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intern.c
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2000-12-05
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/* -*-C-*-
$Id: intern.c,v 9.57 2000/12/05 21:23:44 cph Exp $
Copyright (c) 1987-2000 Massachusetts Institute of Technology
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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/* String hash functions and interning of symbols. */
#include "scheme.h"
#include "prims.h"
#include "trap.h"
#ifdef STDC_HEADERS
# include <string.h>
#else
extern int EXFUN (strlen, (const char *));
#endif
/* These are exported to other parts of the system. */
extern SCHEME_OBJECT EXFUN (string_to_symbol, (SCHEME_OBJECT));
extern SCHEME_OBJECT EXFUN (char_pointer_to_symbol, (unsigned char *));
extern SCHEME_OBJECT EXFUN (memory_to_symbol, (long, unsigned char *));
extern SCHEME_OBJECT EXFUN (find_symbol, (long, unsigned char *));
/* Hashing strings */
#define STRING_HASH_BITS 16
static unsigned int
DEFUN (string_hash, (length, string),
long length AND unsigned char * string)
{
fast unsigned char * scan = string;
fast unsigned char * end = (scan + length);
fast unsigned int result = 0;
while (scan < end)
{
result <<= 1;
result |= (result >> STRING_HASH_BITS);
result ^= (*scan++);
result &= ((1 << STRING_HASH_BITS) - 1);
}
return (result);
}
static Boolean
DEFUN (string_equal, (length1, string1, length2, string2),
long length1 AND unsigned char * string1
AND long length2 AND unsigned char * string2)
{
fast unsigned char * scan1 = string1;
fast unsigned char * scan2 = string2;
fast long length = length1;
fast unsigned char * end1 = (scan1 + length);
if (scan1 == scan2)
return (true);
if (length != length2)
return (false);
while (scan1 < end1)
if ((*scan1++) != (*scan2++))
return (false);
return (true);
}
static SCHEME_OBJECT *
DEFUN (find_symbol_internal, (length, string),
long length AND unsigned char * string)
{
fast SCHEME_OBJECT * bucket;
{
fast SCHEME_OBJECT obarray = (Get_Fixed_Obj_Slot (OBArray));
bucket =
(MEMORY_LOC (obarray,
(((string_hash (length, string))
% (VECTOR_LENGTH (obarray)))
+ 1)));
}
while ((*bucket) != EMPTY_LIST)
{
fast SCHEME_OBJECT symbol = (PAIR_CAR (*bucket));
fast SCHEME_OBJECT name = (FAST_MEMORY_REF (symbol, SYMBOL_NAME));
if (string_equal (length, string,
(STRING_LENGTH (name)), (STRING_LOC (name, 0))))
return (PAIR_CAR_LOC (*bucket));
bucket = (PAIR_CDR_LOC (*bucket));
}
return (bucket);
}
/* Set this to be informed of symbols as they are interned. */
void EXFUN ((*intern_symbol_hook), (SCHEME_OBJECT)) = 0;
static SCHEME_OBJECT
DEFUN (link_new_symbol, (symbol, cell),
SCHEME_OBJECT symbol
AND SCHEME_OBJECT * cell)
{
/* `symbol' does not exist yet in obarray. `cell' points to the
cell containing the final '() in the list. Replace this
with a cons of the new symbol and '() (i.e. extend the
list in the bucket by 1 new element). */
fast SCHEME_OBJECT result = (OBJECT_NEW_TYPE (TC_INTERNED_SYMBOL, symbol));
(*cell) = (cons (result, EMPTY_LIST));
if (intern_symbol_hook != ((void (*) ()) 0))
