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@@ -18,7 +18,37 @@
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#include "lstring.h"
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+/*
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+** equality for long strings
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+*/
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+int luaS_eqlngstr (TString *a, TString *b) {
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+ size_t len = a->tsv.len;
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+ lua_assert(a->tsv.tt == LUA_TLNGSTR && b->tsv.tt == LUA_TLNGSTR);
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+ return (len == b->tsv.len) && (memcmp(getstr(a), getstr(b), len) == 0);
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+}
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+
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+
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+/*
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+** equality for strings
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+*/
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+int luaS_eqstr (TString *a, TString *b) {
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+ return (a->tsv.tt == b->tsv.tt) &&
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+ (a->tsv.tt == LUA_TSHRSTR ? eqshrstr(a, b) : luaS_eqlngstr(a, b));
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+}
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+
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+
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+unsigned int luaS_hash (const char *str, size_t l) {
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+ unsigned int h = cast(unsigned int, l); /* seed */
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+ size_t l1;
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+ for (l1 = 0; l1 < l; l1++)
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+ h = h ^ ((h<<5) + (h>>2) + cast_byte(str[l1]));
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+ return h;
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+}
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+
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+/*
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+** resizes the string table
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+*/
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void luaS_resize (lua_State *L, int newsize) {
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int i;
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stringtable *tb = &G(L)->strt;
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@@ -50,36 +80,47 @@ void luaS_resize (lua_State *L, int newsize) {
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}
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-static TString *newlstr (lua_State *L, const char *str, size_t l,
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- unsigned int h) {
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- size_t totalsize; /* total size of TString object */
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- GCObject **list; /* (pointer to) list where it will be inserted */
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+/*
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+** creates a new string object
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+*/
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+static TString *createstrobj (lua_State *L, const char *str, size_t l,
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+ int tag, unsigned int h, GCObject **list) {
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TString *ts;
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- stringtable *tb = &G(L)->strt;
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- if (l+1 > (MAX_SIZET - sizeof(TString))/sizeof(char))
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- luaM_toobig(L);
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- if (tb->nuse >= cast(lu_int32, tb->size) && tb->size <= MAX_INT/2)
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- luaS_resize(L, tb->size*2); /* too crowded */
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+ size_t totalsize; /* total size of TString object */
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totalsize = sizeof(TString) + ((l + 1) * sizeof(char));
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- list = &tb->hash[lmod(h, tb->size)];
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- ts = &luaC_newobj(L, LUA_TSTRING, totalsize, list, 0)->ts;
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+ ts = &luaC_newobj(L, tag, totalsize, list, 0)->ts;
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ts->tsv.len = l;
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ts->tsv.hash = h;
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ts->tsv.extra = 0;
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memcpy(ts+1, str, l*sizeof(char));
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((char *)(ts+1))[l] = '\0'; /* ending 0 */
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- tb->nuse++;
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return ts;
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}
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-TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
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+/*
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+** creates a new short string, inserting it into string table
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+*/
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+static TString *newshrstr (lua_State *L, const char *str, size_t l,
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+ unsigned int h) {
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+ GCObject **list; /* (pointer to) list where it will be inserted */
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+ stringtable *tb = &G(L)->strt;
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+ TString *s;
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+ if (tb->nuse >= cast(lu_int32, tb->size) && tb->size <= MAX_INT/2)
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+ luaS_resize(L, tb->size*2); /* too crowded */
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+ list = &tb->hash[lmod(h, tb->size)];
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+ s = createstrobj(L, str, l, LUA_TSHRSTR, h, list);
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+ tb->nuse++;
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+ return s;
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+}
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+
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+
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+/*
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+** checks whether short string exists and reuses it or creates a new one
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+*/
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+static TString *internshrstr (lua_State *L, const char *str, size_t l) {
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GCObject *o;
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- unsigned int h = cast(unsigned int, l); /* seed */
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- size_t step = (l>>5)+1; /* if string is too long, don't hash all its chars */
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- size_t l1;
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- for (l1=l; l1>=step; l1-=step) /* compute hash */
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- h = h ^ ((h<<5)+(h>>2)+cast(unsigned char, str[l1-1]));
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+ unsigned int h = luaS_hash(str, l);
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for (o = G(L)->strt.hash[lmod(h, G(L)->strt.size)];
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o != NULL;
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o = gch(o)->next) {
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@@ -92,10 +133,27 @@ TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
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return ts;
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}
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}
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- return newlstr(L, str, l, h); /* not found; create a new string */
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+ return newshrstr(L, str, l, h); /* not found; create a new string */
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}
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+/*
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+** new string (with explicit length)
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+*/
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+TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
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+ if (l <= LUA_MAXSHORTLEN) /* short string? */
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+ return internshrstr(L, str, l);
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+ else {
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+ if (l + 1 > (MAX_SIZET - sizeof(TString))/sizeof(char))
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+ luaM_toobig(L);
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+ return createstrobj(L, str, l, LUA_TLNGSTR, 0, NULL);
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+ }
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+}
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+
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+
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+/*
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+** new zero-terminated string
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+*/
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TString *luaS_new (lua_State *L, const char *str) {
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return luaS_newlstr(L, str, strlen(str));
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}
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Roberto Ierusalimschy