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/* 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
*
* 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), 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(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;
}
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