snapshot of https://github.com/blevesearch/bleve.git (master, 2026-09-15; blobs > 131072B omitted)

geov2/score.go

@@ -0,0 +1,74 @@
+//  Copyright (c) 2026 Couchbase, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 		http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package geov2
+
+// pow4Table precomputes all valid powers of 4 for a uint64.
+// Array size 32 covers exp 0 through 31.
+var pow4Table = [32]uint64{
+	1,                   // 4^0
+	4,                   // 4^1
+	16,                  // 4^2
+	64,                  // 4^3
+	256,                 // 4^4
+	1024,                // 4^5
+	4096,                // 4^6
+	16384,               // 4^7
+	65536,               // 4^8
+	262144,              // 4^9
+	1048576,             // 4^10
+	4194304,             // 4^11
+	16777216,            // 4^12
+	67108864,            // 4^13
+	268435456,           // 4^14
+	1073741824,          // 4^15
+	4294967296,          // 4^16
+	17179869184,         // 4^17
+	68719476736,         // 4^18
+	274877906944,        // 4^19
+	1099511627776,       // 4^20
+	4398046511104,       // 4^21
+	17592186044416,      // 4^22
+	70368744177664,      // 4^23
+	281474976710656,     // 4^24
+	1125899906842624,    // 4^25
+	4503599627370496,    // 4^26
+	18014398509481984,   // 4^27
+	72057594037927936,   // 4^28
+	288230376151711744,  // 4^29
+	1152921504606846976, // 4^30
+	4611686018427387904, // 4^31
+}
+
+// pow4 returns 4^exp quickly using the lookup table.
+func pow4(exp uint64) uint64 {
+	if exp >= 32 {
+		// Handle overflow safely.
+		return 0
+	}
+	return pow4Table[exp]
+}
+
+// returns the overlap of query and index cells based on their levels.
+// Both levels are assumed to be at most 16 (maxCellLevel in the geo repo's
+// region coverer configuration - see geo/geojson/geojson_v2.go), the deepest
+// level used across the geoshape_v2 indexing and query cell coverings;
+// cells deeper than level 16 are outside this function's contract by design.
+func calcScore(queryCellLevel, indexCellLevel uint64) uint64 {
+	if indexCellLevel > queryCellLevel {
+		return pow4(16 - indexCellLevel)
+	} else {
+		return pow4(16 - queryCellLevel)
+	}
+}