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Changed the growth rate of string buffers

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The growth rate of string buffers was reduced from 2 to 1.5 (3/2).
As string buffers start larger (256~1024 bytes), they don't need to
grow that fast. Moreover, a lower rate allows multiplicative growth up
to larger sizes (3/2 of the maximum). (After that, the growth becomes
linear, which is mostly useless.)
This commit is contained in:
Roberto Ierusalimschy 2022-09-06 10:58:55 -03:00
parent 997f11f543
commit 69b77b6fde
2 changed files with 7 additions and 6 deletions
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8
lauxlib.c
View File

@ -526,14 +526,14 @@ static void newbox (lua_State *L) {
/* /*
** Compute new size for buffer 'B', enough to accommodate extra 'sz' ** Compute new size for buffer 'B', enough to accommodate extra 'sz'
** bytes. (The test for "double is not big enough" also gets the ** bytes. (The test for "not big enough" also gets the case when the
** case when the multiplication by 2 overflows.) ** computation of 'newsize' overflows.)
*/ */
static size_t newbuffsize (luaL_Buffer *B, size_t sz) { static size_t newbuffsize (luaL_Buffer *B, size_t sz) {
size_t newsize = B->size * 2; /* double buffer size */ 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 < B->n)) /* overflow in (B->n + sz)? */
return luaL_error(B->L, "buffer too large"); return luaL_error(B->L, "buffer too large");
if (newsize < B->n + sz) /* double is not big enough? */ if (newsize < B->n + sz) /* not big enough? */
newsize = B->n + sz; newsize = B->n + sz;
return newsize; return newsize;
} }

5
luaconf.h
View File

@ -747,14 +747,15 @@
/* /*
@@ LUA_IDSIZE gives the maximum size for the description of the source @@ LUA_IDSIZE gives the maximum size for the description of the source
@@ of a function in debug information. ** of a function in debug information.
** CHANGE it if you want a different size. ** CHANGE it if you want a different size.
*/ */
#define LUA_IDSIZE 60 #define LUA_IDSIZE 60
/* /*
@@ LUAL_BUFFERSIZE is the buffer size used by the lauxlib buffer system. @@ LUAL_BUFFERSIZE is the initial buffer size used by the lauxlib
** buffer system.
*/ */
#define LUAL_BUFFERSIZE ((int)(16 * sizeof(void*) * sizeof(lua_Number))) #define LUAL_BUFFERSIZE ((int)(16 * sizeof(void*) * sizeof(lua_Number)))