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greg |
1.1 |
#ifndef lint
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greg |
2.15 |
static const char RCSid[] = "$Id: savestr.c,v 2.14 2023/06/08 17:48:01 greg Exp $";
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greg |
1.1 |
#endif
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greg |
1.2 |
/*
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greg |
1.1 |
* savestr.c - routines for efficient string storage.
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*
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* Savestr(s) stores a shared read-only string.
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* Freestr(s) indicates a client is finished with a string.
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* All strings must be null-terminated. There is
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* no imposed length limit.
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* Strings stored with savestr(s) can be equated
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greg |
2.5 |
* reliably using their pointer values.
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greg |
1.1 |
* Calls to savestr(s) and freestr(s) should be
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* balanced (obviously). The last call to freestr(s)
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* frees memory associated with the string; it should
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* never be referenced again.
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*
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greg |
2.13 |
* External symbols declared in rtio.h
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greg |
2.5 |
*/
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greg |
2.6 |
#include "copyright.h"
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greg |
1.1 |
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schorsch |
2.7 |
#include <stdlib.h>
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schorsch |
2.9 |
#include "rterror.h"
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#include "rtio.h"
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schorsch |
2.7 |
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greg |
1.1 |
#ifndef NHASH
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greg |
2.15 |
#ifdef SMLMEM
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greg |
2.10 |
#define NHASH 2039 /* hash table size (prime!) */
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greg |
2.15 |
#else
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#define NHASH 17117 /* hash table size (prime!) */
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#endif
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greg |
1.1 |
#endif
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typedef struct s_head {
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struct s_head *next; /* next in hash list */
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int nl; /* links count */
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} S_HEAD; /* followed by the string itself */
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static S_HEAD *stab[NHASH];
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greg |
2.3 |
#define hash(s) (shash(s)%NHASH)
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greg |
1.1 |
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#define string(sp) ((char *)((sp)+1))
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#define salloc(str) (S_HEAD *)malloc(sizeof(S_HEAD)+1+strlen(str))
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greg |
2.5 |
#define sfree(sp) free((void *)(sp))
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greg |
1.1 |
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| 52 |
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char *
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greg |
2.14 |
savestr(const char *str) /* save a string */
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greg |
1.1 |
{
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greg |
2.11 |
int hval;
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S_HEAD *sp;
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greg |
1.1 |
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if (str == NULL)
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return(NULL);
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greg |
2.11 |
if (!*str)
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return "";
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greg |
2.3 |
hval = hash(str);
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greg |
1.1 |
for (sp = stab[hval]; sp != NULL; sp = sp->next)
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if (!strcmp(str, string(sp))) {
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sp->nl++;
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return(string(sp));
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}
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if ((sp = salloc(str)) == NULL) {
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eputs("Out of memory in savestr\n");
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quit(1);
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}
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strcpy(string(sp), str);
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sp->nl = 1;
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sp->next = stab[hval];
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stab[hval] = sp;
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return(string(sp));
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}
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| 80 |
greg |
2.5 |
void
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| 81 |
schorsch |
2.9 |
freestr(char *s) /* free a string */
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| 82 |
greg |
1.1 |
{
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| 83 |
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int hval;
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| 84 |
greg |
2.11 |
S_HEAD *spl, *sp;
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| 85 |
greg |
1.1 |
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greg |
2.11 |
if (s == NULL || !*s)
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| 87 |
greg |
1.1 |
return;
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greg |
2.3 |
hval = hash(s);
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greg |
1.1 |
for (spl = NULL, sp = stab[hval]; sp != NULL; spl = sp, sp = sp->next)
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if (s == string(sp)) {
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if (--sp->nl > 0)
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return;
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if (spl != NULL)
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spl->next = sp->next;
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else
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stab[hval] = sp->next;
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sfree(sp);
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return;
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}
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}
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greg |
2.3 |
int
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| 104 |
greg |
2.14 |
shash(const char *s)
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| 105 |
greg |
1.1 |
{
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| 106 |
greg |
2.11 |
int h = 0;
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| 107 |
greg |
1.1 |
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| 108 |
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while (*s)
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| 109 |
greg |
2.4 |
h = (h<<1 & 0x7fff) ^ (*s++ & 0xff);
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| 110 |
greg |
2.3 |
return(h);
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| 111 |
greg |
1.1 |
}
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