   void write (const char *buf, long length_buf) override;
 262   void puts (const char *linebuffer) override;
 263 };
 264
 265 /* A ui_file implementation that maps onto two ui-file objects.  */
 266
 267 class tee_file : public ui_file
 268 {
 269 public:
 270   /* Create a file which writes to both ONE and TWO.  ONE will remain
 271      open when this object is destroyed; but TWO will be closed.  */
 272   tee_file (ui_file *one, ui_file_up &&two);
 273   ~tee_file () override;
 274
 275   void write (const char *buf, long length_buf) override;
 276   void write_async_safe (const char *buf, long length_buf) override;
 277   void puts (const char *) override;
 278
 279   bool isatty () override;
 280   bool term_out () override;
 281   bool can_emit_style_escape () override;
 282   void flush () override;
 283
 284 private:
 285   /* The two underlying ui_files.  */
 286   ui_file *m_one;
 287   ui_file_up m_two;
 288 };
 289
 290 #endif