1 files changed, 140 insertions, 77 deletions

diff --git a/lua/lstring.c b/lua/lstring.c
index af96c89..9351766 100644
--- a/lua/lstring.c
+++ b/lua/lstring.c
@@ -1,23 +1,30 @@
 /*
-** $Id: lstring.c,v 2.26.1.1 2013/04/12 18:48:47 roberto Exp $
+** $Id: lstring.c,v 2.56 2015/11/23 11:32:51 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 "lprefix.h"
+
+
+#include <string.h>
+
 #include "lua.h"
 
+#include "ldebug.h"
+#include "ldo.h"
 #include "lmem.h"
 #include "lobject.h"
 #include "lstate.h"
 #include "lstring.h"
 
 
+#define MEMERRMSG       "not enough memory"
+
+
 /*
 ** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a string to
 ** compute its hash
@@ -31,99 +38,126 @@
 ** 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);
+  size_t len = a->u.lnglen;
+  lua_assert(a->tt == LUA_TLNGSTR && b->tt == LUA_TLNGSTR);
   return (a == b) ||  /* same instance or... */
-    ((len == b->tsv.len) &&  /* equal length and ... */
+    ((len == b->u.lnglen) &&  /* 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]));
+  for (; l >= step; l -= step)
+    h ^= ((h<<5) + (h>>2) + cast_byte(str[l - 1]));
   return h;
 }
 
 
+unsigned int luaS_hashlongstr (TString *ts) {
+  lua_assert(ts->tt == LUA_TLNGSTR);
+  if (ts->extra == 0) {  /* no hash? */
+    ts->hash = luaS_hash(getstr(ts), ts->u.lnglen, ts->hash);
+    ts->extra = 1;  /* now it has its hash */
+  }
+  return ts->hash;
+}
+
+
 /*
 ** 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;
+  if (newsize > tb->size) {  /* grow table if needed */
+    luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *);
+    for (i = tb->size; i < newsize; i++)
+      tb->hash[i] = NULL;
   }
-  /* rehash */
-  for (i=0; i<tb->size; i++) {
-    GCObject *p = tb->hash[i];
+  for (i = 0; i < tb->size; i++) {  /* rehash */
+    TString *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 */
+      TString *hnext = p->u.hnext;  /* save next */
+      unsigned int h = lmod(p->hash, newsize);  /* new position */
+      p->u.hnext = tb->hash[h];  /* chain it */
       tb->hash[h] = p;
-      resetoldbit(p);  /* see MOVE OLD rule */
-      p = next;
+      p = hnext;
     }
   }
-  if (newsize < tb->size) {
-    /* shrinking slice must be empty */
+  if (newsize < tb->size) {  /* shrink table if needed */
+    /* vanishing slice should be empty */
     lua_assert(tb->hash[newsize] == NULL && tb->hash[tb->size - 1] == NULL);
-    luaM_reallocvector(L, tb->hash, tb->size, newsize, GCObject *);
+    luaM_reallocvector(L, tb->hash, tb->size, newsize, TString *);
   }
   tb->size = newsize;
 }
 
 
 /*
+** Clear API string cache. (Entries cannot be empty, so fill them with
+** a non-collectable string.)
+*/
+void luaS_clearcache (global_State *g) {
+  int i, j;
+  for (i = 0; i < STRCACHE_N; i++)
+    for (j = 0; j < STRCACHE_M; j++) {
+    if (iswhite(g->strcache[i][j]))  /* will entry be collected? */
+      g->strcache[i][j] = g->memerrmsg;  /* replace it with something fixed */
+    }
+}
+
+
+/*
+** Initialize the string table and the string cache
+*/
+void luaS_init (lua_State *L) {
+  global_State *g = G(L);
+  int i, j;
+  luaS_resize(L, MINSTRTABSIZE);  /* initial size of string table */
+  /* pre-create memory-error message */
+  g->memerrmsg = luaS_newliteral(L, MEMERRMSG);
+  luaC_fix(L, obj2gco(g->memerrmsg));  /* it should never be collected */
+  for (i = 0; i < STRCACHE_N; i++)  /* fill cache with valid strings */
+    for (j = 0; j < STRCACHE_M; j++)
+      g->strcache[i][j] = g->memerrmsg;
+}
+
+
+
+/*
 ** creates a new string object
 */
-static TString *createstrobj (lua_State *L, const char *str, size_t l,
-                              int tag, unsigned int h, GCObject **list) {
+static TString *createstrobj (lua_State *L, size_t l, int tag, unsigned int h) {
   TString *ts;
+  GCObject *o;
   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 */
+  totalsize = sizelstring(l);
+  o = luaC_newobj(L, tag, totalsize);
+  ts = gco2ts(o);
+  ts->hash = h;
+  ts->extra = 0;
+  getstr(ts)[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 */
+TString *luaS_createlngstrobj (lua_State *L, size_t l) {
+  TString *ts = createstrobj(L, l, LUA_TLNGSTR, G(L)->seed);
+  ts->u.lnglen = l;
+  return ts;
+}
+
+
+void luaS_remove (lua_State *L, TString *ts) {
   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;
+  TString **p = &tb->hash[lmod(ts->hash, tb->size)];
+  while (*p != ts)  /* find previous element */
+    p = &(*p)->u.hnext;
+  *p = (*p)->u.hnext;  /* remove element from its list */
+  tb->nuse--;
 }
 
