Core mojo API for python.

mojo/public/python/mojo/system.pyx

Index: mojo/public/python/mojo/system.pyx
diff --git a/mojo/public/python/mojo/system.pyx b/mojo/public/python/mojo/system.pyx
new file mode 100644
index 0000000000000000000000000000000000000000..58da5b0e8b556e49ad289bfcb12562b9f2964f95
--- /dev/null
+++ b/mojo/public/python/mojo/system.pyx
@@ -0,0 +1,697 @@
+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# distutils language = c++
+
+cimport c_core
+
+from cpython.buffer cimport PyBUF_CONTIG
+from cpython.buffer cimport PyBUF_CONTIG_RO
+from cpython.buffer cimport Py_buffer
+from cpython.buffer cimport PyBuffer_FillInfo
+from cpython.buffer cimport PyBuffer_Release
+from cpython.buffer cimport PyObject_GetBuffer
+from cpython.mem cimport PyMem_Malloc, PyMem_Free
+from libc.stdint cimport int32_t, int64_t, uint32_t, uint64_t, uintptr_t
+
+def set_system_thunks(system_thunks_as_object):
+  """Bind the basic Mojo Core functions.
+
+  This should only be used by the embedder.
+  """
+  cdef const c_core.MojoSystemThunks* system_thunks = (
+      <const c_core.MojoSystemThunks*><uintptr_t>system_thunks_as_object)
+  c_core.MojoSetSystemThunks(system_thunks)
+
+HANDLE_INVALID = c_core.MOJO_HANDLE_INVALID
+RESULT_OK = c_core.MOJO_RESULT_OK
+RESULT_CANCELLED = c_core.MOJO_RESULT_CANCELLED
+RESULT_UNKNOWN = c_core.MOJO_RESULT_UNKNOWN
+RESULT_INVALID_ARGUMENT = c_core.MOJO_RESULT_INVALID_ARGUMENT
+RESULT_DEADLINE_EXCEEDED = c_core.MOJO_RESULT_DEADLINE_EXCEEDED
+RESULT_NOT_FOUND = c_core.MOJO_RESULT_NOT_FOUND
+RESULT_ALREADY_EXISTS = c_core.MOJO_RESULT_ALREADY_EXISTS
+RESULT_PERMISSION_DENIED = c_core.MOJO_RESULT_PERMISSION_DENIED
+RESULT_RESOURCE_EXHAUSTED = c_core.MOJO_RESULT_RESOURCE_EXHAUSTED
+RESULT_FAILED_PRECONDITION = c_core.MOJO_RESULT_FAILED_PRECONDITION
+RESULT_ABORTED = c_core.MOJO_RESULT_ABORTED
+RESULT_OUT_OF_RANGE = c_core.MOJO_RESULT_OUT_OF_RANGE
+RESULT_UNIMPLEMENTED = c_core.MOJO_RESULT_UNIMPLEMENTED
+RESULT_INTERNAL = c_core.MOJO_RESULT_INTERNAL
+RESULT_UNAVAILABLE = c_core.MOJO_RESULT_UNAVAILABLE
+RESULT_DATA_LOSS = c_core.MOJO_RESULT_DATA_LOSS
+RESULT_BUSY = c_core.MOJO_RESULT_BUSY
+RESULT_SHOULD_WAIT = c_core.MOJO_RESULT_SHOULD_WAIT
+DEADLINE_INDEFINITE = c_core.MOJO_DEADLINE_INDEFINITE
+HANDLE_SIGNAL_NONE = c_core.MOJO_HANDLE_SIGNAL_NONE
+HANDLE_SIGNAL_READABLE = c_core.MOJO_HANDLE_SIGNAL_READABLE
+HANDLE_SIGNAL_WRITABLE = c_core.MOJO_HANDLE_SIGNAL_WRITABLE
+WRITE_MESSAGE_FLAG_NONE = c_core.MOJO_WRITE_MESSAGE_FLAG_NONE
+READ_MESSAGE_FLAG_NONE = c_core.MOJO_READ_MESSAGE_FLAG_NONE
+READ_MESSAGE_FLAG_MAY_DISCARD = c_core.MOJO_READ_MESSAGE_FLAG_MAY_DISCARD
+WRITE_DATA_FLAG_NONE = c_core.MOJO_WRITE_DATA_FLAG_NONE
+WRITE_DATA_FLAG_ALL_OR_NONE = c_core.MOJO_WRITE_DATA_FLAG_ALL_OR_NONE
+READ_DATA_FLAG_NONE = c_core.MOJO_READ_DATA_FLAG_NONE
+READ_DATA_FLAG_ALL_OR_NONE = c_core.MOJO_READ_DATA_FLAG_ALL_OR_NONE
+READ_DATA_FLAG_DISCARD = c_core.MOJO_READ_DATA_FLAG_DISCARD
+READ_DATA_FLAG_QUERY = c_core.MOJO_READ_DATA_FLAG_QUERY
+MAP_BUFFER_FLAG_NONE = c_core.MOJO_MAP_BUFFER_FLAG_NONE
+
+def get_time_ticks_now():
+  """Monotonically increasing tick count representing "right now."
+
+  See mojo/public/c/system/functions.h
+  """
+  return c_core.MojoGetTimeTicksNow()
+
+cdef class _ScopedMemory:
+  """Allocate memory at creation, and deallocate it at destruction."""
+  cdef void* memory
+  def __init__(self, size):
+    self.memory = PyMem_Malloc(size)
+
+  def __dealloc__(self):
+    PyMem_Free(self.memory)
+
+cdef class _ScopedBuffer:
+  """Retrieve pointer to a buffer a creation, and release it at destruction.
+  """
+  cdef Py_buffer _buf
+  cdef void* buf
+  cdef Py_ssize_t len
+
+  def __init__(self, obj, flags=PyBUF_CONTIG_RO):
+    if obj:
+      if PyObject_GetBuffer(obj, &self._buf, flags) < 0:
+        raise TypeError("Unable to read buffer.")

