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/* String-interning set
Copyright (C) 2025 Free Software Foundation, Inc.
This file is part of GDB.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef GDBSUPPORT_STRING_SET_H
#define GDBSUPPORT_STRING_SET_H
#include "gdbsupport/unordered_set.h"
#include <string_view>
namespace gdb
{
/* This is a string-interning set. It manages storage for strings,
ensuring that just a single copy of a given string is kept. The
underlying C string will remain valid for the lifetime of this
object. */
class string_set
{
public:
/* Insert STR into this set. Returns a pointer to the interned
string. */
const char *insert (const char *str)
{
/* We need to take the length to hash the string anyway, so it's
convenient to just wrap it here. */
return insert (std::string_view (str));
}
/* An overload accepting a string view. */
const char *insert (std::string_view str)
{
return m_set.insert (str).first->get ();
}
/* An overload that takes ownership of the string. */
const char *insert (gdb::unique_xmalloc_ptr<char> str)
{
return m_set.insert (local_string (std::move (str))).first->get ();
}
private:
/* The type of string we store. Note that we do not store
std::string here to avoid the small-string optimization
invalidating a pointer on rehash. */
struct local_string
{
explicit local_string (std::string_view str)
: contents (xstrndup (str.data (), str.size ())),
len (str.size ())
{ }
explicit local_string (gdb::unique_xmalloc_ptr<char> str)
: contents (std::move (str)),
len (strlen (contents.get ()))
{ }
const char *get () const
{ return contents.get (); }
std::string_view as_view () const
{ return std::string_view (contents.get (), len); }
/* \0-terminated string contents. */
gdb::unique_xmalloc_ptr<char> contents;
/* Length of the string. */
size_t len;
};
/* Equality object for the set. */
struct str_eq
{
using is_transparent = void;
bool operator() (std::string_view lhs, const local_string &rhs)
const noexcept
{
return lhs == rhs.as_view ();
}
bool operator() (const local_string &lhs, const local_string &rhs)
const noexcept
{
return (*this) (lhs.as_view (), rhs);
}
};
/* Hash object for the set. */
struct str_hash
{
using is_transparent = void;
using is_avalanching = void;
uint64_t operator() (const local_string &rhs) const noexcept
{
return (*this) (rhs.as_view ());
}
uint64_t operator() (std::string_view rhs) const noexcept
{
return ankerl::unordered_dense::hash<std::string_view> () (rhs);
}
};
/* The strings. */
gdb::unordered_set<local_string, str_hash, str_eq> m_set;
};
}
#endif /* GDBSUPPORT_STRING_SET_H */
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