pkg/dart2wasm/lib/util.dart

// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'dart:convert';

import 'package:kernel/ast.dart';
import 'package:kernel/core_types.dart';
import 'package:vm/metadata/direct_call.dart' show DirectCallMetadataRepository;
import 'package:vm/metadata/inferred_type.dart'
    show
        InferredTypeMetadataRepository,
        InferredReturnTypeMetadataRepository,
        InferredArgTypeMetadataRepository;
import 'package:vm/metadata/procedure_attributes.dart'
    show ProcedureAttributesMetadataRepository;
import 'package:vm/metadata/table_selector.dart'
    show TableSelectorMetadataRepository;
import 'package:vm/metadata/unreachable.dart';

final bool compilerAssertsEnabled = (() {
  bool compilerAsserts = false;
  assert(compilerAsserts = true);
  return compilerAsserts;
})();

bool hasPragma(CoreTypes coreTypes, Annotatable node, String name) {
  return getPragma(coreTypes, node, name, defaultValue: '') != null;
}

T? getPragma<T>(
  CoreTypes coreTypes,
  Annotatable node,
  String name, {
  T? defaultValue,
}) {
  for (Expression annotation in node.annotations) {
    if (annotation is ConstantExpression) {
      Constant constant = annotation.constant;
      if (constant is InstanceConstant) {
        if (constant.classNode == coreTypes.pragmaClass) {
          Constant? nameConstant =
              constant.fieldValues[coreTypes.pragmaName.fieldReference];
          if (nameConstant is StringConstant && nameConstant.value == name) {
            Constant? value =
                constant.fieldValues[coreTypes.pragmaOptions.fieldReference];
            if (value == null || value is NullConstant) {
              return defaultValue;
            }
            if (value is PrimitiveConstant<T>) {
              return value.value;
            }
            if (value is! T) {
              throw ArgumentError(
                "$name pragma argument has unexpected type "
                "${value.runtimeType} (expected $T)",
              );
            }
            return value as T;
          }
        }
      }
    }
  }
  return null;
}

bool hasWasmImportPragma(CoreTypes coreTypes, Member member) {
  return hasPragma(coreTypes, member, "wasm:import");
}

ImportName? getWasmImportPragma(CoreTypes coreTypes, Member member) {
  String? importName = getPragma(coreTypes, member, "wasm:import");
  if (importName != null) {
    int dot = importName.indexOf('.');
    if (dot != -1) {
      assert(!member.isInstanceMember);
      String module = importName.substring(0, dot);
      String name = importName.substring(dot + 1);
      return ImportName(module, name);
    }
  }

  return null;
}

final class ImportName {
  final String moduleName;
  final String itemName;

  ImportName(this.moduleName, this.itemName);

  @override
  String toString() {
    return '$moduleName.$itemName';
  }
}

bool hasWasmExportPragma(CoreTypes coreTypes, Member member) {
  return hasPragma(coreTypes, member, "wasm:export");
}

bool hasWasmWeakExportPragma(CoreTypes coreTypes, Member member) {
  return hasPragma(coreTypes, member, "wasm:weak-export");
}

String? getWasmExportPragma(CoreTypes coreTypes, Member member) {
  return getPragma<String>(
    coreTypes,
    member,
    'wasm:export',
    defaultValue: member.name.text,
  );
}

String? getWasmWeakExportPragma(CoreTypes coreTypes, Member member) {
  return getPragma<String>(
    coreTypes,
    member,
    'wasm:weak-export',
    defaultValue: member.name.text,
  );
}

bool hasWasmPureFunctionPragma(CoreTypes coreTypes, Member member) {
  return getPragma<bool>(
        coreTypes,
        member,
        'wasm:pure-function',
        defaultValue: true,
      ) ==
      true;
}

/// Add a `@pragma('wasm:entry-point')` annotation to an annotatable.
T addWasmEntryPointPragma<T extends Annotatable>(T node, CoreTypes coreTypes) =>
    addPragma(node, 'wasm:entry-point', coreTypes);

T addPragma<T extends Annotatable>(
  T node,
  String pragmaName,
  CoreTypes coreTypes, {
  Constant? value,
}) => node
  ..addAnnotation(
    ConstantExpression(
      InstanceConstant(coreTypes.pragmaClass.reference, [], {
        coreTypes.pragmaName.fieldReference: StringConstant(pragmaName),
        coreTypes.pragmaOptions.fieldReference: value ?? NullConstant(),
      }),
    ),
  );

List<int> _intToLittleEndianBytes(int i) {
  List<int> bytes = [];
  bytes.add(i & 0xFF);
  i >>>= 8;
  while (i != 0) {
    bytes.add(i & 0xFF);
    i >>>= 8;
  }
  return bytes;
}

String intToBase64(int i) => base64.encode(_intToLittleEndianBytes(i));

/// Maps ints to minimal length strings.
///
/// For simplicity, this only uses combinations of 1-byte characters. The 2+
/// byte characters don't significantly impact the average string size.
///
/// Will not emit an empty string.
String intToMinString(int i) {
  // Stick to the 92 printable characters (starting after "), from 35 to 126.
  var base = 92;
  assert(i >= 0);
  i += 1;
  final codeUnits = <int>[];
  while (i > 0) {
    int remainder = i % base;
    i ~/= base;
    codeUnits.add(remainder + 35);
  }
  return String.fromCharCodes(codeUnits);
}

/// Maps ints to minimal length strings that are safe to use as JavaScript
/// identifiers.
///
/// Will not emit an empty string.
String intToMinJsSafeString(int i) {
  assert(i >= 0);
  i += 1;
  final codeUnits = <int>[];
  while (i > 0) {
    int remainder = i % 52;
    i ~/= 52;
    if (remainder < 26) {
      codeUnits.add(remainder + 65); // 'A'-'Z'
    } else {
      codeUnits.add(remainder - 26 + 97); // 'a'-'z'
    }
  }
  return String.fromCharCodes(codeUnits);
}

Component createEmptyComponent() {
  return Component()
    ..addMetadataRepository(UnreachableNodeMetadataRepository())
    ..addMetadataRepository(ProcedureAttributesMetadataRepository())
    ..addMetadataRepository(TableSelectorMetadataRepository())
    ..addMetadataRepository(DirectCallMetadataRepository())
    ..addMetadataRepository(InferredTypeMetadataRepository())
    ..addMetadataRepository(InferredReturnTypeMetadataRepository())
    ..addMetadataRepository(InferredArgTypeMetadataRepository());
}