String table (keep all strings handled by Lua)

1 files changed, 186 insertions, 0 deletions

diff --git a/lstring.c b/lstring.c
new file mode 100644
index 00000000..c6c77aa6
--- /dev/null
+++ b/lstring.c
@@ -0,0 +1,186 @@
+/*
+** $Id: lstring.c,v 1.1 1997/08/14 20:23:30 roberto Exp $
+** String table (keep all strings handled by Lua)
+** See Copyright Notice in lua.h
+*/
+
+
+#include <string.h>
+
+#include "lmem.h"
+#include "lobject.h"
+#include "lstring.h"
+#include "lua.h"
+
+
+#define NUM_HASHS  61
+
+typedef struct {
+  int size;
+  int nuse;  /* number of elements (including EMPTYs) */
+  TaggedString **hash;
+} stringtable;
+
+
+static stringtable string_root[NUM_HASHS] = {
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL}, {0, 0, NULL},
+{0, 0, NULL}
+};
+
+
+static TaggedString EMPTY = {LUA_T_STRING, {0}, {{NOT_USED, NOT_USED}}, 2, {0}};
+
+
+
+static unsigned long hash (char *s, int tag)
+{
+  unsigned long h;
+  if (tag != LUA_T_STRING)
+    h = (unsigned long)s;
+  else {
+    h = 0;
+    while (*s)
+      h = ((h<<5)-h)^(unsigned char)*(s++);
+  }
+  return h;
+}
+
+
+static void grow (stringtable *tb)
+{
+  int newsize = luaO_redimension(tb->size);
+  TaggedString **newhash = luaM_newvector(newsize, TaggedString *);
+  int i;
+  for (i=0; i<newsize; i++)
+    newhash[i] = NULL;
+  /* rehash */
+  tb->nuse = 0;
+  for (i=0; i<tb->size; i++) {
+    if (tb->hash[i] != NULL && tb->hash[i] != &EMPTY) {
+      int h = tb->hash[i]->uu.hash%newsize;
+      while (newhash[h])
+        h = (h+1)%newsize;
+      newhash[h] = tb->hash[i];
+      tb->nuse++;
+    }
+  }
+  luaM_free(tb->hash);
+  tb->size = newsize;
+  tb->hash = newhash;
+}
+
+
+static TaggedString *newone(char *buff, int tag, unsigned long h)
+{
+  TaggedString *ts;
+  if (tag == LUA_T_STRING) {
+    ts = (TaggedString *)luaM_malloc(sizeof(TaggedString)+strlen(buff));
+    strcpy(ts->str, buff);
+    ts->u.s.varindex = ts->u.s.constindex = NOT_USED;
+    ts->tag = LUA_T_STRING;
+  }
+  else {
+    ts = (TaggedString *)luaM_malloc(sizeof(TaggedString));
+    ts->u.v = buff;
+    ts->tag = tag == LUA_ANYTAG ? 0 : tag;
+  }
+  ts->marked = 0;
+  ts->uu.hash = h;
+  return ts;
+}
+
+static TaggedString *insert (char *buff, int tag, stringtable *tb)
+{
+  TaggedString *ts;
+  unsigned long h = hash(buff, tag);
+  int i;
+  int j = -1;
+  if ((long)tb->nuse*3 >= (long)tb->size*2)
+    grow(tb);
+  i = h%tb->size;
+  while ((ts = tb->hash[i]) != NULL)
+  {
+    if (ts == &EMPTY)
+      j = i;
+    else if ((ts->tag == LUA_T_STRING) ?
+              (tag == LUA_T_STRING && (strcmp(buff, ts->str) == 0)) :
+              ((tag == ts->tag || tag == LUA_ANYTAG) && buff == ts->u.v))
+      return ts;
+    i = (i+1)%tb->size;
+  }
+  /* not found */
+  ++luaO_nentities;
+  if (j != -1)  /* is there an EMPTY space? */
+    i = j;
+  else
+    tb->nuse++;
+  ts = tb->hash[i] = newone(buff, tag, h);
+  return ts;
+}
+
+TaggedString *luaS_createudata (void *udata, int tag)
+{
+  return insert(udata, tag, &string_root[(unsigned)udata%NUM_HASHS]);
+}
+
+TaggedString *luaS_new (char *str)
+{
+  return insert(str, LUA_T_STRING, &string_root[(unsigned)str[0]%NUM_HASHS]);
+}
+
+TaggedString *luaS_newfixedstring (char *str)
+{
+  TaggedString *ts = luaS_new(str);
+  if (ts->marked == 0)
+    ts->marked = 2;  /* avoid GC */
+  return ts;
+}
+
+
+void luaS_free (TaggedString *l)
+{
+  while (l) {
+    TaggedString *next = l->uu.next;
+    luaM_free(l);
+    l = next;
+  }
+}
+
+
+/*
+** Garbage collection function.
+*/
+TaggedString *luaS_collector (void)
+{
+  TaggedString *frees = NULL;
+  int i;
+  for (i=0; i<NUM_HASHS; i++) {
+    stringtable *tb = &string_root[i];
+    int j;
+    for (j=0; j<tb->size; j++) {
+      TaggedString *t = tb->hash[j];
+      if (t == NULL) continue;
+      if (t->marked == 1)
+        t->marked = 0;
+      else if (!t->marked) {
+        t->uu.next = frees;
+        frees = t;
+        tb->hash[j] = &EMPTY;
+        --luaO_nentities;
+      }
+    }
+  }
+  return frees;
+}
+