stl_util.h 3.7 KB

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  1. // Protocol Buffers - Google's data interchange format
  2. // Copyright 2008 Google Inc. All rights reserved.
  3. // https://developers.google.com/protocol-buffers/
  4. //
  5. // Redistribution and use in source and binary forms, with or without
  6. // modification, are permitted provided that the following conditions are
  7. // met:
  8. //
  9. // * Redistributions of source code must retain the above copyright
  10. // notice, this list of conditions and the following disclaimer.
  11. // * Redistributions in binary form must reproduce the above
  12. // copyright notice, this list of conditions and the following disclaimer
  13. // in the documentation and/or other materials provided with the
  14. // distribution.
  15. // * Neither the name of Google Inc. nor the names of its
  16. // contributors may be used to endorse or promote products derived from
  17. // this software without specific prior written permission.
  18. //
  19. // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  20. // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  21. // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  22. // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  23. // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24. // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25. // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  26. // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  27. // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  28. // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  29. // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30. // from google3/util/gtl/stl_util.h
  31. #ifndef GOOGLE_PROTOBUF_STUBS_STL_UTIL_H__
  32. #define GOOGLE_PROTOBUF_STUBS_STL_UTIL_H__
  33. #include <google/protobuf/stubs/common.h>
  34. #include <algorithm>
  35. namespace google {
  36. namespace protobuf {
  37. // Inside Google, this function implements a horrible, disgusting hack in which
  38. // we reach into the string's private implementation and resize it without
  39. // initializing the new bytes. In some cases doing this can significantly
  40. // improve performance. However, since it's totally non-portable it has no
  41. // place in open source code. Feel free to fill this function in with your
  42. // own disgusting hack if you want the perf boost.
  43. inline void STLStringResizeUninitialized(std::string* s, size_t new_size) {
  44. s->resize(new_size);
  45. }
  46. // As above, but we make sure to follow amortized growth in which we always
  47. // increase the capacity by at least a constant factor >1.
  48. inline void STLStringResizeUninitializedAmortized(std::string* s,
  49. size_t new_size) {
  50. const size_t cap = s->capacity();
  51. if (new_size > cap) {
  52. // Make sure to always grow by at least a factor of 2x.
  53. s->reserve(std::max(new_size, 2 * cap));
  54. }
  55. STLStringResizeUninitialized(s, new_size);
  56. }
  57. // Return a mutable char* pointing to a string's internal buffer,
  58. // which may not be null-terminated. Writing through this pointer will
  59. // modify the string.
  60. //
  61. // string_as_array(&str)[i] is valid for 0 <= i < str.size() until the
  62. // next call to a string method that invalidates iterators.
  63. //
  64. // As of 2006-04, there is no standard-blessed way of getting a
  65. // mutable reference to a string's internal buffer. However, issue 530
  66. // (http://www.open-std.org/JTC1/SC22/WG21/docs/lwg-active.html#530)
  67. // proposes this as the method. According to Matt Austern, this should
  68. // already work on all current implementations.
  69. inline char* string_as_array(std::string* str) {
  70. // DO NOT USE const_cast<char*>(str->data())! See the unittest for why.
  71. return str->empty() ? nullptr : &*str->begin();
  72. }
  73. } // namespace protobuf
  74. } // namespace google
  75. #endif // GOOGLE_PROTOBUF_STUBS_STL_UTIL_H__