 
@@ -131,22 +165,31 @@ static TString *newshrstr (lua_State *L, const char *str, size_t l,
 ** 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;
+  TString *ts;
   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 &&
+  TString **list = &g->strt.hash[lmod(h, g->strt.size)];
+  lua_assert(str != NULL);  /* otherwise 'memcmp'/'memcpy' are undefined */
+  for (ts = *list; ts != NULL; ts = ts->u.hnext) {
+    if (l == ts->shrlen &&
         (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 */
+      /* found! */
+      if (isdead(g, ts))  /* dead (but not collected yet)? */
+        changewhite(ts);  /* resurrect it */
       return ts;
     }
   }
-  return newshrstr(L, str, l, h);  /* not found; create a new string */
+  if (g->strt.nuse >= g->strt.size && g->strt.size <= MAX_INT/2) {
+    luaS_resize(L, g->strt.size * 2);
+    list = &g->strt.hash[lmod(h, g->strt.size)];  /* recompute with new size */
+  }
+  ts = createstrobj(L, l, LUA_TSHRSTR, h);
+  memcpy(getstr(ts), str, l * sizeof(char));
+  ts->shrlen = cast_byte(l);
+  ts->u.hnext = *list;
+  *list = ts;
+  g->strt.nuse++;
+  return ts;
 }
 
 
@@ -157,29 +200,49 @@ 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))
+    TString *ts;
+    if (l >= (MAX_SIZE - sizeof(TString))/sizeof(char))
       luaM_toobig(L);
-    return createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed, NULL);
+    ts = luaS_createlngstrobj(L, l);
+    memcpy(getstr(ts), str, l * sizeof(char));
+    return ts;
   }
 }
 
 
 /*
-** new zero-terminated string
+** Create or reuse a zero-terminated string, first checking in the
+** cache (using the string address as a key). The cache can contain
+** only zero-terminated strings, so it is safe to use 'strcmp' to
+** check hits.
 */
 TString *luaS_new (lua_State *L, const char *str) {
-  return luaS_newlstr(L, str, strlen(str));
+  unsigned int i = point2uint(str) % STRCACHE_N;  /* hash */
+  int j;
+  TString **p = G(L)->strcache[i];
+  for (j = 0; j < STRCACHE_M; j++) {
+    if (strcmp(str, getstr(p[j])) == 0)  /* hit? */
+      return p[j];  /* that is it */
+  }
+  /* normal route */
+  for (j = STRCACHE_M - 1; j > 0; j--)
+    p[j] = p[j - 1];  /* move out last element */
+  /* new element is first in the list */
+  p[0] = luaS_newlstr(L, str, strlen(str));
+  return p[0];
 }
 
 
-Udata *luaS_newudata (lua_State *L, size_t s, Table *e) {
+Udata *luaS_newudata (lua_State *L, size_t s) {
   Udata *u;
-  if (s > MAX_SIZET - sizeof(Udata))
+  GCObject *o;
+  if (s > MAX_SIZE - 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;
+  o = luaC_newobj(L, LUA_TUSERDATA, sizeludata(s));
+  u = gco2u(o);
+  u->len = s;
+  u->metatable = NULL;
+  setuservalue(L, u, luaO_nilobject);
   return u;
 }