dev-npgsql/npgsql: Npgsql is the .NET data provider for PostgreSQL.

src/Npgsql.GeoJSON/Internal/CrsMap.cs
108 строк3 KB
Shay Rojansky
Apply file-scoped namespaces for 6.0 (#4298)
28 янв 2022, 15:13
28 янв 2022, 15:132e0ad2d
using System;

namespace Npgsql.GeoJSON.Internal;

/// <summary>
/// An entry which maps the authority to the inclusive range of SRID.
/// </summary>
readonly struct CrsMapEntry
{
    internal readonly int MinSrid;
    internal readonly int MaxSrid;
    internal readonly string? Authority;

    internal CrsMapEntry(int minSrid, int maxSrid, string? authority)
    {
        MinSrid = minSrid;
        MaxSrid = maxSrid;
        Authority = authority != null
            ? string.IsInterned(authority) ?? authority
            : null;
    }
}

ref struct CrsMapBuilder
{
    CrsMapEntry[] _overrides;
    int _overridenIndex;
    int _wellKnownIndex;

    internal void Add(in CrsMapEntry entry)
    {
        var wellKnown = CrsMap.WellKnown[_wellKnownIndex];
        if (wellKnown.MinSrid == entry.MinSrid &&
            wellKnown.MaxSrid == entry.MaxSrid &&
            string.Equals(wellKnown.Authority, entry.Authority, StringComparison.Ordinal))
        {
            _wellKnownIndex++;
            return;
        }

        if (wellKnown.MinSrid < entry.MinSrid)
        {
            do
                _wellKnownIndex++;
            while (CrsMap.WellKnown.Length < _wellKnownIndex &&
                   CrsMap.WellKnown[_wellKnownIndex].MaxSrid < entry.MaxSrid);
            AddCore(new CrsMapEntry(wellKnown.MinSrid, Math.Min(wellKnown.MaxSrid, entry.MinSrid - 1), null));
        }

        AddCore(entry);
    }

    void AddCore(in CrsMapEntry entry)
    {
        var index = _overridenIndex + 1;
        if (_overrides == null)
            _overrides = new CrsMapEntry[4];
        else
        if (_overrides.Length == index)
            Array.Resize(ref _overrides, _overrides.Length << 1);

        _overrides[_overridenIndex] = entry;
        _overridenIndex = index;
    }

    internal CrsMap Build()
    {
        if (_overrides != null && _overrides.Length < _overridenIndex)
            Array.Resize(ref _overrides, _overridenIndex);

        return new CrsMap(_overrides);
    }
}

readonly partial struct CrsMap
{
    readonly CrsMapEntry[]? _overriden;

    internal CrsMap(CrsMapEntry[]? overriden)
        => _overriden = overriden;

    internal string? GetAuthority(int srid)
        => GetAuthority(_overriden, srid) ?? GetAuthority(WellKnown, srid);

    static string? GetAuthority(CrsMapEntry[]? entries, int srid)
    {
        if (entries == null)
            return null;

        var left = 0;
        var right = entries.Length;
        while (left <= right)
        {
            var middle = left + (right - left) / 2;
            var entry = entries[middle];

            if (srid < entry.MinSrid)
                right = middle - 1;
            else
            if (srid > entry.MaxSrid)
                left = middle + 1;
            else
                return entry.Authority;
        }

        return null;
    }
}