using System;
namespace Npgsql.GeoJSON
{
///
/// An entry which maps the authority to the inclusive range of SRID.
///
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(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(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;
}
}
}