D2377: util: add a file object proxy that can read at most N bytes
This revision was automatically updated to reflect the committed changes. Closed by commit rHG01e29e885600: util: add a file object proxy that can read at most N bytes (authored by indygreg, committed by ). REPOSITORY rHG Mercurial CHANGES SINCE LAST UPDATE https://phab.mercurial-scm.org/D2377?vs=5963&id=5995 REVISION DETAIL https://phab.mercurial-scm.org/D2377 AFFECTED FILES mercurial/util.py tests/test-cappedreader.py CHANGE DETAILS diff --git a/tests/test-cappedreader.py b/tests/test-cappedreader.py new file mode 100644 --- /dev/null +++ b/tests/test-cappedreader.py @@ -0,0 +1,91 @@ +from __future__ import absolute_import, print_function + +import io +import unittest + +from mercurial import ( +util, +) + +class CappedReaderTests(unittest.TestCase): +def testreadfull(self): +source = io.BytesIO(b'x' * 100) + +reader = util.cappedreader(source, 10) +res = reader.read(10) +self.assertEqual(res, b'x' * 10) +self.assertEqual(source.tell(), 10) +source.seek(0) + +reader = util.cappedreader(source, 15) +res = reader.read(16) +self.assertEqual(res, b'x' * 15) +self.assertEqual(source.tell(), 15) +source.seek(0) + +reader = util.cappedreader(source, 100) +res = reader.read(100) +self.assertEqual(res, b'x' * 100) +self.assertEqual(source.tell(), 100) +source.seek(0) + +reader = util.cappedreader(source, 50) +res = reader.read() +self.assertEqual(res, b'x' * 50) +self.assertEqual(source.tell(), 50) +source.seek(0) + +def testreadnegative(self): +source = io.BytesIO(b'x' * 100) + +reader = util.cappedreader(source, 20) +res = reader.read(-1) +self.assertEqual(res, b'x' * 20) +self.assertEqual(source.tell(), 20) +source.seek(0) + +reader = util.cappedreader(source, 100) +res = reader.read(-1) +self.assertEqual(res, b'x' * 100) +self.assertEqual(source.tell(), 100) +source.seek(0) + +def testreadmultiple(self): +source = io.BytesIO(b'x' * 100) + +reader = util.cappedreader(source, 10) +for i in range(10): +res = reader.read(1) +self.assertEqual(res, b'x') +self.assertEqual(source.tell(), i + 1) + +self.assertEqual(source.tell(), 10) +res = reader.read(1) +self.assertEqual(res, b'') +self.assertEqual(source.tell(), 10) +source.seek(0) + +reader = util.cappedreader(source, 45) +for i in range(4): +res = reader.read(10) +self.assertEqual(res, b'x' * 10) +self.assertEqual(source.tell(), (i + 1) * 10) + +res = reader.read(10) +self.assertEqual(res, b'x' * 5) +self.assertEqual(source.tell(), 45) + +def readlimitpasteof(self): +source = io.BytesIO(b'x' * 100) + +reader = util.cappedreader(source, 1024) +res = reader.read(1000) +self.assertEqual(res, b'x' * 100) +self.assertEqual(source.tell(), 100) +res = reader.read(1000) +self.assertEqual(res, b'') +self.assertEqual(source.tell(), 100) + +if __name__ == '__main__': +import silenttestrunner +silenttestrunner.main(__name__) diff --git a/mercurial/util.py b/mercurial/util.py --- a/mercurial/util.py +++ b/mercurial/util.py @@ -1980,6 +1980,35 @@ limit -= len(s) yield s +class cappedreader(object): +"""A file object proxy that allows reading up to N bytes. + +Given a source file object, instances of this type allow reading up to +N bytes from that source file object. Attempts to read past the allowed +limit are treated as EOF. + +It is assumed that I/O is not performed on the original file object +in addition to I/O that is performed by this instance. If there is, +state tracking will get out of sync and unexpected results will ensue. +""" +def __init__(self, fh, limit): +"""Allow reading up to bytes from .""" +self._fh = fh +self._left = limit + +def read(self, n=-1): +if not self._left: +return b'' + +if n < 0: +n = self._left + +data = self._fh.read(min(n, self._left)) +self._left -= len(data) +assert self._left >= 0 + +return data + def makedate(timestamp=None): '''Return a unix timestamp (or the current time) as a (unixtime, offset) tuple based off the local timezone.''' To: indygreg, #hg-reviewers, lothiraldan, yuja Cc: lothiraldan, mercurial-devel ___ Mercurial-devel mailing list Mercurial-devel@mercurial-scm.org https://www.mercurial-scm.org/mailman/listinfo/mercurial-devel
D2377: util: add a file object proxy that can read at most N bytes
lothiraldan accepted this revision. lothiraldan added a comment. LGTM REPOSITORY rHG Mercurial REVISION DETAIL https://phab.mercurial-scm.org/D2377 To: indygreg, #hg-reviewers, lothiraldan Cc: lothiraldan, mercurial-devel ___ Mercurial-devel mailing list Mercurial-devel@mercurial-scm.org https://www.mercurial-scm.org/mailman/listinfo/mercurial-devel