[pkl (ping after 24h if needed), 2014/08/21 09:32:47]

style: Be consistent with string quotes. Stick with either single or double
quotes.

[qsr, 2014/08/21 12:10:05]

Done.

+      self.buf = self._buf.buf
+      self.len = self._buf.len
+    else:
+      self.buf = NULL
+      self.len = 0
+
+  def __dealloc__(self):
+    if self.buf:
+      PyBuffer_Release(&self._buf)
+
+def _slice_buffer(buffer, size):
+  """Slice the given buffer, reducing it to the given size. Return None if None

[pkl (ping after 24h if needed), 2014/08/21 09:32:47]

nit: Line break with a blank line after "...given size." and then put "Return
None if..." .

[qsr, 2014/08/21 12:10:05]

Done.

+  is passed in.
+  """
+  if not buffer:

[pkl (ping after 24h if needed), 2014/08/21 09:32:47]

How about test with this?
  if type(buffer) not in (types.ListType, types.TupleType):
    return buffer

This safely filters out bad input like buffer=True, buffer=1, buffer="x", etc.

[qsr, 2014/08/21 12:10:05]

 This is an internal method. Do we want to pay the runtime cost for internal
validation?

+    return buffer
+  return buffer[:size]
+
+cdef class _NativeMemoryView(object):
+  """Create a python buffer wrapping the given memory.
+
+  Will also retain the given handle until this object is deallocated.
+  """
+  cdef void* _memory
+  cdef uint32_t _size
+  cdef char _read_only
+  cdef char _wrapped
+  cdef object _handle
+
+  def __init__(self, handle):
+    self._handle = handle
+
+  def __cinit__(self):
+    self._memory = NULL
+    self._size = 0
+    self._read_only = True
+    self._wrapped = False
+
+  cdef wrap(self,
+            const void* memory,
+            uint32_t size,
+            read_only=True):
+    """Makes this buffer wraps the given memory.
+
+    Must be called before using this buffer, and must only be called once.
+    """
+    assert not self._wrapped
+    self._wrapped = True
+    self._memory = <void*>memory
+    self._size = size
+    self._read_only = read_only
+
+  # buffer interface (PEP 3118)
+  def __getbuffer__(self, Py_buffer *view, int flags):
+    assert self._wrapped
+    if view == NULL:
+      return
+    PyBuffer_FillInfo(view,
+                      self,
+                      self._memory,
+                      self._size,
+                      self._read_only,
+                      flags)
+
+  def __releasebuffer__(self, Py_buffer *view):
+    assert self._wrapped
+    pass
+
+  # legacy buffer interface
+  def __getsegcount__(self, Py_ssize_t *sizes):
+    assert self._wrapped
+    if sizes != NULL:
+      sizes[0] = self._size
+    return 1
+
+  def __getreadbuffer__(self, Py_ssize_t index, void **data):
+    assert self._wrapped
+    if index != 0:
+      raise SystemError('Index out of bounds: %d' % index)
+    data[0] = self._memory
+    return self._size
+
