Symbol Class Reference

Symbols are unique objects with a name stored in a hash table. More...

#include <symbol.hh>

Collaboration diagram for Symbol:

List of all members.

Public Member Functions
ostream &	print (ostream &fout) const
	print a symbol on a stream
Private Member Functions
	Symbol (const char *str, unsigned int hsh, Symbol *nxt)
	Constructs a new symbol ready to be placed in the hash table.
	~Symbol ()
	The Destructor is never used.
bool	equiv (unsigned int hash, const char *str) const
	Check if the name of the symbol is equal to string str.
Static Private Member Functions
static unsigned int	calcHashKey (const char *str)
	Compute the 32-bits hash key of string str.
static Symbol *	get (const string &str)
	Get the symbol of name str.
static Symbol *	get (const char *str)
	Get the symbol of name str.
static Symbol *	prefix (const char *str)
	Creates a new symbol of name prefixed by str.
static bool	isnew (const char *str)
	Returns true if no symbol of name str exists.
Private Attributes
char *	fName
	Name of the symbol.
unsigned int	fHash
	Hash key computed from the name and used to determine the hash table entry.
Symbol *	fNext
	Next symbol in the hash table entry.
void *	fData
	Field to user disposal to store additional data.
Static Private Attributes
static const int	kHashTableSize = 511
	Size of the hash table (a prime number is recommended)
static Symbol *	gSymbolTable [kHashTableSize]
	Hash table used to store the symbols.
Friends
Symbol *	symbol (const char *str)
	Returns (and creates if new) the symbol of name str.
Symbol *	symbol (const string &str)
	Returns (and creates if new) the symbol of name str.
Symbol *	unique (const char *str)
	Returns a new unique symbol of name strxxx.
const char *	name (Symbol *sym)
	Returns the name of a symbol.
void *	getUserData (Symbol *sym)
	Returns user data.
void	setUserData (Symbol *sym, void *d)
	Set user data.

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Detailed Description

Symbols are unique objects with a name stored in a hash table.

Definition at line 53 of file symbol.hh.

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Constructor & Destructor Documentation

Symbol::Symbol	(	const char *	str,
		unsigned int	hsh,
		Symbol *	nxt
	)		[private]

Constructs a new symbol ready to be placed in the hash table.

Constructs a symbol ready to be placed in the hash table.

It makes a private copy of its name.

Parameters:

str	the name of the symbol
hsh	the hash key of the symbol
nxt	a pointer to the next symbol in the hash table entry

Definition at line 158 of file symbol.cpp.

References len().

{
    int len = strlen(str);
    
    fName = new char [len+1];
    memcpy(fName, str, len+1);
    fHash = hsh;
    fNext = nxt;
    fData = 0;
}

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Symbol::~Symbol

(

)

[private]

The Destructor is never used.

Definition at line 169 of file symbol.cpp.

{
    delete [] fName;
}

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Member Function Documentation

unsigned int Symbol::calcHashKey

(

const char *

str

)

[static, private]

Compute the 32-bits hash key of string str.

Parameters:

str	the string

Returns:

a 32-bits hash key

Definition at line 140 of file symbol.cpp.

{
    unsigned int h = 0;

    while (*str) h = (h << 1) ^ (h >> 20) ^ (*str++);
    return h;
}

bool Symbol::equiv	(	unsigned int	hash,
		const char *	str
	)		const [private]

Check if the name of the symbol is equal to string str.

Check if the name of the symbol is equal to string str This method is used by isnew() and make() when searching the hashtable for an existing symbol.

Parameters:

hash	the hash key of the string (used to speedup the comparison)
str	the string to compare

Returns:

true if the name of the symbol and str are the same

Definition at line 127 of file symbol.cpp.

Referenced by get(), and isnew().

{
    return (fHash == hash) && (strcmp(fName,str) == 0);
}

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Symbol * Symbol::get

(

const string &

str

)

[static, private]

Get the symbol of name str.

Search the hash table for the symbol of name str or returns a new one.

Parameters:

str	the name of the symbol

Returns:

a symbol of name str

Definition at line 46 of file symbol.cpp.

Referenced by symbol().

