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#ifndef IVL_StringHeap_H
#define IVL_StringHeap_H
/*
* Copyright (c) 2002-2021 Stephen Williams (steve@icarus.com)
*
* This source code is free software; you can redistribute it
* and/or modify it in source code form under the terms of the GNU
* General Public License as published by the Free Software
* Foundation; either version 2 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, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
# include <string>
class perm_string {
public:
perm_string() : text_(0) { }
perm_string(const perm_string&that) : text_(that.text_) { }
~perm_string() { }
inline bool nil() const { return text_ == 0; }
perm_string& operator = (const perm_string&that)
{ text_ = that.text_; return *this; }
const char*str() const { return text_; }
operator const char* () const { return str(); }
// This is an escape for making perm_string objects out of
// literals. For example, perm_string::literal("Label"); Please
// do *not* cheat and pass arbitrary const char* items here.
static perm_string literal(const char*t) { return perm_string(t); }
private:
friend class StringHeap;
friend class StringHeapLex;
explicit perm_string(const char*t) : text_(t) { };
private:
const char*text_;
};
extern const perm_string empty_perm_string;
extern bool operator == (perm_string a, perm_string b);
extern bool operator == (perm_string a, const char* b);
extern bool operator != (perm_string a, perm_string b);
extern bool operator != (perm_string a, const char* b);
extern bool operator > (perm_string a, perm_string b);
extern bool operator < (perm_string a, perm_string b);
extern bool operator >= (perm_string a, perm_string b);
extern bool operator <= (perm_string a, perm_string b);
extern std::ostream& operator << (std::ostream&out, perm_string that);
/*
* The string heap is a way to permanently allocate strings
* efficiently. They only take up the space of the string characters
* and the terminating nul, there is no malloc overhead.
*/
class StringHeap {
public:
StringHeap();
~StringHeap();
const char*add(const char*);
perm_string make(const char*);
private:
char*cell_base_;
unsigned cell_ptr_;
private: // not implemented
StringHeap(const StringHeap&);
StringHeap& operator= (const StringHeap&);
};
/*
* A lexical string heap is a string heap that makes an effort to
* return the same pointer for identical strings. This saves further
* space by not allocating duplicate strings, so in a system with lots
* of identifiers, this can theoretically save more space.
*/
class StringHeapLex : private StringHeap {
public:
StringHeapLex();
~StringHeapLex();
const char*add(const char*);
perm_string make(const char*);
perm_string make(const std::string&);
unsigned add_count() const;
unsigned add_hit_count() const;
void cleanup();
private:
enum { HASH_SIZE = 4096 };
const char*hash_table_[HASH_SIZE];
unsigned add_count_;
unsigned hit_count_;
private: // not implemented
StringHeapLex(const StringHeapLex&);
StringHeapLex& operator= (const StringHeapLex&);
};
#endif /* IVL_StringHeap_H */
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