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-rw-r--r--butl/pager.cxx191
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diff --git a/butl/pager.cxx b/butl/pager.cxx
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+// file : butl/pager.cxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license : MIT; see accompanying LICENSE file
+
+#include <butl/pager>
+
+#ifndef _WIN32
+# include <unistd.h> // close(), STDOUT_FILENO
+# include <sys/ioctl.h> // ioctl()
+#else
+# ifndef WIN32_LEAN_AND_MEAN
+# define WIN32_LEAN_AND_MEAN
+# endif
+# include <windows.h> // GetConsoleScreenBufferInfo(), GetStdHandle()
+# include <io.h> // _close()
+#endif
+
+#include <chrono>
+#include <thread> // this_thread::sleep_for()
+#include <cstring> // strchr()
+#include <system_error>
+
+using namespace std;
+
+namespace butl
+{
+ pager::
+ pager (const string& name,
+ bool verbose,
+ const string* pager,
+ const vector<string>* pager_options)
+ {
+ // If we are using the default pager, try to get the terminal width
+ // so that we can center the output.
+ //
+ if (pager == nullptr)
+ {
+ size_t col (0);
+
+#ifndef _WIN32
+# ifdef TIOCGWINSZ
+ struct winsize w;
+ if (ioctl (STDOUT_FILENO, TIOCGWINSZ, &w) == 0)
+ col = static_cast<size_t> (w.ws_col);
+# endif
+#else
+#error TODO: needs testing
+ CONSOLE_SCREEN_BUFFER_INFO w;
+ if (GetConsoleScreenBufferInfo (GetStdHandle (STD_OUTPUT_HANDLE), &w))
+ col = static_cast<size_t> (w.srWindow.Right - w.srWindow.Left + 1);
+#endif
+ if (col > 80)
+ indent_.assign ((col - 80) / 2, ' ');
+ }
+
+ vector<const char*> args;
+ string prompt;
+
+ if (pager != nullptr)
+ {
+ if (pager->empty ())
+ return; // No pager should be used.
+
+ args.push_back (pager->c_str ());
+ }
+ else
+ {
+ // By default try less (again, no pun intended).
+ //
+ prompt = "-Ps" + name + " (press q to quit, h for help)";
+
+ args.push_back ("less");
+ args.push_back ("-R"); // Handle ANSI color.
+ args.push_back (prompt.c_str ());
+ }
+
+ // Add extra pager options.
+ //
+ if (pager_options != nullptr)
+ for (const string& o: *pager_options)
+ args.push_back (o.c_str ());
+
+ args.push_back (nullptr);
+
+ if (verbose)
+ {
+ for (const char* const* p (args.data ()); *p != nullptr; ++p)
+ {
+ if (p != args.data ())
+ cerr << ' ';
+
+ // Quote if empty or contains spaces.
+ //
+ bool q (**p == '\0' || strchr (*p, ' ') != nullptr);
+
+ if (q)
+ cerr << '"';
+
+ cerr << *p;
+
+ if (q)
+ cerr << '"';
+ }
+ cerr << endl;
+ }
+
+ // Ignore errors and go without a pager unless the pager was specified
+ // by the user.
+ //
+ try
+ {
+ p_ = process (args.data (), -1); // Redirect child's STDIN to a pipe.
+
+ // Wait a bit and see if the pager has exited before reading anything
+ // (e.g., because exec() couldn't find the program). If you know a
+ // cleaner way to handle this, let me know (and no, a select()-based
+ // approach doesn't work; the pipe is buffered and therefore is always
+ // ready for writing).
+ //
+ this_thread::sleep_for (chrono::milliseconds (50));
+
+ bool r;
+ if (p_.try_wait (r))
+ {
+#ifndef _WIN32
+ ::close (p_.out_fd);
+#else
+ _close (p_.out_fd);
+#endif
+ if (pager != nullptr)
+ throw system_error (ECHILD, system_category ());
+ }
+ else
+ os_.open (p_.out_fd);
+ }
+ catch (const process_error& e)
+ {
+ if (e.child ())
+ {
+ cerr << args[0] << ": unable to execute: " << e.what () << endl;
+ exit (1);
+ }
+
+ // Ignore unless it was a user-specified pager.
+ //
+ if (pager != nullptr)
+ throw; // Re-throw as system_error.
+ }
+
+ // Setup the indentation machinery.
+ //
+ if (!indent_.empty ())
+ buf_ = stream ().rdbuf (this);
+ }
+
+ bool pager::
+ wait ()
+ {
+ // Teardown the indentation machinery.
+ //
+ if (buf_ != nullptr)
+ {
+ stream ().rdbuf (buf_);
+ buf_ = nullptr;
+ }
+
+ os_.close ();
+ return p_.wait ();
+ }
+
+ pager::int_type pager::
+ overflow (int_type c)
+ {
+ if (prev_ == '\n' && c != '\n') // Don't indent blanks.
+ {
+ auto n (static_cast<streamsize> (indent_.size ()));
+
+ if (buf_->sputn (indent_.c_str (), n) != n)
+ return traits_type::eof ();
+ }
+
+ prev_ = c;
+ return buf_->sputc (c);
+ }
+
+ int pager::
+ sync ()
+ {
+ return buf_->pubsync ();
+ }
+}