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96 lines
3.6 KiB
C++
96 lines
3.6 KiB
C++
/*
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* Copyright (c) 2023, kleines Filmröllchen <filmroellchen@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "GenericTypes.h"
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#include <AK/BinarySearch.h>
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#include <AK/Error.h>
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#include <AK/Optional.h>
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namespace Audio {
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size_t SeekTable::size() const
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{
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return m_seek_points.size();
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}
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ReadonlySpan<SeekPoint> SeekTable::seek_points() const
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{
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return m_seek_points.span();
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}
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Vector<SeekPoint>& SeekTable::seek_points()
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{
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return m_seek_points;
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}
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Optional<SeekPoint const&> SeekTable::seek_point_before(u64 sample_index) const
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{
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if (m_seek_points.is_empty())
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return {};
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size_t nearby_seek_point_index = 0;
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AK::binary_search(m_seek_points, sample_index, &nearby_seek_point_index, [](auto const& sample_index, auto const& seekpoint_candidate) {
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// Subtraction with i64 cast may cause overflow.
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if (sample_index > seekpoint_candidate.sample_index)
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return 1;
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if (sample_index == seekpoint_candidate.sample_index)
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return 0;
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return -1;
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});
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// Binary search will always give us a close index, but it may be too large or too small.
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// By doing the index adjustment in this order, we will always find a seek point before the given sample.
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while (nearby_seek_point_index < m_seek_points.size() - 1 && m_seek_points[nearby_seek_point_index].sample_index < sample_index)
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++nearby_seek_point_index;
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while (nearby_seek_point_index > 0 && m_seek_points[nearby_seek_point_index].sample_index > sample_index)
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--nearby_seek_point_index;
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if (m_seek_points[nearby_seek_point_index].sample_index > sample_index)
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return {};
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return m_seek_points[nearby_seek_point_index];
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}
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Optional<u64> SeekTable::seek_point_sample_distance_around(u64 sample_index) const
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{
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if (m_seek_points.is_empty())
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return {};
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size_t nearby_seek_point_index = 0;
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AK::binary_search(m_seek_points, sample_index, &nearby_seek_point_index, [](auto const& sample_index, auto const& seekpoint_candidate) {
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// Subtraction with i64 cast may cause overflow.
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if (sample_index > seekpoint_candidate.sample_index)
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return 1;
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if (sample_index == seekpoint_candidate.sample_index)
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return 0;
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return -1;
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});
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while (nearby_seek_point_index < m_seek_points.size() && m_seek_points[nearby_seek_point_index].sample_index <= sample_index)
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++nearby_seek_point_index;
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// There is no seek point beyond the sample index.
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if (nearby_seek_point_index >= m_seek_points.size())
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return {};
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auto upper_seek_point_index = nearby_seek_point_index;
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while (nearby_seek_point_index > 0 && m_seek_points[nearby_seek_point_index].sample_index > sample_index)
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--nearby_seek_point_index;
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auto lower_seek_point_index = nearby_seek_point_index;
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VERIFY(upper_seek_point_index >= lower_seek_point_index);
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return m_seek_points[upper_seek_point_index].sample_index - m_seek_points[lower_seek_point_index].sample_index;
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}
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ErrorOr<void> SeekTable::insert_seek_point(SeekPoint seek_point)
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{
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if (auto previous_seek_point = seek_point_before(seek_point.sample_index); previous_seek_point.has_value() && previous_seek_point->sample_index == seek_point.sample_index) {
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// Do not insert a duplicate seek point.
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return {};
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}
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// FIXME: This could be even faster if we used binary search while finding the insertion point.
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return m_seek_points.try_insert_before_matching(seek_point, [&](auto const& other_seek_point) {
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return seek_point.sample_index < other_seek_point.sample_index;
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});
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}
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}
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