text: // Copyright 2014 the V8 project authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include "src/execution/arguments-inl.h"
  #include "src/heap/heap-inl.h"
  #include "src/logging/counters.h"
  #include "src/numbers/conversions.h"
  #include "src/objects/js-array-inl.h"
  #include "src/objects/objects-inl.h"
  #include "src/objects/slots.h"
  #include "src/objects/smi.h"
  #include "src/regexp/regexp-utils.h"
  #include "src/runtime/runtime-utils.h"
  #include "src/strings/string-builder-inl.h"
  #include "src/strings/string-search.h"
  
  namespace v8 {
  namespace internal {
  
  RUNTIME_FUNCTION(Runtime_GetSubstitution) {
    HandleScope scope(isolate);
    DCHECK_EQ(5, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, matched, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 1);
    CONVERT_SMI_ARG_CHECKED(position, 2);
    CONVERT_ARG_HANDLE_CHECKED(String, replacement, 3);
    CONVERT_SMI_ARG_CHECKED(start_index, 4);
  
    // A simple match without captures.
    class SimpleMatch : public String::Match {
     public:
      SimpleMatch(Handle<String> match, Handle<String> prefix,
                  Handle<String> suffix)
          : match_(match), prefix_(prefix), suffix_(suffix) {}
  
      Handle<String> GetMatch() override { return match_; }
      Handle<String> GetPrefix() override { return prefix_; }
      Handle<String> GetSuffix() override { return suffix_; }
  
      int CaptureCount() override { return 0; }
      bool HasNamedCaptures() override { return false; }
      MaybeHandle<String> GetCapture(int i, bool* capture_exists) override {
        *capture_exists = false;
        return match_;  // Return arbitrary string handle.
      }
      MaybeHandle<String> GetNamedCapture(Handle<String> name,
                                          CaptureState* state) override {
        UNREACHABLE();
      }
  
     private:
      Handle<String> match_, prefix_, suffix_;
    };
  
    Handle<String> prefix =
        isolate->factory()->NewSubString(subject, 0, position);
    Handle<String> suffix = isolate->factory()->NewSubString(
        subject, position + matched->length(), subject->length());
    SimpleMatch match(matched, prefix, suffix);
  
    RETURN_RESULT_OR_FAILURE(
        isolate,
        String::GetSubstitution(isolate, &match, replacement, start_index));
  }
  
  // This may return an empty MaybeHandle if an exception is thrown or
  // we abort due to reaching the recursion limit.
  MaybeHandle<String> StringReplaceOneCharWithString(
      Isolate* isolate, Handle<String> subject, Handle<String> search,
      Handle<String> replace, bool* found, int recursion_limit) {
    StackLimitCheck stackLimitCheck(isolate);
    if (stackLimitCheck.HasOverflowed() || (recursion_limit == 0)) {
      return MaybeHandle<String>();
    }
    recursion_limit--;
    if (subject->IsConsString()) {
      ConsString cons = ConsString::cast(*subject);
      Handle<String> first = handle(cons.first(), isolate);
      Handle<String> second = handle(cons.second(), isolate);
      Handle<String> new_first;
      if (!StringReplaceOneCharWithString(isolate, first, search, replace, found,
                                          recursion_limit).ToHandle(&new_first)) {
        return MaybeHandle<String>();
      }
      if (*found) return isolate->factory()->NewConsString(new_first, second);
  
      Handle<String> new_second;
      if (!StringReplaceOneCharWithString(isolate, second, search, replace, found,
                                          recursion_limit)
               .ToHandle(&new_second)) {
        return MaybeHandle<String>();
      }
      if (*found) return isolate->factory()->NewConsString(first, new_second);
  
      return subject;
    } else {
      int index = String::IndexOf(isolate, subject, search, 0);
      if (index == -1) return subject;
      *found = true;
      Handle<String> first = isolate->factory()->NewSubString(subject, 0, index);
      Handle<String> cons1;
      ASSIGN_RETURN_ON_EXCEPTION(
          isolate, cons1, isolate->factory()->NewConsString(first, replace),
          String);
      Handle<String> second =
          isolate->factory()->NewSubString(subject, index + 1, subject->length());
      return isolate->factory()->NewConsString(cons1, second);
    }
  }
  
  RUNTIME_FUNCTION(Runtime_StringReplaceOneCharWithString) {
    HandleScope scope(isolate);
    DCHECK_EQ(3, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, search, 1);
    CONVERT_ARG_HANDLE_CHECKED(String, replace, 2);
  
