svn commit: trunk/busybox/libbb
vda at busybox.net
vda at busybox.net
Tue Jul 8 20:41:57 UTC 2008
Author: vda
Date: 2008-07-08 13:41:57 -0700 (Tue, 08 Jul 2008)
New Revision: 22695
Log:
add xrealloc_vector.c
Added:
trunk/busybox/libbb/xrealloc_vector.c
Changeset:
Added: trunk/busybox/libbb/xrealloc_vector.c
===================================================================
--- trunk/busybox/libbb/xrealloc_vector.c (rev 0)
+++ trunk/busybox/libbb/xrealloc_vector.c 2008-07-08 20:41:57 UTC (rev 22695)
@@ -0,0 +1,36 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Utility routines.
+ *
+ * Copyright (C) 2008 Denys Vlasenko
+ *
+ * Licensed under GPLv2, see file LICENSE in this tarball for details.
+ */
+
+#include "libbb.h"
+
+/* Resize (grow) malloced vector.
+ *
+ * #define magic packed two parameters into one:
+ * sizeof = sizeof_and_shift >> 8
+ * shift = (sizeof_and_shift) & 0xff
+ * (TODO: encode "I want it zeroed" in lowest bit?)
+ *
+ * Lets say shift = 4. 1 << 4 == 0x10.
+ * If idx == 0, 0x10, 0x20 etc, vector[] is resized to next higher
+ * idx step, plus one: if idx == 0x20, vector[] is resized to 0x31,
+ * thus last usable element is vector[0x30].
+ *
+ * In other words: after xrealloc_vector(v, 4, idx) it's ok to use
+ * at least v[idx] and v[idx+1], for all idx values.
+ */
+void* FAST_FUNC xrealloc_vector_helper(void *vector, unsigned sizeof_and_shift, int idx)
+{
+ int mask = 1 << (uint8_t)sizeof_and_shift;
+
+ if (!(idx & (mask - 1))) {
+ sizeof_and_shift >>= 8;
+ vector = xrealloc(vector, sizeof_and_shift * (idx + mask + 1));
+ }
+ return vector;
+}
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