mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-11-24 12:46:38 +00:00
68 lines
1.6 KiB
Go
68 lines
1.6 KiB
Go
//go:build unix && !sqlite3_nosys
|
|
|
|
package alloc
|
|
|
|
import (
|
|
"math"
|
|
|
|
"github.com/tetratelabs/wazero/experimental"
|
|
"golang.org/x/sys/unix"
|
|
)
|
|
|
|
func NewMemory(_, max uint64) experimental.LinearMemory {
|
|
// Round up to the page size.
|
|
rnd := uint64(unix.Getpagesize() - 1)
|
|
max = (max + rnd) &^ rnd
|
|
|
|
if max > math.MaxInt {
|
|
// This ensures int(max) overflows to a negative value,
|
|
// and unix.Mmap returns EINVAL.
|
|
max = math.MaxUint64
|
|
}
|
|
|
|
// Reserve max bytes of address space, to ensure we won't need to move it.
|
|
// A protected, private, anonymous mapping should not commit memory.
|
|
b, err := unix.Mmap(-1, 0, int(max), unix.PROT_NONE, unix.MAP_PRIVATE|unix.MAP_ANON)
|
|
if err != nil {
|
|
panic(err)
|
|
}
|
|
return &mmappedMemory{buf: b[:0]}
|
|
}
|
|
|
|
// The slice covers the entire mmapped memory:
|
|
// - len(buf) is the already committed memory,
|
|
// - cap(buf) is the reserved address space.
|
|
type mmappedMemory struct {
|
|
buf []byte
|
|
}
|
|
|
|
func (m *mmappedMemory) Reallocate(size uint64) []byte {
|
|
com := uint64(len(m.buf))
|
|
res := uint64(cap(m.buf))
|
|
if com < size && size <= res {
|
|
// Round up to the page size.
|
|
rnd := uint64(unix.Getpagesize() - 1)
|
|
new := (size + rnd) &^ rnd
|
|
|
|
// Commit additional memory up to new bytes.
|
|
err := unix.Mprotect(m.buf[com:new], unix.PROT_READ|unix.PROT_WRITE)
|
|
if err != nil {
|
|
return nil
|
|
}
|
|
|
|
// Update committed memory.
|
|
m.buf = m.buf[:new]
|
|
}
|
|
// Limit returned capacity because bytes beyond
|
|
// len(m.buf) have not yet been committed.
|
|
return m.buf[:size:len(m.buf)]
|
|
}
|
|
|
|
func (m *mmappedMemory) Free() {
|
|
err := unix.Munmap(m.buf[:cap(m.buf)])
|
|
if err != nil {
|
|
panic(err)
|
|
}
|
|
m.buf = nil
|
|
}
|