kc3-lang/angle/src/compiler/translator/ImmutableString.h

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• Author : Jamie Madill
  Date : 2018-06-20 11:46:43
  Hash : b779b12c
  Message : Add kEmptyImmutableString. We can use this instead of ImmutableString(""). Bug: angleproject:2665 Change-Id: I8b3d5d3075838b9f2caa1627071202e48a5fdc83 Reviewed-on: https://chromium-review.googlesource.com/1108085 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Luc Ferron <lucferron@chromium.org>

• src/compiler/translator/ImmutableString.h

• //
  // Copyright (c) 2018 The ANGLE Project Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  //
  // ImmutableString.h: Wrapper for static or pool allocated char arrays, that are guaranteed to be
  // valid and unchanged for the duration of the compilation.
  //
  
  #ifndef COMPILER_TRANSLATOR_IMMUTABLESTRING_H_
  #define COMPILER_TRANSLATOR_IMMUTABLESTRING_H_
  
  #include <string>
  
  #include "common/string_utils.h"
  #include "compiler/translator/Common.h"
  
  namespace sh
  {
  
  namespace
  {
  constexpr size_t constStrlen(const char *str)
  {
      if (str == nullptr)
      {
          return 0u;
      }
      size_t len = 0u;
      while (*(str + len) != '\0')
      {
          ++len;
      }
      return len;
  }
  }
  
  class ImmutableString
  {
    public:
      // The data pointer passed in must be one of:
      //  1. nullptr (only valid with length 0).
      //  2. a null-terminated static char array like a string literal.
      //  3. a null-terminated pool allocated char array. This can't be c_str() of a local TString,
      //     since when a TString goes out of scope it clears its first character.
      explicit constexpr ImmutableString(const char *data) : mData(data), mLength(constStrlen(data))
      {
      }
  
      constexpr ImmutableString(const char *data, size_t length) : mData(data), mLength(length) {}
  
      ImmutableString(const std::string &str)
          : mData(AllocatePoolCharArray(str.c_str(), str.size())), mLength(str.size())
      {
      }
  
      constexpr ImmutableString(const ImmutableString &) = default;
  
      ImmutableString &operator=(const ImmutableString &) = default;
  
      constexpr const char *data() const { return mData ? mData : ""; }
      constexpr size_t length() const { return mLength; }
  
      char operator[](size_t index) const { return data()[index]; }
  
      constexpr bool empty() const { return mLength == 0; }
      bool beginsWith(const char *prefix) const { return angle::BeginsWith(data(), prefix); }
      constexpr bool beginsWith(const ImmutableString &prefix) const
      {
          return mLength >= prefix.length() && memcmp(data(), prefix.data(), prefix.length()) == 0;
      }
      bool contains(const char *substr) const { return strstr(data(), substr) != nullptr; }
  
      constexpr bool operator==(const ImmutableString &b) const
      {
          if (mLength != b.mLength)
          {
              return false;
          }
          return memcmp(data(), b.data(), mLength) == 0;
      }
      constexpr bool operator!=(const ImmutableString &b) const { return !(*this == b); }
      constexpr bool operator==(const char *b) const
      {
          if (b == nullptr)
          {
              return empty();
          }
          return strcmp(data(), b) == 0;
      }
      constexpr bool operator!=(const char *b) const { return !(*this == b); }
      bool operator==(const std::string &b) const
      {
          return mLength == b.length() && memcmp(data(), b.c_str(), mLength) == 0;
      }
      bool operator!=(const std::string &b) const { return !(*this == b); }
  
      constexpr bool operator<(const ImmutableString &b) const
      {
          if (mLength < b.mLength)
          {
              return true;
          }
          if (mLength > b.mLength)
          {
              return false;
          }
          return (memcmp(data(), b.data(), mLength) < 0);
      }
  
      template <size_t hashBytes>
      struct FowlerNollVoHash
      {
          static const size_t kFnvOffsetBasis;
          static const size_t kFnvPrime;
  
          constexpr size_t operator()(const ImmutableString &a) const
          {
              const char *data = a.data();
              size_t hash      = kFnvOffsetBasis;
              while ((*data) != '\0')
              {
                  hash = hash ^ (*data);
                  hash = hash * kFnvPrime;
                  ++data;
              }
              return hash;
          }
      };
  
      // This hash encodes the opening parentheses location (if any), name length and whether the name
      // contains { or [ characters in addition to a 19-bit hash. This way the hash is more useful for
      // lookups. The string passed in should be at most 63 characters.
      uint32_t mangledNameHash() const;
  
    private:
      const char *mData;
      size_t mLength;
  };
  
  constexpr ImmutableString kEmptyImmutableString("");
  }  // namespace sh
  
  std::ostream &operator<<(std::ostream &os, const sh::ImmutableString &str);
  
  #endif  // COMPILER_TRANSLATOR_IMMUTABLESTRING_H_