An incremental decoder of bytes into characters and lines

The DecodeAccumulator class

The DecodeAccumulator class implements an incremental decoder: an object that may be fed bytes (one or several at a time) as they are e.g. read from a network stream or a subprocess's output, and that adds to a result string as soon as enough bytes have been accumulated to produce a character in the specified encoding.

Note that DecodeAccumulator objects are immutable value objects: the add() method does not modify its invocant, but returns a new DecodeAccumulator object instead.

Sample usage:

while True:
    bb = subprocess.stdout.read(1024)
    if len(bb) == 0:
        break
    acc = acc.add(bb)
    assert(not acc.done)
    if acc.splitter.lines:
        # at least one full line was produced
        (acc, lines) = acc.pop_lines()
        print('\n'.join(lines)

if acc.buf:
    print('Leftover bytes left in the buffer!', file=sys.stderr)

if acc.splitter.buf:
    print('Incomplete line: ' + acc.splitter.buf)

final = acc.add(None)
assert(final.splitter.buf == '')
assert(final.splitter.done)
assert(final.done)
if acc.splitter.buf:
    assert(len(final.splitter.lines) == len(acc.splitter.lines) + 1)

The splitter classes: UniversalNewlines, FixedEOLSplitter, NullSplitter

The decode_acc.newlines module provides three classes that may be used to split a text string into lines in different ways. The UniversalNewlines class does its best to simulate the "universal newlines" behavior of file objects. The FixedEOLSplitter class uses a specified string as a line terminator to split on. The NullSplitter class does not do any splitting.

Sample usage:

spl = newlines.UniversalNewlines()
for char in input_string:
    spl = spl.add(char)
spl.add(None)

for (idx, line) in enumerate(spl.lines):
    print('line {idx}: {line}'.format(idx=idx, line=line))

License and copyright

Copyright (c) 2018  Peter Pentchev <roam@ringlet.net>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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