Initial QSfera import

Server/vendor/github.com/blevesearch/geo/s2/buffer_pool.go

@@ -0,0 +1,69 @@
+//  Copyright (c) 2023 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 s2
+
+// GeoBufferPool represents a pool of buffers ranging from a given
+// max size to a min size in steps of 2. It uses a lazy approach only allocating
+// the buffers when it is needed.
+
+type GeoBufferPool struct {
+	buffers [][]byte
+	maxSize int
+	minSize int
+}
+
+func NewGeoBufferPool(maxSize int, minSize int) *GeoBufferPool {
+	// Calculating the number of buffers required. Assuming that
+	// the value of minSize is correct, the buffers will be of size
+	// minSize, 2 * minSize, 4 * minSize and so on till it is less
+	// than or equal to the maxSize. If it is not equal to maxSize,
+	// then a suitable value less than maxSize will be set as maxSize
+	length := 0
+	temp := minSize
+	for temp <= maxSize {
+		length = length + 1
+		temp = temp * 2
+	}
+	maxSize = temp / 2
+
+	return &GeoBufferPool{
+		buffers: make([][]byte, length),
+		maxSize: maxSize,
+		minSize: minSize,
+	}
+}
+
+func (b *GeoBufferPool) Get(size int) ([]byte) {
+	if b == nil {
+		// GeoBufferPool not setup
+		return make([]byte, size)
+	}
+
+	bufSize := b.minSize
+
+	for i := range b.buffers {
+		if size <= bufSize || i == len(b.buffers) - 1 {
+			if b.buffers[i] == nil {
+				b.buffers[i] = make([]byte, bufSize)
+			}
+
+			return b.buffers[i]
+		}
+
+		bufSize = bufSize * 2
+	}
+
+	return nil
+}