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| 6 | #include <cstdlib> |
6 | #include <cstdlib> |
| 7 | |
7 | |
| 8 | #include <tr1/unordered_set> |
8 | #include <tr1/unordered_set> |
| 9 | |
9 | |
| 10 | #include "shstr.h" |
10 | #include "shstr.h" |
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11 | #include "util.h" |
| 11 | |
12 | |
| 12 | struct hash |
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| 13 | { |
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| 14 | std::size_t operator ()(const char *s) const |
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| 15 | { |
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| 16 | unsigned long hash = 0; |
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| 17 | unsigned int i = 0; |
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| 18 | |
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| 19 | /* use the one-at-a-time hash function, which supposedly is |
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| 20 | * better than the djb2-like one used by perl5.005, but |
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| 21 | * certainly is better then the bug used here before. |
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| 22 | * see http://burtleburtle.net/bob/hash/doobs.html |
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| 23 | */ |
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| 24 | while (*s) |
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| 25 | { |
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| 26 | hash += *s++; |
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| 27 | hash += hash << 10; |
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| 28 | hash ^= hash >> 6; |
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| 29 | } |
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| 30 | |
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| 31 | hash += hash << 3; |
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| 32 | hash ^= hash >> 11; |
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| 33 | hash += hash << 15; |
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| 34 | |
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| 35 | return hash; |
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| 36 | } |
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| 37 | }; |
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| 38 | |
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| 39 | struct equal |
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| 40 | { |
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| 41 | bool operator ()(const char *a, const char *b) const |
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| 42 | { |
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| 43 | return !strcmp (a, b); |
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| 44 | } |
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| 45 | }; |
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| 46 | |
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| 47 | typedef std::tr1::unordered_set<const char *, hash, equal> HT; |
13 | typedef std::tr1::unordered_set<const char *, str_hash, str_equal> HT; |
| 48 | |
14 | |
| 49 | static HT ht; |
15 | static HT ht; |
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16 | |
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17 | static const char *makevec (const char *s) |
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18 | { |
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19 | int len = strlen (s); |
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20 | |
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21 | const char *v = (const char *)(2 + (int *)malloc (sizeof (int) * 2 + len + 1)); |
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22 | |
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23 | shstr::length (v) = len; |
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24 | shstr::refcnt (v) = 1; |
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25 | |
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26 | memcpy ((char *)v, s, len + 1); |
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27 | |
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28 | return v; |
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29 | } |
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30 | |
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31 | const char *shstr::null = makevec ("<nil>"); |
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32 | |
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33 | // what weird misoptimisation is this again? |
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34 | const shstr undead_name ("undead"); |
| 50 | |
35 | |
| 51 | const char * |
36 | const char * |
| 52 | shstr::find (const char *s) |
37 | shstr::find (const char *s) |
| 53 | { |
38 | { |
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39 | if (!s) |
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40 | return s; |
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41 | |
| 54 | HT::iterator i = ht.find (s); |
42 | HT::iterator i = ht.find (s); |
| 55 | |
43 | |
| 56 | return i != ht.end () |
44 | return i != ht.end () |
| 57 | ? (char *)*i |
45 | ? *i |
| 58 | : 0; |
46 | : 0; |
| 59 | } |
47 | } |
| 60 | |
48 | |
| 61 | const char * |
49 | const char * |
| 62 | shstr::intern (const char *s) |
50 | shstr::intern (const char *s) |
| 63 | { |
51 | { |
| 64 | HT::iterator i = ht.find (s); |
52 | if (!s) |
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53 | return null; |
| 65 | |
54 | |
| 66 | if (i != ht.end ()) |
55 | if (const char *found = find (s)) |
| 67 | return (char *)*i; |
56 | { |
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57 | ++refcnt (found); |
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58 | return found; |
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59 | } |
| 68 | |
60 | |
| 69 | int len = strlen (s); |
61 | s = makevec (s); |
| 70 | |
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| 71 | int *v = (int *)malloc (sizeof (int) * 2 + len + 1); |
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| 72 | |
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| 73 | v [0] = len; |
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| 74 | v [1] = 0; |
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| 75 | |
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| 76 | v += 2; |
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| 77 | |
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| 78 | memcpy (v, s, len + 1); |
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| 79 | |
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| 80 | ht.insert ((char *)v); |
62 | ht.insert (s); |
| 81 | |
63 | return s; |
| 82 | return (char *)v; |
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| 83 | } |
64 | } |
| 84 | |
65 | |
| 85 | // TODO: periodically test refcounts == 0 for a few strings (e.g. one hash bucket, |
66 | // periodically test refcounts == 0 for a few strings |
| 86 | // exploiting the fatc that iterators stay valid for unordered_set). |
67 | // this is the ONLY thing that erases stuff from ht. keep it that way. |
| 87 | void |
68 | void |
| 88 | shstr::gc () |
69 | shstr::gc () |
| 89 | { |
70 | { |
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71 | static const char *curpos; |
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72 | |
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73 | HT::iterator i = curpos ? ht.find (curpos) : ht.begin (); |
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74 | |
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75 | if (i == ht.end ()) |
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76 | i = ht.begin (); |
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77 | |
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78 | // go through all strings roughly once every 4 minutes |
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79 | int n = ht.size () / 256 + 16; |
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80 | |
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81 | for (;;) |
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82 | { |
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83 | if (i == ht.end ()) |
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84 | { |
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85 | curpos = 0; |
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86 | return; |
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87 | } |
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88 | else if (!--n) |
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89 | break; |
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90 | else if (!refcnt (*i)) |
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91 | { |
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92 | HT::iterator o = i++; |
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93 | const char *s = *o; |
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94 | ht.erase (o); |
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95 | |
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96 | //printf ("GC %4d %3d %d >%s<%d\n", (int)ht.size (), n, shstr::refcnt (s), s, shstr::length (s)); |
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97 | free (-2 + (int *)s); |
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98 | } |
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99 | else |
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100 | ++i; |
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101 | } |
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102 | |
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103 | curpos = *i; |
| 90 | } |
104 | } |
| 91 | |
105 | |
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106 | //TODO: this should of course not be here |
| 92 | /* buf_overflow() - we don't want to exceed the buffer size of |
107 | /* buf_overflow() - we don't want to exceed the buffer size of |
| 93 | * buf1 by adding on buf2! Returns true if overflow will occur. |
108 | * buf1 by adding on buf2! Returns true if overflow will occur. |
| 94 | */ |
109 | */ |
| 95 | |
110 | |
| 96 | int |
111 | int |