{
    char    buf[1024];
    int     i;
    int     n = str.length();
    
    if (n>1023) n = 1023;
    for (i = 0; i < n; i++) { buf[i] = str[i]; }
    buf[i] = 0;
    
    return Symbol::get(buf);
}

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Symbol * Symbol::get

(

const char *

str

)

[static, private]

Get the symbol of name str.

Search the hash table for the symbol of name str or returns a new one.

Parameters:

str	the name of the symbol

Returns:

a symbol of name str

Definition at line 67 of file symbol.cpp.

References equiv(), and fNext.

{
    unsigned int            hsh  = calcHashKey(str);
    int             bckt = hsh % kHashTableSize;
    Symbol*         item = gSymbolTable[bckt];

    while ( item && !item->equiv(hsh,str) ) item = item->fNext;
    Symbol* r = item ? item : gSymbolTable[bckt] = new Symbol(str, hsh, gSymbolTable[bckt]);
    return r;
}

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bool Symbol::isnew

(

const char *

str

)

[static, private]

Returns true if no symbol of name str exists.

Static method that searches the symbol table for a string.

Parameters:

str	string to search

Returns:

true if the string is NOT in the table (it is a new string)

Definition at line 85 of file symbol.cpp.

References equiv(), and fNext.

{
    unsigned int            hsh  = calcHashKey(str);
    int             bckt = hsh % kHashTableSize;
    Symbol*         item = gSymbolTable[bckt];
    
    while ( item && !item->equiv(hsh,str) ) item = item->fNext;
    return item == 0;
}

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Symbol * Symbol::prefix

(

const char *

str

)

[static, private]

Creates a new symbol of name prefixed by str.

Creates a new symbol with a name obtained by concatenating the str prefix with a number in order to make it unique.

Parameters:

str	the prefix of the name

Returns:

a symbol of name prefix++n

Definition at line 102 of file symbol.cpp.

References name().

Referenced by unique().

{
    char    name[256];
    
    static map<const char*, unsigned int> gPrefixCounters;
    
    for (int n = 0; n<10000; n++) {
        snprintf(name, 256, "%s%d", str, gPrefixCounters[str]++);
        if (isnew(name)) return get(name);
    }
    assert(false);
    return get("UNIQUEOVERFLOW");
}   

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ostream & Symbol::print

(

ostream &

fout

)

const

print a symbol on a stream

< print a symbol on a stream

Definition at line 174 of file symbol.cpp.

Referenced by operator<<().

{
    return fout << fName;
}

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Friends And Related Function Documentation

void* getUserData

(

Symbol *

sym

)

[friend]

Returns user data.

Definition at line 100 of file symbol.hh.

const char* name

(

Symbol *

sym

)

[friend]

Returns the name of a symbol.

Definition at line 98 of file symbol.hh.

void setUserData	(	Symbol *	sym,
		void *	d
	)		[friend]

Set user data.

Definition at line 101 of file symbol.hh.

Symbol* symbol

(

const char *

str

)

[friend]

Returns (and creates if new) the symbol of name str.

Definition at line 95 of file symbol.hh.

Symbol* symbol

(

const string &

str

)

[friend]

Returns (and creates if new) the symbol of name str.

Definition at line 96 of file symbol.hh.

Symbol* unique

(

const char *

str

)

[friend]

Returns a new unique symbol of name strxxx.

Definition at line 97 of file symbol.hh.

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Member Data Documentation

void* Symbol::fData [private]

Field to user disposal to store additional data.

Definition at line 66 of file symbol.hh.

Referenced by getUserData(), and setUserData().

unsigned int Symbol::fHash [private]

Hash key computed from the name and used to determine the hash table entry.

Definition at line 64 of file symbol.hh.

char* Symbol::fName [private]

Name of the symbol.

Definition at line 63 of file symbol.hh.

Referenced by name().

Symbol* Symbol::fNext [private]

Next symbol in the hash table entry.

Definition at line 65 of file symbol.hh.

Referenced by get(), and isnew().

Symbol * Symbol::gSymbolTable [static, private]

Hash table used to store the symbols.

Definition at line 59 of file symbol.hh.

const int Symbol::kHashTableSize = 511 [static, private]

Size of the hash table (a prime number is recommended)

Definition at line 58 of file symbol.hh.

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The documentation for this class was generated from the following files:

• symbol.hh
• symbol.cpp