# copyright 2004 Michael D. Stenner <mstenner@ece.arizona.edu>
# license: LGPL
class xreverse:
def __init__(self, file_object, buf_size=1024*8):
self.fo = fo = file_object
fo.seek(0, 2) # go to the end of the file
self.pos = fo.tell() # where we are
self.buffer = '' # data buffer
self.lbuf = [] # buffer for parsed lines
self.done = 0 # we've read the last line
self.jump = -1 * buf_size
while 1:
try: fo.seek(self.jump, 1)
except IOError: fo.seek(0)
new_position = fo.tell()
new = fo.read(self.pos - new_position)
fo.seek(new_position)
self.pos = new_position
self.buffer = new + self.buffer
if '\n' in new: break
if self.pos == 0: return self.buffer
nl = self.buffer.split('\n')
nlb = [ i + '\n' for i in nl[1:-1] ]
if not self.buffer[-1] == '\n': nlb.append(nl[-1])
self.buffer = nl[0]
self.lbuf = nlb
def __iter__(self): return self
def next(self):
try:
return self.lbuf.pop()
except IndexError:
fo = self.fo
while 1:
#get the next chunk of data
try: fo.seek(self.jump, 1)
except IOError: fo.seek(0)
new_position = fo.tell()
new = fo.read(self.pos - new_position)
fo.seek(new_position)
self.pos = new_position
nl = (new + self.buffer).split('\n')
self.buffer = nl.pop(0)
self.lbuf = [ i + '\n' for i in nl ]
if self.lbuf: return self.lbuf.pop()
elif self.pos == 0:
if self.done:
raise StopIteration
else:
self.done = 1
return self.buffer + '\n'
def dump(rtype, fn):
import sys
fo = file(fn)
for line in rtype(fo):
sys.stdout.write(line)
fo.close()
def rereverse(rtype, fn):
fo = file(fn)
rev = [ line for line in xreverse(fo) ]
rev.reverse()
sys.stdout.writelines(rev)
def test_compare(rtype, fn):
import sys, os
t1 = os.times()
fo = file(fn)
for line in rtype(fo):
pass
fo.close()
t2 = os.times()
fo = file(fn)
for line in fo.readlines():
pass
fo.close()
t3 = os.times()
for i in range(5):
print t2[i] - t1[i], t3[i] - t2[i]
if __name__ == '__main__':
import sys
fn = sys.argv[1]
#dump(xreverse, fn)
#test_compare(xreverse, fn)
rereverse(xreverse, fn)
