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Added assertions for proper use of string buffers

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This commit is contained in:
Roberto Ierusalimschy 2021-03-02 11:39:42 -03:00
parent 9a2de786de
commit cf23a93d82
1 changed files with 17 additions and 5 deletions
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22
lauxlib.c
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@ -515,6 +515,15 @@ static void newbox (lua_State *L) {
#define buffonstack(B) ((B)->b != (B)->init.b)
/*
** Whenever buffer is accessed, slot 'idx' must either be a box (which
** cannot be NULL) or it is a placeholder for the buffer.
*/
#define checkbufferlevel(B,idx) \
lua_assert(buffonstack(B) ? lua_touserdata(B->L, idx) != NULL \
: lua_touserdata(B->L, idx) == (void*)B)
/*
** Compute new size for buffer 'B', enough to accommodate extra 'sz'
** bytes.
@ -531,10 +540,11 @@ static size_t newbuffsize (luaL_Buffer *B, size_t sz) {
/*
** Returns a pointer to a free area with at least 'sz' bytes in buffer
** 'B'. 'boxidx' is the relative position in the stack where the
** buffer's box is or should be.
** 'B'. 'boxidx' is the relative position in the stack where is the
** buffer's box or its placeholder.
*/
static char *prepbuffsize (luaL_Buffer *B, size_t sz, int boxidx) {
checkbufferlevel(B, boxidx);
if (B->size - B->n >= sz) /* enough space? */
return B->b + B->n;
else {
@ -545,6 +555,7 @@ static char *prepbuffsize (luaL_Buffer *B, size_t sz, int boxidx) {
if (buffonstack(B)) /* buffer already has a box? */
newbuff = (char *)resizebox(L, boxidx, newsize); /* resize it */
else { /* no box yet */
lua_remove(L, boxidx); /* remove placeholder */
newbox(L); /* create a new box */
lua_insert(L, boxidx); /* move box to its intended position */
lua_toclose(L, boxidx);
@ -581,11 +592,11 @@ LUALIB_API void luaL_addstring (luaL_Buffer *B, const char *s) {
LUALIB_API void luaL_pushresult (luaL_Buffer *B) {
lua_State *L = B->L;
checkbufferlevel(B, -1);
lua_pushlstring(L, B->b, B->n);
if (buffonstack(B)) {
if (buffonstack(B))
lua_closeslot(L, -2); /* close the box */
lua_remove(L, -2); /* remove box from the stack */
}
lua_remove(L, -2); /* remove box or placeholder from the stack */
}
@ -620,6 +631,7 @@ LUALIB_API void luaL_buffinit (lua_State *L, luaL_Buffer *B) {
B->b = B->init.b;
B->n = 0;
B->size = LUAL_BUFFERSIZE;
lua_pushlightuserdata(L, (void*)B); /* push placeholder */
}