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# -*- coding: utf-8 -*-
"""
requests_toolbelt.multipart.encoder
===================================
This holds all of the implementation details of the MultipartEncoder
"""
import contextlib
import io
import os
from uuid import uuid4
from .._compat import fields
class MultipartEncoder(object):
"""
The ``MultipartEncoder`` oject is a generic interface to the engine that
will create a ``multipart/form-data`` body for you.
The basic usage is:
.. code-block:: python
import requests
from requests_toolbelt import MultipartEncoder
encoder = MultipartEncoder({'field': 'value',
'other_field', 'other_value'})
r = requests.post('https://httpbin.org/post', data=encoder,
headers={'Content-Type': encoder.content_type})
If you do not need to take advantage of streaming the post body, you can
also do:
.. code-block:: python
r = requests.post('https://httpbin.org/post',
data=encoder.to_string(),
headers={'Content-Type': encoder.content_type})
If you want the encoder to use a specific order, you can use an
OrderedDict or more simply, a list of tuples:
.. code-block:: python
encoder = MultipartEncoder([('field', 'value'),
('other_field', 'other_value')])
.. versionchanged:: 0.4.0
You can also provide tuples as part values as you would provide them to
requests' ``files`` parameter.
.. code-block:: python
encoder = MultipartEncoder({
'field': ('file_name', b'{"a": "b"}', 'application/json',
{'X-My-Header': 'my-value'})
])
.. warning::
This object will end up directly in :mod:`httplib`. Currently,
:mod:`httplib` has a hard-coded read size of **8192 bytes**. This
means that it will loop until the file has been read and your upload
could take a while. This is **not** a bug in requests. A feature is
being considered for this object to allow you, the user, to specify
what size should be returned on a read. If you have opinions on this,
please weigh in on `this issue`_.
.. _this issue:
https://github.com/sigmavirus24/requests-toolbelt/issues/75
"""
def __init__(self, fields, boundary=None, encoding='utf-8'):
#: Boundary value either passed in by the user or created
self.boundary_value = boundary or uuid4().hex
# Computed boundary
self.boundary = '--{0}'.format(self.boundary_value)
#: Encoding of the data being passed in
self.encoding = encoding
# Pre-encoded boundary
self._encoded_boundary = b''.join([
encode_with(self.boundary, self.encoding),
encode_with('\r\n', self.encoding)
])
#: Fields provided by the user
self.fields = fields
#: Whether or not the encoder is finished
self.finished = False
#: Pre-computed parts of the upload
self.parts = []
# Pre-computed parts iterator
self._iter_parts = iter([])
# The part we're currently working with
self._current_part = None
# Cached computation of the body's length
self._len = None
# Our buffer
self._buffer = CustomBytesIO(encoding=encoding)
# Pre-compute each part's headers
self._prepare_parts()
# Load boundary into buffer
self._write_boundary()
@property
def len(self):
"""Length of the multipart/form-data body.
requests will first attempt to get the length of the body by calling
``len(body)`` and then by checking for the ``len`` attribute.
On 32-bit systems, the ``__len__`` method cannot return anything
larger than an integer (in C) can hold. If the total size of the body
is even slightly larger than 4GB users will see an OverflowError. This
manifested itself in `bug #80`_.
As such, we now calculate the length lazily as a property.
.. _bug #80:
https://github.com/sigmavirus24/requests-toolbelt/issues/80
"""
# If _len isn't already calculated, calculate, return, and set it
return self._len or self._calculate_length()
def __repr__(self):
return '<MultipartEncoder: {0!r}>'.format(self.fields)
def _calculate_length(self):
"""
This uses the parts to calculate the length of the body.
This returns the calculated length so __len__ can be lazy.
"""
boundary_len = len(self.boundary) # Length of --{boundary}
# boundary length + header length + body length + len('\r\n') * 2
self._len = sum(
(boundary_len + total_len(p) + 4) for p in self.parts
) + boundary_len + 4
return self._len
def _calculate_load_amount(self, read_size):
"""This calculates how many bytes need to be added to the buffer.
When a consumer read's ``x`` from the buffer, there are two cases to
satisfy:
1. Enough data in the buffer to return the requested amount
2. Not enough data
This function uses the amount of unread bytes in the buffer and
determines how much the Encoder has to load before it can return the
requested amount of bytes.
