froofle/protobuf/internal/output_stream.py

# Protocol Buffers - Google's data interchange format
# Copyright 2008 Google Inc.  All rights reserved.
# http://code.google.com/p/protobuf/
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
#     * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#     * 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.
#     * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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"""OutputStream is the primitive interface for sticking bits on the wire.

All protocol buffer serialization can be expressed in terms of
the OutputStream primitives provided here.
"""

__author__ = 'robinson@google.com (Will Robinson)'

import array
import struct
from froofle.protobuf import message
from froofle.protobuf.internal import wire_format



# Note that much of this code is ported from //net/proto/ProtocolBuffer, and
# that the interface is strongly inspired by CodedOutputStream from the C++
# proto2 implementation.


class OutputStream(object):

  """Contains all logic for writing bits, and ToString() to get the result."""

  def __init__(self):
    self._buffer = array.array('B')

  def AppendRawBytes(self, raw_bytes):
    """Appends raw_bytes to our internal buffer."""
    self._buffer.fromstring(raw_bytes)

  def AppendLittleEndian32(self, unsigned_value):
    """Appends an unsigned 32-bit integer to the internal buffer,
    in little-endian byte order.
    """
    if not 0 <= unsigned_value <= wire_format.UINT32_MAX:
      raise message.EncodeError(
          'Unsigned 32-bit out of range: %d' % unsigned_value)
    self._buffer.fromstring(struct.pack(
        wire_format.FORMAT_UINT32_LITTLE_ENDIAN, unsigned_value))

  def AppendLittleEndian64(self, unsigned_value):
    """Appends an unsigned 64-bit integer to the internal buffer,
    in little-endian byte order.
    """
    if not 0 <= unsigned_value <= wire_format.UINT64_MAX:
      raise message.EncodeError(
          'Unsigned 64-bit out of range: %d' % unsigned_value)
    self._buffer.fromstring(struct.pack(
        wire_format.FORMAT_UINT64_LITTLE_ENDIAN, unsigned_value))

  def AppendVarint32(self, value):
    """Appends a signed 32-bit integer to the internal buffer,
    encoded as a varint.  (Note that a negative varint32 will
    always require 10 bytes of space.)
    """
    if not wire_format.INT32_MIN <= value <= wire_format.INT32_MAX:
      raise message.EncodeError('Value out of range: %d' % value)
    self.AppendVarint64(value)

  def AppendVarUInt32(self, value):
    """Appends an unsigned 32-bit integer to the internal buffer,
    encoded as a varint.
    """
    if not 0 <= value <= wire_format.UINT32_MAX:
      raise message.EncodeError('Value out of range: %d' % value)
    self.AppendVarUInt64(value)

  def AppendVarint64(self, value):
    """Appends a signed 64-bit integer to the internal buffer,
    encoded as a varint.
    """
    if not wire_format.INT64_MIN <= value <= wire_format.INT64_MAX:
      raise message.EncodeError('Value out of range: %d' % value)
    if value < 0:
      value += (1 << 64)
    self.AppendVarUInt64(value)

  def AppendVarUInt64(self, unsigned_value):
    """Appends an unsigned 64-bit integer to the internal buffer,
    encoded as a varint.
    """
    if not 0 <= unsigned_value <= wire_format.UINT64_MAX:
      raise message.EncodeError('Value out of range: %d' % unsigned_value)
    while True:
      bits = unsigned_value & 0x7f
      unsigned_value >>= 7
      if not unsigned_value:
        self._buffer.append(bits)
        break
      self._buffer.append(0x80|bits)

  def ToString(self):
    """Returns a string containing the bytes in our internal buffer."""
    return self._buffer.tostring()