122 lines
2.4 KiB
Go
122 lines
2.4 KiB
Go
// +build pool_sanitize
|
|
|
|
package pbytes
|
|
|
|
import (
|
|
"reflect"
|
|
"runtime"
|
|
"sync/atomic"
|
|
"syscall"
|
|
"unsafe"
|
|
|
|
"golang.org/x/sys/unix"
|
|
)
|
|
|
|
const magic = uint64(0x777742)
|
|
|
|
type guard struct {
|
|
magic uint64
|
|
size int
|
|
owners int32
|
|
}
|
|
|
|
const guardSize = int(unsafe.Sizeof(guard{}))
|
|
|
|
type Pool struct {
|
|
min, max int
|
|
}
|
|
|
|
func New(min, max int) *Pool {
|
|
return &Pool{min, max}
|
|
}
|
|
|
|
// Get returns probably reused slice of bytes with at least capacity of c and
|
|
// exactly len of n.
|
|
func (p *Pool) Get(n, c int) []byte {
|
|
if n > c {
|
|
panic("requested length is greater than capacity")
|
|
}
|
|
|
|
pageSize := syscall.Getpagesize()
|
|
pages := (c+guardSize)/pageSize + 1
|
|
size := pages * pageSize
|
|
|
|
bts := alloc(size)
|
|
|
|
g := (*guard)(unsafe.Pointer(&bts[0]))
|
|
*g = guard{
|
|
magic: magic,
|
|
size: size,
|
|
owners: 1,
|
|
}
|
|
|
|
return bts[guardSize : guardSize+n]
|
|
}
|
|
|
|
func (p *Pool) GetCap(c int) []byte { return p.Get(0, c) }
|
|
func (p *Pool) GetLen(n int) []byte { return Get(n, n) }
|
|
|
|
// Put returns given slice to reuse pool.
|
|
func (p *Pool) Put(bts []byte) {
|
|
hdr := *(*reflect.SliceHeader)(unsafe.Pointer(&bts))
|
|
ptr := hdr.Data - uintptr(guardSize)
|
|
|
|
g := (*guard)(unsafe.Pointer(ptr))
|
|
if g.magic != magic {
|
|
panic("unknown slice returned to the pool")
|
|
}
|
|
if n := atomic.AddInt32(&g.owners, -1); n < 0 {
|
|
panic("multiple Put() detected")
|
|
}
|
|
|
|
// Disable read and write on bytes memory pages. This will cause panic on
|
|
// incorrect access to returned slice.
|
|
mprotect(ptr, false, false, g.size)
|
|
|
|
runtime.SetFinalizer(&bts, func(b *[]byte) {
|
|
mprotect(ptr, true, true, g.size)
|
|
free(*(*[]byte)(unsafe.Pointer(&reflect.SliceHeader{
|
|
Data: ptr,
|
|
Len: g.size,
|
|
Cap: g.size,
|
|
})))
|
|
})
|
|
}
|
|
|
|
func alloc(n int) []byte {
|
|
b, err := unix.Mmap(-1, 0, n, unix.PROT_READ|unix.PROT_WRITE|unix.PROT_EXEC, unix.MAP_SHARED|unix.MAP_ANONYMOUS)
|
|
if err != nil {
|
|
panic(err.Error())
|
|
}
|
|
return b
|
|
}
|
|
|
|
func free(b []byte) {
|
|
if err := unix.Munmap(b); err != nil {
|
|
panic(err.Error())
|
|
}
|
|
}
|
|
|
|
func mprotect(ptr uintptr, r, w bool, size int) {
|
|
// Need to avoid "EINVAL addr is not a valid pointer,
|
|
// or not a multiple of PAGESIZE."
|
|
start := ptr & ^(uintptr(syscall.Getpagesize() - 1))
|
|
|
|
prot := uintptr(syscall.PROT_EXEC)
|
|
switch {
|
|
case r && w:
|
|
prot |= syscall.PROT_READ | syscall.PROT_WRITE
|
|
case r:
|
|
prot |= syscall.PROT_READ
|
|
case w:
|
|
prot |= syscall.PROT_WRITE
|
|
}
|
|
|
|
_, _, err := syscall.Syscall(syscall.SYS_MPROTECT,
|
|
start, uintptr(size), prot,
|
|
)
|
|
if err != 0 {
|
|
panic(err.Error())
|
|
}
|
|
}
|