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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> // STDOUT_FILENO
# include <sys/ioctl.h> // ioctl()
# include <chrono>
# include <thread> // this_thread::sleep_for()
#else
# include <butl/win32-utility>
#endif
#include <cstring> // strchr()
#include <system_error>
#include <butl/fdstream> // fdclose()
using namespace std;
namespace butl
{
pager::
pager (const string& name,
bool verbose,
const string* pager,
const vector<string>* pager_options)
// Create successfully exited process. Will "wait" for it if fallback to
// non-interactive execution path.
//
: p_ (optional<process::status_type> (0))
{
// 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
// This works properly on PowerShell, while for the regular console
// (cmd.exe) it always returns 80 columns.
//
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).
//
// MINGW GCC 4.9 doesn't implement this_thread so use Win32 Sleep().
//
#ifndef _WIN32
this_thread::sleep_for (chrono::milliseconds (50));
#else
Sleep (50);
#endif
bool r;
if (p_.try_wait (r))
{
fdclose (p_.out_fd);
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 (bool ie)
{
// Teardown the indentation machinery.
//
if (buf_ != nullptr)
{
stream ().rdbuf (buf_);
buf_ = nullptr;
}
// Prevent ofdstream::close() from throwing in the ignore errors mode.
//
if (ie)
os_.exceptions (ofdstream::goodbit);
os_.close ();
return p_.wait (ie);
}
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 ();
}
}
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