In some case，the bytes_queue may lead panic

[contestjia]

What is the issue you are having?

goroutine 1 [running]:
github.com/allegro/bigcache/v3/queue.(*BytesQueue).peek(0xc000107f00, 0x100)
	F:/gotest/pkg/mod/github.com/allegro/bigcache/[email protected]/queue/bytes_queue.go:241 +0x130
github.com/allegro/bigcache/v3/queue.(*BytesQueue).Pop(0xc000107f00)
	F:/gotest/pkg/mod/github.com/allegro/bigcache/[email protected]/queue/bytes_queue.go:162 +0x26
main.main()
	F:/gotest/src/algorithm/switch/switch.go:24 +0x187

Minimal, Complete, and Verifiable Example

package main

import (
	"github.com/allegro/bigcache/v3/queue"
)

func FixSizeByteSlice(n int) []byte {
	b := make([]byte, n)
	for i := range b {
		b[i] = 0xff
	}
	return b
}
func main() {
	queue := queue.NewBytesQueue(2*256+2, 655360, true)
	queue.Push(FixSizeByteSlice(254))
	queue.Push(FixSizeByteSlice(254))
	queue.Pop()
	queue.Push(FixSizeByteSlice(127))
	queue.Push(FixSizeByteSlice(259))
	queue.Pop()
	queue.Pop()
	queue.Pop()
}

Environment:

• Version (git sha or release):v3.0.1
• OS (e.g. from /etc/os-release or winver.exe): windows/amd64
• go version: go1.17

[contestjia]

I read the source，the code in allocateAdditionalMemory may lead panic

    if q.tail <= q.head {
			if q.tail != q.head {
				headerEntrySize := getUvarintSize(uint32(q.head - q.tail))
				emptyBlobLen := q.head - q.tail - headerEntrySize
				q.push(make([]byte, emptyBlobLen), emptyBlobLen)
			}

			q.head = leftMarginIndex
			q.tail = q.rightMargin
		}

if q.head - q.tail=128, the headerEntrySize equals to 2, but the emptyBlobLen=126,and in q.push the headerEntrySize=1,not equal to 2

[contestjia]

And I use BigCache reproduce the panic:

package main

import (
        "time"

        "github.com/allegro/bigcache/v3"
)

func FixSizeByteSlice(n int) []byte {
        b := make([]byte, n)
        for i := range b {
                b[i] = 0xff
        }
        return b
}
func main() {
        cache, _ := bigcache.NewBigCache(bigcache.Config{
                Shards:       1,
                LifeWindow:   3 * time.Second,
                MaxEntrySize: 52,
        })
        cache.Set("a", FixSizeByteSlice(235))
        time.Sleep(2 * time.Second)
        cache.Set("b", FixSizeByteSlice(235))
        // expire the first element
        time.Sleep(2 * time.Second)
        // insert the before head
        cache.Set("c", FixSizeByteSlice(108))
        // reallocate the memory
        cache.Set("d", FixSizeByteSlice(1024))
        time.Sleep(4 * time.Second)
        cache.Set("e", FixSizeByteSlice(3))
        cache.Set("f", FixSizeByteSlice(3))
        cache.Set("g", FixSizeByteSlice(3))
}

panic: runtime error: slice bounds out of range [:32898] with capacity 3130

goroutine 1 [running]:
github.com/allegro/bigcache/v3/queue.(*BytesQueue).peek(0xc0000c6008, 0x100, 0xaf63da4c8601e926, 0x5b1cc0, 0x62d, 0x0, 0x100000000000000, 0xc0000c6090)
        /root/go/pkg/mod/github.com/allegro/bigcache/[email protected]/queue/bytes_queue.go:241 +0x17c
github.com/allegro/bigcache/v3/queue.(*BytesQueue).Peek(...)
        /root/go/pkg/mod/github.com/allegro/bigcache/[email protected]/queue/bytes_queue.go:186
github.com/allegro/bigcache/v3.(*cacheShard).set(0xc0000c6000, 0x4d5e40, 0x1, 0xaf63da4c8601e926, 0xc000110006, 0x3, 0x3, 0x3, 0xc000110006)
        /root/go/pkg/mod/github.com/allegro/bigcache/[email protected]/shard.go:133 +0xd8
github.com/allegro/bigcache/v3.(*BigCache).Set(0xc00009c820, 0x4d5e40, 0x1, 0xc000110006, 0x3, 0x3, 0x0, 0x0)
        /root/go/pkg/mod/github.com/allegro/bigcache/[email protected]/bigcache.go:133 +0xac
main.main()
        /root/go-test/bigcache/bigcache.go:34 +0x31e