diff options
Diffstat (limited to 'utils/ipc/mojo/public/tools/mojom/mojom/generate/pack.py')
-rw-r--r-- | utils/ipc/mojo/public/tools/mojom/mojom/generate/pack.py | 151 |
1 files changed, 130 insertions, 21 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 index 88b77c98..61240426 100644 --- a/utils/ipc/mojo/public/tools/mojom/mojom/generate/pack.py +++ b/utils/ipc/mojo/public/tools/mojom/mojom/generate/pack.py @@ -1,7 +1,8 @@ -# Copyright 2013 The Chromium Authors. All rights reserved. +# Copyright 2013 The Chromium Authors # Use of this source code is governed by a BSD-style license that can be # found in the LICENSE file. +import copy from mojom.generate import module as mojom # This module provides a mechanism for determining the packed order and offsets @@ -15,7 +16,7 @@ from mojom.generate import module as mojom HEADER_SIZE = 8 -class PackedField(object): +class PackedField: kind_to_size = { mojom.BOOL: 1, mojom.INT8: 1, @@ -75,18 +76,55 @@ class PackedField(object): return 8 return cls.GetSizeForKind(kind) - def __init__(self, field, index, ordinal): + def __init__(self, + field, + index, + ordinal, + original_field=None, + sub_ordinal=None, + linked_value_packed_field=None): """ Args: field: the original field. index: the position of the original field in the struct. ordinal: the ordinal of the field for serialization. + original_field: See below. + sub_ordinal: See below. + linked_value_packed_field: See below. + + original_field, sub_ordinal, and linked_value_packed_field are used to + support nullable ValueKind fields. For legacy reasons, nullable ValueKind + fields actually generate two PackedFields. This allows: + + - backwards compatibility prior to Mojo support for nullable ValueKinds. + - correct packing of fields for the aforementioned backwards compatibility. + + When translating Fields to PackedFields, the original field is turned into + two PackedFields: the first PackedField always has type mojom.BOOL, while + the second PackedField has the non-nullable version of the field's kind. + + When constructing these PackedFields, original_field references the field + as defined in the mojom; the name as defined in the mojom will be used for + all layers above the wire/data layer. + + sub_ordinal is used to sort the two PackedFields correctly with respect to + each other: the first mojom.BOOL field always has sub_ordinal 0, while the + second field always has sub_ordinal 1. + + Finally, linked_value_packed_field is used by the serialization and + deserialization helpers, which generally just iterate over a PackedStruct's + PackedField's in ordinal order. This allows the helpers to easily reference + any related PackedFields rather than having to lookup related PackedFields + by index while iterating. """ self.field = field self.index = index self.ordinal = ordinal - self.size = self.GetSizeForKind(field.kind) - self.alignment = self.GetAlignmentForKind(field.kind) + self.original_field = original_field + self.sub_ordinal = sub_ordinal + self.linked_value_packed_field = linked_value_packed_field + self.size = self.GetSizeForKind(self.field.kind) + self.alignment = self.GetAlignmentForKind(self.field.kind) self.offset = None self.bit = None self.min_version = None @@ -120,7 +158,33 @@ def GetPayloadSizeUpToField(field): return offset + pad -class PackedStruct(object): +def IsNullableValueKindPackedField(field): + """Returns true if `field` is derived from a nullable ValueKind field. + + Nullable ValueKind fields often require special handling in the bindings due + to the way the implementation is constrained for wire compatibility. + """ + assert isinstance(field, PackedField) + return field.sub_ordinal is not None + + +def IsPrimaryNullableValueKindPackedField(field): + """Returns true if `field` is derived from a nullable ValueKind mojom field + and is the "primary" field. + + The primary field is a bool PackedField that controls if the field should be + considered as present or not; it will have a reference to the PackedField that + holds the actual value representation if considered present. + + Bindings code that translates between the wire protocol and the higher layers + can use this to simplify mapping multiple PackedFields to the single field + that is logically exposed to bindings consumers. + """ + assert isinstance(field, PackedField) + return field.linked_value_packed_field is not None + + +class PackedStruct: def __init__(self, struct): self.struct = struct # |packed_fields| contains all the fields, in increasing offset order. @@ -139,9 +203,41 @@ class PackedStruct(object): for index, field in enumerate(struct.fields): if field.ordinal is not None: ordinal = field.ordinal - src_fields.append(PackedField(field, index, ordinal)) + # Nullable value types are a bit weird: they generate two PackedFields + # despite being a single ValueKind. This is for wire compatibility to + # ease the transition from legacy mojom syntax where nullable value types + # were not supported. + if isinstance(field.kind, mojom.ValueKind) and field.kind.is_nullable: + # The suffixes intentionally use Unicode codepoints which are considered + # valid C++/Java/JavaScript identifiers, yet are unlikely to be used in + # actual user code. + has_value_field = copy.copy(field) + has_value_field.name = f'{field.mojom_name}_$flag' + has_value_field.kind = mojom.BOOL + + value_field = copy.copy(field) + value_field.name = f'{field.mojom_name}_$value' + value_field.kind = field.kind.MakeUnnullableKind() + + value_packed_field = PackedField(value_field, + index, + ordinal, + original_field=field, + sub_ordinal=1, + linked_value_packed_field=None) + has_value_packed_field = PackedField( + has_value_field, + index, + ordinal, + original_field=field, + sub_ordinal=0, + linked_value_packed_field=value_packed_field) + src_fields.append(has_value_packed_field) + src_fields.append(value_packed_field) + else: + src_fields.append(PackedField(field, index, ordinal)) ordinal += 1 - src_fields.sort(key=lambda field: field.ordinal) + src_fields.sort(key=lambda field: (field.ordinal, field.sub_ordinal)) # Set |min_version| for each field. next_min_version = 0 @@ -156,10 +252,11 @@ class PackedStruct(object): 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)) + raise Exception( + "Non-nullable reference 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 @@ -186,7 +283,7 @@ class PackedStruct(object): dst_fields.append(src_field) -class ByteInfo(object): +class ByteInfo: def __init__(self): self.is_padding = False self.packed_fields = [] @@ -214,10 +311,11 @@ def GetByteLayout(packed_struct): return byte_info -class VersionInfo(object): - def __init__(self, version, num_fields, num_bytes): +class VersionInfo: + def __init__(self, version, num_fields, num_packed_fields, num_bytes): self.version = version self.num_fields = num_fields + self.num_packed_fields = num_packed_fields self.num_bytes = num_bytes @@ -235,24 +333,35 @@ def GetVersionInfo(packed_struct): versions = [] last_version = 0 last_num_fields = 0 + last_num_packed_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, + VersionInfo(last_version, last_num_fields, last_num_packed_fields, last_payload_size + HEADER_SIZE)) last_version = packed_field.min_version - last_num_fields += 1 + # Nullable numeric fields (e.g. `int32?`) expand to two packed fields, so to + # avoid double-counting, only increment if the field is: + # - not used for representing a nullable value kind field, or + # - the primary field representing the nullable value kind field. + last_num_fields += 1 if ( + not IsNullableValueKindPackedField(packed_field) + or IsPrimaryNullableValueKindPackedField(packed_field)) else 0 + + last_num_packed_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) + last_payload_size = max(GetPayloadSizeUpToField(packed_field), + last_payload_size) - assert len(versions) == 0 or last_num_fields != versions[-1].num_fields + assert len( + versions) == 0 or last_num_packed_fields != versions[-1].num_packed_fields versions.append( - VersionInfo(last_version, last_num_fields, + VersionInfo(last_version, last_num_fields, last_num_packed_fields, last_payload_size + HEADER_SIZE)) return versions |