1 files changed, 258 insertions, 0 deletions
diff --git a/utils/ipc/mojo/public/tools/mojom/mojom/generate/pack.py b/utils/ipc/mojo/public/tools/mojom/mojom/generate/pack.py
new file mode 100644
index 00000000..88b77c98
--- /dev/null
+++ b/utils/ipc/mojo/public/tools/mojom/mojom/generate/pack.py
@@ -0,0 +1,258 @@
+# Copyright 2013 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.
+
+from mojom.generate import module as mojom
+
+# This module provides a mechanism for determining the packed order and offsets
+# of a mojom.Struct.
+#
+# ps = pack.PackedStruct(struct)
+# ps.packed_fields will access a list of PackedField objects, each of which
+# will have an offset, a size and a bit (for mojom.BOOLs).
+
+# Size of struct header in bytes: num_bytes [4B] + version [4B].
+HEADER_SIZE = 8
+
+
+class PackedField(object):
+  kind_to_size = {
+      mojom.BOOL: 1,
+      mojom.INT8: 1,
+      mojom.UINT8: 1,
+      mojom.INT16: 2,
+      mojom.UINT16: 2,
+      mojom.INT32: 4,
+      mojom.UINT32: 4,
+      mojom.FLOAT: 4,
+      mojom.HANDLE: 4,
+      mojom.MSGPIPE: 4,
+      mojom.SHAREDBUFFER: 4,
+      mojom.PLATFORMHANDLE: 4,
+      mojom.DCPIPE: 4,
+      mojom.DPPIPE: 4,
+      mojom.NULLABLE_HANDLE: 4,
+      mojom.NULLABLE_MSGPIPE: 4,
+      mojom.NULLABLE_SHAREDBUFFER: 4,
+      mojom.NULLABLE_PLATFORMHANDLE: 4,
+      mojom.NULLABLE_DCPIPE: 4,
+      mojom.NULLABLE_DPPIPE: 4,
+      mojom.INT64: 8,
+      mojom.UINT64: 8,
+      mojom.DOUBLE: 8,
+      mojom.STRING: 8,
+      mojom.NULLABLE_STRING: 8
+  }
+
+  @classmethod
+  def GetSizeForKind(cls, kind):
+    if isinstance(kind, (mojom.Array, mojom.Map, mojom.Struct, mojom.Interface,
+                         mojom.AssociatedInterface, mojom.PendingRemote,
+                         mojom.PendingAssociatedRemote)):
+      return 8
+    if isinstance(kind, mojom.Union):
+      return 16
+    if isinstance(kind, (mojom.InterfaceRequest, mojom.PendingReceiver)):
+      kind = mojom.MSGPIPE
+    if isinstance(
+        kind,
+        (mojom.AssociatedInterfaceRequest, mojom.PendingAssociatedReceiver)):
+      return 4
+    if isinstance(kind, mojom.Enum):
+      # TODO(mpcomplete): what about big enums?
+      return cls.kind_to_size[mojom.INT32]
+    if not kind in cls.kind_to_size:
+      raise Exception("Undefined type: %s. Did you forget to import the file "
+                      "containing the definition?" % kind.spec)
+    return cls.kind_to_size[kind]
+
+  @classmethod
+  def GetAlignmentForKind(cls, kind):
+    if isinstance(kind, (mojom.Interface, mojom.AssociatedInterface,
+                         mojom.PendingRemote, mojom.PendingAssociatedRemote)):
+      return 4
+    if isinstance(kind, mojom.Union):
+      return 8
+    return cls.GetSizeForKind(kind)
+
+  def __init__(self, field, index, ordinal):
+    """
+    Args:
+      field: the original field.
+      index: the position of the original field in the struct.
+      ordinal: the ordinal of the field for serialization.
+    """
+    self.field = field
+    self.index = index
+    self.ordinal = ordinal
+    self.size = self.GetSizeForKind(field.kind)
+    self.alignment = self.GetAlignmentForKind(field.kind)
+    self.offset = None
+    self.bit = None
+    self.min_version = None
+
+
+def GetPad(offset, alignment):
+  """Returns the pad necessary to reserve space so that |offset + pad| equals to
+  some multiple of |alignment|."""
+  return (alignment - (offset % alignment)) % alignment
+
+
+def GetFieldOffset(field, last_field):
+  """Returns a 2-tuple of the field offset and bit (for BOOLs)."""
+  if (field.field.kind == mojom.BOOL and last_field.field.kind == mojom.BOOL
+      and last_field.bit < 7):
+    return (last_field.offset, last_field.bit + 1)
+
+  offset = last_field.offset + last_field.size
+  pad = GetPad(offset, field.alignment)
+  return (offset + pad, 0)
+
+
+def GetPayloadSizeUpToField(field):
+  """Returns the payload size (not including struct header) if |field| is the
+  last field.
