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#!/usr/local/bin/ruby
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require "curses"
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# A curses based file viewer
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class FileViewer
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# Create a new fileviewer, and view the file.
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def initialize(filename)
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@data_lines = []
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@screen = nil
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@top = nil
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init_curses
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load_file(filename)
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interact
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end
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# Perform the curses setup
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def init_curses
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# signal(SIGINT, finish)
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Curses.init_screen
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Curses.nonl
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Curses.cbreak
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Curses.noecho
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@screen = Curses.stdscr
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@screen.scrollok(true)
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#$screen.keypad(true)
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end
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# Load the file into memory, and put
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# the first part on the curses display.
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def load_file(filename)
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fp = open(filename, "r") do |fp|
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# slurp the file
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fp.each_line { |l|
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@data_lines.push(l.chop)
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}
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end
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@top = 0
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@data_lines[0..@screen.maxy-1].each_with_index{|line, idx|
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@screen.setpos(idx, 0)
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@screen.addstr(line)
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}
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@screen.setpos(0,0)
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@screen.refresh
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rescue
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raise "cannot open file '#{filename}' for reading"
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end
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# Scroll the display up by one line
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def scroll_up
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if( @top > 0 )
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@screen.scrl(-1)
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@top -= 1
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str = @data_lines[@top]
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if( str )
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@screen.setpos(0, 0)
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@screen.addstr(str)
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end
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return true
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else
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return false
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end
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end
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# Scroll the display down by one line
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def scroll_down
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if( @top + @screen.maxy < @data_lines.length )
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@screen.scrl(1)
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@top += 1
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str = @data_lines[@top + @screen.maxy - 1]
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if( str )
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@screen.setpos(@screen.maxy - 1, 0)
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@screen.addstr(str)
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end
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return true
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else
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return false
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end
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end
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# Allow the user to interact with the display.
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# This uses EMACS-like keybindings, and also
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# vi-like keybindings as well, except that left
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# and right move to the beginning and end of the
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# file, respectively.
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def interact
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while true
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result = true
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c = Curses.getch
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case c
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when Curses::KEY_DOWN, Curses::KEY_CTRL_N, ?j
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result = scroll_down
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when Curses::KEY_UP, Curses::KEY_CTRL_P, ?k
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result = scroll_up
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when Curses::KEY_NPAGE, ?\s # white space
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for i in 0..(@screen.maxy - 2)
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if( ! scroll_down )
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if( i == 0 )
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result = false
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end
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break
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end
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end
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when Curses::KEY_PPAGE
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for i in 0..(@screen.maxy - 2)
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if( ! scroll_up )
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if( i == 0 )
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result = false
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end
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break
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end
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end
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when Curses::KEY_LEFT, Curses::KEY_CTRL_T, ?h
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while( scroll_up )
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end
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when Curses::KEY_RIGHT, Curses::KEY_CTRL_B, ?l
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while( scroll_down )
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end
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when ?q
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break
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else
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@screen.setpos(0,0)
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@screen.addstr("[unknown key `#{Curses.keyname(c)}'=#{c}] ")
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end
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if( !result )
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Curses.beep
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end
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@screen.setpos(0,0)
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end
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Curses.close_screen
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end
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end
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# If we are being run as a main program...
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if __FILE__ == $0
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if ARGV.size != 1 then
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printf("usage: #{$0} file\n");
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exit
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end
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viewer = FileViewer.new(ARGV[0])
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end
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