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Optimize memory handling in conversion function

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Handling memory in this function is almost a Catch-22 between too many
mallocs and frees fragmenting memory in systems with bad allocators and
string concatenations abusing the Lua garbage collector. To avoid this,
now it uses a static buffer in the stack and a luaL_Buffer to handle
the concatenations. This remove all direct calls to memory allocators
from the library and lets Lua use its own.
This commit is contained in:
Alexandre Erwin Ittner 2013-10-23 00:08:28 -02:00
parent 49eb7b534f
commit d41e0d345d
1 changed files with 18 additions and 24 deletions
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42
luaiconv.c
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@ -96,18 +96,22 @@ static int Liconv_open(lua_State *L) {
return 1;
}
/* Use a fixed-size buffer in the stack to avoid a lot of small mallocs
* and prevent memory fragmentation. This should not be a problem in any
* contemporary general purpose system but, if you are running in a very
* limited stack system you may use a smaller buffer, but the luaL_Buffer
* will compensate this with more reallocs and memcpys.
*/
#define CONV_BUF_SIZE 256
static int Liconv(lua_State *L) {
iconv_t cd = get_iconv_t(L, 1);
size_t ibleft = lua_rawlen(L, 2);
char *inbuf = (char*) luaL_checkstring(L, 2);
char *outbuf;
char *outbufs;
size_t obsize = (ibleft > CONV_BUF_SIZE) ? ibleft : CONV_BUF_SIZE;
size_t obleft = obsize;
char outbufs[CONV_BUF_SIZE];
char *outbuf = outbufs;
size_t obleft = CONV_BUF_SIZE;
size_t ret = -1;
int hasone = 0;
if (cd == NULL) {
lua_pushstring(L, "");
@ -115,44 +119,34 @@ static int Liconv(lua_State *L) {
return 2;
}
outbuf = (char*) malloc(obsize * sizeof(char));
if (outbuf == NULL) {
lua_pushstring(L, "");
lua_pushnumber(L, ERROR_NO_MEMORY);
return 2;
}
outbufs = outbuf;
luaL_Buffer b;
luaL_buffinit(L, &b);
do {
ret = iconv(cd, &inbuf, &ibleft, &outbuf, &obleft);
if (ret == (size_t)(-1)) {
lua_pushlstring(L, outbufs, obsize - obleft);
if (hasone == 1)
lua_concat(L, 2);
hasone = 1;
luaL_addlstring(&b, outbufs, CONV_BUF_SIZE - obleft);
if (errno == EILSEQ) {
luaL_pushresult(&b);
lua_pushnumber(L, ERROR_INVALID);
free(outbufs);
return 2; /* Invalid character sequence */
} else if (errno == EINVAL) {
luaL_pushresult(&b);
lua_pushnumber(L, ERROR_INCOMPLETE);
free(outbufs);
return 2; /* Incomplete character sequence */
} else if (errno == E2BIG) {
obleft = obsize;
obleft = CONV_BUF_SIZE;
outbuf = outbufs;
} else {
luaL_pushresult(&b);
lua_pushnumber(L, ERROR_UNKNOWN);
free(outbufs);
return 2; /* Unknown error */
}
}
} while (ret == (size_t) -1);
lua_pushlstring(L, outbufs, obsize - obleft);
if (hasone == 1)
lua_concat(L, 2);
free(outbufs);
luaL_addlstring(&b, outbufs, CONV_BUF_SIZE - obleft);
luaL_pushresult(&b);
lua_pushnil(L);
return 2; /* Done */
}