b1a597e0c3
Prefix sets were broken beyond any repair and have to be reimplemented. They are reimplemented using a trie with bitmasks in nodes. There is also change in the interpretation of minus prefix pattern, but the old interpretation was already inconsistent with the documentation and broken. There is also some bugfixes in filter code related to set variables.
69 lines
1.6 KiB
C
69 lines
1.6 KiB
C
/*
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* BIRD Library -- Generic Bit Operations
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*
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* (c) 1998 Martin Mares <mj@ucw.cz>
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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*/
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#include "nest/bird.h"
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#include "bitops.h"
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/**
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* u32_mkmask - create a bit mask
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* @n: number of bits
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*
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* u32_mkmask() returns an unsigned 32-bit integer which binary
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* representation consists of @n ones followed by zeroes.
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*/
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u32
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u32_mkmask(unsigned n)
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{
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return n ? ~((1 << (32 - n)) - 1) : 0;
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}
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/**
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* u32_masklen - calculate length of a bit mask
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* @x: bit mask
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*
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* This function checks whether the given integer @x represents
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* a valid bit mask (binary representation contains first ones, then
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* zeroes) and returns the number of ones or -1 if the mask is invalid.
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*/
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int
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u32_masklen(u32 x)
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{
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int l = 0;
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u32 n = ~x;
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if (n & (n+1)) return -1;
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if (x & 0x0000ffff) { x &= 0x0000ffff; l += 16; }
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if (x & 0x00ff00ff) { x &= 0x00ff00ff; l += 8; }
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if (x & 0x0f0f0f0f) { x &= 0x0f0f0f0f; l += 4; }
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if (x & 0x33333333) { x &= 0x33333333; l += 2; }
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if (x & 0x55555555) l++;
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if (x & 0xaaaaaaaa) l++;
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return l;
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}
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/**
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* u32_log2 - compute a binary logarithm.
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* @v: number
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*
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* This function computes a integral part of binary logarithm of given
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* integer @v and returns it. The computed value is also an index of the
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* first non-zero bit position.
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*/
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u32
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u32_log2(u32 v)
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{
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u32 r, shift;
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r = (v > 0xFFFF) << 4; v >>= r;
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shift = (v > 0xFF ) << 3; v >>= shift; r |= shift;
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shift = (v > 0xF ) << 2; v >>= shift; r |= shift;
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shift = (v > 0x3 ) << 1; v >>= shift; r |= shift;
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r |= (v >> 1);
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return r;
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}
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