+  def __getwritebuffer__(self, Py_ssize_t index, void **data):
+    assert self._wrapped
+    if index != 0:
+      raise SystemError('Index out of bounds: %d' % index)
+    if self._read_only:
+      raise TypeError("Buffer is read-only.")
+    data[0] = self._memory
+    return self._size
+
+class MojoException(Exception):
+  """Exception wrapping a mojo result error code."""
+
+  def __init__(self, mojo_result):
+    self.mojo_result = mojo_result
+
+def wait_many(handles_and_signals, deadline):
+  """Waits on a list of handles.
+
+  Args:
+    handles_and_signals: list of pairs of handle and signal.

[pkl (ping after 24h if needed), 2014/08/21 09:32:47]

nit: s/pairs/tuples/

[qsr, 2014/08/21 12:10:05]

Done.

+
+  See mojo/public/c/system/functions.h
+  """
+  cdef uint32_t length = len(handles_and_signals)
+  cdef _ScopedMemory handles_alloc = _ScopedMemory(
+      sizeof(c_core.MojoHandle) * length)
+  cdef _ScopedMemory signals_alloc = _ScopedMemory(
+      sizeof(c_core.MojoHandleSignals) * length)
+  cdef c_core.MojoHandle* handles = <c_core.MojoHandle*>handles_alloc.memory
+  cdef c_core.MojoHandleSignals* signals = (
+      <c_core.MojoHandleSignals*>signals_alloc.memory)
+  cdef int index = 0
+  for (h, s) in handles_and_signals:
+    handles[index] = (<Handle?>h)._mojo_handle
+    signals[index] = s
+    index += 1
+  cdef c_core.MojoResult result = c_core.MOJO_RESULT_OK
+  cdef c_core.MojoDeadline cdeadline = deadline
+  with nogil:
+    result = c_core.MojoWaitMany(handles, signals, length, cdeadline)
+  return result
+
+cdef class DataPipeTwoPhaseBuffer(object):
+  """Return value for two phases read and write.
+
+  The buffer field contain the python buffer where data can be read or write.

[pkl (ping after 24h if needed), 2014/08/21 09:32:47]

s/contain/contains/
s/write/written/

[qsr, 2014/08/21 12:10:05]

Done.

+  When done with the buffer, the |end| method must be called with the number of
+  bytes read or written.
+  """
+
+  cdef object _buffer
+  cdef Handle _handle
+  cdef char _read
+
+  def __init__(self, handle, buffer, read=True):
+    self._buffer = buffer
+    self._handle = handle
+    self._read = read
+
+  def end(self, num_bytes):
+    self._buffer = None
+    cdef c_core.MojoResult result
+    if self._read:
+      result = c_core.MojoEndReadData(self._handle._mojo_handle, num_bytes)
+    else:
+      result = c_core.MojoEndWriteData(self._handle._mojo_handle, num_bytes)
+    self._handle = None
+    return result
+
+  @property
+  def buffer(self):
+    return self._buffer
+
+  def __dealloc__(self):
+    if self._buffer:
+      self.end(0)

[pkl (ping after 24h if needed), 2014/08/21 09:32:47]

Looks like you are doing some clean up work here by calling end(0). Wouldn't it
be an assert/error if self._buffer is not None because end() was not called?

