Dircache: Improve freed name memory recallocation
There's only a need to check every MAX_TINYNAME+1 bytes and that the
last character of the needed size 0xff in order to verify the size
of the block since the minimum indirectly-stored string is
MAX_TINYNAME+1.
Change-Id: Ic789376b8575bab9266fcd54c610db0961de5d7f
diff --git a/firmware/common/dircache.c b/firmware/common/dircache.c
index e8f149c..0cdaf1b 100644
--- a/firmware/common/dircache.c
+++ b/firmware/common/dircache.c
@@ -781,56 +781,66 @@
if (dircache.namesfree >= size)
{
/* scan for a free gap starting at the hint point - first fit */
- unsigned char *start = get_name(dircache.nextnamefree), *p = start;
- unsigned char *namesend = get_name(dircache.names + dircache.sizenames);
- size_t gapsize = 0;
+ unsigned char * const start = get_name(dircache.nextnamefree);
+ unsigned char * const bufend = get_name(dircache.names + dircache.sizenames);
+ unsigned char *p = start;
+ unsigned char *end = bufend;
- while (gapsize < size)
+ while (1)
{
- if ((p = memchr(p, 0xff, namesend - p)))
+ if ((size_t)(bufend - p) >= size && (p = memchr(p, 0xff, end - p)))
{
/* found a sentinel; see if there are enough in a row */
- gapsize = 1;
- while (*++p == 0xff && gapsize < size)
- gapsize++;
+ unsigned char *q = p + size - 1;
+
+ /* check end byte and every MAX_TINYNAME+1 bytes from the end;
+ the minimum-length indirectly allocated string that could be
+ in between must have at least one character at one of those
+ locations */
+ while (q > p && *q == 0xff)
+ q -= MAX_TINYNAME+1;
+
+ if (q <= p)
+ {
+ nameidx = get_nameidx(p);
+ break;
+ }
+
+ p += size;
}
else
{
- if (namesend == start)
+ if (end == start)
break; /* exhausted */
/* wrap */
- namesend = start;
+ end = start;
p = get_name(dircache.names);
- if (p == namesend)
+ if (p == end)
break; /* initial hint was at names start */
}
}
- if (gapsize >= size)
+ if (nameidx)
{
- unsigned char *namep = p - gapsize;
- nameidx = get_nameidx(namep);
-
- if (*p == 0xff)
+ unsigned char *q = p + size;
+ if (q[0] == 0xff && q[MAX_TINYNAME] != 0xff)
{
- /* if only a tiny block remains after buffer, claim it too */
- size_t tinysize = 1;
- while (*++p == 0xff && tinysize <= MAX_TINYNAME)
- tinysize++;
-
- if (tinysize <= MAX_TINYNAME)
+ /* if only a tiny block remains after buffer, claim it and
+ hide it from scans since it's too small for indirect
+ allocation */
+ do
{
- /* mark with tiny block sentinel */
- memset(p - tinysize, 0xfe, tinysize);
- size += tinysize;
+ *q = 0xfe;
+ size++;
}
+ while (*++q == 0xff);
}
dircache.namesfree -= size;
dircache.sizeused += size;
- set_namesfree_hint(namep + size);
+ set_namesfree_hint(p + size);
}
}