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# Copyright 2025 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
from dataclasses import dataclass
from enum import Enum
from typing import Optional
class AggregationKind(Enum):
"""Allowed aggregation types for data that uses "aggregate" declaration."""
NONE = "none"
ARRAY = "array"
MAP = "map"
@dataclass
class AggregationDetails:
"""Aggregation rules, if specified by the processed JSON file."""
kind: AggregationKind
name: Optional[str]
export_items: bool
elements: dict[str, str]
map_key_type: Optional[str]
def GetSortedArrayElements(self) -> list[str]:
"""Returns sorted list of names of all elements."""
return sorted(self.elements.keys())
def GetSortedMapElements(self) -> list[tuple[str, str]]:
"""Returns sorted mapping of all elements, including aliases."""
keys = sorted(self.elements.keys())
return [(key, self.elements[key]) for key in keys]
def GetAggregationDetails(description) -> AggregationDetails:
"""Extracts aggregation details from a JSON structure.
This function processes a JSON data object to determine its aggregation
properties. Aggregation details are specified within an optional "aggregation"
descriptor in the JSON input. If the descriptor is missing, no aggregation is
performed.
**Aggregation Descriptor Structure:**
- `type` (str): Defines the aggregation type. Options include:
- `"none"`: No aggregation (default/implied if descriptor is missing).
- `"array"`: Uses `std::span<Type>` for aggregation.
- `"map"`: Uses `base::fixed_flat_map<std::string_view, Type>` for
aggregation.
- `name` (str): The name assigned to the generated array or map.
- `export_items` (bool, optional): Whether aggregated items should be
exported (defaults to `true`).
- `map_aliases` (dict[str, str]) - if the aggregation `type` is set to
`"map"`, this field allows specifying additional aliases - elements
pointing to already defined structures.
- `map_key_type` (str) - the type representing the map key. Must be a
constexpr-constructible from const char[].
**Default Behavior:**
- If the `aggregation` descriptor is missing, the function defaults to:
- `type = "none"`
- `export_items = True`
- The `name` field is only relevant when aggregation is `array` or `map`.
**Parameters:**
description (dict): input JSON data file (not schema).
**Returns:**
AggregationDetails populated with relevant fields. This is always
returned, even if the data object does not include aggregation descriptor.
"""
aggregation = description.get('aggregation', {})
kind = AggregationKind(aggregation.get('type', 'none'))
name = aggregation.get('name', None)
export_items = aggregation.get('export_items', True)
map_aliases = aggregation.get('map_aliases', {})
map_key_type = None
if kind != AggregationKind.NONE and not name:
raise Exception("Aggregation container needs a `name`.")
elements = {}
for element in description.get('elements', {}).keys():
elements.update({element: element})
confirmed_aliases = {}
if kind == AggregationKind.MAP:
map_key_type = aggregation.get('map_key_type', 'std::string_view')
for alias, element in map_aliases.items():
# Confirmation check for duplicate entries.
# Note: we do not need to verify duplicate aliases, because `map_aliases`
# is already a dict - all keys should be unique.
if elements.get(alias, None):
raise Exception(f"Alias `{alias}` already defined as element.")
# Detect that alias does not point to a valid element.
if not elements.get(element, None):
raise Exception(f"Aliased element `{element}` does not exist.")
confirmed_aliases.update({alias: element})
elements.update(confirmed_aliases)
return AggregationDetails(kind, name, export_items, elements, map_key_type)
def GenerateCCAggregation(type_name: str,
aggregation: AggregationDetails) -> Optional[str]:
"""
Generates C++ aggregation code based on the aggregation kind.
Parameters:
type_name (str): The type name to be used in the aggregation.
aggregation (AggregationDetails): The aggregation details.
Returns:
Optional[str]: The generated C++ aggregation code if applicable, otherwise None.
"""
if aggregation.kind == AggregationKind.ARRAY:
return _GenerateCCArray(type_name, aggregation)
if aggregation.kind == AggregationKind.MAP:
return _GenerateCCMap(type_name, aggregation)
return None
def _GenerateCCArray(type_name: str, aggregation: AggregationDetails) -> str:
"""
Generates C++ code for an array aggregation.
Parameters:
type_name (str): The type name to be used in the aggregation.
aggregation (AggregationDetails): The aggregation details.
Returns:
str: The generated C++ array aggregation code.
"""
res = f'\nconst auto {aggregation.name} =\n'
res += f' std::array<const {type_name}*, {len(aggregation.elements)}>'
res += '({{\n'
for element_name in aggregation.elements.values():
res += f' &{element_name},\n'
res += '}});\n'
return res
def _GenerateCCMap(type_name: str, aggregation: AggregationDetails) -> str:
"""
Generates C++ code for a map aggregation.
Parameters:
type_name (str): The type name to be used in the aggregation.
aggregation (AggregationDetails): The aggregation details.
Returns:
str: The generated C++ map aggregation code.
"""
key_type = aggregation.map_key_type
res = f'\nconst auto {aggregation.name} =\n'
res += f' base::MakeFixedFlatMap<{key_type}, const {type_name}*>'
res += '({\n'
for (alias_name, element_name) in aggregation.GetSortedMapElements():
res += f' {{{key_type}("{alias_name}"), &{element_name}}},\n'
res += '});\n'
return res
def GenerateHHAggregation(type_name: str,
aggregation: AggregationDetails) -> Optional[str]:
"""
Generates header file aggregation code based on the aggregation kind.
Parameters:
type_name (str): The type name to be used in the aggregation.
aggregation (AggregationDetails): The aggregation details.
Returns:
Optional[str]: The generated header file aggregation code if applicable, otherwise None.
"""
if aggregation.kind == AggregationKind.ARRAY:
return _GenerateHHArray(type_name, aggregation)
if aggregation.kind == AggregationKind.MAP:
return _GenerateHHMap(type_name, aggregation)
return None
def _GenerateHHArray(type_name: str, aggregation: AggregationDetails) -> str:
"""
Generates header file code for an array aggregation.
Parameters:
type_name (str): The type name to be used in the aggregation.
aggregation (AggregationDetails): The aggregation details.
Returns:
str: The generated header file array aggregation declaration.
"""
res = '\nextern const '
res += f'std::array<const {type_name}*, {len(aggregation.elements)}> '
res += f'{aggregation.name};\n'
return res
def _GenerateHHMap(type_name: str, aggregation: AggregationDetails) -> str:
"""
Generates header file code for a map aggregation.
Parameters:
type_name (str): The type name to be used in the aggregation.
aggregation (AggregationDetails): The aggregation details.
Returns:
str: The generated header file map aggregation declaration.
"""
res = '\nextern const '
res += f'base::fixed_flat_map<{aggregation.map_key_type}, '
res += f'const {type_name}*, {len(aggregation.GetSortedMapElements())}> '
res += f'{aggregation.name};\n'
return res
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