commit 6d042a178fba32d10ec23c98fb2fd284397ccddc
parent eabf425c76e0089eb88e102e2a44d8c8a37bc213
Author: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Mon, 13 Nov 2023 13:12:06 -0300
Auxiliary buffer uses external strings
The buffer system from the auxiliary library reuses its buffer
as external memory when closing long strings.
Diffstat:
3 files changed, 40 insertions(+), 27 deletions(-)
diff --git a/lauxlib.c b/lauxlib.c
@@ -470,18 +470,27 @@ typedef struct UBox {
} UBox;
+/* Resize the buffer used by a box. Optimize for the common case of
+** resizing to the old size. (For instance, __gc will resize the box
+** to 0 even after it was closed. 'pushresult' may also resize it to a
+** final size that is equal to the one set when the buffer was created.)
+*/
static void *resizebox (lua_State *L, int idx, size_t newsize) {
- void *ud;
- lua_Alloc allocf = lua_getallocf(L, &ud);
UBox *box = (UBox *)lua_touserdata(L, idx);
- void *temp = allocf(ud, box->box, box->bsize, newsize);
- if (l_unlikely(temp == NULL && newsize > 0)) { /* allocation error? */
- lua_pushliteral(L, "not enough memory");
- lua_error(L); /* raise a memory error */
+ if (box->bsize == newsize) /* not changing size? */
+ return box->box; /* keep the buffer */
+ else {
+ void *ud;
+ lua_Alloc allocf = lua_getallocf(L, &ud);
+ void *temp = allocf(ud, box->box, box->bsize, newsize);
+ if (l_unlikely(temp == NULL && newsize > 0)) { /* allocation error? */
+ lua_pushliteral(L, "not enough memory");
+ lua_error(L); /* raise a memory error */
+ }
+ box->box = temp;
+ box->bsize = newsize;
+ return temp;
}
- box->box = temp;
- box->bsize = newsize;
- return temp;
}
@@ -526,15 +535,15 @@ static void newbox (lua_State *L) {
/*
** Compute new size for buffer 'B', enough to accommodate extra 'sz'
-** bytes. (The test for "not big enough" also gets the case when the
-** computation of 'newsize' overflows.)
+** bytes plus one for a terminating zero. (The test for "not big enough"
+** also gets the case when the computation of 'newsize' overflows.)
*/
static size_t newbuffsize (luaL_Buffer *B, size_t sz) {
size_t newsize = (B->size / 2) * 3; /* buffer size * 1.5 */
- if (l_unlikely(MAX_SIZET - sz < B->n)) /* overflow in (B->n + sz)? */
+ if (l_unlikely(MAX_SIZET - sz - 1 < B->n)) /* overflow in (B->n + sz + 1)? */
return luaL_error(B->L, "buffer too large");
- if (newsize < B->n + sz) /* not big enough? */
- newsize = B->n + sz;
+ if (newsize < B->n + sz + 1) /* not big enough? */
+ newsize = B->n + sz + 1;
return newsize;
}
@@ -594,9 +603,22 @@ 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)) /* using static buffer? */
+ lua_pushlstring(L, B->b, B->n); /* save result as regular string */
+ else { /* reuse buffer already allocated */
+ UBox *box = (UBox *)lua_touserdata(L, -1);
+ void *ud;
+ lua_Alloc allocf = lua_getallocf(L, &ud); /* function to free buffer */
+ size_t len = B->n; /* final string length */
+ char *s;
+ resizebox(L, -1, len + 1); /* adjust box size to content size */
+ s = (char*)box->box; /* final buffer address */
+ s[len] = '\0'; /* add ending zero */
+ /* clear box, as 'lua_pushextlstring' will take control over buffer */
+ box->bsize = 0; box->box = NULL;
+ lua_pushextlstring(L, s, len, allocf, ud);
lua_closeslot(L, -2); /* close the box */
+ }
lua_remove(L, -2); /* remove box or placeholder from the stack */
}
diff --git a/testes/gc.lua b/testes/gc.lua
@@ -460,10 +460,7 @@ do -- tests for string keys in weak tables
a[string.rep("a", 2^22)] = 25 -- long string key -> number value
a[string.rep("b", 2^22)] = {} -- long string key -> colectable value
a[{}] = 14 -- colectable key
- assert(collectgarbage("count") > m + 2^13) -- 2^13 == 2 * 2^22 in KB
collectgarbage()
- assert(collectgarbage("count") >= m + 2^12 and
- collectgarbage("count") < m + 2^13) -- one key was collected
local k, v = next(a) -- string key with number value preserved
assert(k == string.rep("a", 2^22) and v == 25)
assert(next(a, k) == nil) -- everything else cleared
diff --git a/testes/locals.lua b/testes/locals.lua
@@ -728,14 +728,8 @@ if rawget(_G, "T") then
-- first buffer was released by 'toclose'
assert(T.totalmem() - m <= extra)
- -- error in creation of final string
- T.totalmem(m + 2 * lim + extra)
- assert(not pcall(table.concat, a))
- -- second buffer was released by 'toclose'
- assert(T.totalmem() - m <= extra)
-
- -- userdata, buffer, buffer, final string
- T.totalmem(m + 4*lim + extra)
+ -- userdata, buffer, final string
+ T.totalmem(m + 2*lim + extra)
assert(#table.concat(a) == 2*lim)
T.totalmem(0) -- remove memory limit
