util.dart

// Copyright (c) 2011, 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.

library;

// ignore: implementation_imports
import 'package:front_end/src/api_unstable/dart2js.dart'
    show $BACKSLASH, $CR, $DEL, $DQ, $LF, $LS, $PS, $TAB;

export 'maplet.dart';
export 'setlet.dart';

/// Helper functions for creating hash codes.
class Hashing {
  /// If an integer is masked by this constant, the result is guaranteed to be
  /// in Smi range.
  static const int smiMask = 0x3fffffff;

  /// Mix the bits of [value] and merge them with [existing].
  static int mixHashCodeBits(int existing, int value) {
    // Spread the bits of value. Try to stay in the 30-bit range to
    // avoid overflowing into a more expensive integer representation.
    int h = value & 0x1fffffff;
    h += ((h & 0x3fff) << 15) ^ 0x1fffcd7d;
    h ^= (h >> 10);
    h += ((h & 0x3ffffff) << 3);
    h ^= (h >> 6);
    h += ((h & 0x7ffffff) << 2) + ((h & 0x7fff) << 14);
    h ^= (h >> 16);
    // Combine the two hash values.
    int high = existing >> 15;
    int low = existing & 0x7fff;
    return ((high * 13) ^ (low * 997) ^ h) & smiMask;
  }

  /// Returns a hash value computed from all the characters in the string.
  static int stringHash(String s) {
    int hash = mixHashCodeBits(0, s.length);
    for (int i = 0; i < s.length; i++) {
      hash = mixHashCodeBits(hash, s.codeUnitAt(i));
    }
    return hash;
  }

  /// Mix the bits of `object.hashCode` with [existing].
  static int objectHash(Object? object, [int existing = 0]) {
    return mixHashCodeBits(existing, object.hashCode);
  }

  /// Mix the bits of `.hashCode` all non-null objects.
  static int objectsHash(
    Object? obj1, [
    Object? obj2,
    Object? obj3,
    Object? obj4,
    Object? obj5,
  ]) {
    int hash = 0;
    if (obj5 != null) hash = objectHash(obj5, hash);
    if (obj4 != null) hash = objectHash(obj4, hash);
    if (obj3 != null) hash = objectHash(obj3, hash);
    if (obj2 != null) hash = objectHash(obj2, hash);
    return objectHash(obj1, hash);
  }

  /// Mix the bits of the element hash codes of [list] with [existing].
  static int listHash(List<Object?>? list, [int existing = 0]) {
    int h = existing;
    if (list != null) {
      int length = list.length;
      for (int i = 0; i < length; i++) {
        h = mixHashCodeBits(h, list[i].hashCode);
      }
    }
    return h;
  }

  /// Mix the bits of the element hash codes of [iterable] with [existing].
  static int setHash<E>(Iterable<E>? iterable, [int existing = 0]) {
    int h = existing;
    if (iterable != null) {
      for (E e in iterable) {
        h += objectsHash(e);
      }
    }
    return h & smiMask;
  }

  /// Mix the bits of the hash codes of the unordered key/value from [map] with
  /// [existing].
  static int unorderedMapHash(Map<Object?, Object?> map, [int existing = 0]) {
    if (map.isEmpty) return existing;
    List<int> hashCodes = List.filled(map.length, 0);
    int i = 0;
    for (var entry in map.entries) {
      hashCodes[i++] = objectHash(entry.key, objectHash(entry.value));
    }
    hashCodes.sort();
    int h = existing;
    for (int hashCode in hashCodes) {
      h = mixHashCodeBits(h, hashCode);
    }
    return h;
  }

  /// Mix the bits of the key/value hash codes from [map] with [existing].
  static int mapHash(Map<Object?, Object?> map, [int existing = 0]) {
    int h = existing;
    for (var key in map.keys) {
      h = mixHashCodeBits(h, key.hashCode);
      h = mixHashCodeBits(h, map[key].hashCode);
    }
    return h;
  }
}

bool identicalElements<E>(List<E>? a, List<E>? b) {
  if (identical(a, b)) return true;
  if (a == null || b == null) return false;
  if (a.length != b.length) return false;
  for (int index = 0; index < a.length; index++) {
    if (!identical(a[index], b[index])) {
      return false;
    }
  }
  return true;
}

