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/* |
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* shstr.C |
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*/ |
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|
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#include <cstring> |
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#include <cstdlib> |
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|
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#include <tr1/unordered_set> |
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|
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#include "shstr.h" |
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|
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struct hash |
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{ |
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std::size_t operator ()(const char *s) const |
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{ |
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unsigned long hash = 0; |
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unsigned int i = 0; |
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|
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/* use the one-at-a-time hash function, which supposedly is |
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* better than the djb2-like one used by perl5.005, but |
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* certainly is better then the bug used here before. |
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* see http://burtleburtle.net/bob/hash/doobs.html |
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*/ |
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while (*s) |
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{ |
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hash += *s++; |
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hash += hash << 10; |
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hash ^= hash >> 6; |
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} |
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|
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hash += hash << 3; |
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hash ^= hash >> 11; |
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hash += hash << 15; |
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|
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return hash; |
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} |
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}; |
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|
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struct equal |
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{ |
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bool operator ()(const char *a, const char *b) const |
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{ |
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return !strcmp (a, b); |
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} |
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}; |
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|
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typedef std::tr1::unordered_set<const char *, hash, equal> HT; |
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|
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static HT ht; |
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|
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static const char *makevec (const char *s) |
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{ |
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int len = strlen (s); |
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|
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const char *v = (const char *)(2 + (int *)malloc (sizeof (int) * 2 + len + 1)); |
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|
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shstr::length (v) = len; |
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shstr::refcnt (v) = 1; |
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|
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memcpy ((char *)v, s, len + 1); |
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|
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return s; |
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} |
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|
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const char *shstr::null = makevec ("<nil>"); |
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|
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const char * |
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shstr::find (const char *s) |
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{ |
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if (!s) |
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return s; |
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|
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HT::iterator i = ht.find (s); |
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|
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return i != ht.end () |
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? *i |
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: 0; |
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} |
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|
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const char * |
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shstr::intern (const char *s) |
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{ |
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if (!s) |
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return null; |
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|
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if (const char *found = find (s)) |
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{ |
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++refcnt (found); |
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return found; |
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} |
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|
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s = makevec (s); |
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ht.insert (s); |
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return s; |
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} |
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|
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// periodically test refcounts == 0 for a few strings |
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// this is the ONLY thing that erases stuff from ht. keep it that way. |
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void |
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shstr::gc () |
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{ |
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static const char *curpos; |
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|
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HT::iterator i = curpos ? ht.find (curpos) : ht.begin (); |
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|
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if (i == ht.end ()) |
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i = ht.begin (); |
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|
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// go through all strings roughly once every 4 minutes |
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int n = ht.size () / 256 + 16; |
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|
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for (;;) |
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{ |
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if (i == ht.end ()) |
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{ |
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curpos = 0; |
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return; |
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} |
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else if (!--n) |
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break; |
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else if (!refcnt (*i)) |
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{ |
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HT::iterator o = i++; |
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const char *s = *o; |
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ht.erase (o); |
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|
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//printf ("GC %4d %3d %d >%s<%d\n", (int)ht.size (), n, shstr::refcnt (s), s, shstr::length (s)); |
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free (-2 + (int *)s); |
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} |
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else |
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++i; |
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} |
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|
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curpos = *i; |
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} |
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|
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//TODO: this should of course not be here |
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/* buf_overflow() - we don't want to exceed the buffer size of |
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* buf1 by adding on buf2! Returns true if overflow will occur. |
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*/ |
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|
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int |
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buf_overflow (const char *buf1, const char *buf2, int bufsize) |
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{ |
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int len1 = 0, len2 = 0; |
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|
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if (buf1) |
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len1 = strlen (buf1); |
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if (buf2) |
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len2 = strlen (buf2); |
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if ((len1 + len2) >= bufsize) |
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return 1; |
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return 0; |
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} |
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|
