1/* vi: set sw=4 ts=4: */ 2/* 3 * Utility routines. 4 * 5 * Copyright (C) 2008 Denys Vlasenko 6 * 7 * Licensed under GPLv2, see file LICENSE in this tarball for details. 8 */ 9 10#include "libbb.h" 11 12/* Resize (grow) malloced vector. 13 * 14 * #define magic packed two parameters into one: 15 * sizeof = sizeof_and_shift >> 8 16 * shift = (sizeof_and_shift) & 0xff 17 * 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]. 22 * 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. 25 * 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 31 * idx++; 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]. 34 */ 35void* FAST_FUNC xrealloc_vector_helper(void *vector, unsigned sizeof_and_shift, int idx) 36{ 37 int mask = 1 << (uint8_t)sizeof_and_shift; 38 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)); 43 } 44 return vector; 45} 46