[qsr, 2014/08/21 12:10:05]

Hum... I was thinking about letting this pass, but that is probably an error
from the user, changed.

+
+cdef class MappedBuffer(object):
+  """Return value for the |map| operation on shared buffer handles.
+
+  The buffer field contain the python buffer where data can be read or write.

[pkl (ping after 24h if needed), 2014/08/21 09:32:47]

ditto: contains. written.

[qsr, 2014/08/21 12:10:05]

Done.

+  When done with the buffer, the |unmao| method must be called.

[pkl (ping after 24h if needed), 2014/08/21 09:32:48]

s/unmao/unmap/

[qsr, 2014/08/21 12:10:05]

Done.

+  """
+
+  cdef object _buffer
+  cdef object _handle
+  cdef object _cleanup
+
+  def __init__(self, handle, buffer, cleanup):
+    self._buffer = buffer
+    self._handle = handle
+    self._cleanup = cleanup
+
+  def unmap(self):
+    self._buffer = None
+    cdef c_core.MojoResult result = self._cleanup()
+    self._cleanup = None
+    self._handle = None
+    return result
+
+  @property
+  def buffer(self):
+    return self._buffer
+
+  def __dealloc__(self):
+    if self._buffer:
+      self.unmap()
+
+cdef class Handle(object):
+  """A mojo object."""
+
+  cdef c_core.MojoHandle _mojo_handle
+
+  def __init__(self, mojo_handle = c_core.MOJO_HANDLE_INVALID):
+    self._mojo_handle = mojo_handle
+
+  def _invalidate(self):
+    """Invalidate the current handle.
+
+    The close operation is not called. It is the responsability of the caller to
+    ensure that the handle is not leaked.
+    """
+    self._mojo_handle = c_core.MOJO_HANDLE_INVALID
+
+  def is_valid(self):
+    """Returns whether this handle is valid."""
+    return self._mojo_handle != c_core.MOJO_HANDLE_INVALID
+
+  def close(self):
+    """Closes this handle.
+
+    See mojo/public/c/system/functions.h
+    """
+    cdef c_core.MojoResult result = c_core.MOJO_RESULT_OK
+    if self.is_valid():
+      result = c_core.MojoClose(self._mojo_handle)
+      self._invalidate()
+    return result
+
+  def __dealloc__(self):
+    self.close()
+
+  def wait(self, signals, deadline):
+    """Waits on the given handle.
+
+    See mojo/public/c/system/functions.h
+    """
+    cdef c_core.MojoHandle handle = self._mojo_handle
+    cdef c_core.MojoHandleSignals csignals = signals
+    cdef c_core.MojoDeadline cdeadline = deadline
+    cdef c_core.MojoResult result
+    with nogil:
+      result = c_core.MojoWait(handle, csignals, cdeadline)
+    return result
+
+  def write_message(self,
+                    buffer=None,
+                    handles=None,
+                    flags=WRITE_MESSAGE_FLAG_NONE):
+    """
+    Writes a message to the message pipe.

[pkl (ping after 24h if needed), 2014/08/21 09:32:47]

style: move this to the line with """

[qsr, 2014/08/21 12:10:05]

Done.

