prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Error when trying to read 0 byte from StreamingBody
  Referring to the read method of `StreamingBody`:
  https://github.com/boto/botocore/blob/c632931a6cc5eab4113c976d430bcb9c059f829f/botocore/response.py#L69-L81
  
  If anyone asks for 0 bytes from a StreamingBody, the conditional on line 76 will pass because chunk is empty (since 0 bytes were asked for) and amount was set to 0 (not None). This leads to the content length verification, which will fail because you've read 0 bytes so far out of the entire content.
  
  Might be an odd use case, but I feel like is a valid use case.
  In fact, I ran into this issue when trying to use the `ijson` package [link](https://pypi.python.org/pypi/ijson).
  That library uses `.read(0)` in order to figure out what type of encoding the stream reader should use. Whether that's the best way to do it or not, I'm not entirely sure. But I feel like `.read(0)` should still be supported.
  
  If you guys agree that it should be supported, maybe considering a condition like this:
  ```
  if (not chunk and amt > 0) or amt is None:
  ```
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `botocore/response.py`
  Content:
  ```
  1 # Copyright (c) 2012-2013 Mitch Garnaat http://garnaat.org/
  2 # Copyright 2012-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.
  3 #
  4 # Licensed under the Apache License, Version 2.0 (the "License"). You
  5 # may not use this file except in compliance with the License. A copy of
  6 # the License is located at
  7 #
  8 # http://aws.amazon.com/apache2.0/
  9 #
  10 # or in the "license" file accompanying this file. This file is
  11 # distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
  12 # ANY KIND, either express or implied. See the License for the specific
  13 # language governing permissions and limitations under the License.
  14 
  15 import sys
  16 import xml.etree.cElementTree
  17 import logging
  18 
  19 from botocore import ScalarTypes
  20 from botocore.hooks import first_non_none_response
  21 from botocore.compat import json, set_socket_timeout, XMLParseError
  22 from botocore.exceptions import IncompleteReadError
  23 from botocore import parsers
  24 
  25 
  26 logger = logging.getLogger(__name__)
  27 
  28 
  29 class StreamingBody(object):
  30     """Wrapper class for an http response body.
  31 
  32     This provides a few additional conveniences that do not exist
  33     in the urllib3 model:
  34 
  35         * Set the timeout on the socket (i.e read() timeouts)
  36         * Auto validation of content length, if the amount of bytes
  37           we read does not match the content length, an exception
  38           is raised.
  39 
  40     """
  41     def __init__(self, raw_stream, content_length):
  42         self._raw_stream = raw_stream
  43         self._content_length = content_length
  44         self._amount_read = 0
  45 
  46     def set_socket_timeout(self, timeout):
  47         """Set the timeout seconds on the socket."""
  48         # The problem we're trying to solve is to prevent .read() calls from
  49         # hanging.  This can happen in rare cases.  What we'd like to ideally
  50         # do is set a timeout on the .read() call so that callers can retry
  51         # the request.
  52         # Unfortunately, this isn't currently possible in requests.
  53         # See: https://github.com/kennethreitz/requests/issues/1803
  54         # So what we're going to do is reach into the guts of the stream and
  55         # grab the socket object, which we can set the timeout on.  We're
  56         # putting in a check here so in case this interface goes away, we'll
  57         # know.
  58         try:
  59             # To further complicate things, the way to grab the
  60             # underlying socket object from an HTTPResponse is different
  61             # in py2 and py3.  So this code has been pushed to botocore.compat.
  62             set_socket_timeout(self._raw_stream, timeout)
  63         except AttributeError:
  64             logger.error("Cannot access the socket object of "
  65                          "a streaming response.  It's possible "
  66                          "the interface has changed.", exc_info=True)
  67             raise
  68 
  69     def read(self, amt=None):
  70         """Read at most amt bytes from the stream.
  71 
  72         If the amt argument is omitted, read all data.
  73         """
  74         chunk = self._raw_stream.read(amt)
  75         self._amount_read += len(chunk)
  76         if not chunk or amt is None:
  77             # If the server sends empty contents or
  78             # we ask to read all of the contents, then we know
  79             # we need to verify the content length.
