Fix allocation handling and remove Lua state reference from buffers.

Fix backported from Redis, thanks to Yoav Steinberg for the fix and Oran
Agra for additional discussions about the fix.

Author: antirez

lua_cmsgpack.c

@@ -91,7 +91,6 @@ void memrevifle(void *ptr, size_t len) {
  * behavior.  */
 
 typedef struct mp_buf {
-    lua_State *L;
     unsigned char *b;
     size_t len, free;
 } mp_buf;
@@ -111,27 +110,26 @@ mp_buf *mp_buf_new(lua_State *L) {
     /* Old size = 0; new size = sizeof(*buf) */
     buf = (mp_buf*)mp_realloc(L, NULL, 0, sizeof(*buf));
 
-    buf->L = L;
     buf->b = NULL;
     buf->len = buf->free = 0;
     return buf;
 }
 
-void mp_buf_append(mp_buf *buf, const unsigned char *s, size_t len) {
+void mp_buf_append(lua_State *L, mp_buf *buf, const unsigned char *s, size_t len) {
     if (buf->free < len) {
-        size_t newlen = buf->len+len;
+        size_t newsize = (buf->len+len)*2;
 
-        buf->b = (unsigned char*)mp_realloc(buf->L, buf->b, buf->len, newlen*2);
-        buf->free = newlen;
+        buf->b = (unsigned char*)mp_realloc(L, buf->b, buf->len + buf->free, newsize);
+        buf->free = newsize - buf->len;
     }
     memcpy(buf->b+buf->len,s,len);
     buf->len += len;
     buf->free -= len;
 }
 
-void mp_buf_free(mp_buf *buf) {
-    mp_realloc(buf->L, buf->b, buf->len, 0); /* realloc to 0 = free */
-    mp_realloc(buf->L, buf, sizeof(*buf), 0);
+void mp_buf_free(lua_State *L, mp_buf *buf) {
+    mp_realloc(L, buf->b, buf->len + buf->free, 0); /* realloc to 0 = free */
+    mp_realloc(L, buf, sizeof(*buf), 0);
 }
 
 /* ---------------------------- String cursor ----------------------------------
@@ -173,7 +171,7 @@ void mp_cur_init(mp_cur *cursor, const unsigned char *s, size_t len) {
 
 /* ------------------------- Low level MP encoding -------------------------- */
 
-void mp_encode_bytes(mp_buf *buf, const unsigned char *s, size_t len) {
+void mp_encode_bytes(lua_State *L, mp_buf *buf, const unsigned char *s, size_t len) {
     unsigned char hdr[5];
     int hdrlen;
 
@@ -197,12 +195,12 @@ void mp_encode_bytes(mp_buf *buf, const unsigned char *s, size_t len) {
         hdr[4] = len&0xff;
         hdrlen = 5;
     }
-    mp_buf_append(buf,hdr,hdrlen);
-    mp_buf_append(buf,s,len);
+    mp_buf_append(L,buf,hdr,hdrlen);
+    mp_buf_append(L,buf,s,len);
 }
 
 /* we assume IEEE 754 internal format for single and double precision floats. */
-void mp_encode_double(mp_buf *buf, double d) {
+void mp_encode_double(lua_State *L, mp_buf *buf, double d) {
     unsigned char b[9];
     float f = d;
 
@@ -211,16 +209,16 @@ void mp_encode_double(mp_buf *buf, double d) {
         b[0] = 0xca;    /* float IEEE 754 */
         memcpy(b+1,&f,4);
         memrevifle(b+1,4);
-        mp_buf_append(buf,b,5);
+        mp_buf_append(L,buf,b,5);
     } else if (sizeof(d) == 8) {
         b[0] = 0xcb;    /* double IEEE 754 */
         memcpy(b+1,&d,8);
         memrevifle(b+1,8);
-        mp_buf_append(buf,b,9);
+        mp_buf_append(L,buf,b,9);
     }
 }
 
-void mp_encode_int(mp_buf *buf, int64_t n) {
+void mp_encode_int(lua_State *L, mp_buf *buf, int64_t n) {
     unsigned char b[9];
     int enclen;
 
