[3320] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * Utility routines.
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| 4 | *
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| 5 | * Copyright (C) 2008 Denys Vlasenko
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| 6 | *
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| 7 | * Licensed under GPLv2, see file LICENSE in this source tree.
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| 8 | */
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| 9 |
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| 10 | #include "libbb.h"
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| 11 |
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| 12 | /* Resize (grow) malloced vector.
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| 13 | *
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| 14 | * #define magic packed two parameters into one:
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| 15 | * sizeof = sizeof_and_shift >> 8
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| 16 | * shift = (sizeof_and_shift) & 0xff
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| 17 | *
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| 18 | * Lets say shift = 4. 1 << 4 == 0x10.
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| 19 | * If idx == 0, 0x10, 0x20 etc, vector[] is resized to next higher
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| 20 | * idx step, plus one: if idx == 0x20, vector[] is resized to 0x31,
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| 21 | * thus last usable element is vector[0x30].
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| 22 | *
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| 23 | * In other words: after xrealloc_vector(v, 4, idx), with any idx,
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| 24 | * it's ok to use at least v[idx] and v[idx+1].
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| 25 | * v[idx+2] etc generally are not ok.
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| 26 | *
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| 27 | * New elements are zeroed out, but only if realloc was done
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| 28 | * (not on every call). You can depend on v[idx] and v[idx+1] being
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| 29 | * zeroed out if you use it like this:
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| 30 | * v = xrealloc_vector(v, 4, idx);
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| 31 | * v[idx].some_fields = ...; - the rest stays 0/NULL
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| 32 | * idx++;
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| 33 | * If you do not advance idx like above, you should be more careful.
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| 34 | * Next call to xrealloc_vector(v, 4, idx) may or may not zero out v[idx].
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| 35 | */
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| 36 | void* FAST_FUNC xrealloc_vector_helper(void *vector, unsigned sizeof_and_shift, int idx)
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| 37 | {
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| 38 | int mask = 1 << (uint8_t)sizeof_and_shift;
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| 39 |
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| 40 | if (!(idx & (mask - 1))) {
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| 41 | sizeof_and_shift >>= 8; /* sizeof(vector[0]) */
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| 42 | vector = xrealloc(vector, sizeof_and_shift * (idx + mask + 1));
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| 43 | memset((char*)vector + (sizeof_and_shift * idx), 0, sizeof_and_shift * (mask + 1));
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| 44 | }
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| 45 | return vector;
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| 46 | }
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