D2377: util: add a file object proxy that can read at most N bytes
indygreg created this revision. Herald added a subscriber: mercurial-devel. Herald added a reviewer: hg-reviewers. REVISION SUMMARY Sometimes we have data of a known size within a stream. For performance reasons, we don't want to pre-read this data (we want to allow consumers to read on demand). For simplicitly reasons, we don't want callers to necessarily know their data is coming from within an outer stream and there is a limit to how much they should read. The class introduced by this commit provides a very simple proxy around an underlying file object that allows the consumer to .read() up to N bytes from the file object. Attempts to read past this many bytes results in a simulated EOF. REPOSITORY rHG Mercurial REVISION DETAIL https://phab.mercurial-scm.org/D2377 AFFECTED FILES mercurial/util.py tests/test-cappedreader.py CHANGE DETAILS diff --git a/tests/test-cappedreader.py b/tests/test-cappedreader.py new file mode 100644 --- /dev/null +++ b/tests/test-cappedreader.py @@ -0,0 +1,91 @@ +from __future__ import absolute_import, print_function + +import io +import unittest + +from mercurial import ( +util, +) + +class CappedReaderTests(unittest.TestCase): +def testreadfull(self): +source = io.BytesIO(b'x' * 100) + +reader = util.cappedreader(source, 10) +res = reader.read(10) +self.assertEqual(res, b'x' * 10) +self.assertEqual(source.tell(), 10) +source.seek(0) + +reader = util.cappedreader(source, 15) +res = reader.read(16) +self.assertEqual(res, b'x' * 15) +self.assertEqual(source.tell(), 15) +source.seek(0) + +reader = util.cappedreader(source, 100) +res = reader.read(100) +self.assertEqual(res, b'x' * 100) +self.assertEqual(source.tell(), 100) +source.seek(0) + +reader = util.cappedreader(source, 50) +res = reader.read() +self.assertEqual(res, b'x' * 50) +self.assertEqual(source.tell(), 50) +source.seek(0) + +def testreadnegative(self): +source = io.BytesIO(b'x' * 100) + +reader = util.cappedreader(source, 20) +res = reader.read(-1) +self.assertEqual(res, b'x' * 20) +self.assertEqual(source.tell(), 20) +source.seek(0) + +reader = util.cappedreader(source, 100) +res = reader.read(-1) +self.assertEqual(res, b'x' * 100) +self.assertEqual(source.tell(), 100) +source.seek(0) + +def testreadmultiple(self): +source = io.BytesIO(b'x' * 100) + +reader = util.cappedreader(source, 10) +for i in range(10): +res = reader.read(1) +self.assertEqual(res, b'x') +self.assertEqual(source.tell(), i + 1) + +self.assertEqual(source.tell(), 10) +res = reader.read(1) +self.assertEqual(res, b'') +self.assertEqual(source.tell(), 10) +source.seek(0) + +reader = util.cappedreader(source, 45) +for i in range(4): +res = reader.read(10) +self.assertEqual(res, b'x' * 10) +self.assertEqual(source.tell(), (i + 1) * 10) + +res = reader.read(10) +self.assertEqual(res, b'x' * 5) +self.assertEqual(source.tell(), 45) + +def readlimitpasteof(self): +source = io.BytesIO(b'x' * 100) + +reader = util.cappedreader(source, 1024) +res = reader.read(1000) +self.assertEqual(res, b'x' * 100) +self.assertEqual(source.tell(), 100) +res = reader.read(1000) +self.assertEqual(res, b'') +self.assertEqual(source.tell(), 100) + +if __name__ == '__main__': +import silenttestrunner +silenttestrunner.main(__name__) diff --git a/mercurial/util.py b/mercurial/util.py --- a/mercurial/util.py +++ b/mercurial/util.py @@ -1980,6 +1980,35 @@ limit -= len(s) yield s +class cappedreader(object): +"""A file object proxy that allows reading up to N bytes. + +Given a source file object, instances of this type allow reading up to +N bytes from that source file object. Attempts to read past the allowed +limit are treated as EOF. + +It is assumed that I/O is not performed on the original file object +in addition to I/O that is performed by this instance. If there is, +state tracking will get out of sync and unexpected results will ensue. +""" +def __init__(self, fh, limit): +"""Allow reading up to bytes from .""" +self._fh = fh +self._left = limit + +def read(self, n=-1): +if not self._left: +return b'' + +if n < 0: +n = self._left + +data = self._fh.read(min(n, self._left)) +self._left -= len(data) +assert self._left >= 0 + +return data + def makedate(timestamp=None): '''Return a unix timestamp (or the current time) as a (unixtime, offset) tuple based o
