dbef1173b
Denis Vlasenko
2008-07-08
Subject
add xrealloc_vector.c
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libbb/xrealloc_vector.c+36 -0
| @@ -0,0 +1,36 @@ | |
| + | /* 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 |
| + | * (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. |
| + | */ |
| + | 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; |
| + | vector = xrealloc(vector, sizeof_and_shift * (idx + mask + 1)); |
| + | } |
| + | return vector; |
| + | } |