@@ -289,10 +287,10 @@ void mp_encode_int(mp_buf *buf, int64_t n) {
             enclen = 9;
         }
     }
-    mp_buf_append(buf,b,enclen);
+    mp_buf_append(L,buf,b,enclen);
 }
 
-void mp_encode_array(mp_buf *buf, int64_t n) {
+void mp_encode_array(lua_State *L, mp_buf *buf, int64_t n) {
     unsigned char b[5];
     int enclen;
 
@@ -312,10 +310,10 @@ void mp_encode_array(mp_buf *buf, int64_t n) {
         b[4] = n & 0xff;
         enclen = 5;
     }
-    mp_buf_append(buf,b,enclen);
+    mp_buf_append(L,buf,b,enclen);
 }
 
-void mp_encode_map(mp_buf *buf, int64_t n) {
+void mp_encode_map(lua_State *L, mp_buf *buf, int64_t n) {
     unsigned char b[5];
     int enclen;
 
@@ -335,7 +333,7 @@ void mp_encode_map(mp_buf *buf, int64_t n) {
         b[4] = n & 0xff;
         enclen = 5;
     }
-    mp_buf_append(buf,b,enclen);
+    mp_buf_append(L,buf,b,enclen);
 }
 
 /* --------------------------- Lua types encoding --------------------------- */
@@ -345,12 +343,12 @@ void mp_encode_lua_string(lua_State *L, mp_buf *buf) {
     const char *s;
 
     s = lua_tolstring(L,-1,&len);
-    mp_encode_bytes(buf,(const unsigned char*)s,len);
+    mp_encode_bytes(L,buf,(const unsigned char*)s,len);
 }
 
 void mp_encode_lua_bool(lua_State *L, mp_buf *buf) {
     unsigned char b = lua_toboolean(L,-1) ? 0xc3 : 0xc2;
-    mp_buf_append(buf,&b,1);
+    mp_buf_append(L,buf,&b,1);
 }
 
 /* Lua 5.3 has a built in 64-bit integer type */
@@ -360,7 +358,7 @@ void mp_encode_lua_integer(lua_State *L, mp_buf *buf) {
 #else
     lua_Integer i = lua_tointeger(L,-1);
 #endif
-    mp_encode_int(buf, (int64_t)i);
+    mp_encode_int(L, buf, (int64_t)i);
 }
 
 /* Lua 5.2 and lower only has 64-bit doubles, so we need to
@@ -372,7 +370,7 @@ void mp_encode_lua_number(lua_State *L, mp_buf *buf) {
     if (IS_INT64_EQUIVALENT(n)) {
         mp_encode_lua_integer(L, buf);
     } else {
-        mp_encode_double(buf,(double)n);
+        mp_encode_double(L,buf,(double)n);
     }
 }
 
@@ -386,7 +384,7 @@ void mp_encode_lua_table_as_array(lua_State *L, mp_buf *buf, int level) {
     size_t len = lua_rawlen(L,-1), j;
 #endif
 
-    mp_encode_array(buf,len);
+    mp_encode_array(L,buf,len);
     for (j = 1; j <= len; j++) {
         lua_pushnumber(L,j);
         lua_gettable(L,-2);
@@ -409,7 +407,7 @@ void mp_encode_lua_table_as_map(lua_State *L, mp_buf *buf, int level) {
     }
 
     /* Step two: actually encoding of the map. */
-    mp_encode_map(buf,len);
+    mp_encode_map(L,buf,len);
     lua_pushnil(L);
     while(lua_next(L,-2)) {
         /* Stack: ... key value */
@@ -474,10 +472,9 @@ void mp_encode_lua_table(lua_State *L, mp_buf *buf, int level) {
 
 void mp_encode_lua_null(lua_State *L, mp_buf *buf) {
     unsigned char b[1];
-    (void)L;
 
     b[0] = 0xc0;
-    mp_buf_append(buf,b,1);
+    mp_buf_append(L,buf,b,1);
 }
 
 void mp_encode_lua_type(lua_State *L, mp_buf *buf, int level) {
@@ -534,7 +531,7 @@ int mp_pack(lua_State *L) {
         buf->free += buf->len;
         buf->len = 0;
     }
-    mp_buf_free(buf);
+    mp_buf_free(L, buf);
 
     /* Concatenate all nargs buffers together */
     lua_concat(L, nargs);