text: //===-- ConstString.h -------------------------------------------*- C++ -*-===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef liblldb_ConstString_h_
  #define liblldb_ConstString_h_
  
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Support/FormatVariadic.h"
  
  #include <stddef.h>
  
  namespace lldb_private {
  class Stream;
  }
  namespace llvm {
  class raw_ostream;
  }
  
  namespace lldb_private {
  
  /// \class ConstString ConstString.h "lldb/Utility/ConstString.h"
  /// A uniqued constant string class.
  ///
  /// Provides an efficient way to store strings as uniqued strings. After the
  /// strings are uniqued, finding strings that are equal to one another is very
  /// fast as just the pointers need to be compared. It also allows for many
  /// common strings from many different sources to be shared to keep the memory
  /// footprint low.
  ///
  /// No reference counting is done on strings that are added to the string
  /// pool, once strings are added they are in the string pool for the life of
  /// the program.
  class ConstString {
  public:
    /// Default constructor
    ///
    /// Initializes the string to an empty string.
    ConstString() : m_string(nullptr) {}
  
    /// Copy constructor
    ///
    /// Copies the string value in \a rhs into this object.
    ///
    /// \param[in] rhs
    ///     Another string object to copy.
    ConstString(const ConstString &rhs) : m_string(rhs.m_string) {}
  
    explicit ConstString(const llvm::StringRef &s);
  
    /// Construct with C String value
    ///
    /// Constructs this object with a C string by looking to see if the
    /// C string already exists in the global string pool. If it doesn't
    /// exist, it is added to the string pool.
    ///
    /// \param[in] cstr
    ///     A NULL terminated C string to add to the string pool.
    explicit ConstString(const char *cstr);
  
    /// Construct with C String value with max length
    ///
    /// Constructs this object with a C string with a length. If \a max_cstr_len
    /// is greater than the actual length of the string, the string length will
    /// be truncated. This allows substrings to be created without the need to
    /// NULL terminate the string as it is passed into this function.
    ///
    /// \param[in] cstr
    ///     A pointer to the first character in the C string. The C
    ///     string can be NULL terminated in a buffer that contains
    ///     more characters than the length of the string, or the
    ///     string can be part of another string and a new substring
    ///     can be created.
    ///
    /// \param[in] max_cstr_len
    ///     The max length of \a cstr. If the string length of \a cstr
    ///     is less than \a max_cstr_len, then the string will be
    ///     truncated. If the string length of \a cstr is greater than
    ///     \a max_cstr_len, then only max_cstr_len bytes will be used
    ///     from \a cstr.
    explicit ConstString(const char *cstr, size_t max_cstr_len);
  
    /// Destructor
    ///
    /// Since constant string values are currently not reference counted, there
    /// isn't much to do here.
    ~ConstString() = default;
  
    /// C string equality binary predicate function object for ConstString
    /// objects.
    struct StringIsEqual {
      /// C equality test.
      ///
      /// Two C strings are equal when they are contained in ConstString objects
      /// when their pointer values are equal to each other.
      ///
      /// \return
      ///     Returns \b true if the C string in \a lhs is equal to
      ///     the C string value in \a rhs, \b false otherwise.
      bool operator()(const char *lhs, const char *rhs) const {
        return lhs == rhs;
      }
    };
  
    /// Convert to bool operator.
    ///
    /// This allows code to check a ConstString object to see if it contains a
    /// valid string using code such as:
    ///
    /// \code
    /// ConstString str(...);
    /// if (str)
    /// { ...
    /// \endcode
    ///
    /// \return
    ///     /b True this object contains a valid non-empty C string, \b
    ///     false otherwise.
    explicit operator bool() const { return !IsEmpty(); }
  
    /// Assignment operator
    ///
    /// Assigns the string in this object with the value from \a rhs.
    ///
    /// \param[in] rhs
    ///     Another string object to copy into this object.
    ///
    /// \return
    ///     A const reference to this object.
    ConstString operator=(ConstString rhs) {
      m_string = rhs.m_string;
      return *this;
    }
  
    /// Equal to operator
    ///
    /// Returns true if this string is equal to the string in \a rhs. This
    /// operation is very fast as it results in a pointer comparison since all
    /// strings are in a uniqued in a global string pool.
    ///
    /// \param[in] rhs
    ///     Another string object to compare this object to.
    ///
    /// \return
    ///     \li \b true if this object is equal to \a rhs.
    ///     \li \b false if this object is not equal to \a rhs.
    bool operator==(ConstString rhs) const {
      // We can do a pointer compare to compare these strings since they must
      // come from the same pool in order to be equal.
      return m_string == rhs.m_string;
    }
  