+
+    This method can only be used on a handle obtained from |MessagePipe()|.
+
+    See mojo/public/c/system/message_pipe.h
+    """
+    cdef _ScopedBuffer buffer_as_buffer = _ScopedBuffer(buffer)
+    cdef uint32_t input_buffer_length = buffer_as_buffer.len
+    cdef c_core.MojoHandle* input_handles = NULL
+    cdef uint32_t input_handles_length = 0
+    cdef _ScopedMemory handles_alloc = None
+    if handles:
+      input_handles_length = len(handles)
+      handles_alloc = _ScopedMemory(sizeof(c_core.MojoHandle) *
+                                    input_handles_length)
+      input_handles = <c_core.MojoHandle*>handles_alloc.memory
+      for i in xrange(input_handles_length):
+        input_handles[i] = (<Handle?>handles[i])._mojo_handle
+    cdef c_core.MojoResult res = c_core.MojoWriteMessage(self._mojo_handle,
+                                                         buffer_as_buffer.buf,
+                                                         input_buffer_length,
+                                                         input_handles,
+                                                         input_handles_length,
+                                                         flags)
+    if res == c_core.MOJO_RESULT_OK and handles:
+      # Handles have been transferred. Let's invalidate those.
+      for handle in handles:
+        handle._invalidate()
+    return res
+
+  def read_message(self,
+                   buffer=None,
+                   max_number_of_handles=0,
+                   flags=READ_MESSAGE_FLAG_NONE):
+    """Reads a message from the message pipe.
+
+    This method can only be used on a handle obtained from |MessagePipe()|.
+
+    This method returns a triplet of value (code, data, sizes):
+    - if code is RESULT_OK, sizes will be None, and data will be a pair of
+      (buffer, handles) where buffer is a view of the input buffer with the read
+      data, and handles is a list of received handles.
+    - if code is RESULT_RESOURCE_EXHAUSTED, data will be None and sizes will be
+      a pair of (buffer_size, handles_size) where buffer_size is the size of the
+      next message data and handles_size is the number of handles in the next
+      message.
+    - if code is any other value, data and sizes will be None.
+
+    See mojo/public/c/system/message_pipe.h
+    """
+    cdef _ScopedBuffer buffer_as_buffer = _ScopedBuffer(buffer, PyBUF_CONTIG)
+    cdef uint32_t input_buffer_length = buffer_as_buffer.len
+    cdef c_core.MojoHandle* input_handles = NULL
+    cdef uint32_t input_handles_length = 0
+    cdef _ScopedMemory handles_alloc = None
+    if max_number_of_handles > 0:
+      input_handles_length = max_number_of_handles
+      handles_alloc = _ScopedMemory(sizeof(c_core.MojoHandle) *
+                                    input_handles_length)
+      input_handles = <c_core.MojoHandle*>handles_alloc.memory
+    cdef res = c_core.MojoReadMessage(self._mojo_handle,
+                                      buffer_as_buffer.buf,
+                                      &input_buffer_length,
+                                      input_handles,
+                                      &input_handles_length,
+                                      flags)
+    if res == c_core.MOJO_RESULT_RESOURCE_EXHAUSTED:
+      return (res, None, (input_buffer_length, input_handles_length))
+    if res == c_core.MOJO_RESULT_OK:
+      returned_handles = [Handle(input_handles[i])
+                          for i in xrange(input_handles_length)]
+      return (res,
+              (_slice_buffer(buffer, input_buffer_length), returned_handles),
+              None)
+    return (res, None, None)
+
+  def write_data(self, buffer=None, flags=WRITE_DATA_FLAG_NONE):
+    """
+    Writes the given data to the data pipe producer.
+