(*intern_symbol_hook) (result);
return (result);
}
SCHEME_OBJECT
DEFUN (find_symbol, (length, string), long length AND unsigned char * string)
{
SCHEME_OBJECT result = (* (find_symbol_internal (length, string)));
return ((result == EMPTY_LIST) ? SHARP_F : result);
}
static SCHEME_OBJECT
DEFUN (make_symbol, (string, cell),
SCHEME_OBJECT string AND
SCHEME_OBJECT * cell)
{
Primitive_GC_If_Needed (2);
{
SCHEME_OBJECT symbol = (MAKE_POINTER_OBJECT (TC_UNINTERNED_SYMBOL, Free));
(Free [SYMBOL_NAME]) = string;
(Free [SYMBOL_GLOBAL_VALUE]) = UNBOUND_OBJECT;
Free += 2;
return (link_new_symbol (symbol, cell));
}
}
SCHEME_OBJECT
DEFUN (memory_to_symbol, (length, string),
long length AND
unsigned char * string)
{
SCHEME_OBJECT * cell = (find_symbol_internal (length, string));
return
(((*cell) == EMPTY_LIST)
? (make_symbol ((memory_to_string (length, string)), cell))
: (*cell));
}
SCHEME_OBJECT
DEFUN (char_pointer_to_symbol, (string), unsigned char * string)
{
return (memory_to_symbol ((strlen (string)), string));
}
SCHEME_OBJECT
DEFUN (string_to_symbol, (string), SCHEME_OBJECT string)
{
SCHEME_OBJECT * cell =
(find_symbol_internal ((STRING_LENGTH (string)),
(STRING_LOC (string, 0))));
return (((*cell) == EMPTY_LIST) ? (make_symbol (string, cell)) : (*cell));
}
SCHEME_OBJECT
DEFUN (intern_symbol, (symbol), SCHEME_OBJECT symbol)
{
SCHEME_OBJECT name = (FAST_MEMORY_REF (symbol, SYMBOL_NAME));
SCHEME_OBJECT * cell =
(find_symbol_internal ((STRING_LENGTH (name)), (STRING_LOC (name, 0))));
return (((*cell) == EMPTY_LIST)
? (link_new_symbol (symbol, cell))
: (*cell));
}
DEFINE_PRIMITIVE ("FIND-SYMBOL", Prim_find_symbol, 1, 1,
"(FIND-SYMBOL STRING)\n\
Returns the symbol whose name is STRING, or #F if no such symbol exists.")
{
SCHEME_OBJECT string;
PRIMITIVE_HEADER (1);
CHECK_ARG (1, STRING_P);
string = (ARG_REF (1));
PRIMITIVE_RETURN
(find_symbol ((STRING_LENGTH (string)), (STRING_LOC (string, 0))));
}
DEFINE_PRIMITIVE ("STRING->SYMBOL", Prim_string_to_symbol, 1, 1,
"(STRING->SYMBOL STRING)\n\
Returns the symbol whose name is STRING, constructing a new symbol if needed.")
{
PRIMITIVE_HEADER (1);
CHECK_ARG (1, STRING_P);
PRIMITIVE_RETURN (string_to_symbol (ARG_REF (1)));
}
DEFINE_PRIMITIVE ("STRING-HASH", Prim_string_hash, 1, 1,
"(STRING-HASH STRING)\n\
Return a hash value for a string. This uses the hashing\n\
algorithm used for interning symbols. It is intended for use by\n\
the reader in creating interned symbols.")
{
SCHEME_OBJECT string;
PRIMITIVE_HEADER (1);
CHECK_ARG (1, STRING_P);
string = (ARG_REF (1));
PRIMITIVE_RETURN
(LONG_TO_UNSIGNED_FIXNUM (string_hash ((STRING_LENGTH (string)),
(STRING_LOC (string, 0)))));
}
DEFINE_PRIMITIVE ("STRING-HASH-MOD", Prim_string_hash_mod, 2, 2,
"(STRING-HASH-MOD STRING DENOMINATOR)\n\
DENOMINATOR must be a nonnegative integer.\n\
Equivalent to (MOD (STRING-HASH STRING) DENOMINATOR).")
{
SCHEME_OBJECT string;
PRIMITIVE_HEADER (2);
CHECK_ARG (1, STRING_P);
string = (ARG_REF (1));
PRIMITIVE_RETURN
(LONG_TO_UNSIGNED_FIXNUM
((string_hash ((STRING_LENGTH (string)),
(STRING_LOC (string, 0))))
% (arg_nonnegative_integer (2))));
}