    // If the cons string tree is too deep, we simply abort the recursion and
    // retry with a flattened subject string.
    const int kRecursionLimit = 0x1000;
    bool found = false;
    Handle<String> result;
    if (StringReplaceOneCharWithString(isolate, subject, search, replace, &found,
                                       kRecursionLimit).ToHandle(&result)) {
      return *result;
    }
    if (isolate->has_pending_exception())
      return ReadOnlyRoots(isolate).exception();
  
    subject = String::Flatten(isolate, subject);
    if (StringReplaceOneCharWithString(isolate, subject, search, replace, &found,
                                       kRecursionLimit).ToHandle(&result)) {
      return *result;
    }
    if (isolate->has_pending_exception())
      return ReadOnlyRoots(isolate).exception();
    // In case of empty handle and no pending exception we have stack overflow.
    return isolate->StackOverflow();
  }
  
  RUNTIME_FUNCTION(Runtime_StringTrim) {
    HandleScope scope(isolate);
    DCHECK_EQ(2, args.length());
    Handle<String> string = args.at<String>(0);
    CONVERT_SMI_ARG_CHECKED(mode, 1);
    String::TrimMode trim_mode = static_cast<String::TrimMode>(mode);
    return *String::Trim(isolate, string, trim_mode);
  }
  
  // ES6 #sec-string.prototype.includes
  // String.prototype.includes(searchString [, position])
  RUNTIME_FUNCTION(Runtime_StringIncludes) {
    HandleScope scope(isolate);
    DCHECK_EQ(3, args.length());
  
    Handle<Object> receiver = args.at(0);
    if (receiver->IsNullOrUndefined(isolate)) {
      THROW_NEW_ERROR_RETURN_FAILURE(
          isolate, NewTypeError(MessageTemplate::kCalledOnNullOrUndefined,
                                isolate->factory()->NewStringFromAsciiChecked(
                                    "String.prototype.includes")));
    }
    Handle<String> receiver_string;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, receiver_string,
                                       Object::ToString(isolate, receiver));
  
    // Check if the search string is a regExp and fail if it is.
    Handle<Object> search = args.at(1);
    Maybe<bool> is_reg_exp = RegExpUtils::IsRegExp(isolate, search);
    if (is_reg_exp.IsNothing()) {
      DCHECK(isolate->has_pending_exception());
      return ReadOnlyRoots(isolate).exception();
    }
    if (is_reg_exp.FromJust()) {
      THROW_NEW_ERROR_RETURN_FAILURE(
          isolate, NewTypeError(MessageTemplate::kFirstArgumentNotRegExp,
                                isolate->factory()->NewStringFromStaticChars(
                                    "String.prototype.includes")));
    }
    Handle<String> search_string;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, search_string,
                                       Object::ToString(isolate, args.at(1)));
    Handle<Object> position;
    ASSIGN_RETURN_FAILURE_ON_EXCEPTION(isolate, position,
                                       Object::ToInteger(isolate, args.at(2)));
  
    uint32_t index = receiver_string->ToValidIndex(*position);
    int index_in_str =
        String::IndexOf(isolate, receiver_string, search_string, index);
    return *isolate->factory()->ToBoolean(index_in_str != -1);
  }
  
  // ES6 #sec-string.prototype.indexof
  // String.prototype.indexOf(searchString [, position])
  RUNTIME_FUNCTION(Runtime_StringIndexOf) {
    HandleScope scope(isolate);
    DCHECK_EQ(3, args.length());
    return String::IndexOf(isolate, args.at(0), args.at(1), args.at(2));
  }
  
  // ES6 #sec-string.prototype.indexof
  // String.prototype.indexOf(searchString, position)
  // Fast version that assumes that does not perform conversions of the incoming
  // arguments.
  RUNTIME_FUNCTION(Runtime_StringIndexOfUnchecked) {
    HandleScope scope(isolate);
    DCHECK_EQ(3, args.length());
    Handle<String> receiver_string = args.at<String>(0);
    Handle<String> search_string = args.at<String>(1);
    int index = std::min(std::max(args.smi_at(2), 0), receiver_string->length());
  
    return Smi::FromInt(String::IndexOf(isolate, receiver_string, search_string,
                                        static_cast<uint32_t>(index)));
  }
  
