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1.1 root 1: /*********************************************************************
2: * COPYRIGHT NOTICE *
3: **********************************************************************
4: * This software is copyright (C) 1982 by Pavel Curtis *
5: * *
6: * Permission is granted to reproduce and distribute *
7: * this file by any means so long as no fee is charged *
8: * above a nominal handling fee and so long as this *
9: * notice is always included in the copies. *
10: * *
11: * Other rights are reserved except as explicitly granted *
12: * by written permission of the author. *
13: * Pavel Curtis *
14: * Computer Science Dept. *
15: * 405 Upson Hall *
16: * Cornell University *
17: * Ithaca, NY 14853 *
18: * *
19: * Ph- (607) 256-4934 *
20: * *
21: * Pavel.Cornell@Udel-Relay (ARPAnet) *
22: * decvax!cornell!pavel (UUCPnet) *
23: *********************************************************************/
24:
25: /*
26: * comp_hash.c --- Routines to deal with the hashtable of capability
27: * names.
28: *
29: * $Log: comp_hash.c,v $
30: * Revision 1.1 92/03/13 10:45:37 bin
31: * Initial revision
32: *
33: * Revision 2.1 82/10/25 14:45:34 pavel
34: * Added Copyright Notice
35: *
36: * Revision 2.0 82/10/24 15:16:34 pavel
37: * Beta-one Test Release
38: *
39: * Revision 1.3 82/08/23 22:29:33 pavel
40: * The REAL Alpha-one Release Version
41: *
42: * Revision 1.2 82/08/19 19:09:46 pavel
43: * Alpha Test Release One
44: *
45: * Revision 1.1 82/08/12 18:36:23 pavel
46: * Initial revision
47: *
48: *
49: */
50:
51: #ifndef COHERENT
52: static char RCSid[] =
53: "$Header: /src386/usr/bin/tic/RCS/comp_hash.c,v 1.1 92/03/13 10:45:37 bin Exp $";
54: #endif
55:
56: #include "compiler.h"
57: #include "term.h"
58:
59:
60:
61: /*
62: * make_hash_table()
63: *
64: * Takes the entries in cap_table[] and hashes them into cap_hash_table[]
65: * by name. There are Captabsize entries in cap_table[] and Hashtabsize
66: * slots in cap_hash_table[].
67: *
68: */
69:
70: make_hash_table()
71: {
72: int i;
73: int hashvalue;
74: int collisions = 0;
75:
76: for (i=0; i < Captabsize; i++)
77: {
78: hashvalue = hash_function(cap_table[i].nte_name);
79: DEBUG(9, "%d\n", hashvalue);
80:
81: if (cap_hash_table[hashvalue] != (struct name_table_entry *) 0)
82: collisions++;
83:
84: cap_table[i].nte_link = cap_hash_table[hashvalue];
85: cap_hash_table[hashvalue] = &cap_table[i];
86: }
87:
88: DEBUG(3, "Hash table complete\n%d collisions ", collisions);
89: DEBUG(3, "out of %d entries\n", Captabsize);
90: }
91:
92:
93:
94: /*
95: * int hash_function(string)
96: *
97: * Computes the hashing function on the given string.
98: *
99: * The current hash function is the sum of each consectutive pair
100: * of characters, taken as two-byte integers, mod Hashtabsize.
101: *
102: */
103:
104: static
105: int
106: hash_function(string)
107: char *string;
108: {
109: long sum = 0;
110:
111: while (*string)
112: {
113: sum += *string + (*(string + 1) << 8);
114: string++;
115: }
116:
117: return (sum % Hashtabsize);
118: }
119:
120:
121:
122: /*
123: * struct name_table_entry *
124: * find_entry(string)
125: *
126: * Finds the entry for the given string in the hash table if present.
127: * Returns a pointer to the entry in the table or 0 if not found.
128: *
129: */
130:
131: struct name_table_entry *
132: find_entry(string)
133: char *string;
134: {
135: int hashvalue;
136: struct name_table_entry *ptr;
137:
138: hashvalue = hash_function(string);
139:
140: ptr = cap_hash_table[hashvalue];
141:
142: while (ptr != (struct name_table_entry *) 0 &&
143: strcmp(ptr->nte_name, string) != 0)
144: ptr = ptr->nte_link;
145:
146: return (ptr);
147: }
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