TOMSCI: Adding lua_newbuf() API

tomsci · Nov 18, 2018 · 09bdc6c · 09bdc6c
1 parent 61fad77
commit 09bdc6c
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Showing 4 changed files with 71 additions and 6 deletions.
diff --git a/components/lua/lapi.c b/components/lua/lapi.c
@@ -467,6 +467,46 @@ LUA_API void lua_pushrolstring (lua_State *L, const char *s, size_t len) {
 }
 
 
+LUA_API void *lua_newbuf(lua_State *L, size_t len) {
+  TString *ts = cast(TString *, luaM_malloc(L, (len+1)*sizeof(char)+sizeof(TString)));
+  ts->tsv.len = len;
+  ts->tsv.tt = LUA_TNIL;
+  ts->tsv.marked = 0; /* so sizestring works */
+  return ts + 1;
+}
+
+
+LUA_API void *lua_reallocbuf(lua_State *L, void *buf, size_t newlen) {
+  size_t oldsz, newsz;
+  TString *ts = cast(TString *, buf) - 1;
+  if (ts->tsv.tt != LUA_TNIL) {
+      lua_pushliteral(L, "Attempt to modify an invalid buf");
+      lua_error(L);
+    }
+  oldsz = (ts->tsv.len+1)*sizeof(char)+sizeof(TString);
+  if (newlen == 0) {
+    /* Free the buffer */
+    luaM_freemem(L, ts, oldsz);
+    return NULL;
+  }
+  newsz = (newlen+1)*sizeof(char)+sizeof(TString);
+  ts = cast(TString *, luaM_realloc_(L, ts, oldsz, newsz));
+  ts->tsv.len = newlen;
+  return ts + 1;
+}
+
+
+LUA_API void lua_pushbuf(lua_State *L, void *buf) {
+  TString *ts = cast(TString *, buf) - 1;
+  lua_lock(L);
+  luaC_checkGC(L);
+  luaS_buftostr(L, ts);
+  setsvalue2s(L, L->top, ts);
+  api_incr_top(L);
+  lua_unlock(L);
+}
+
+
 LUA_API void lua_pushstring (lua_State *L, const char *s) {
   if (s == NULL)
     lua_pushnil(L);

diff --git a/components/lua/lstring.c b/components/lua/lstring.c
@@ -18,6 +18,7 @@
 #include "lstate.h"
 #include "lstring.h"
 
+#define LUAS_PREALLOCED_STRING    2
 #define LUAS_READONLY_STRING      1
 #define LUAS_REGULAR_STRING       0
 
@@ -53,25 +54,35 @@ void luaS_resize (lua_State *L, int newsize) {
 }
 
 static TString *newlstr (lua_State *L, const char *str, size_t l,
-                                       unsigned int h, int readonly) {
+                                       unsigned int h, int strtype) {
   TString *ts;
   stringtable *tb;
   if (l+1 > (MAX_SIZET - sizeof(TString))/sizeof(char))
     luaM_toobig(L);
   tb = &G(L)->strt;
   if ((tb->nuse + 1) > cast(lu_int32, tb->size) && tb->size <= MAX_INT/2)
     luaS_resize(L, tb->size*2);  /* too crowded */
-  ts = cast(TString *, luaM_malloc(L, readonly ? sizeof(char**)+sizeof(TString) : (l+1)*sizeof(char)+sizeof(TString)));
+  if (strtype == LUAS_PREALLOCED_STRING)
+    ts = cast(TString *, str) - 1;
+  else
+    ts = cast(TString *, luaM_malloc(L, strtype == LUAS_READONLY_STRING ? sizeof(char**)+sizeof(TString) : (l+1)*sizeof(char)+sizeof(TString)));
   ts->tsv.len = l;
   ts->tsv.hash = h;
   ts->tsv.marked = luaC_white(G(L));
   ts->tsv.tt = LUA_TSTRING;
-  if (!readonly) {
+  switch (strtype) {
+  case LUAS_REGULAR_STRING:
     memcpy(ts+1, str, l*sizeof(char));
+    /* Drop through */
+  case LUAS_PREALLOCED_STRING:
     ((char *)(ts+1))[l] = '\0';  /* ending 0 */
-  } else {
+    break;
+  case LUAS_READONLY_STRING:
     *(char **)(ts+1) = (char *)str;
     luaS_readonly(ts);
+    break;
+  default:
+    break;
   }
   h = lmod(h, tb->size);
   ts->tsv.next = tb->hash[h];  /* chain new entry */
@@ -81,7 +92,7 @@ static TString *newlstr (lua_State *L, const char *str, size_t l,
 }
 
 
-static TString *luaS_newlstr_helper (lua_State *L, const char *str, size_t l, int readonly) {
+static TString *luaS_newlstr_helper (lua_State *L, const char *str, size_t l, int strtype) {
   GCObject *o;
   unsigned int h = cast(unsigned int, l);  /* seed */
   size_t step = (l>>5)+1;  /* if string is too long, don't hash all its chars */
@@ -98,7 +109,7 @@ static TString *luaS_newlstr_helper (lua_State *L, const char *str, size_t l, in
       return ts;
     }
   }
-  return newlstr(L, str, l, h, readonly);  /* not found */
+  return newlstr(L, str, l, h, strtype);  /* not found */
 }
 
 static int lua_is_ptr_in_ro_area(const char *p) {
@@ -146,3 +157,7 @@ Udata *luaS_newudata (lua_State *L, size_t s, Table *e) {
   return u;
 }
 
+
+void luaS_buftostr (lua_State *L, TString *ts) {
+  luaS_newlstr_helper(L, cast(const char *, ts + 1), ts->tsv.len, LUAS_PREALLOCED_STRING);
+}
diff --git a/components/lua/lstring.h b/components/lua/lstring.h
@@ -31,4 +31,6 @@ LUAI_FUNC Udata *luaS_newudata (lua_State *L, size_t s, Table *e);
 LUAI_FUNC TString *luaS_newlstr (lua_State *L, const char *str, size_t l);
 LUAI_FUNC TString *luaS_newrolstr (lua_State *L, const char *str, size_t l);
 
+LUAI_FUNC void luaS_buftostr (lua_State *L, TString *ts);
+
 #endif
diff --git a/components/lua/lua.h b/components/lua/lua.h
@@ -254,6 +254,14 @@ LUA_API lua_Alloc (lua_getallocf) (lua_State *L, void **ud);
 LUA_API void lua_setallocf (lua_State *L, lua_Alloc f, void *ud);
 
 
+/*
+** Buffer management
+*/
+LUA_API void *(lua_newbuf) (lua_State *L, size_t len);
+LUA_API void *(lua_reallocbuf) (lua_State *L, void *buf, size_t newlen);
+LUA_API void (lua_pushbuf) (lua_State *L, void *buf);
+#define lua_freebuf(L, b) lua_reallocbuf(L, (b), 0)
+
 
 /*
 ** ===============================================================