  RUNTIME_FUNCTION(Runtime_StringLastIndexOf) {
    HandleScope handle_scope(isolate);
    return String::LastIndexOf(isolate, args.at(0), args.at(1),
                               isolate->factory()->undefined_value());
  }
  
  RUNTIME_FUNCTION(Runtime_StringSubstring) {
    HandleScope scope(isolate);
    DCHECK_EQ(3, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, string, 0);
    CONVERT_INT32_ARG_CHECKED(start, 1);
    CONVERT_INT32_ARG_CHECKED(end, 2);
    DCHECK_LE(0, start);
    DCHECK_LE(start, end);
    DCHECK_LE(end, string->length());
    isolate->counters()->sub_string_runtime()->Increment();
    return *isolate->factory()->NewSubString(string, start, end);
  }
  
  RUNTIME_FUNCTION(Runtime_StringAdd) {
    HandleScope scope(isolate);
    DCHECK_EQ(2, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, str1, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, str2, 1);
    isolate->counters()->string_add_runtime()->Increment();
    RETURN_RESULT_OR_FAILURE(isolate,
                             isolate->factory()->NewConsString(str1, str2));
  }
  
  
  RUNTIME_FUNCTION(Runtime_InternalizeString) {
    HandleScope handles(isolate);
    DCHECK_EQ(1, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, string, 0);
    return *isolate->factory()->InternalizeString(string);
  }
  
  RUNTIME_FUNCTION(Runtime_StringCharCodeAt) {
    HandleScope handle_scope(isolate);
    DCHECK_EQ(2, args.length());
  
    CONVERT_ARG_HANDLE_CHECKED(String, subject, 0);
    CONVERT_NUMBER_CHECKED(uint32_t, i, Uint32, args[1]);
  
    // Flatten the string.  If someone wants to get a char at an index
    // in a cons string, it is likely that more indices will be
    // accessed.
    subject = String::Flatten(isolate, subject);
  
    if (i >= static_cast<uint32_t>(subject->length())) {
      return ReadOnlyRoots(isolate).nan_value();
    }
  
    return Smi::FromInt(subject->Get(i));
  }
  
  RUNTIME_FUNCTION(Runtime_StringBuilderConcat) {
    HandleScope scope(isolate);
    DCHECK_EQ(3, args.length());
    CONVERT_ARG_HANDLE_CHECKED(JSArray, array, 0);
    int32_t array_length;
    if (!args[1].ToInt32(&array_length)) {
      THROW_NEW_ERROR_RETURN_FAILURE(isolate, NewInvalidStringLengthError());
    }
    CONVERT_ARG_HANDLE_CHECKED(String, special, 2);
  
    size_t actual_array_length = 0;
    CHECK(TryNumberToSize(array->length(), &actual_array_length));
    CHECK_GE(array_length, 0);
    CHECK(static_cast<size_t>(array_length) <= actual_array_length);
  
    // This assumption is used by the slice encoding in one or two smis.
    DCHECK_GE(Smi::kMaxValue, String::kMaxLength);
  
    CHECK(array->HasFastElements());
    JSObject::EnsureCanContainHeapObjectElements(array);
  
    int special_length = special->length();
    if (!array->HasObjectElements()) {
      return isolate->Throw(ReadOnlyRoots(isolate).illegal_argument_string());
    }
  
    int length;
    bool one_byte = special->IsOneByteRepresentation();
  
    {
      DisallowHeapAllocation no_gc;
      FixedArray fixed_array = FixedArray::cast(array->elements());
      if (fixed_array.length() < array_length) {
        array_length = fixed_array.length();
      }
  
      if (array_length == 0) {
        return ReadOnlyRoots(isolate).empty_string();
      } else if (array_length == 1) {
        Object first = fixed_array.get(0);
        if (first.IsString()) return first;
      }
      length = StringBuilderConcatLength(special_length, fixed_array,
                                         array_length, &one_byte);
    }
  
    if (length == -1) {
      return isolate->Throw(ReadOnlyRoots(isolate).illegal_argument_string());
    }
    if (length == 0) {
      return ReadOnlyRoots(isolate).empty_string();
    }
  
    if (one_byte) {
      Handle<SeqOneByteString> answer;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, answer, isolate->factory()->NewRawOneByteString(length));
      DisallowHeapAllocation no_gc;
      StringBuilderConcatHelper(*special, answer->GetChars(no_gc),
                                FixedArray::cast(array->elements()),
                                array_length);
      return *answer;
    } else {
      Handle<SeqTwoByteString> answer;
      ASSIGN_RETURN_FAILURE_ON_EXCEPTION(
          isolate, answer, isolate->factory()->NewRawTwoByteString(length));
      DisallowHeapAllocation no_gc;
      StringBuilderConcatHelper(*special, answer->GetChars(no_gc),
                                FixedArray::cast(array->elements()),
                                array_length);
      return *answer;
    }
  }
  
