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# mainloop/stringbuffer.py -- efficient buffering of strings as a queue
#
# Copyright (C) 2012, 2014-2015 Codethink Limited
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 2 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License along
# with this program. If not, see <http://www.gnu.org/licenses/>.
class StringBuffer(object):
'''Buffer data for a file descriptor.
The data may arrive in small pieces, and it is buffered in a way that
avoids excessive string catenation or splitting.
'''
def __init__(self):
self.strings = []
self.len = 0
def add(self, data):
'''Add data to buffer.'''
self.strings.append(data)
self.len += len(data)
def remove(self, num_bytes):
'''Remove specified number of bytes from buffer.'''
while num_bytes > 0 and self.strings:
first = self.strings[0]
if len(first) <= num_bytes:
num_bytes -= len(first)
del self.strings[0]
self.len -= len(first)
else:
self.strings[0] = first[num_bytes:]
self.len -= num_bytes
num_bytes = 0
def peek(self):
'''Return contents of buffer as one string.'''
if len(self.strings) == 0:
return ''
elif len(self.strings) == 1:
return self.strings[0]
else:
self.strings = [''.join(self.strings)]
return self.strings[0]
def read(self, max_bytes):
'''Return up to max_bytes from the buffer.
Less is returned if the buffer does not contain at least max_bytes.
The returned data will remain in the buffer; use remove to remove
it.
'''
use = []
size = 0
for s in self.strings:
n = max_bytes - size
if len(s) <= n:
use.append(s)
size += len(s)
else:
use.append(s[:n])
size += n
break
return ''.join(use)
def readline(self):
'''Return a complete line (ends with '\n') or None.'''
for i, s in enumerate(self.strings):
newline = s.find('\n')
if newline != -1:
if newline+1 == len(s):
use = self.strings[:i+1]
del self.strings[:i+1]
else:
pre = s[:newline+1]
use = self.strings[:i] + [pre]
del self.strings[:i]
self.strings[0] = s[newline+1:]
return ''.join(use)
return None
def __len__(self):
return self.len
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