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   virtual void flush ()
  74   {}
  75 };
  76
  77 typedef std::unique_ptr<ui_file> ui_file_up;
  78
  79 /* A ui_file that writes to nowhere.  */
  80
  81 class null_file : public ui_file
  82 {
  83 public:
  84   void write (const char *buf, long length_buf) override;
  85   void write_async_safe (const char *buf, long sizeof_buf) override;
  86   void puts (const char *str) override;
  87 };
  88
  89 /* A preallocated null_file stream.  */
  90 extern null_file null_stream;
  91
  92 extern void gdb_flush (ui_file *);
  93
  94 extern int ui_file_isatty (struct ui_file *);
  95
  96 extern void ui_file_write (struct ui_file *file, const char *buf,
  97                            long length_buf);
  98
  99 extern void ui_file_write_async_safe (struct ui_file *file, const char *buf,
 100                                       long length_buf);
 101
 102 extern long ui_file_read (struct ui_file *file, char *buf, long length_buf);
 103
 104 /* A std::string-based ui_file.  Can be used as a scratch buffer for
 105    collecting output.  */
 106
 107 class string_file : public ui_file
 108 {
 109 public:
 110   string_file () {}
 111   ~string_file () override;
 112
 113   /* Override ui_file methods.  */
 114
 115   void write (const char *buf, long length_buf) override;
 116
 117   long read (char *buf, long length_buf) override
 118   { gdb_assert_not_reached ("a string_file is not readable"); }
 119
 120   /* string_file-specific public API.  */
 121
 122   /* Accesses the std::string containing the entire output collected
 123      so far.
 124
 125      Returns a non-const reference so that it's easy to move the
 126      string contents out of the string_file.  E.g.:
 127
 128       string_file buf;
 129       buf.printf (....);
 130       buf.printf (....);
 131       return std::move (buf.string ());
 132   */
 133   std::string &string () { return m_string; }
 134
 135   /* Provide a few convenience methods with the same API as the
 136      underlying std::string.  */
 137   const char *data () const { return m_string.data (); }
 138   const char *c_str () const { return m_string.c_str (); }
 139   size_t size () const { return m_string.size (); }
 140   bool empty () const { return m_string.empty (); }
 141   void clear () { return m_string.clear (); }
 142
 143 private:
 144   /* The internal buffer.  */
 145   std::string m_string;
 146 };
 147
 148 /* A ui_file implementation that maps directly onto <stdio.h>'s FILE.
 149    A stdio_file can either own its underlying file, or not.  If it
 150    owns the file, then destroying the stdio_file closes the underlying
 151    file, otherwise it is left open.  */
 152
 153 class stdio_file : public ui_file
 154 {
 155 public:
 156   /* Create a ui_file from a previously opened FILE.  CLOSE_P
 157      indicates whether the underlying file should be closed when the
 158      stdio_file is destroyed.  */
 159   explicit stdio_file (FILE *file, bool close_p = false);
 160
 161   /* Create an stdio_file that is not managing any file yet.  Call
 162      open to actually open something.  */
 163   stdio_file ();
 164
 165   ~stdio_file () override;
 166
 167   /* Open NAME in mode MODE, and own the resulting file.  Returns true
 168      on success, false otherwise.  If the stdio_file previously owned
 169      a file, it is closed.  */
 170   bool open (const char *name, const char *mode);
 171
 172   void flush () override;
 173
 174   void write (const char *buf, long length_buf) override;
 175
 176   void write_async_safe (const char *buf, long length_buf) override;
 177
 178   void puts (const char *) override;
 179
 180   long read (char *buf, long length_buf) override;
 181
 182   bool isatty () override;
 183
 184 private:
 185   /* Sets the internal stream to FILE, and saves the FILE's file
 186      descriptor in M_FD.  */
 187   void set_stream (FILE *file);
 188
 189   /* The file.  */
 190   FILE *m_file;
 191
 192   /* The associated file descriptor is extracted ahead of time for
 193      stdio_file::write_async_safe's benefit, in case fileno isn't
 194      async-safe.  */
 195   int m_fd;
 196
 197   /* If true, M_FILE is closed on destruction.  */
 198   bool m_close_p;
 199 };
 200
 201 typedef std::unique_ptr<stdio_file> stdio_file_up;
 202
 203 /* Like stdio_file, but specifically for stderr.
 204
 205    This exists because there is no real line-buffering on Windows, see
 206    <http://msdn.microsoft.com/en-us/library/86cebhfs%28v=vs.71%29.aspx>
 207    so the stdout is either fully-buffered or non-buffered.  We can't
 208    make stdout non-buffered, because of two concerns:
 209
 210     1. Non-buffering hurts performance.
 211     2. Non-buffering may change GDB's behavior when it is interacting
 212        with a front-end, such as Emacs.
 213
 214    We leave stdout as fully buffered, but flush it first when
 215    something is written to stderr.
 216
 217    Note that the 'write_async_safe' method is not overridden, because
 218    there's no way to flush a stream in an async-safe manner.
 219    Fortunately, it doesn't really matter, because:
 220
 221     1. That method is only used for printing internal debug output
 222        from signal handlers.
 223
 224     2. Windows hosts don't have a concept of async-safeness.  Signal
 225        handlers run in a separate thread, so they can call the regular
 226        non-async-safe output routines freely.
 227 */
 228 class stderr_file : public stdio_file
 229 {
 230 public:
 231   explicit stderr_file (FILE *stream);
 232
 233   /* Override the output routines to flush gdb_stdout before deferring
 234      to stdio_file for the actual outputting.  */
 235   void write (const char *buf, long length_buf) override;
 236   void puts (const char *linebuffer) override;
 237 };
 238
 239 /* A ui_file implementation that maps onto two ui-file objects.  */
 240
 241 class tee_file : public ui_file
 242 {
 243 public:
 244   /* Create a file which writes to both ONE and TWO.  CLOSE_ONE and
 245      CLOSE_TWO indicate whether the original files should be closed
 246      when the new file is closed.  */
 247   tee_file (ui_file *one, bool close_one,
 248             ui_file *two, bool close_two);
 249   ~tee_file () override;
 250
 251   void write (const char *buf, long length_buf) override;
 252   void write_async_safe (const char *buf, long length_buf) override;
 253   void puts (const char *) override;
 254
 255   bool isatty () override;
 256   void flush () override;
 257
 258 private:
 259   /* The two underlying ui_files, and whether they should each be
 260      closed on destruction.  */
 261   ui_file *m_one, *m_two;
 262   bool m_close_one, m_close_two;
 263 };
 264
 265 #endif