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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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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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? (char *)*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 s; |
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|
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if (const char *found = find (s)) |
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return found; |
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|
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int len = strlen (s); |
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|
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int *v = (int *)malloc (sizeof (int) * 2 + len + 1); |
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|
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v [0] = len; |
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v [1] = 0; |
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|
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v += 2; |
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|
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memcpy (v, s, len + 1); |
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|
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ht.insert ((char *)v); |
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|
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return (char *)v; |
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} |
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|
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// TODO: periodically test refcounts == 0 for a few strings (e.g. one hash bucket, |
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// exploiting the fatc that iterators stay valid for unordered_set). |
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void |
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shstr::gc () |
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{ |
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} |
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|
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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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|
