1 /* vi: set sw=4 ts=4: */
5 * Copyright (C) 2008 Denys Vlasenko
7 * Licensed under GPLv2, see file LICENSE in this tarball for details.
12 /* Resize (grow) malloced vector.
14 * #define magic packed two parameters into one:
15 * sizeof = sizeof_and_shift >> 8
16 * shift = (sizeof_and_shift) & 0xff
18 * Lets say shift = 4. 1 << 4 == 0x10.
19 * If idx == 0, 0x10, 0x20 etc, vector[] is resized to next higher
20 * idx step, plus one: if idx == 0x20, vector[] is resized to 0x31,
21 * thus last usable element is vector[0x30].
23 * In other words: after xrealloc_vector(v, 4, idx) it's ok to use
24 * at least v[idx] and v[idx+1], for all idx values.
26 * New elements are zeroed out, but only if realloc was done
27 * (not on every call). You can depend on v[idx] and v[idx+1] being
28 * zeroed out if you use it like this:
29 * v = xrealloc_vector(v, 4, idx);
30 * v[idx].some_fields = ...; - the rest stays 0/NULL
32 * If you do not advance idx like above, you should be more careful.
33 * Next call to xrealloc_vector(v, 4, idx) may or may not zero out v[idx].
35 void* FAST_FUNC
xrealloc_vector_helper(void *vector
, unsigned sizeof_and_shift
, int idx
)
37 int mask
= 1 << (uint8_t)sizeof_and_shift
;
39 if (!(idx
& (mask
- 1))) {
40 sizeof_and_shift
>>= 8; /* sizeof(vector[0]) */
41 vector
= xrealloc(vector
, sizeof_and_shift
* (idx
+ mask
+ 1));
42 memset((char*)vector
+ (sizeof_and_shift
* idx
), 0, sizeof_and_shift
* (mask
+ 1));