    /// Equal to operator against a non-ConstString value.
    ///
    /// Returns true if this string is equal to the string in \a rhs. This
    /// overload is usually slower than comparing against a ConstString value.
    /// However, if the rhs string not already a ConstString and it is impractical
    /// to turn it into a non-temporary variable, then this overload is faster.
    ///
    /// \param[in] rhs
    ///     Another string object to compare this object to.
    ///
    /// \return
    ///     \li \b true if this object is equal to \a rhs.
    ///     \li \b false if this object is not equal to \a rhs.
    bool operator==(const char *rhs) const {
      // ConstString differentiates between empty strings and nullptr strings, but
      // StringRef doesn't. Therefore we have to do this check manually now.
      if (m_string == nullptr && rhs != nullptr)
        return false;
      if (m_string != nullptr && rhs == nullptr)
        return false;
  
      return GetStringRef() == rhs;
    }
  
    /// Not equal to operator
    ///
    /// Returns true if this string is not equal to the string in \a rhs. This
    /// operation is very fast as it results in a pointer comparison since all
    /// strings are in a uniqued in a global string pool.
    ///
    /// \param[in] rhs
    ///     Another string object to compare this object to.
    ///
    /// \return
    ///     \li \b true if this object is not equal to \a rhs.
    ///     \li \b false if this object is equal to \a rhs.
    bool operator!=(ConstString rhs) const {
      return m_string != rhs.m_string;
    }
  
    /// Not equal to operator against a non-ConstString value.
    ///
    /// Returns true if this string is not equal to the string in \a rhs. This
    /// overload is usually slower than comparing against a ConstString value.
    /// However, if the rhs string not already a ConstString and it is impractical
    /// to turn it into a non-temporary variable, then this overload is faster.
    ///
    /// \param[in] rhs
    ///     Another string object to compare this object to.
    ///
    /// \return \b true if this object is not equal to \a rhs, false otherwise.
    bool operator!=(const char *rhs) const { return !(*this == rhs); }
  
    bool operator<(ConstString rhs) const;
  
    /// Get the string value as a C string.
    ///
    /// Get the value of the contained string as a NULL terminated C string
    /// value.
    ///
    /// If \a value_if_empty is nullptr, then nullptr will be returned.
    ///
    /// \return Returns \a value_if_empty if the string is empty, otherwise
    ///     the C string value contained in this object.
    const char *AsCString(const char *value_if_empty = nullptr) const {
      return (IsEmpty() ? value_if_empty : m_string);
    }
  
    /// Get the string value as a llvm::StringRef
    ///
    /// \return
    ///     Returns a new llvm::StringRef object filled in with the
    ///     needed data.
    llvm::StringRef GetStringRef() const {
      return llvm::StringRef(m_string, GetLength());
    }
  
    /// Get the string value as a C string.
    ///
    /// Get the value of the contained string as a NULL terminated C string
    /// value. Similar to the ConstString::AsCString() function, yet this
    /// function will always return nullptr if the string is not valid. So this
    /// function is a direct accessor to the string pointer value.
    ///
    /// \return
    ///     Returns nullptr the string is invalid, otherwise the C string
    ///     value contained in this object.
    const char *GetCString() const { return m_string; }
  
    /// Get the length in bytes of string value.
    ///
    /// The string pool stores the length of the string, so we can avoid calling
    /// strlen() on the pointer value with this function.
    ///
    /// \return
    ///     Returns the number of bytes that this string occupies in
    ///     memory, not including the NULL termination byte.
    size_t GetLength() const;
  
    /// Clear this object's state.
    ///
    /// Clear any contained string and reset the value to the empty string
    /// value.
    void Clear() { m_string = nullptr; }
  
    /// Equal to operator
    ///
    /// Returns true if this string is equal to the string in \a rhs. If case
    /// sensitive equality is tested, this operation is very fast as it results
    /// in a pointer comparison since all strings are in a uniqued in a global
    /// string pool.
    ///
    /// \param[in] lhs
    ///     The Left Hand Side const ConstString object reference.
    ///
    /// \param[in] rhs
    ///     The Right Hand Side const ConstString object reference.
    ///
    /// \param[in] case_sensitive
    ///     Case sensitivity. If true, case sensitive equality
    ///     will be tested, otherwise character case will be ignored
    ///
    /// \return \b true if this object is equal to \a rhs, \b false otherwise.
    static bool Equals(ConstString lhs, ConstString rhs,
                       const bool case_sensitive = true);
  
    /// Compare two string objects.
    ///
    /// Compares the C string values contained in \a lhs and \a rhs and returns
    /// an integer result.
    ///
    /// NOTE: only call this function when you want a true string
    /// comparison. If you want string equality use the, use the == operator as
    /// it is much more efficient. Also if you want string inequality, use the
    /// != operator for the same reasons.
    ///
    /// \param[in] lhs
    ///     The Left Hand Side const ConstString object reference.
    ///
    /// \param[in] rhs
    ///     The Right Hand Side const ConstString object reference.
    ///
    /// \param[in] case_sensitive
    ///     Case sensitivity of compare. If true, case sensitive compare
    ///     will be performed, otherwise character case will be ignored
    ///
    /// \return -1 if lhs < rhs, 0 if lhs == rhs, 1 if lhs > rhs
    static int Compare(ConstString lhs, ConstString rhs,
                       const bool case_sensitive = true);
  