bool equalElements<E>(List<E>? a, List<E>? b) {
  if (identical(a, b)) return true;
  if (a == null || b == null) return false;
  if (a.length != b.length) return false;
  for (int index = 0; index < a.length; index++) {
    if (a[index] != b[index]) {
      return false;
    }
  }
  return true;
}

bool equalSets<E>(Set<E>? a, Set<E>? b) {
  if (identical(a, b)) return true;
  if (a == null || b == null) return false;
  return a.length == b.length && a.containsAll(b) && b.containsAll(a);
}

bool equalMaps<K, V>(Map<K, V>? a, Map<K, V>? b) {
  if (identical(a, b)) return true;
  if (a == null || b == null) return false;
  if (a.length != b.length) return false;
  for (K key in a.keys) {
    if (a[key] != b[key]) return false;
  }
  return true;
}

/// File name prefix used to shorten the file name in stack traces printed by
/// [trace].
String? stackTraceFilePrefix;

/// Writes the characters of [string] on [buffer].  The characters
/// are escaped as suitable for JavaScript and JSON.  [buffer] is
/// anything which supports [:write:] and [:writeCharCode:], for example,
/// [StringSink].  Note that JS supports \xnn and \unnnn whereas JSON only
/// supports the \unnnn notation.  Therefore we use the \unnnn notation.
void writeJsonEscapedCharsOn(String string, StringSink buffer) {
  void addCodeUnitEscaped(StringSink buffer, int code) {
    assert(code < 0x10000);
    buffer.write(r'\u');
    if (code < 0x1000) {
      buffer.write('0');
      if (code < 0x100) {
        buffer.write('0');
        if (code < 0x10) {
          buffer.write('0');
        }
      }
    }
    buffer.write(code.toRadixString(16));
  }

  void writeEscapedOn(String string, StringSink buffer) {
    for (int i = 0; i < string.length; i++) {
      int code = string.codeUnitAt(i);
      if (code == $DQ) {
        buffer.write(r'\"');
      } else if (code == $TAB) {
        buffer.write(r'\t');
      } else if (code == $LF) {
        buffer.write(r'\n');
      } else if (code == $CR) {
        buffer.write(r'\r');
      } else if (code == $DEL) {
        addCodeUnitEscaped(buffer, $DEL);
      } else if (code == $LS) {
        // This Unicode line terminator and $PS are invalid in JS string
        // literals.
        addCodeUnitEscaped(buffer, $LS); // 0x2028.
      } else if (code == $PS) {
        addCodeUnitEscaped(buffer, $PS); // 0x2029.
      } else if (code == $BACKSLASH) {
        buffer.write(r'\\');
      } else {
        if (code < 0x20) {
          addCodeUnitEscaped(buffer, code);
          // We emit DEL (ASCII 0x7f) as an escape because it would be confusing
          // to have it unescaped in a string literal.  We also escape
          // everything above 0x7f because that means we don't have to worry
          // about whether the web server serves it up as Latin1 or UTF-8.
        } else if (code < 0x7f) {
          buffer.writeCharCode(code);
        } else {
          // This will output surrogate pairs in the form \udxxx\udyyy, rather
          // than the more logical \u{zzzzzz}.  This should work in JavaScript
          // (especially old UCS-2 based implementations) and is the only
          // format that is allowed in JSON.
          addCodeUnitEscaped(buffer, code);
        }
      }
    }
  }

  for (int i = 0; i < string.length; i++) {
    int code = string.codeUnitAt(i);
    if (code < 0x20 ||
        code == $DEL ||
        code == $DQ ||
        code == $LS ||
        code == $PS ||
        code == $BACKSLASH ||
        code >= 0x80) {
      writeEscapedOn(string, buffer);
      return;
    }
  }
  buffer.write(string);
}

int longestCommonPrefixLength(List<Object?> a, List<Object?> b) {
  int index = 0;
  for (; index < a.length && index < b.length; index++) {
    if (a[index] != b[index]) {
      break;
    }
  }
  return index;
}

/// Returns [suggestedName] if it is not in [usedNames]. Otherwise concatenates
/// the smallest number that makes it not appear in [usedNames].
///
/// Adds the result to [usedNames].
String makeUnique(
  String suggestedName,
  Set<String> usedNames, [
  String separator = '',
]) {
  String result = suggestedName;
  if (usedNames.contains(suggestedName)) {
    int counter = 0;
    while (usedNames.contains(result)) {
      counter++;
      result = "$suggestedName$separator$counter";
    }
  }
  usedNames.add(result);
  return result;
}