[utils] Move SimpleStringBuilder out of utils

Now that SimpleStringBuilder is only used in conversions.cc, it can be
moved there making it easier to assess its safety and limit further
use of this potentially unsafe API. (Additionally unused methods Reset
and size are removed).

Bug: v8:11917
Change-Id: I0515fe4f34bb8f7e7ea464b75394fa3d03939af1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2978253
Commit-Queue: Dan Elphick <delphick@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75300}

src/numbers/conversions.cc

@@ -20,7 +20,6 @@
 #include "src/objects/string-inl.h"
 #include "src/strings/char-predicates-inl.h"
 #include "src/utils/allocation.h"
-#include "src/utils/utils.h"
 
 #if defined(_STLP_VENDOR_CSTD)
 // STLPort doesn't import fpclassify into the std namespace.
@@ -32,6 +31,113 @@
 namespace v8 {
 namespace internal {
 
+// Helper class for building result strings in a character buffer. The
+// purpose of the class is to use safe operations that checks the
+// buffer bounds on all operations in debug mode.
+// This simple base class does not allow formatted output.
+class SimpleStringBuilder {
+ public:
+  // Create a string builder with a buffer of the given size. The
+  // buffer is allocated through NewArray<char> and must be
+  // deallocated by the caller of Finalize().
+  explicit SimpleStringBuilder(int size) {
+    buffer_ = base::Vector<char>::New(size);
+    position_ = 0;
+  }
+
+  SimpleStringBuilder(char* buffer, int size)
+      : buffer_(buffer, size), position_(0) {}
+
+  ~SimpleStringBuilder() {
+    if (!is_finalized()) Finalize();
+  }
+
+  // Get the current position in the builder.
+  int position() const {
+    DCHECK(!is_finalized());
+    return position_;
+  }
+
+  // Add a single character to the builder. It is not allowed to add
+  // 0-characters; use the Finalize() method to terminate the string
+  // instead.
+  void AddCharacter(char c) {
+    DCHECK_NE(c, '\0');
+    DCHECK(!is_finalized() && position_ < buffer_.length());
+    buffer_[position_++] = c;
+  }
+
+  // Add an entire string to the builder. Uses strlen() internally to
+  // compute the length of the input string.
+  void AddString(const char* s) {
+    size_t len = strlen(s);
+    DCHECK_GE(kMaxInt, len);
+    AddSubstring(s, static_cast<int>(len));
+  }
+
+  // Add the first 'n' characters of the given 0-terminated string 's' to the
+  // builder. The input string must have enough characters.
+  void AddSubstring(const char* s, int n) {
+    DCHECK(!is_finalized() && position_ + n <= buffer_.length());
+    DCHECK_LE(n, strlen(s));
+    std::memcpy(&buffer_[position_], s, n * kCharSize);
+    position_ += n;
+  }
+
+  // Add character padding to the builder. If count is non-positive,
+  // nothing is added to the builder.
+  void AddPadding(char c, int count) {
+    for (int i = 0; i < count; i++) {
+      AddCharacter(c);
+    }
+  }
+
+  // Add the decimal representation of the value.
+  void AddDecimalInteger(int value) {
+    uint32_t number = static_cast<uint32_t>(value);
+    if (value < 0) {
+      AddCharacter('-');
+      number = static_cast<uint32_t>(-value);
+    }
+    int digits = 1;
+    for (uint32_t factor = 10; digits < 10; digits++, factor *= 10) {
+      if (factor > number) break;
+    }
+    position_ += digits;
+    for (int i = 1; i <= digits; i++) {
+      buffer_[position_ - i] = '0' + static_cast<char>(number % 10);
+      number /= 10;
+    }
+  }
+
+  // Finalize the string by 0-terminating it and returning the buffer.
+  char* Finalize() {
+    DCHECK(!is_finalized() && position_ <= buffer_.length());
+    // If there is no space for null termination, overwrite last character.
+    if (position_ == buffer_.length()) {
+      position_--;
+      // Print ellipsis.
+      for (int i = 3; i > 0 && position_ > i; --i) buffer_[position_ - i] = '.';
+    }
+    buffer_[position_] = '\0';
+    // Make sure nobody managed to add a 0-character to the
+    // buffer while building the string.
+    DCHECK(strlen(buffer_.begin()) == static_cast<size_t>(position_));
+    position_ = -1;
+    DCHECK(is_finalized());
+    return buffer_.begin();
+  }
+
+ protected:
+  base::Vector<char> buffer_;
+  int position_;
+
+  bool is_finalized() const { return position_ < 0; }
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(SimpleStringBuilder);
+};
+
 inline double JunkStringValue() {
   return bit_cast<double, uint64_t>(kQuietNaNMask);
 }

