35 lines
987 B
Go
35 lines
987 B
Go
package s2
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import gs2 "github.com/golang/geo/s2"
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// Range returns a token range to find nearby cells within the specified S2 level.
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func Range(token string, level int) (start, end string) {
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token = NormalizeToken(token)
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cell := gs2.CellIDFromToken(token)
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if !cell.IsValid() {
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return start, end
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}
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// See https://s2geometry.io/resources/s2cell_statistics.html
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cellLevel := cell.Level()
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// Range level must not be greater than the cell level.
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if level > cellLevel {
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level = cellLevel
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}
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// Get parent cell ID for the given level.
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parentCell := cell.Parent(level)
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// Return computed S2 cell token range.
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return parentCell.Prev().ChildBeginAtLevel(cellLevel).ToToken(), parentCell.Next().ChildBeginAtLevel(cellLevel).ToToken()
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}
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// PrefixedRange returns a prefixed token range to find nearby cells within the specified S2 level.
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func PrefixedRange(token string, level int) (start, end string) {
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start, end = Range(token, level)
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return Prefix(start), Prefix(end)
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}
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