  
  // Copies Latin1 characters to the given fixed array looking up
  // one-char strings in the cache. Gives up on the first char that is
  // not in the cache and fills the remainder with smi zeros. Returns
  // the length of the successfully copied prefix.
  static int CopyCachedOneByteCharsToArray(Heap* heap, const uint8_t* chars,
                                           FixedArray elements, int length) {
    DisallowHeapAllocation no_gc;
    FixedArray one_byte_cache = heap->single_character_string_cache();
    Object undefined = ReadOnlyRoots(heap).undefined_value();
    int i;
    WriteBarrierMode mode = elements.GetWriteBarrierMode(no_gc);
    for (i = 0; i < length; ++i) {
      Object value = one_byte_cache.get(chars[i]);
      if (value == undefined) break;
      elements.set(i, value, mode);
    }
    if (i < length) {
      MemsetTagged(elements.RawFieldOfElementAt(i), Smi::kZero, length - i);
    }
  #ifdef DEBUG
    for (int j = 0; j < length; ++j) {
      Object element = elements.get(j);
      DCHECK(element == Smi::kZero ||
             (element.IsString() && String::cast(element).LooksValid()));
    }
  #endif
    return i;
  }
  
  // Converts a String to JSArray.
  // For example, "foo" => ["f", "o", "o"].
  RUNTIME_FUNCTION(Runtime_StringToArray) {
    HandleScope scope(isolate);
    DCHECK_EQ(2, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, s, 0);
    CONVERT_NUMBER_CHECKED(uint32_t, limit, Uint32, args[1]);
  
    s = String::Flatten(isolate, s);
    const int length = static_cast<int>(Min<uint32_t>(s->length(), limit));
  
    Handle<FixedArray> elements;
    int position = 0;
    if (s->IsFlat() && s->IsOneByteRepresentation()) {
      // Try using cached chars where possible.
      elements = isolate->factory()->NewUninitializedFixedArray(length);
  
      DisallowHeapAllocation no_gc;
      String::FlatContent content = s->GetFlatContent(no_gc);
      if (content.IsOneByte()) {
        Vector<const uint8_t> chars = content.ToOneByteVector();
        // Note, this will initialize all elements (not only the prefix)
        // to prevent GC from seeing partially initialized array.
        position = CopyCachedOneByteCharsToArray(isolate->heap(), chars.begin(),
                                                 *elements, length);
      } else {
        MemsetTagged(elements->data_start(),
                     ReadOnlyRoots(isolate).undefined_value(), length);
      }
    } else {
      elements = isolate->factory()->NewFixedArray(length);
    }
    for (int i = position; i < length; ++i) {
      Handle<Object> str =
          isolate->factory()->LookupSingleCharacterStringFromCode(s->Get(i));
      elements->set(i, *str);
    }
  
  #ifdef DEBUG
    for (int i = 0; i < length; ++i) {
      DCHECK_EQ(String::cast(elements->get(i)).length(), 1);
    }
  #endif
  
    return *isolate->factory()->NewJSArrayWithElements(elements);
  }
  
  RUNTIME_FUNCTION(Runtime_StringLessThan) {
    HandleScope handle_scope(isolate);
    DCHECK_EQ(2, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, x, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, y, 1);
    ComparisonResult result = String::Compare(isolate, x, y);
    DCHECK_NE(result, ComparisonResult::kUndefined);
    return isolate->heap()->ToBoolean(
        ComparisonResultToBool(Operation::kLessThan, result));
  }
  
  RUNTIME_FUNCTION(Runtime_StringLessThanOrEqual) {
    HandleScope handle_scope(isolate);
    DCHECK_EQ(2, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, x, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, y, 1);
    ComparisonResult result = String::Compare(isolate, x, y);
    DCHECK_NE(result, ComparisonResult::kUndefined);
    return isolate->heap()->ToBoolean(
        ComparisonResultToBool(Operation::kLessThanOrEqual, result));
  }
  
