mirror of https://github.com/lua/lua
Hash always use all characters in a long string
Hashes for long strings are computed only when they are used as keys in a table, not a too common case. And, in that case, it is to easy to force collisions changing only the characters which are not part of the hash.
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parent
c23cc86c54
commit
9a89fb1c9d
2
lstate.c
2
lstate.c
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@ -76,7 +76,7 @@ static unsigned int luai_makeseed (lua_State *L) {
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addbuff(buff, p, &h); /* local variable */
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addbuff(buff, p, &lua_newstate); /* public function */
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lua_assert(p == sizeof(buff));
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return luaS_hash(buff, p, h, 1);
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return luaS_hash(buff, p, h);
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}
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#endif
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20
lstring.c
20
lstring.c
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@ -22,16 +22,6 @@
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#include "lstring.h"
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/*
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** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a long string to
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** compute its hash
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*/
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#if !defined(LUAI_HASHLIMIT)
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#define LUAI_HASHLIMIT 5
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#endif
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/*
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** Maximum size for string table.
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*/
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@ -50,10 +40,9 @@ int luaS_eqlngstr (TString *a, TString *b) {
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}
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unsigned int luaS_hash (const char *str, size_t l, unsigned int seed,
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size_t step) {
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unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) {
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unsigned int h = seed ^ cast_uint(l);
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for (; l >= step; l -= step)
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for (; l > 0; l--)
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h ^= ((h<<5) + (h>>2) + cast_byte(str[l - 1]));
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return h;
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}
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@ -63,8 +52,7 @@ unsigned int luaS_hashlongstr (TString *ts) {
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lua_assert(ts->tt == LUA_VLNGSTR);
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if (ts->extra == 0) { /* no hash? */
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size_t len = ts->u.lnglen;
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size_t step = (len >> LUAI_HASHLIMIT) + 1;
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ts->hash = luaS_hash(getstr(ts), len, ts->hash, step);
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ts->hash = luaS_hash(getstr(ts), len, ts->hash);
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ts->extra = 1; /* now it has its hash */
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}
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return ts->hash;
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@ -201,7 +189,7 @@ static TString *internshrstr (lua_State *L, const char *str, size_t l) {
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TString *ts;
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global_State *g = G(L);
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stringtable *tb = &g->strt;
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unsigned int h = luaS_hash(str, l, g->seed, 1);
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unsigned int h = luaS_hash(str, l, g->seed);
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TString **list = &tb->hash[lmod(h, tb->size)];
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lua_assert(str != NULL); /* otherwise 'memcmp'/'memcpy' are undefined */
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for (ts = *list; ts != NULL; ts = ts->u.hnext) {
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@ -41,8 +41,7 @@
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#define eqshrstr(a,b) check_exp((a)->tt == LUA_VSHRSTR, (a) == (b))
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LUAI_FUNC unsigned int luaS_hash (const char *str, size_t l,
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unsigned int seed, size_t step);
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LUAI_FUNC unsigned int luaS_hash (const char *str, size_t l, unsigned int seed);
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LUAI_FUNC unsigned int luaS_hashlongstr (TString *ts);
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LUAI_FUNC int luaS_eqlngstr (TString *a, TString *b);
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LUAI_FUNC void luaS_resize (lua_State *L, int newsize);
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1
ltests.c
1
ltests.c
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@ -523,7 +523,6 @@ static lu_mem checkgraylist (global_State *g, GCObject *o) {
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((void)g); /* better to keep it available if we need to print an object */
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while (o) {
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lua_assert(!!isgray(o) ^ (getage(o) == G_TOUCHED2));
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//lua_assert(isgray(o) || getage(o) == G_TOUCHED2);
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lua_assert(!testbit(o->marked, TESTBIT));
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if (keepinvariant(g))
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l_setbit(o->marked, TESTBIT); /* mark that object is in a gray list */
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