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// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include "bucket_stripe_utils.h"
#include <vespa/vespalib/util/alloc.h>
#include <cassert>
namespace storage {
namespace {
constexpr uint8_t used_bits_of(uint64_t key) noexcept {
return static_cast<uint8_t>(key & 0b11'1111ULL);
}
}
size_t
stripe_of_bucket_key(uint64_t key, uint8_t n_stripe_bits) noexcept
{
if (n_stripe_bits == 0) {
return 0;
}
assert(used_bits_of(key) >= n_stripe_bits);
// Since bucket keys have count-bits at the LSB positions, we want to look at the MSBs instead.
return (key >> (64 - n_stripe_bits));
}
uint8_t
calc_num_stripe_bits(size_t n_stripes) noexcept
{
assert(n_stripes > 0);
if (n_stripes == 1) {
return 0;
}
assert(n_stripes <= MaxStripes);
assert(n_stripes == vespalib::roundUp2inN(n_stripes));
auto result = vespalib::Optimized::msbIdx(n_stripes);
assert(result <= MaxStripeBits);
return result;
}
}
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