tar: support -T - and -X -

[oweals/busybox.git] / libbb / xrealloc_vector.c

diff --git a/libbb/xrealloc_vector.c b/libbb/xrealloc_vector.c
index ccc961b7b47db1f13762cd4ca05081627ae2c50b..e8d31b7e4a3b1e53221e6412d7f3d05c7ac27449 100644 (file)
--- a/libbb/xrealloc_vector.c
+++ b/libbb/xrealloc_vector.c
@@ -4,7 +4,7 @@
  *
  * Copyright (C) 2008 Denys Vlasenko
  *
- * Licensed under GPLv2, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2, see file LICENSE in this source tree.
  */
 
 #include "libbb.h"
@@ -14,23 +14,33 @@
  *  #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.
+ * In other words: after xrealloc_vector(v, 4, idx), with any idx,
+ * it's ok to use at least v[idx] and v[idx+1].
+ * v[idx+2] etc generally are not ok.
+ *
+ * New elements are zeroed out, but only if realloc was done
+ * (not on every call). You can depend on v[idx] and v[idx+1] being
+ * zeroed out if you use it like this:
+ *  v = xrealloc_vector(v, 4, idx);
+ *  v[idx].some_fields = ...; - the rest stays 0/NULL
+ *  idx++;
+ * If you do not advance idx like above, you should be more careful.
+ * Next call to xrealloc_vector(v, 4, idx) may or may not zero out v[idx].
  */
 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;
+               sizeof_and_shift >>= 8; /* sizeof(vector[0]) */
                vector = xrealloc(vector, sizeof_and_shift * (idx + mask + 1));
+               memset((char*)vector + (sizeof_and_shift * idx), 0, sizeof_and_shift * (mask + 1));
        }
        return vector;
 }