diff options
Diffstat (limited to 'lua/src/lstring.c')
| -rw-r--r-- | lua/src/lstring.c | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/lua/src/lstring.c b/lua/src/lstring.c new file mode 100644 index 0000000..af96c89 --- /dev/null +++ b/lua/src/lstring.c @@ -0,0 +1,185 @@ +/* +** $Id: lstring.c,v 2.26.1.1 2013/04/12 18:48:47 roberto Exp $ +** String table (keeps all strings handled by Lua) +** See Copyright Notice in lua.h +*/ + + +#include <string.h> + +#define lstring_c +#define LUA_CORE + +#include "lua.h" + +#include "lmem.h" +#include "lobject.h" +#include "lstate.h" +#include "lstring.h" + + +/* +** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a string to +** compute its hash +*/ +#if !defined(LUAI_HASHLIMIT) +#define LUAI_HASHLIMIT 5 +#endif + + +/* +** equality for long strings +*/ +int luaS_eqlngstr (TString *a, TString *b) { + size_t len = a->tsv.len; + lua_assert(a->tsv.tt == LUA_TLNGSTR && b->tsv.tt == LUA_TLNGSTR); + return (a == b) || /* same instance or... */ + ((len == b->tsv.len) && /* equal length and ... */ + (memcmp(getstr(a), getstr(b), len) == 0)); /* equal contents */ +} + + +/* +** equality for strings +*/ +int luaS_eqstr (TString *a, TString *b) { + return (a->tsv.tt == b->tsv.tt) && + (a->tsv.tt == LUA_TSHRSTR ? eqshrstr(a, b) : luaS_eqlngstr(a, b)); +} + + +unsigned int luaS_hash (const char *str, size_t l, unsigned int seed) { + unsigned int h = seed ^ cast(unsigned int, l); + size_t l1; + size_t step = (l >> LUAI_HASHLIMIT) + 1; + for (l1 = l; l1 >= step; l1 -= step) + h = h ^ ((h<<5) + (h>>2) + cast_byte(str[l1 - 1])); + return h; +} + + +/* +** resizes the string table +*/ +void luaS_resize (lua_State *L, int newsize) { + int i; + stringtable *tb = &G(L)->strt; + /* cannot resize while GC is traversing strings */ + luaC_runtilstate(L, ~bitmask(GCSsweepstring)); + if (newsize > tb->size) { + luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *); + for (i = tb->size; i < newsize; i++) tb->hash[i] = NULL; + } + /* rehash */ + for (i=0; i<tb->size; i++) { + GCObject *p = tb->hash[i]; + tb->hash[i] = NULL; + while (p) { /* for each node in the list */ + GCObject *next = gch(p)->next; /* save next */ + unsigned int h = lmod(gco2ts(p)->hash, newsize); /* new position */ + gch(p)->next = tb->hash[h]; /* chain it */ + tb->hash[h] = p; + resetoldbit(p); /* see MOVE OLD rule */ + p = next; + } + } + if (newsize < tb->size) { + /* shrinking slice must be empty */ + lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL); + luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *); + } + tb->size = newsize; +} + + +/* +** creates a new string object +*/ +static TString *createstrobj (lua_State *L, const char *str, size_t l, + int tag, unsigned int h, GCObject **list) { + TString *ts; + size_t totalsize; /* total size of TString object */ + totalsize = sizeof(TString) + ((l + 1) * sizeof(char)); + ts = &luaC_newobj(L, tag, totalsize, list, 0)->ts; + ts->tsv.len = l; + ts->tsv.hash = h; + ts->tsv.extra = 0; + memcpy(ts+1, str, l*sizeof(char)); + ((char *)(ts+1))[l] = '\0'; /* ending 0 */ + return ts; +} + + +/* +** creates a new short string, inserting it into string table +*/ +static TString *newshrstr (lua_State *L, const char *str, size_t l, + unsigned int h) { + GCObject **list; /* (pointer to) list where it will be inserted */ + stringtable *tb = &G(L)->strt; + TString *s; + if (tb->nuse >= cast(lu_int32, tb->size) && tb->size <= MAX_INT/2) + luaS_resize(L, tb->size*2); /* too crowded */ + list = &tb->hash[lmod(h, tb->size)]; + s = createstrobj(L, str, l, LUA_TSHRSTR, h, list); + tb->nuse++; + return s; +} + + +/* +** checks whether short string exists and reuses it or creates a new one +*/ +static TString *internshrstr (lua_State *L, const char *str, size_t l) { + GCObject *o; + global_State *g = G(L); + unsigned int h = luaS_hash(str, l, g->seed); + for (o = g->strt.hash[lmod(h, g->strt.size)]; + o != NULL; + o = gch(o)->next) { + TString *ts = rawgco2ts(o); + if (h == ts->tsv.hash && + l == ts->tsv.len && + (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) { + if (isdead(G(L), o)) /* string is dead (but was not collected yet)? */ + changewhite(o); /* resurrect it */ + return ts; + } + } + return newshrstr(L, str, l, h); /* not found; create a new string */ +} + + +/* +** new string (with explicit length) +*/ +TString *luaS_newlstr (lua_State *L, const char *str, size_t l) { + if (l <= LUAI_MAXSHORTLEN) /* short string? */ + return internshrstr(L, str, l); + else { + if (l + 1 > (MAX_SIZET - sizeof(TString))/sizeof(char)) + luaM_toobig(L); + return createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed, NULL); + } +} + + +/* +** new zero-terminated string +*/ +TString *luaS_new (lua_State *L, const char *str) { + return luaS_newlstr(L, str, strlen(str)); +} + + +Udata *luaS_newudata (lua_State *L, size_t s, Table *e) { + Udata *u; + if (s > MAX_SIZET - sizeof(Udata)) + luaM_toobig(L); + u = &luaC_newobj(L, LUA_TUSERDATA, sizeof(Udata) + s, NULL, 0)->u; + u->uv.len = s; + u->uv.metatable = NULL; + u->uv.env = e; + return u; +} + |