:param int read_size: the number of bytes the consumer requests
:returns: int -- the number of bytes that must be loaded into the
buffer before the read can be satisfied. This will be strictly
non-negative
"""
amount = read_size - total_len(self._buffer)
return amount if amount > 0 else 0
def _load(self, amount):
"""Load ``amount`` number of bytes into the buffer."""
self._buffer.smart_truncate()
part = self._current_part or self._next_part()
while amount == -1 or amount > 0:
written = 0
if not part.bytes_left_to_write():
written += self._write(b'\r\n')
written += self._write_boundary()
part = self._next_part()
if not part:
written += self._write_closing_boundary()
self.finished = True
break
written += part.write_to(self._buffer, amount)
if amount != -1:
amount -= written
def _next_part(self):
try:
p = self._current_part = next(self._iter_parts)
except StopIteration:
p = None
return p
def _iter_fields(self):
_fields = self.fields
if hasattr(self.fields, 'items'):
_fields = list(self.fields.items())
for k, v in _fields:
file_name = None
file_type = None
file_headers = None
if isinstance(v, (list, tuple)):
if len(v) == 2:
file_name, file_pointer = v
elif len(v) == 3:
file_name, file_pointer, file_type = v
else:
file_name, file_pointer, file_type, file_headers = v
else:
file_pointer = v
field = fields.RequestField(name=k, data=file_pointer,
filename=file_name,
headers=file_headers)
field.make_multipart(content_type=file_type)
yield field
def _prepare_parts(self):
"""This uses the fields provided by the user and creates Part objects.
It populates the `parts` attribute and uses that to create a
generator for iteration.
"""
enc = self.encoding
self.parts = [Part.from_field(f, enc) for f in self._iter_fields()]
self._iter_parts = iter(self.parts)
def _write(self, bytes_to_write):
"""Write the bytes to the end of the buffer.
:param bytes bytes_to_write: byte-string (or bytearray) to append to
the buffer
:returns: int -- the number of bytes written
"""
return self._buffer.append(bytes_to_write)
def _write_boundary(self):
"""Write the boundary to the end of the buffer."""
return self._write(self._encoded_boundary)
def _write_closing_boundary(self):
"""Write the bytes necessary to finish a multipart/form-data body."""
with reset(self._buffer):
self._buffer.seek(-2, 2)
self._buffer.write(b'--\r\n')
return 2
def _write_headers(self, headers):
"""Write the current part's headers to the buffer."""
return self._write(encode_with(headers, self.encoding))
@property
def content_type(self):
return str(
'multipart/form-data; boundary={0}'.format(self.boundary_value)
)
def to_string(self):
"""Return the entirety of the data in the encoder.
.. note::
This simply reads all of the data it can. If you have started
streaming or reading data from the encoder, this method will only
return whatever data is left in the encoder.
.. note::
This method affects the internal state of the encoder. Calling
this method will exhaust the encoder.
:returns: the multipart message
:rtype: bytes
"""
return self.read()
def read(self, size=-1):
"""Read data from the streaming encoder.
:param int size: (optional), If provided, ``read`` will return exactly
that many bytes. If it is not provided, it will return the
remaining bytes.
:returns: bytes
"""
if self.finished:
return self._buffer.read(size)
bytes_to_load = size
if bytes_to_load != -1 and bytes_to_load is not None:
bytes_to_load = self._calculate_load_amount(int(size))
self._load(bytes_to_load)
return self._buffer.read(size)
def IDENTITY(monitor):
return monitor
class MultipartEncoderMonitor(object):
"""
An object used to monitor the progress of a :class:`MultipartEncoder`.
The :class:`MultipartEncoder` should only be responsible for preparing and
streaming the data. For anyone who wishes to monitor it, they shouldn't be
using that instance to manage that as well. Using this class, they can
monitor an encoder and register a callback. The callback receives the
instance of the monitor.
To use this monitor, you construct your :class:`MultipartEncoder` as you
normally would.
.. code-block:: python
from requests_toolbelt import (MultipartEncoder,
MultipartEncoderMonitor)
import requests
def callback(encoder, bytes_read):
# Do something with this information
pass
m = MultipartEncoder(fields={'field0': 'value0'})
monitor = MultipartEncoderMonitor(m, callback)
headers = {'Content-Type': montior.content_type}
r = requests.post('https://httpbin.org/post', data=monitor,
headers=headers)
Alternatively, if your use case is very simple, you can use the following
pattern.
