// Copyright 2024 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package trie

// bytesPool is a pool for byte slices. It is safe for concurrent use.
type bytesPool struct {
	c chan []byte
	w int
}

// newBytesPool creates a new bytesPool. The sliceCap sets the capacity of
// newly allocated slices, and the nitems determines how many items the pool
// will hold, at maximum.
func newBytesPool(sliceCap, nitems int) *bytesPool {
	return &bytesPool{
		c: make(chan []byte, nitems),
		w: sliceCap,
	}
}

// Get returns a slice. Safe for concurrent use.
func (bp *bytesPool) Get() []byte {
	select {
	case b := <-bp.c:
		return b
	default:
		return make([]byte, 0, bp.w)
	}
}

// GetWithSize returns a slice with specified byte slice size.
func (bp *bytesPool) GetWithSize(s int) []byte {
	b := bp.Get()
	if cap(b) < s {
		return make([]byte, s)
	}
	return b[:s]
}

// Put returns a slice to the pool. Safe for concurrent use. This method
// will ignore slices that are too small or too large (>3x the cap)
func (bp *bytesPool) Put(b []byte) {
	if c := cap(b); c < bp.w || c > 3*bp.w {
		return
	}
	select {
	case bp.c <- b:
	default:
	}
}