    /// Dump the object description to a stream.
    ///
    /// Dump the string value to the stream \a s. If the contained string is
    /// empty, print \a value_if_empty to the stream instead. If \a
    /// value_if_empty is nullptr, then nothing will be dumped to the stream.
    ///
    /// \param[in] s
    ///     The stream that will be used to dump the object description.
    ///
    /// \param[in] value_if_empty
    ///     The value to dump if the string is empty. If nullptr, nothing
    ///     will be output to the stream.
    void Dump(Stream *s, const char *value_if_empty = nullptr) const;
  
    /// Dump the object debug description to a stream.
    ///
    /// \param[in] s
    ///     The stream that will be used to dump the object description.
    void DumpDebug(Stream *s) const;
  
    /// Test for empty string.
    ///
    /// \return
    ///     \li \b true if the contained string is empty.
    ///     \li \b false if the contained string is not empty.
    bool IsEmpty() const { return m_string == nullptr || m_string[0] == '\0'; }
  
    /// Test for null string.
    ///
    /// \return
    ///     \li \b true if there is no string associated with this instance.
    ///     \li \b false if there is a string associated with this instance.
    bool IsNull() const { return m_string == nullptr; }
  
    /// Set the C string value.
    ///
    /// Set the string value in the object by uniquing the \a cstr string value
    /// in our global string pool.
    ///
    /// If the C string already exists in the global string pool, it finds the
    /// current entry and returns the existing value. If it doesn't exist, it is
    /// added to the string pool.
    ///
    /// \param[in] cstr
    ///     A NULL terminated C string to add to the string pool.
    void SetCString(const char *cstr);
  
    void SetString(const llvm::StringRef &s);
  
    /// Set the C string value and its mangled counterpart.
    ///
    /// Object files and debug symbols often use mangled string to represent the
    /// linkage name for a symbol, function or global. The string pool can
    /// efficiently store these values and their counterparts so when we run
    /// into another instance of a mangled name, we can avoid calling the name
    /// demangler over and over on the same strings and then trying to unique
    /// them.
    ///
    /// \param[in] demangled
    ///     The demangled string to correlate with the \a mangled name.
    ///
    /// \param[in] mangled
    ///     The already uniqued mangled ConstString to correlate the
    ///     soon to be uniqued version of \a demangled.
    void SetStringWithMangledCounterpart(llvm::StringRef demangled,
                                         ConstString mangled);
  
    /// Retrieve the mangled or demangled counterpart for a mangled or demangled
    /// ConstString.
    ///
    /// Object files and debug symbols often use mangled string to represent the
    /// linkage name for a symbol, function or global. The string pool can
    /// efficiently store these values and their counterparts so when we run
    /// into another instance of a mangled name, we can avoid calling the name
    /// demangler over and over on the same strings and then trying to unique
    /// them.
    ///
    /// \param[in] counterpart
    ///     A reference to a ConstString object that might get filled in
    ///     with the demangled/mangled counterpart.
    ///
    /// \return
    ///     /b True if \a counterpart was filled in with the counterpart
    ///     /b false otherwise.
    bool GetMangledCounterpart(ConstString &counterpart) const;
  
    /// Set the C string value with length.
    ///
    /// Set the string value in the object by uniquing \a cstr_len bytes
    /// starting at the \a cstr string value in our global string pool. If trim
    /// is true, then \a cstr_len indicates a maximum length of the CString and
    /// if the actual length of the string is less, then it will be trimmed.
    ///
    /// If the C string already exists in the global string pool, it finds the
    /// current entry and returns the existing value. If it doesn't exist, it is
    /// added to the string pool.
    ///
    /// \param[in] cstr
    ///     A NULL terminated C string to add to the string pool.
    ///
    /// \param[in] cstr_len
    ///     The maximum length of the C string.
    void SetCStringWithLength(const char *cstr, size_t cstr_len);
  
    /// Set the C string value with the minimum length between \a fixed_cstr_len
    /// and the actual length of the C string. This can be used for data
    /// structures that have a fixed length to store a C string where the string
    /// might not be NULL terminated if the string takes the entire buffer.
    void SetTrimmedCStringWithLength(const char *cstr, size_t fixed_cstr_len);
  
    /// Get the memory cost of this object.
    ///
    /// Return the size in bytes that this object takes in memory. This returns
    /// the size in bytes of this object, which does not include any the shared
    /// string values it may refer to.
    ///
    /// \return
    ///     The number of bytes that this object occupies in memory.
    ///
    /// \see ConstString::StaticMemorySize ()
    size_t MemorySize() const { return sizeof(ConstString); }
  
    /// Get the size in bytes of the current global string pool.
    ///
    /// Reports the size in bytes of all shared C string values, containers and
    /// any other values as a byte size for the entire string pool.
    ///
    /// \return
    ///     The number of bytes that the global string pool occupies
    ///     in memory.
    static size_t StaticMemorySize();
  
  protected:
    // Member variables
    const char *m_string;
  };
  
  /// Stream the string value \a str to the stream \a s
  Stream &operator<<(Stream &s, ConstString str);
  
  } // namespace lldb_private
  
  namespace llvm {
  template <> struct format_provider<lldb_private::ConstString> {
    static void format(const lldb_private::ConstString &CS, llvm::raw_ostream &OS,
                       llvm::StringRef Options);
  };
  }
  
  #endif // liblldb_ConstString_h_
  