  80             self._verify_content_length()
  81         return chunk
  82 
  83     def _verify_content_length(self):
  84         # See: https://github.com/kennethreitz/requests/issues/1855
  85         # Basically, our http library doesn't do this for us, so we have
  86         # to do this ourself.
  87         if self._content_length is not None and \
  88                 self._amount_read != int(self._content_length):
  89             raise IncompleteReadError(
  90                 actual_bytes=self._amount_read,
  91                 expected_bytes=int(self._content_length))
  92 
  93     def close(self):
  94         """Close the underlying http response stream."""
  95         self._raw_stream.close()
  96 
  97 
  98 def get_response(operation_model, http_response):
  99     protocol = operation_model.metadata['protocol']
  100     response_dict = {
  101         'headers': http_response.headers,
  102         'status_code': http_response.status_code,
  103     }
  104     # TODO: Unfortunately, we have to have error logic here.
  105     # If it looks like an error, in the streaming response case we
  106     # need to actually grab the contents.
  107     if response_dict['status_code'] >= 300:
  108         response_dict['body'] = http_response.content
  109     elif operation_model.has_streaming_output:
  110         response_dict['body'] = StreamingBody(
  111             http_response.raw, response_dict['headers'].get('content-length'))
  112     else:
  113         response_dict['body'] = http_response.content
  114 
  115     parser = parsers.create_parser(protocol)
  116     return http_response, parser.parse(response_dict,
  117                                        operation_model.output_shape)
  118
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/botocore/response.py b/botocore/response.py
  --- a/botocore/response.py
  +++ b/botocore/response.py
  @@ -73,7 +73,7 @@
           """
           chunk = self._raw_stream.read(amt)
           self._amount_read += len(chunk)
  -        if not chunk or amt is None:
  +        if amt is None or (not chunk and amt > 0):
               # If the server sends empty contents or
               # we ask to read all of the contents, then we know
               # we need to verify the content length.
  
verification_info: {"golden_diff": "diff --git a/botocore/response.py b/botocore/response.py\n--- a/botocore/response.py\n+++ b/botocore/response.py\n@@ -73,7 +73,7 @@\n         \"\"\"\n         chunk = self._raw_stream.read(amt)\n         self._amount_read += len(chunk)\n-        if not chunk or amt is None:\n+        if amt is None or (not chunk and amt > 0):\n             # If the server sends empty contents or\n             # we ask to read all of the contents, then we know\n             # we need to verify the content length.\n", "issue": "Error when trying to read 0 byte from StreamingBody\nReferring to the read method of `StreamingBody`:\r\nhttps://github.com/boto/botocore/blob/c632931a6cc5eab4113c976d430bcb9c059f829f/botocore/response.py#L69-L81\r\n\r\nIf anyone asks for 0 bytes from a StreamingBody, the conditional on line 76 will pass because chunk is empty (since 0 bytes were asked for) and amount was set to 0 (not None). This leads to the content length verification, which will fail because you've read 0 bytes so far out of the entire content.\r\n\r\nMight be an odd use case, but I feel like is a valid use case.\r\nIn fact, I ran into this issue when trying to use the `ijson` package [link](https://pypi.python.org/pypi/ijson).\r\nThat library uses `.read(0)` in order to figure out what type of encoding the stream reader should use. Whether that's the best way to do it or not, I'm not entirely sure. But I feel like `.read(0)` should still be supported.\r\n\r\nIf you guys agree that it should be supported, maybe considering a condition like this:\r\n```\r\nif (not chunk and amt > 0) or amt is None:\r\n```\n", "before_files": [{"content": "# Copyright (c) 2012-2013 Mitch Garnaat http://garnaat.org/\n# Copyright 2012-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.\n#\n# Licensed under the Apache License, Version 2.0 (the \"License\"). You\n# may not use this file except in compliance with the License. A copy of\n# the License is located at\n#\n# http://aws.amazon.com/apache2.0/\n#\n# or in the \"license\" file accompanying this file. This file is\n# distributed on an \"AS IS\" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF\n# ANY KIND, either express or implied. See the License for the specific\n# language governing permissions and limitations under the License.