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authorBoris Kolpackov <boris@codesynthesis.com>2016-01-30 15:42:32 +0200
committerBoris Kolpackov <boris@codesynthesis.com>2016-01-30 15:42:32 +0200
commitf60a701fdbdf4d88dc138cfca005269633a10c1d (patch)
treebfd6be6a3aadd659ea423f4d8773a59160fecefe
parentae02c68df6f26ff24b008ca047ae7750eeecedac (diff)
Add pager class that allows to send output through pager program (less, more)
-rw-r--r--butl/buildfile1
-rw-r--r--butl/pager86
-rw-r--r--butl/pager.cxx191
3 files changed, 278 insertions, 0 deletions
diff --git a/butl/buildfile b/butl/buildfile
index de51ad5..f075e30 100644
--- a/butl/buildfile
+++ b/butl/buildfile
@@ -8,6 +8,7 @@ lib{butl}: \
{hxx ixx cxx}{ filesystem } \
{hxx }{ multi-index } \
{hxx }{ optional } \
+{hxx cxx}{ pager } \
{hxx ixx txx cxx}{ path } \
{hxx }{ path-io } \
{hxx }{ path-map } \
diff --git a/butl/pager b/butl/pager
new file mode 100644
index 0000000..4b39c2e
--- /dev/null
+++ b/butl/pager
@@ -0,0 +1,86 @@
+// file : butl/pager -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license : MIT; see accompanying LICENSE file
+
+#ifndef BUTL_PAGER
+#define BUTL_PAGER
+
+#include <string>
+#include <vector>
+#include <iostream>
+
+#include <butl/process>
+#include <butl/fdstream>
+
+namespace butl
+{
+ // Try to run the output through a pager program, such as more or less (no
+ // pun intended, less is used by default). If the default pager program is
+ // used, then the output is indented so that 80-character long lines will
+ // appear centered in the terminal. If the default pager program fails to
+ // start, then the output is sent directly to STDOUT.
+ //
+ // If the pager program is specified and is empty, then no pager is used
+ // and the output is sent directly to STDOUT.
+ //
+ // Throw std::system_error if there are problems with the pager program.
+ //
+ // Typical usage:
+ //
+ // try
+ // {
+ // pager p ("help for foo");
+ // ostream& os (p.stream ());
+ //
+ // os << "Foo is such and so ...";
+ //
+ // if (!p.wait ())
+ // ... // Pager program returned non-zero status.
+ // }
+ // catch (const std::system_error& e)
+ // {
+ // cerr << "pager error: " << e.what () << endl;
+ // }
+ //
+ class pager: protected std::streambuf
+ {
+ public:
+ ~pager () {wait ();}
+
+ // If verbose is true, then print (to STDERR) the pager command line.
+ //
+ pager (const std::string& name,
+ bool verbose = false,
+ const std::string* pager = nullptr,
+ const std::vector<std::string>* pager_options = nullptr);
+
+ std::ostream&
+ stream () {return os_.is_open () ? os_ : std::cout;}
+
+ bool
+ wait ();
+
+ // The streambuf output interface that implements indentation. You can
+ // override it to implement custom output pre-processing.
+ //
+ protected:
+ using int_type = std::streambuf::int_type;
+ using traits_type = std::streambuf::traits_type;
+
+ virtual int_type
+ overflow (int_type);
+
+ virtual int
+ sync ();
+
+ private:
+ process p_;
+ ofdstream os_;
+
+ std::string indent_;
+ int_type prev_ = '\n'; // Previous character.
+ std::streambuf* buf_ = nullptr;
+ };
+};
+
+#endif // BUTL_PAGER
diff --git a/butl/pager.cxx b/butl/pager.cxx
new file mode 100644
index 0000000..4d0d9eb
--- /dev/null
+++ b/butl/pager.cxx
@@ -0,0 +1,191 @@
+// 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 ();
+ }
+}