.. code-block:: python
from requests_toolbelt import MultipartEncoderMonitor
import requests
def callback(encoder, bytes_read):
# Do something with this information
pass
monitor = MultipartEncoderMonitor.from_fields(
fields={'field0': 'value0'}, callback
)
headers = {'Content-Type': montior.content_type}
r = requests.post('https://httpbin.org/post', data=monitor,
headers=headers)
"""
def __init__(self, encoder, callback=None):
#: Instance of the :class:`MultipartEncoder` being monitored
self.encoder = encoder
#: Optionally function to call after a read
self.callback = callback or IDENTITY
#: Number of bytes already read from the :class:`MultipartEncoder`
#: instance
self.bytes_read = 0
#: Avoid the same problem in bug #80
self.len = self.encoder.len
@classmethod
def from_fields(cls, fields, boundary=None, encoding='utf-8',
callback=None):
encoder = MultipartEncoder(fields, boundary, encoding)
return cls(encoder, callback)
@property
def content_type(self):
return self.encoder.content_type
def to_string(self):
return self.read()
def read(self, size=-1):
string = self.encoder.read(size)
self.bytes_read += len(string)
self.callback(self)
return string
def encode_with(string, encoding):
"""Encoding ``string`` with ``encoding`` if necessary.
:param str string: If string is a bytes object, it will not encode it.
Otherwise, this function will encode it with the provided encoding.
:param str encoding: The encoding with which to encode string.
:returns: encoded bytes object
"""
if not (string is None or isinstance(string, bytes)):
return string.encode(encoding)
return string
def readable_data(data, encoding):
"""Coerce the data to an object with a ``read`` method."""
if hasattr(data, 'read'):
return data
return CustomBytesIO(data, encoding)
def total_len(o):
if hasattr(o, '__len__'):
return len(o)
if hasattr(o, 'len'):
return o.len
if hasattr(o, 'fileno'):
try:
fileno = o.fileno()
except io.UnsupportedOperation:
pass
else:
return os.fstat(fileno).st_size
if hasattr(o, 'getvalue'):
# e.g. BytesIO, cStringIO.StringIO
return len(o.getvalue())
@contextlib.contextmanager
def reset(buffer):
"""Keep track of the buffer's current position and write to the end.
This is a context manager meant to be used when adding data to the buffer.
It eliminates the need for every function to be concerned with the
position of the cursor in the buffer.
"""
original_position = buffer.tell()
buffer.seek(0, 2)
yield
buffer.seek(original_position, 0)
def coerce_data(data, encoding):
"""Ensure that every object's __len__ behaves uniformly."""
if not isinstance(data, CustomBytesIO):
if hasattr(data, 'getvalue'):
return CustomBytesIO(data.getvalue(), encoding)
if hasattr(data, 'fileno'):
return FileWrapper(data)
if not hasattr(data, 'read'):
return CustomBytesIO(data, encoding)
return data
def to_list(fields):
if hasattr(fields, 'items'):
return list(fields.items())
return list(fields)
class Part(object):
def __init__(self, headers, body):
self.headers = headers
self.body = body
self.headers_unread = True
self.len = len(self.headers) + total_len(self.body)
@classmethod
def from_field(cls, field, encoding):
"""Create a part from a Request Field generated by urllib3."""
headers = encode_with(field.render_headers(), encoding)
body = coerce_data(field.data, encoding)
return cls(headers, body)
def bytes_left_to_write(self):
"""Determine if there are bytes left to write.
:returns: bool -- ``True`` if there are bytes left to write, otherwise
``False``
"""
to_read = 0
if self.headers_unread:
to_read += len(self.headers)
return (to_read + total_len(self.body)) > 0
def write_to(self, buffer, size):
"""Write the requested amount of bytes to the buffer provided.
The number of bytes written may exceed size on the first read since we
load the headers ambitiously.
:param CustomBytesIO buffer: buffer we want to write bytes to
:param int size: number of bytes requested to be written to the buffer
:returns: int -- number of bytes actually written
"""
written = 0
if self.headers_unread:
written += buffer.append(self.headers)
self.headers_unread = False
while total_len(self.body) > 0 and (size == -1 or written < size):
amount_to_read = size
if size != -1:
amount_to_read = size - written
written += buffer.append(self.body.read(amount_to_read))
return written
class CustomBytesIO(io.BytesIO):
def __init__(self, buffer=None, encoding='utf-8'):
buffer = encode_with(buffer, encoding)
super(CustomBytesIO, self).__init__(buffer)
def _get_end(self):
current_pos = self.tell()
self.seek(0, 2)
length = self.tell()
self.seek(current_pos, 0)
return length
@property
def len(self):
length = self._get_end()
return length - self.tell()
def append(self, bytes):
with reset(self):
written = self.write(bytes)
return written
def smart_truncate(self):
to_be_read = total_len(self)
already_read = self._get_end() - to_be_read
if already_read >= to_be_read:
old_bytes = self.read()
self.seek(0, 0)
self.truncate()
self.write(old_bytes)
self.seek(0, 0) # We want to be at the beginning
class FileWrapper(object):
def __init__(self, file_object):
self.fd = file_object
@property
def len(self):
return total_len(self.fd) - self.fd.tell()
def read(self, length=-1):
return self.fd.read(length)
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