src/utils/utils.cc

@@ -18,64 +18,6 @@
 namespace v8 {
 namespace internal {
 
-SimpleStringBuilder::SimpleStringBuilder(int size) {
-  buffer_ = base::Vector<char>::New(size);
-  position_ = 0;
-}
-
-void SimpleStringBuilder::AddString(const char* s) {
-  size_t len = strlen(s);
-  DCHECK_GE(kMaxInt, len);
-  AddSubstring(s, static_cast<int>(len));
-}
-
-void SimpleStringBuilder::AddSubstring(const char* s, int n) {
-  DCHECK(!is_finalized() && position_ + n <= buffer_.length());
-  DCHECK_LE(n, strlen(s));
-  std::memcpy(&buffer_[position_], s, n * kCharSize);
-  position_ += n;
-}
-
-void SimpleStringBuilder::AddPadding(char c, int count) {
-  for (int i = 0; i < count; i++) {
-    AddCharacter(c);
-  }
-}
-
-void SimpleStringBuilder::AddDecimalInteger(int32_t value) {
-  uint32_t number = static_cast<uint32_t>(value);
-  if (value < 0) {
-    AddCharacter('-');
-    number = static_cast<uint32_t>(-value);
-  }
-  int digits = 1;
-  for (uint32_t factor = 10; digits < 10; digits++, factor *= 10) {
-    if (factor > number) break;
-  }
-  position_ += digits;
-  for (int i = 1; i <= digits; i++) {
-    buffer_[position_ - i] = '0' + static_cast<char>(number % 10);
-    number /= 10;
-  }
-}
-
-char* SimpleStringBuilder::Finalize() {
-  DCHECK(!is_finalized() && position_ <= buffer_.length());
-  // If there is no space for null termination, overwrite last character.
-  if (position_ == buffer_.length()) {
-    position_--;
-    // Print ellipsis.
-    for (int i = 3; i > 0 && position_ > i; --i) buffer_[position_ - i] = '.';
-  }
-  buffer_[position_] = '\0';
-  // Make sure nobody managed to add a 0-character to the
-  // buffer while building the string.
-  DCHECK(strlen(buffer_.begin()) == static_cast<size_t>(position_));
-  position_ = -1;
-  DCHECK(is_finalized());
-  return buffer_.begin();
-}
-
 std::ostream& operator<<(std::ostream& os, FeedbackSlot slot) {
   return os << "#" << slot.id_;
 }

src/utils/utils.h

@@ -396,72 +396,6 @@ inline int TenToThe(int exponent) {
   return answer;
 }
 
-// Helper class for building result strings in a character buffer. The
-// purpose of the class is to use safe operations that checks the
-// buffer bounds on all operations in debug mode.
-// This simple base class does not allow formatted output.
-class SimpleStringBuilder {
- public:
-  // Create a string builder with a buffer of the given size. The
-  // buffer is allocated through NewArray<char> and must be
-  // deallocated by the caller of Finalize().
-  explicit SimpleStringBuilder(int size);
-
-  SimpleStringBuilder(char* buffer, int size)
-      : buffer_(buffer, size), position_(0) {}
-
-  ~SimpleStringBuilder() {
-    if (!is_finalized()) Finalize();
-  }
-
-  int size() const { return buffer_.length(); }
-
-  // Get the current position in the builder.
-  int position() const {
-    DCHECK(!is_finalized());
-    return position_;
-  }
-
-  // Reset the position.
-  void Reset() { position_ = 0; }
-
-  // Add a single character to the builder. It is not allowed to add
-  // 0-characters; use the Finalize() method to terminate the string
-  // instead.
-  void AddCharacter(char c) {
-    DCHECK_NE(c, '\0');
-    DCHECK(!is_finalized() && position_ < buffer_.length());
-    buffer_[position_++] = c;
-  }
-
-  // Add an entire string to the builder. Uses strlen() internally to
-  // compute the length of the input string.
-  void AddString(const char* s);
-
-  // Add the first 'n' characters of the given 0-terminated string 's' to the
-  // builder. The input string must have enough characters.
-  void AddSubstring(const char* s, int n);
-
-  // Add character padding to the builder. If count is non-positive,
-  // nothing is added to the builder.
-  void AddPadding(char c, int count);
-
-  // Add the decimal representation of the value.
-  void AddDecimalInteger(int value);
-
-  // Finalize the string by 0-terminating it and returning the buffer.
-  char* Finalize();
-
- protected:
-  base::Vector<char> buffer_;
-  int position_;
-
-  bool is_finalized() const { return position_ < 0; }
-
- private:
-  DISALLOW_IMPLICIT_CONSTRUCTORS(SimpleStringBuilder);
-};
-
 // Bit field extraction.
 inline uint32_t unsigned_bitextract_32(int msb, int lsb, uint32_t x) {
   return (x >> lsb) & ((1 << (1 + msb - lsb)) - 1);