blob: 98fa9678e07997fb71c6b938dea098863d604a1f [file] [log] [blame]
 /* 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; }