Add Infra

vendor/github.com/jackc/pgx/v5/internal/iobufpool/iobufpool.go

@@ -0,0 +1,57 @@
+// Package iobufpool implements a global segregated-fit pool of buffers for IO.
+package iobufpool
+
+import "sync"
+
+const minPoolExpOf2 = 8
+
+var pools [18]*sync.Pool
+
+func init() {
+	for i := range pools {
+		bufLen := 1 << (minPoolExpOf2 + i)
+		pools[i] = &sync.Pool{New: func() any { return make([]byte, bufLen) }}
+	}
+}
+
+// Get gets a []byte of len size with cap <= size*2.
+func Get(size int) []byte {
+	i := getPoolIdx(size)
+	if i >= len(pools) {
+		return make([]byte, size)
+	}
+	return pools[i].Get().([]byte)[:size]
+}
+
+func getPoolIdx(size int) int {
+	size--
+	size >>= minPoolExpOf2
+	i := 0
+	for size > 0 {
+		size >>= 1
+		i++
+	}
+
+	return i
+}
+
+// Put returns buf to the pool.
+func Put(buf []byte) {
+	i := putPoolIdx(cap(buf))
+	if i < 0 {
+		return
+	}
+
+	pools[i].Put(buf)
+}
+
+func putPoolIdx(size int) int {
+	minPoolSize := 1 << minPoolExpOf2
+	for i := range pools {
+		if size == minPoolSize<<i {
+			return i
+		}
+	}
+
+	return -1
+}