runtime/base/stringpiece.h

/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef ART_RUNTIME_BASE_STRINGPIECE_H_
#define ART_RUNTIME_BASE_STRINGPIECE_H_

#include <string.h>
#include <string>

namespace art {

// A string-like object that points to a sized piece of memory.
//
// Functions or methods may use const StringPiece& parameters to accept either
// a "const char*" or a "string" value that will be implicitly converted to
// a StringPiece.  The implicit conversion means that it is often appropriate
// to include this .h file in other files rather than forward-declaring
// StringPiece as would be appropriate for most other Google classes.
class StringPiece {
 public:
  // standard STL container boilerplate
  typedef char value_type;
  typedef const char* pointer;
  typedef const char& reference;
  typedef const char& const_reference;
  typedef size_t size_type;
  typedef ptrdiff_t difference_type;
  static constexpr size_type npos = size_type(-1);
  typedef const char* const_iterator;
  typedef const char* iterator;
  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
  typedef std::reverse_iterator<iterator> reverse_iterator;

  // We provide non-explicit singleton constructors so users can pass
  // in a "const char*" or a "string" wherever a "StringPiece" is
  // expected.
  StringPiece() : ptr_(nullptr), length_(0) { }
  StringPiece(const char* str)  // NOLINT implicit constructor desired
    : ptr_(str), length_((str == nullptr) ? 0 : strlen(str)) { }
  StringPiece(const std::string& str)  // NOLINT implicit constructor desired
    : ptr_(str.data()), length_(str.size()) { }
  StringPiece(const char* offset, size_t len) : ptr_(offset), length_(len) { }

  // data() may return a pointer to a buffer with embedded NULs, and the
  // returned buffer may or may not be null terminated.  Therefore it is
  // typically a mistake to pass data() to a routine that expects a NUL
  // terminated string.
  const char* data() const { return ptr_; }
  size_type size() const { return length_; }
  size_type length() const { return length_; }
  bool empty() const { return length_ == 0; }

  void clear() {
    ptr_ = nullptr;
    length_ = 0;
  }
  void set(const char* data, size_type len) {
    ptr_ = data;
    length_ = len;
  }
  void set(const char* str) {
    ptr_ = str;
    if (str != nullptr) {
      length_ = strlen(str);
    } else {
      length_ = 0;
    }
  }
  void set(const void* data, size_type len) {
    ptr_ = reinterpret_cast<const char*>(data);
    length_ = len;
  }

#if defined(NDEBUG)
  char operator[](size_type i) const {
    return ptr_[i];
  }
#else
  char operator[](size_type i) const;
#endif

  void remove_prefix(size_type n) {
    ptr_ += n;
    length_ -= n;
  }

  void remove_suffix(size_type n) {
    length_ -= n;
  }

  int compare(const StringPiece& x) const;

  std::string as_string() const {
    return std::string(data(), size());
  }
  // We also define ToString() here, since many other string-like
  // interfaces name the routine that converts to a C++ string
  // "ToString", and it's confusing to have the method that does that
  // for a StringPiece be called "as_string()".  We also leave the
  // "as_string()" method defined here for existing code.
  std::string ToString() const {
    return std::string(data(), size());
  }

  void CopyToString(std::string* target) const;
  void AppendToString(std::string* target) const;

  // Does "this" start with "x"
  bool starts_with(const StringPiece& x) const {
    return ((length_ >= x.length_) &&
            (memcmp(ptr_, x.ptr_, x.length_) == 0));
  }

  // Does "this" end with "x"
  bool ends_with(const StringPiece& x) const {
    return ((length_ >= x.length_) &&
            (memcmp(ptr_ + (length_-x.length_), x.ptr_, x.length_) == 0));
  }

  iterator begin() const { return ptr_; }
  iterator end() const { return ptr_ + length_; }
  const_reverse_iterator rbegin() const {
    return const_reverse_iterator(ptr_ + length_);
  }
  const_reverse_iterator rend() const {
    return const_reverse_iterator(ptr_);
  }

  size_type copy(char* buf, size_type n, size_type pos = 0) const;

  size_type find(const StringPiece& s, size_type pos = 0) const;
  size_type find(char c, size_type pos = 0) const;
  size_type rfind(const StringPiece& s, size_type pos = npos) const;
  size_type rfind(char c, size_type pos = npos) const;

  StringPiece substr(size_type pos, size_type n = npos) const;

 private:
  // Pointer to char data, not necessarily zero terminated.
  const char* ptr_;
  // Length of data.
  size_type   length_;
};

// This large function is defined inline so that in a fairly common case where
// one of the arguments is a literal, the compiler can elide a lot of the
// following comparisons.
inline bool operator==(const StringPiece& x, const StringPiece& y) {
  StringPiece::size_type len = x.size();
  if (len != y.size()) {
    return false;
  }

  const char* p1 = x.data();
  const char* p2 = y.data();
  if (p1 == p2) {
    return true;
  }
  if (len == 0) {
    return true;
  }

  // Test last byte in case strings share large common prefix
  if (p1[len-1] != p2[len-1]) return false;
  if (len == 1) return true;

  // At this point we can, but don't have to, ignore the last byte.  We use
  // this observation to fold the odd-length case into the even-length case.
  len &= ~1;

  return memcmp(p1, p2, len) == 0;
}

inline bool operator==(const StringPiece& x, const char* y) {
  if (y == nullptr) {
    return x.size() == 0;
  } else {
    return strncmp(x.data(), y, x.size()) == 0 && y[x.size()] == '\0';
  }
}

inline bool operator!=(const StringPiece& x, const StringPiece& y) {
  return !(x == y);
}

inline bool operator!=(const StringPiece& x, const char* y) {
  return !(x == y);
}

inline bool operator<(const StringPiece& x, const StringPiece& y) {
  const int r = memcmp(x.data(), y.data(),
                       std::min(x.size(), y.size()));
  return ((r < 0) || ((r == 0) && (x.size() < y.size())));
}

inline bool operator>(const StringPiece& x, const StringPiece& y) {
  return y < x;
}

inline bool operator<=(const StringPiece& x, const StringPiece& y) {
  return !(x > y);
}

inline bool operator>=(const StringPiece& x, const StringPiece& y) {
  return !(x < y);
}

extern std::ostream& operator<<(std::ostream& o, const StringPiece& piece);

}  // namespace art

#endif  // ART_RUNTIME_BASE_STRINGPIECE_H_