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Get rid of the malloc in shuffle(), by defining a subfunction

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memswap() which declares a fixed-size buffer on the stack and uses
it multiple times if necessary.

[originally from svn r6107]
This commit is contained in:
Simon Tatham
2005-07-17 12:12:16 +00:00
parent a31934f233
commit 782a4f3fec
1 changed files with 18 additions and 7 deletions
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25
misc.c
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@ -194,21 +194,32 @@ void game_mkhighlight(frontend *fe, float *ret,
}
}
void memswap(void *av, void *bv, int size)
{
char tmpbuf[512];
char *a = av, *b = bv;
while (size > 0) {
int thislen = min(size, sizeof(tmpbuf));
memcpy(tmpbuf, a, thislen);
memcpy(a, b, thislen);
memcpy(b, tmpbuf, thislen);
a += thislen;
b += thislen;
size -= thislen;
}
}
void shuffle(void *array, int nelts, int eltsize, random_state *rs)
{
char *tmp = smalloc(eltsize);
char *carray = (char *)array;
int i;
for (i = nelts; i-- > 1 ;) {
int j = random_upto(rs, i+1);
if (j != i) {
memcpy(tmp, carray + eltsize * i, eltsize);
memcpy(carray + eltsize * i, carray + eltsize * j, eltsize);
memcpy(carray + eltsize * j, tmp, eltsize);
}
if (j != i)
memswap(carray + eltsize * i, carray + eltsize * j, eltsize);
}
sfree(tmp);
}
void draw_rect_outline(frontend *fe, int x, int y, int w, int h, int colour)