\n\nimport sys\nimport xml.etree.cElementTree\nimport logging\n\nfrom botocore import ScalarTypes\nfrom botocore.hooks import first_non_none_response\nfrom botocore.compat import json, set_socket_timeout, XMLParseError\nfrom botocore.exceptions import IncompleteReadError\nfrom botocore import parsers\n\n\nlogger = logging.getLogger(__name__)\n\n\nclass StreamingBody(object):\n    \"\"\"Wrapper class for an http response body.\n\n    This provides a few additional conveniences that do not exist\n    in the urllib3 model:\n\n        * Set the timeout on the socket (i.e read() timeouts)\n        * Auto validation of content length, if the amount of bytes\n          we read does not match the content length, an exception\n          is raised.\n\n    \"\"\"\n    def __init__(self, raw_stream, content_length):\n        self._raw_stream = raw_stream\n        self._content_length = content_length\n        self._amount_read = 0\n\n    def set_socket_timeout(self, timeout):\n        \"\"\"Set the timeout seconds on the socket.\"\"\"\n        # The problem we're trying to solve is to prevent .read() calls from\n        # hanging.  This can happen in rare cases.  What we'd like to ideally\n        # do is set a timeout on the .read() call so that callers can retry\n        # the request.\n        # Unfortunately, this isn't currently possible in requests.\n        # See: https://github.com/kennethreitz/requests/issues/1803\n        # So what we're going to do is reach into the guts of the stream and\n        # grab the socket object, which we can set the timeout on.  We're\n        # putting in a check here so in case this interface goes away, we'll\n        # know.\n        try:\n            # To further complicate things, the way to grab the\n            # underlying socket object from an HTTPResponse is different\n            # in py2 and py3.  So this code has been pushed to botocore.compat.\n            set_socket_timeout(self._raw_stream, timeout)\n        except AttributeError:\n            logger.error(\"Cannot access the socket object of \"\n                         \"a streaming response.  It's possible \"\n                         \"the interface has changed.\", exc_info=True)\n            raise\n\n    def read(self, amt=None):\n        \"\"\"Read at most amt bytes from the stream.\n\n        If the amt argument is omitted, read all data.\n        \"\"\"\n        chunk = self._raw_stream.read(amt)\n        self._amount_read += len(chunk)\n        if not chunk or amt is None:\n            # If the server sends empty contents or\n            # we ask to read all of the contents, then we know\n            # we need to verify the content length.\n            self._verify_content_length()\n        return chunk\n\n    def _verify_content_length(self):\n        # See: https://github.com/kennethreitz/requests/issues/1855\n        # Basically, our http library doesn't do this for us, so we have\n        # to do this ourself.\n        if self._content_length is not None and \\\n                self._amount_read != int(self._content_length):\n            raise IncompleteReadError(\n                actual_bytes=self._amount_read,\n                expected_bytes=int(self._content_length))\n\n    def close(self):\n        \"\"\"Close the underlying http response stream.\"\"\"\n        self._raw_stream.close()\n\n\ndef get_response(operation_model, http_response):\n    protocol = operation_model.metadata['protocol']\n    response_dict = {\n        'headers': http_response.headers,\n        'status_code': http_response.status_code,\n    }\n    # TODO: Unfortunately, we have to have error logic here.\n    # If it looks like an error, in the streaming response case we\n    # need to actually grab the contents.\n    if response_dict['status_code'] >= 300:\n        response_dict['body'] = http_response.content\n    elif operation_model.has_streaming_output:\n        response_dict['body'] = StreamingBody(\n            http_response.raw, response_dict['headers'].get('content-length'))\n    else:\n        response_dict['body'] = http_response.content\n\n    parser = parsers.create_parser(protocol)\n    return http_response, parser.parse(response_dict,\n                                       operation_model.output_shape)\n", "path": "botocore/response.py"}], "after_files": [{"content": "# Copyright (c) 2012-2013 Mitch Garnaat http://garnaat.org/\n# Copyright 2012-2014 Amazon.com, Inc. or its affiliates. All Rights Reserved.