  RUNTIME_FUNCTION(Runtime_StringGreaterThan) {
    HandleScope handle_scope(isolate);
    DCHECK_EQ(2, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, x, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, y, 1);
    ComparisonResult result = String::Compare(isolate, x, y);
    DCHECK_NE(result, ComparisonResult::kUndefined);
    return isolate->heap()->ToBoolean(
        ComparisonResultToBool(Operation::kGreaterThan, result));
  }
  
  RUNTIME_FUNCTION(Runtime_StringGreaterThanOrEqual) {
    HandleScope handle_scope(isolate);
    DCHECK_EQ(2, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, x, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, y, 1);
    ComparisonResult result = String::Compare(isolate, x, y);
    DCHECK_NE(result, ComparisonResult::kUndefined);
    return isolate->heap()->ToBoolean(
        ComparisonResultToBool(Operation::kGreaterThanOrEqual, result));
  }
  
  RUNTIME_FUNCTION(Runtime_StringEqual) {
    HandleScope handle_scope(isolate);
    DCHECK_EQ(2, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, x, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, y, 1);
    return isolate->heap()->ToBoolean(String::Equals(isolate, x, y));
  }
  
  RUNTIME_FUNCTION(Runtime_FlattenString) {
    HandleScope scope(isolate);
    DCHECK_EQ(1, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, str, 0);
    return *String::Flatten(isolate, str);
  }
  
  RUNTIME_FUNCTION(Runtime_StringMaxLength) {
    SealHandleScope shs(isolate);
    return Smi::FromInt(String::kMaxLength);
  }
  
  RUNTIME_FUNCTION(Runtime_StringCompareSequence) {
    HandleScope handle_scope(isolate);
    DCHECK_EQ(3, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, string, 0);
    CONVERT_ARG_HANDLE_CHECKED(String, search_string, 1);
    CONVERT_NUMBER_CHECKED(int, start, Int32, args[2]);
  
    // Check if start + searchLength is in bounds.
    DCHECK_LE(start + search_string->length(), string->length());
  
    FlatStringReader string_reader(isolate, String::Flatten(isolate, string));
    FlatStringReader search_reader(isolate,
                                   String::Flatten(isolate, search_string));
  
    for (int i = 0; i < search_string->length(); i++) {
      if (string_reader.Get(start + i) != search_reader.Get(i)) {
        return ReadOnlyRoots(isolate).false_value();
      }
    }
  
    return ReadOnlyRoots(isolate).true_value();
  }
  
  RUNTIME_FUNCTION(Runtime_StringEscapeQuotes) {
    HandleScope handle_scope(isolate);
    DCHECK_EQ(1, args.length());
    CONVERT_ARG_HANDLE_CHECKED(String, string, 0);
  
    // Equivalent to global replacement `string.replace(/"/g, "&quot")`, but this
    // does not modify any global state (e.g. the regexp match info).
  
    const int string_length = string->length();
    Handle<String> quotes =
        isolate->factory()->LookupSingleCharacterStringFromCode('"');
  
    int index = String::IndexOf(isolate, string, quotes, 0);
  
    // No quotes, nothing to do.
    if (index == -1) return *string;
  
    // Find all quotes.
    std::vector<int> indices = {index};
    while (index + 1 < string_length) {
      index = String::IndexOf(isolate, string, quotes, index + 1);
      if (index == -1) break;
      indices.emplace_back(index);
    }
  
    // Build the replacement string.
    Handle<String> replacement =
        isolate->factory()->NewStringFromAsciiChecked("&quot;");
    const int estimated_part_count = static_cast<int>(indices.size()) * 2 + 1;
    ReplacementStringBuilder builder(isolate->heap(), string,
                                     estimated_part_count);
  
    int prev_index = -1;  // Start at -1 to avoid special-casing the first match.
    for (int index : indices) {
      const int slice_start = prev_index + 1;
      const int slice_end = index;
      if (slice_end > slice_start) {
        builder.AddSubjectSlice(slice_start, slice_end);
      }
      builder.AddString(replacement);
      prev_index = index;
    }
  
    if (prev_index < string_length - 1) {
      builder.AddSubjectSlice(prev_index + 1, string_length);
    }
  
    return *builder.ToString().ToHandleChecked();
  }
  
  }  // namespace internal
  }  // namespace v8
  