pdutils/gapbuffer.py at master · mooseman/pdutils · GitHub

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#  gapbuffer.py
#  A gap-buffer in Python.
#  ( See http://en.wikipedia.org/wiki/Gap_buffer )

#  Gap buffers are often used in text editors.
#  They divide the text into two strings with a
#  gap at the position of the cursor (where text
#  is inserted).
#  This code is released to the public domain.
#  "Share and enjoy..."  ;)

#  TO DO  - add insert, delete, copy and move
#  text operations.
#  Also add find and replace operations.


import string

class gapbuffer(object):
  def __init__(self, text):
     self.text = text
     self.cursorpos = len(self.text)
     self.gapsize = 5
     self.gap = "[" + " "*self.gapsize + "]"
     self.text = self.text[0:self.cursorpos] + self.gap


  def display(self):
     print self.text

  def cursorpos(self):
     return self.cursorpos

  # Create a gap at cursorpos.
  def makegap(self):
     self.text = self.text[0:self.cursorpos] + self.gap \
       + self.text[self.cursorpos:len(self.text)]

  # Remove the gap before we move it
  def removegap(self):
     self.text = self.text[0:self.cursorpos] \
       + self.text[self.cursorpos+len(self.gap):len(self.text)]

  # Insert some text
  def insert_txt(self, text):
     self.removegap()
     self.text = self.text[0:self.cursorpos] + text + self.gap \
       + self.text[self.cursorpos:len(self.text)]
     self.cursorpos += len(text)
     self.makegap()

  # Remove text
  def remove_txt(self, pos):
     pass

  # Copy text
  def copy_txt(self):
     pass

  # Move text
  def move_txt(self):
     pass


  # Show the character immediately before the gap.
  def cursorchar(self):
     return self.text[self.cursorpos-1]

  def movecursor(self, num):
     self.removegap()
     self.cursorpos += num
     self.makegap()

  def buffer1(self):
     return self.text[0:self.cursorpos]

  def buffer2(self):
     return self.text[self.cursorpos+len(self.gap):len(self.text)]


#  Test the class
a = gapbuffer("Mary had a little lamb, its fleece was white as snow")

# Print the text
a.display()

# Prints the position of the cursor.
print a.cursorpos

# Move the cursor
a.movecursor(-14)
print a.cursorpos

# Print the character at the cursor
print a.cursorchar()

a.display()

print a.buffer1()
print a.buffer2()

# Move the cursor again
a.movecursor(-16)
print a.cursorpos

# Print the character at the cursor
print a.cursorchar()

a.display()

print a.buffer1()
print a.buffer2()

# Insert some text
a.insert_txt("Foobar")

print a.buffer1()
print a.buffer2()