protobuf/src/google/protobuf/stubs/stl_util.h

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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// https://developers.google.com/protocol-buffers/
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// from google3/util/gtl/stl_util.h
 
#ifndef GOOGLE_PROTOBUF_STUBS_STL_UTIL_H__
#define GOOGLE_PROTOBUF_STUBS_STL_UTIL_H__
 
#include <google/protobuf/stubs/common.h>
 
#include <algorithm>
 
namespace google {
namespace protobuf {
 
// Inside Google, this function implements a horrible, disgusting hack in which
// we reach into the string's private implementation and resize it without
// initializing the new bytes.  In some cases doing this can significantly
// improve performance.  However, since it's totally non-portable it has no
// place in open source code.  Feel free to fill this function in with your
// own disgusting hack if you want the perf boost.
inline void STLStringResizeUninitialized(std::string* s, size_t new_size) {
  s->resize(new_size);
}
 
// As above, but we make sure to follow amortized growth in which we always
// increase the capacity by at least a constant factor >1.
inline void STLStringResizeUninitializedAmortized(std::string* s,
                                                  size_t new_size) {
  const size_t cap = s->capacity();
  if (new_size > cap) {
    // Make sure to always grow by at least a factor of 2x.
    s->reserve(std::max(new_size, 2 * cap));
  }
  STLStringResizeUninitialized(s, new_size);
}
 
// Return a mutable char* pointing to a string's internal buffer,
// which may not be null-terminated. Writing through this pointer will
// modify the string.
//
// string_as_array(&str)[i] is valid for 0 <= i < str.size() until the
// next call to a string method that invalidates iterators.
//
// As of 2006-04, there is no standard-blessed way of getting a
// mutable reference to a string's internal buffer. However, issue 530
// (http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-active.html#530)
// proposes this as the method. According to Matt Austern, this should
// already work on all current implementations.
inline char* string_as_array(std::string* str) {
  // DO NOT USE const_cast<char*>(str->data())! See the unittest for why.
  return str->empty() ? nullptr : &*str->begin();
}
 
}  // namespace protobuf
}  // namespace google
 
#endif  // GOOGLE_PROTOBUF_STUBS_STL_UTIL_H__