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long strings are created directly in final position when possible

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(instead of using an auxiliar buffer to first create the string
and then allocate the final string and copy result there)
This commit is contained in:
Roberto Ierusalimschy
2015-09-08 12:41:05 -03:00
parent 502214f8a5
commit 41964648ee
11 changed files with 62 additions and 58 deletions
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41
lvm.c
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@@ -1,5 +1,5 @@
/*
** $Id: lvm.c,v 2.249 2015/08/03 19:50:49 roberto Exp roberto $
** $Id: lvm.c,v 2.250 2015/08/03 20:40:26 roberto Exp roberto $
** Lua virtual machine
** See Copyright Notice in lua.h
*/
@@ -445,6 +445,17 @@ int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) {
#define isemptystr(o) (ttisshrstring(o) && tsvalue(o)->shrlen == 0)
/* copy strings in stack from top - n up to top - 1 to buffer */
static void copy2buff (StkId top, int n, char *buff) {
size_t tl = 0; /* size already copied */
do {
size_t l = vslen(top - n); /* length of string being copied */
memcpy(buff + tl, svalue(top - n), l * sizeof(char));
tl += l;
} while (--n > 0);
}
/*
** Main operation for concatenation: concat 'total' values in the stack,
** from 'L->top - total' up to 'L->top - 1'.
@@ -464,24 +475,24 @@ void luaV_concat (lua_State *L, int total) {
else {
/* at least two non-empty string values; get as many as possible */
size_t tl = vslen(top - 1);
char *buffer;
int i;
/* collect total length */
for (i = 1; i < total && tostring(L, top-i-1); i++) {
size_t l = vslen(top - i - 1);
TString *ts;
/* collect total length and number of strings */
for (n = 1; n < total && tostring(L, top - n - 1); n++) {
size_t l = vslen(top - n - 1);
if (l >= (MAX_SIZE/sizeof(char)) - tl)
luaG_runerror(L, "string length overflow");
tl += l;
}
buffer = luaZ_openspace(L, &G(L)->buff, tl);
tl = 0;
n = i;
do { /* copy all strings to buffer */
size_t l = vslen(top - i);
memcpy(buffer+tl, svalue(top-i), l * sizeof(char));
tl += l;
} while (--i > 0);
setsvalue2s(L, top-n, luaS_newlstr(L, buffer, tl)); /* create result */
if (tl <= LUAI_MAXSHORTLEN) { /* is result a short string? */
char buff[LUAI_MAXSHORTLEN];
copy2buff(top, n, buff); /* copy strings to buffer */
ts = luaS_newlstr(L, buff, tl);
}
else { /* long string; copy strings directly to final result */
ts = luaS_createlngstrobj(L, tl);
copy2buff(top, n, getaddrstr(ts));
}
setsvalue2s(L, top - n, ts); /* create result */
}
total -= n-1; /* got 'n' strings to create 1 new */
L->top -= n-1; /* popped 'n' strings and pushed one */