\n#\n# Licensed under the Apache License, Version 2.0 (the \"License\"). You\n# may not use this file except in compliance with the License. A copy of\n# the License is located at\n#\n# http://aws.amazon.com/apache2.0/\n#\n# or in the \"license\" file accompanying this file. This file is\n# distributed on an \"AS IS\" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF\n# ANY KIND, either express or implied. See the License for the specific\n# language governing permissions and limitations under the License.\n\nimport sys\nimport xml.etree.cElementTree\nimport logging\n\nfrom botocore import ScalarTypes\nfrom botocore.hooks import first_non_none_response\nfrom botocore.compat import json, set_socket_timeout, XMLParseError\nfrom botocore.exceptions import IncompleteReadError\nfrom botocore import parsers\n\n\nlogger = logging.getLogger(__name__)\n\n\nclass StreamingBody(object):\n    \"\"\"Wrapper class for an http response body.\n\n    This provides a few additional conveniences that do not exist\n    in the urllib3 model:\n\n        * Set the timeout on the socket (i.e read() timeouts)\n        * Auto validation of content length, if the amount of bytes\n          we read does not match the content length, an exception\n          is raised.\n\n    \"\"\"\n    def __init__(self, raw_stream, content_length):\n        self._raw_stream = raw_stream\n        self._content_length = content_length\n        self._amount_read = 0\n\n    def set_socket_timeout(self, timeout):\n        \"\"\"Set the timeout seconds on the socket.\"\"\"\n        # The problem we're trying to solve is to prevent .read() calls from\n        # hanging.  This can happen in rare cases.  What we'd like to ideally\n        # do is set a timeout on the .read() call so that callers can retry\n        # the request.\n        # Unfortunately, this isn't currently possible in requests.\n        # See: https://github.com/kennethreitz/requests/issues/1803\n        # So what we're going to do is reach into the guts of the stream and\n        # grab the socket object, which we can set the timeout on.  We're\n        # putting in a check here so in case this interface goes away, we'll\n        # know.\n        try:\n            # To further complicate things, the way to grab the\n            # underlying socket object from an HTTPResponse is different\n            # in py2 and py3.  So this code has been pushed to botocore.compat.\n            set_socket_timeout(self._raw_stream, timeout)\n        except AttributeError:\n            logger.error(\"Cannot access the socket object of \"\n                         \"a streaming response.  It's possible \"\n                         \"the interface has changed.\", exc_info=True)\n            raise\n\n    def read(self, amt=None):\n        \"\"\"Read at most amt bytes from the stream.\n\n        If the amt argument is omitted, read all data.\n        \"\"\"\n        chunk = self._raw_stream.read(amt)\n        self._amount_read += len(chunk)\n        if amt is None or (not chunk and amt > 0):\n            # If the server sends empty contents or\n            # we ask to read all of the contents, then we know\n            # we need to verify the content length.\n            self._verify_content_length()\n        return chunk\n\n    def _verify_content_length(self):\n        # See: https://github.com/kennethreitz/requests/issues/1855\n        # Basically, our http library doesn't do this for us, so we have\n        # to do this ourself.\n        if self._content_length is not None and \\\n                self._amount_read != int(self._content_length):\n            raise IncompleteReadError(\n                actual_bytes=self._amount_read,\n                expected_bytes=int(self._content_length))\n\n    def close(self):\n        \"\"\"Close the underlying http response stream.\"\"\"\n        self._raw_stream.close()\n\n\ndef get_response(operation_model, http_response):\n    protocol = operation_model.metadata['protocol']\n    response_dict = {\n        'headers': http_response.headers,\n        'status_code': http_response.status_code,\n    }\n    # TODO: Unfortunately, we have to have error logic here.\n    # If it looks like an error, in the streaming response case we\n    # need to actually grab the contents.\n    if response_dict['status_code'] >= 300:\n        response_dict['body'] = http_response.content\n    elif operation_model.has_streaming_output:\n        response_dict['body'] = StreamingBody(\n            http_response.raw, response_dict['headers'].get('content-length'))\n    else:\n        response_dict['body'] = http_response.content\n\n    parser = parsers.create_parser(protocol)\n    return http_response, parser.parse(response_dict,\n                                       operation_model.output_shape)\n", "path": "botocore/response.py"}]}