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Diffstat (limited to 'butl/pager.cxx')
| -rw-r--r-- | butl/pager.cxx | 191 |
1 files changed, 191 insertions, 0 deletions
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 (); + } +} |