+    This method can only be used on a producer handle obtained from
+    |DataPipe()|.
+
+    This method returns a tuple (code, num_bytes).
+    - If code is RESULT_OK, num_bytes is the number of written bytes.
+    - Otherwise, num_bytes is None.
+
+    See mojo/public/c/system/data_pipe.h
+    """
+    cdef _ScopedBuffer buffer_as_buffer = _ScopedBuffer(buffer)
+    cdef uint32_t input_buffer_length = buffer_as_buffer.len
+    cdef c_core.MojoResult res = c_core.MojoWriteData(self._mojo_handle,
+                                                      buffer_as_buffer.buf,
+                                                      &input_buffer_length,
+                                                      flags)
+    if res == c_core.MOJO_RESULT_OK:
+      return (res, input_buffer_length)
+    return (res, None)
+
+  def begin_write_data(self,
+                       min_size=None,
+                       flags=WRITE_DATA_FLAG_NONE):
+    """
+    Begins a two-phase write to the data pipe producer.
+
+    This method can only be used on a producer handle obtained from
+    |DataPipe()|.
+
+    This method returns a tuple (code, two_phase_buffer).
+    - If code is RESULT_OK, two_phase_buffer is a writable
+      DataPipeTwoPhaseBuffer
+    - Otherwise, two_phase_buffer is None.
+
+    See mojo/public/c/system/data_pipe.h
+    """
+    cdef void* out_buffer
+    cdef uint32_t out_size = 0
+    if min_size:
+      flags |= c_core.MOJO_WRITE_DATA_FLAG_ALL_OR_NONE
+      out_size = min_size
+    cdef c_core.MojoResult res = c_core.MojoBeginWriteData(self._mojo_handle,
+                                                           &out_buffer,
+                                                           &out_size,
+                                                           flags)
+    if res != c_core.MOJO_RESULT_OK:
+      return (res, None)
+    cdef _NativeMemoryView view_buffer = _NativeMemoryView(self)
+    view_buffer.wrap(out_buffer, out_size, read_only=False)
+    return (res, DataPipeTwoPhaseBuffer(self, memoryview(view_buffer), False))
+
+  def read_data(self, buffer=None, flags=READ_DATA_FLAG_NONE):
+    """Reads data from the data pipe consumer.
+
+    This method can only be used on a consumer handle obtained from
+    |DataPipe()|.
+
+    This method returns a tuple (code, buffer)
+    - if code is RESULT_OK, buffer will be a view of the input buffer with the
+      read data.
+    - otherwise, buffer will be None.
+
+    See mojo/public/c/system/data_pipe.h
+    """
+    cdef _ScopedBuffer buffer_as_buffer = _ScopedBuffer(buffer)
+    cdef uint32_t input_buffer_length = buffer_as_buffer.len
+    cdef c_core.MojoResult res = c_core.MojoReadData(self._mojo_handle,
+                                                     buffer_as_buffer.buf,
+                                                     &input_buffer_length,
+                                                     flags)
+    if res == c_core.MOJO_RESULT_OK:
+      return (res, _slice_buffer(buffer, input_buffer_length))
+    return (res, None)
+
+  def query_data(self, flags=READ_DATA_FLAG_NONE):
+    """Queries the amount of data available on the data pipe consumer.
+
+    This method can only be used on a consumer handle obtained from
+    |DataPipe()|.
+
+    This method returns a tuple (code, num_bytes)
+    - if code is RESULT_OK, num_bytes will be the number of bytes available on
+      the data pipe consumer.
+    - otherwise, num_bytes will be None.
+
+    See mojo/public/c/system/data_pipe.h
+    """
+    cdef uint32_t num_bytes = 0
+    cdef c_core.MojoResult res = c_core.MojoReadData(
+        self._mojo_handle,
+        NULL,
+        &num_bytes,
+        flags|c_core.MOJO_READ_DATA_FLAG_QUERY)
+    return (res, num_bytes)
+
+  def begin_read_data(self, min_size = None, flags=READ_DATA_FLAG_NONE):

