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@@ -14,7 +14,6 @@
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* #define magic packed two parameters into one:
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* sizeof = sizeof_and_shift >> 8
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* shift = (sizeof_and_shift) & 0xff
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- * (TODO: encode "I want it zeroed" in lowest bit?)
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*
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* Lets say shift = 4. 1 << 4 == 0x10.
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* If idx == 0, 0x10, 0x20 etc, vector[] is resized to next higher
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@@ -23,14 +22,25 @@
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*
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* In other words: after xrealloc_vector(v, 4, idx) it's ok to use
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* at least v[idx] and v[idx+1], for all idx values.
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+ *
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+ * New elements are zeroed out, but only if realloc was done
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+ * (not on every call). You can depend on v[idx] and v[idx+1] being
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+ * zeroed out if you use it like this:
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+ * v = xrealloc_vector(v, 4, idx);
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+ * v[idx].some_fields = ...; - the rest stays 0/NULL
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+ * idx++;
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+ * If you do not advance idx like above, you should be more careful.
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+ * Next call to xrealloc_vector(v, 4, idx) may or may not zero out v[idx].
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*/
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void* FAST_FUNC xrealloc_vector_helper(void *vector, unsigned sizeof_and_shift, int idx)
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{
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int mask = 1 << (uint8_t)sizeof_and_shift;
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if (!(idx & (mask - 1))) {
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- sizeof_and_shift >>= 8;
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+ sizeof_and_shift >>= 8; /* sizeof(vector[0]) */
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vector = xrealloc(vector, sizeof_and_shift * (idx + mask + 1));
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+ vector += idx;
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+ memset(vector, 0, sizeof_and_shift * (mask + 1));
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}
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return vector;
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}
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