+  """
+  if not field:
+    return 0
+  offset = field.offset + field.size
+  pad = GetPad(offset, 8)
+  return offset + pad
+
+
+class PackedStruct(object):
+  def __init__(self, struct):
+    self.struct = struct
+    # |packed_fields| contains all the fields, in increasing offset order.
+    self.packed_fields = []
+    # |packed_fields_in_ordinal_order| refers to the same fields as
+    # |packed_fields|, but in ordinal order.
+    self.packed_fields_in_ordinal_order = []
+
+    # No fields.
+    if (len(struct.fields) == 0):
+      return
+
+    # Start by sorting by ordinal.
+    src_fields = self.packed_fields_in_ordinal_order
+    ordinal = 0
+    for index, field in enumerate(struct.fields):
+      if field.ordinal is not None:
+        ordinal = field.ordinal
+      src_fields.append(PackedField(field, index, ordinal))
+      ordinal += 1
+    src_fields.sort(key=lambda field: field.ordinal)
+
+    # Set |min_version| for each field.
+    next_min_version = 0
+    for packed_field in src_fields:
+      if packed_field.field.min_version is None:
+        assert next_min_version == 0
+      else:
+        assert packed_field.field.min_version >= next_min_version
+        next_min_version = packed_field.field.min_version
+      packed_field.min_version = next_min_version
+
+      if (packed_field.min_version != 0
+          and mojom.IsReferenceKind(packed_field.field.kind)
+          and not packed_field.field.kind.is_nullable):
+        raise Exception("Non-nullable fields are only allowed in version 0 of "
+                        "a struct. %s.%s is defined with [MinVersion=%d]." %
+                        (self.struct.name, packed_field.field.name,
+                         packed_field.min_version))
+
+    src_field = src_fields[0]
+    src_field.offset = 0
+    src_field.bit = 0
+    dst_fields = self.packed_fields
+    dst_fields.append(src_field)
+
+    # Then find first slot that each field will fit.
+    for src_field in src_fields[1:]:
+      last_field = dst_fields[0]
+      for i in range(1, len(dst_fields)):
+        next_field = dst_fields[i]
+        offset, bit = GetFieldOffset(src_field, last_field)
+        if offset + src_field.size <= next_field.offset:
+          # Found hole.
+          src_field.offset = offset
+          src_field.bit = bit
+          dst_fields.insert(i, src_field)
+          break
+        last_field = next_field
+      if src_field.offset is None:
+        # Add to end
+        src_field.offset, src_field.bit = GetFieldOffset(src_field, last_field)
+        dst_fields.append(src_field)
+
+
+class ByteInfo(object):
+  def __init__(self):
+    self.is_padding = False
+    self.packed_fields = []
+
+
+def GetByteLayout(packed_struct):
+  total_payload_size = GetPayloadSizeUpToField(
+      packed_struct.packed_fields[-1] if packed_struct.packed_fields else None)
+  byte_info = [ByteInfo() for i in range(total_payload_size)]
+
+  limit_of_previous_field = 0
+  for packed_field in packed_struct.packed_fields:
+    for i in range(limit_of_previous_field, packed_field.offset):
+      byte_info[i].is_padding = True
+    byte_info[packed_field.offset].packed_fields.append(packed_field)
+    limit_of_previous_field = packed_field.offset + packed_field.size
+
+  for i in range(limit_of_previous_field, len(byte_info)):
+    byte_info[i].is_padding = True
+
+  for byte in byte_info:
+    # A given byte cannot both be padding and have a fields packed into it.
+    assert not (byte.is_padding and byte.packed_fields)
+
+  return byte_info
+
+
+class VersionInfo(object):
+  def __init__(self, version, num_fields, num_bytes):
+    self.version = version
+    self.num_fields = num_fields
+    self.num_bytes = num_bytes
+
+
+def GetVersionInfo(packed_struct):
+  """Get version information for a struct.
+
+  Args:
+    packed_struct: A PackedStruct instance.
+
+  Returns:
+    A non-empty list of VersionInfo instances, sorted by version in increasing
+    order.
+    Note: The version numbers may not be consecutive.
+  """
+  versions = []
+  last_version = 0
+  last_num_fields = 0
+  last_payload_size = 0
+
+  for packed_field in packed_struct.packed_fields_in_ordinal_order:
+    if packed_field.min_version != last_version:
+      versions.append(
+          VersionInfo(last_version, last_num_fields,
+                      last_payload_size + HEADER_SIZE))
+      last_version = packed_field.min_version
+
+    last_num_fields += 1
+    # The fields are iterated in ordinal order here. However, the size of a
+    # version is determined by the last field of that version in pack order,
+    # instead of ordinal order. Therefore, we need to calculate the max value.
+    last_payload_size = max(
+        GetPayloadSizeUpToField(packed_field), last_payload_size)
+
+  assert len(versions) == 0 or last_num_fields != versions[-1].num_fields
+  versions.append(
+      VersionInfo(last_version, last_num_fields,
+                  last_payload_size + HEADER_SIZE))
+  return versions