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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <vector>
#include <unordered_map>
#include <limits>
#include <cstdint>
namespace search::index { class DocIdAndFeatures; }
namespace search::diskindex {
/*
* Class used to reconstruct field lengths based on element lengths in
* posting list file.
*/
class FieldLengthScanner {
class FieldLengthEntry {
uint16_t _field_length;
uint16_t _elements; // first 16 elements
static uint16_t make_element_mask(uint32_t element_id) { return (1u << element_id); }
public:
FieldLengthEntry() noexcept
: _field_length(0),
_elements(0)
{
}
void add_element_length(uint32_t element_length) {
// Cap field length
if (element_length < std::numeric_limits<uint16_t>::max()) {
uint32_t field_length32 = _field_length + element_length;
_field_length = std::min(field_length32, static_cast<uint32_t>(std::numeric_limits<uint16_t>::max()));
} else {
_field_length = std::numeric_limits<uint16_t>::max();
}
}
void add_element_length(uint32_t element_length, uint32_t element_id) {
uint16_t element_mask = make_element_mask(element_id);
if (!(_elements & element_mask)) {
_elements |= element_mask;
add_element_length(element_length);
}
}
uint16_t get_field_length() const { return _field_length; }
};
std::vector<FieldLengthEntry> _field_length_vector;
static constexpr uint32_t element_id_bias = 16;
// bit vectors for element >= element_id_bias
std::unordered_map<uint32_t, std::vector<bool>> _scanned_elements_map;
public:
FieldLengthScanner(uint32_t doc_id_limit);
~FieldLengthScanner();
void scan_features(const index::DocIdAndFeatures &features);
uint16_t get_field_length(uint32_t doc_id) const { return _field_length_vector[doc_id].get_field_length(); }
};
}
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