slice.h

//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//

#ifndef KUDU_UTIL_SLICE_H_
#define KUDU_UTIL_SLICE_H_

// NOTE: using stdint.h instead of cstdint because this file is supposed
//       to be processed by a compiler lacking C++11 support.
#include <stdint.h>

#include <cassert>
#include <cstddef>
#include <cstring>
#include <iosfwd>
#include <map>
#include <string>

#ifdef KUDU_HEADERS_USE_RICH_SLICE
#include "kudu/gutil/strings/fastmem.h"
#include "kudu/gutil/strings/stringpiece.h"
#include "kudu/util/faststring.h"
#endif
#include "kudu/util/kudu_export.h"

namespace kudu {

class Status;

class KUDU_EXPORT Slice {
 public:
  Slice() : data_(reinterpret_cast<const uint8_t *>("")),
            size_(0) { }

  Slice(const uint8_t* d, size_t n) : data_(d), size_(n) { }

  Slice(const char* d, size_t n) :
    data_(reinterpret_cast<const uint8_t *>(d)),
    size_(n) { }

  Slice(const std::string& s) : // NOLINT(runtime/explicit)
    data_(reinterpret_cast<const uint8_t *>(s.data())),
    size_(s.size()) { }

  Slice(const char* s) : // NOLINT(runtime/explicit)
    data_(reinterpret_cast<const uint8_t *>(s)),
    size_(strlen(s)) { }

#ifdef KUDU_HEADERS_USE_RICH_SLICE
  Slice(const faststring &s) // NOLINT(runtime/explicit)
    : data_(s.data()),
      size_(s.size()) {
  }

  Slice(const StringPiece& s) // NOLINT(runtime/explicit)
    : data_(reinterpret_cast<const uint8_t*>(s.data())),
      size_(s.size()) {
  }
#endif

  const uint8_t* data() const { return data_; }

  uint8_t *mutable_data() { return const_cast<uint8_t *>(data_); }

  size_t size() const { return size_; }

  bool empty() const { return size_ == 0; }

  const uint8_t &operator[](size_t n) const {
    assert(n < size());
    return data_[n];
  }

  void clear() {
    data_ = reinterpret_cast<const uint8_t *>("");
    size_ = 0;
  }

  void remove_prefix(size_t n) {
    assert(n <= size());
    data_ += n;
    size_ -= n;
  }

  void truncate(size_t n) {
    assert(n <= size());
    size_ = n;
  }

  Status check_size(size_t expected_size) const;

  std::string ToString() const;

  std::string ToDebugString(size_t max_len = 0) const;

  int compare(const Slice& b) const;

  bool starts_with(const Slice& x) const {
    return ((size_ >= x.size_) &&
            (MemEqual(data_, x.data_, x.size_)));
  }

  struct Comparator {
    bool operator()(const Slice& a, const Slice& b) const {
      return a.compare(b) < 0;
    }
  };

  void relocate(uint8_t* d) {
    if (data_ != d) {
      memcpy(d, data_, size_);
      data_ = d;
    }
  }

 private:
  friend bool operator==(const Slice& x, const Slice& y);

  static bool MemEqual(const void* a, const void* b, size_t n) {
#ifdef KUDU_HEADERS_USE_RICH_SLICE
    return strings::memeq(a, b, n);
#else
    return memcmp(a, b, n) == 0;
#endif
  }

  static int MemCompare(const void* a, const void* b, size_t n) {
#ifdef KUDU_HEADERS_USE_RICH_SLICE
    return strings::fastmemcmp_inlined(a, b, n);
#else
    return memcmp(a, b, n);
#endif
  }

  const uint8_t* data_;
  size_t size_;

  // Intentionally copyable
};

inline bool operator==(const Slice& x, const Slice& y) {
  return ((x.size() == y.size()) &&
          (Slice::MemEqual(x.data(), y.data(), x.size())));
}

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

inline std::ostream& operator<<(std::ostream& o, const Slice& s) {
  return o << s.ToDebugString(16); // should be enough for anyone...
}

inline int Slice::compare(const Slice& b) const {
  const int min_len = (size_ < b.size_) ? size_ : b.size_;
  int r = MemCompare(data_, b.data_, min_len);
  if (r == 0) {
    if (size_ < b.size_) r = -1;
    else if (size_ > b.size_) r = +1;
  }
  return r;
}

template <typename T>
struct SliceMap {
  typedef std::map<Slice, T, Slice::Comparator> type;
};

}  // namespace kudu

#endif  // KUDU_UTIL_SLICE_H_