[pkl (ping after 24h if needed), 2014/08/21 09:32:47]

style: no space around =

[qsr, 2014/08/21 12:10:05]

Done.

+    """
+    Begins a two-phase read to the data pipe consumer.
+
+    This method can only be used on a consumer handle obtained from
+    |DataPipe()|.
+
+    This method returns a tuple (code, two_phase_buffer).
+    - If code is RESULT_OK, two_phase_buffer is a readable
+      DataPipeTwoPhaseBuffer
+    - Otherwise, two_phase_buffer is None.
+
+    See mojo/public/c/system/data_pipe.h
+    """
+    cdef const void* out_buffer
+    cdef uint32_t out_size = 0
+    if min_size:
+      flags |= c_core.MOJO_READ_DATA_FLAG_ALL_OR_NONE
+      out_size = min_size
+    cdef c_core.MojoResult res = c_core.MojoBeginReadData(self._mojo_handle,
+                                                          &out_buffer,
+                                                          &out_size,
+                                                          flags)
+    if res != c_core.MOJO_RESULT_OK:
+      return (res, None)
+    cdef _NativeMemoryView view_buffer = _NativeMemoryView(self)
+    view_buffer.wrap(out_buffer, out_size, read_only=True)
+    return (res, DataPipeTwoPhaseBuffer(self, memoryview(view_buffer), True))
+
+  def duplicate(self, options=None):
+    """Duplicate the shared buffer handle.
+
+    This method can only be used on a handle obtained from
+    |create_shared_buffer()| or |duplicate()|.
+
+    See mojo/public/c/system/buffer.h
+    """
+    cdef c_core.MojoDuplicateBufferHandleOptions coptions
+    cdef c_core.MojoDuplicateBufferHandleOptions* coptions_ptr = NULL
+    cdef c_core.MojoHandle cnew_handle = c_core.MOJO_HANDLE_INVALID
+    if options:
+      coptions.struct_size = sizeof(c_core.MojoDuplicateBufferHandleOptions)
+      coptions.flags = options.flags
+      coptions_ptr = &coptions
+    cdef c_core.MojoResult result = c_core.MojoDuplicateBufferHandle(
+        self._mojo_handle, coptions_ptr, &cnew_handle)
+    new_handle = Handle(cnew_handle)
+    if result != c_core.MOJO_RESULT_OK:
+      raise MojoException(result)
+    return new_handle
+
+  def map(self, offset, num_bytes, flags=MAP_BUFFER_FLAG_NONE):
+    """Maps the part (at offset |offset| of length |num_bytes|) of the buffer.
+
+    This method can only be used on a handle obtained from
+    |create_shared_buffer()| or |duplicate()|.
+
+    This method returns a tuple (code, mapped_buffer).
+    - If code is RESULT_OK, mapped_buffer is a readable/writable
+      MappedBuffer
+    - Otherwise, mapped_buffer is None.
+
+    See mojo/public/c/system/buffer.h
+    """
+    cdef void* buffer
+    res = c_core.MojoMapBuffer(self._mojo_handle,
+                               offset,
+                               num_bytes,
+                               &buffer,
+                               flags)
+    if res != c_core.MOJO_RESULT_OK:
+      return (res, None)
+    cdef _NativeMemoryView view_buffer = _NativeMemoryView(self)
+    view_buffer.wrap(buffer, num_bytes, read_only=False)
+    return (res, MappedBuffer(self,
+                              memoryview(view_buffer),
+                              lambda: c_core.MojoUnmapBuffer(buffer)))
+
+class CreateMessagePipeOptions(object):
+  """Options for creating a message pipe.
+
+  See mojo/public/c/system/message_pipe.h
+  """
+  FLAG_NONE = c_core.MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_NONE
+
+  def __init__(self):
+    self.flags = CreateMessagePipeOptions.FLAG_NONE
+
+class MessagePipe(object):
+  """Creates a message pipe.
+
+  The two ends of the message pipe are accessible with the members handle0 and
+  handle1.
+
+  See mojo/public/c/system/message_pipe.h
+  """
+  def __init__(self, options=None):
+    cdef c_core.MojoCreateMessagePipeOptions coptions
+    cdef c_core.MojoCreateMessagePipeOptions* coptions_ptr = NULL
+    cdef c_core.MojoHandle chandle0 = c_core.MOJO_HANDLE_INVALID
+    cdef c_core.MojoHandle chandle1 = c_core.MOJO_HANDLE_INVALID
+    if options:
+      coptions.struct_size = sizeof(c_core.MojoCreateMessagePipeOptions)
+      coptions.flags = options.flags
+      coptions_ptr = &coptions
+    cdef c_core.MojoResult result = c_core.MojoCreateMessagePipe(coptions_ptr,
+                                                                 &chandle0,
+                                                                 &chandle1)
+    self.handle0 = Handle(chandle0)
+    self.handle1 = Handle(chandle1)
+    if result != c_core.MOJO_RESULT_OK:
+      raise c_core.MojoException(result)
+
+
+class CreateDataPipeOptions(object):
+  """Options for creating a data pipe.
+
+  See mojo/public/c/system/data_pipe.h
+  """
+  FLAG_NONE = c_core.MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_NONE
+  FLAG_MAY_DISCARD = c_core.MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_MAY_DISCARD
+
+  def __init__(self):
+    self.flags = CreateDataPipeOptions.FLAG_NONE
+    self.element_num_bytes = 1
+    self.capacity_num_bytes = 0
+
+class DataPipe(object):
+  """Creates a data pipe.
+
+  The producer end of the data pipe is accessible with the member
+  producer_handle and the consumer end of the data pipe is accessible with the
+  member cconsumer_handle.
+
+  See mojo/public/c/system/data_pipe.h
+  """
+  def __init__(self, options=None):
+    cdef c_core.MojoCreateDataPipeOptions coptions
+    cdef c_core.MojoCreateDataPipeOptions* coptions_ptr = NULL
+    cdef c_core.MojoHandle cproducer_handle = c_core.MOJO_HANDLE_INVALID
+    cdef c_core.MojoHandle cconsumer_handle = c_core.MOJO_HANDLE_INVALID
+    if options:
+      coptions.struct_size = sizeof(c_core.MojoCreateDataPipeOptions)
+      coptions.flags = options.flags
+      coptions.element_num_bytes = options.element_num_bytes
+      coptions.capacity_num_bytes = options.capacity_num_bytes
+      coptions_ptr = &coptions
+    cdef c_core.MojoResult result = c_core.MojoCreateDataPipe(coptions_ptr,
+                                                              &cproducer_handle,
+                                                              &cconsumer_handle)
+    self.producer_handle = Handle(cproducer_handle)
+    self.consumer_handle = Handle(cconsumer_handle)
+    if result != c_core.MOJO_RESULT_OK:
+      raise MojoException(result)
+
+class CreateSharedBufferOptions(object):
+  """Options for creating a shared buffer.
+
+  See mojo/public/c/system/buffer.h
+  """
+  FLAG_NONE = c_core.MOJO_CREATE_SHARED_BUFFER_OPTIONS_FLAG_NONE
+
+  def __init__(self):
+    self.flags = CreateSharedBufferOptions.FLAG_NONE
+
+def create_shared_buffer(num_bytes, options=None):
+  """Creates a buffer of size |num_bytes| bytes that can be shared.
+
+  See mojo/public/c/system/buffer.h
+  """
+  cdef c_core.MojoCreateSharedBufferOptions coptions
+  cdef c_core.MojoCreateSharedBufferOptions* coptions_ptr = NULL
+  cdef c_core.MojoHandle chandle = c_core.MOJO_HANDLE_INVALID
+  if options:
+    coptions.struct_size = sizeof(c_core.MojoCreateSharedBufferOptions)
+    coptions.flags = options.flags
+    coptions_ptr = &coptions
+  cdef c_core.MojoResult result = c_core.MojoCreateSharedBuffer(coptions_ptr,
+                                                                num_bytes,
+                                                                &chandle)
+  handle = Handle(chandle)
+  if result != c_core.MOJO_RESULT_OK:
+    raise MojoException(result)
+  return handle
+
+class DuplicateSharedBufferOptions(object):
+  """Options for duplicating a shared buffer.
+
+  See mojo/public/c/system/buffer.h
+  """
+  FLAG_NONE = c_core.MOJO_DUPLICATE_BUFFER_HANDLE_OPTIONS_FLAG_NONE
+
+  def __init__(self):
+    self.flags = DuplicateSharedBufferOptions.FLAG_NONE