github.com/neonyo/sys@v0.0.0-20230720094341-b1ee14be3ce8/unix/mremap.go (about)

     1  // Copyright 2023 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build linux || netbsd
     6  // +build linux netbsd
     7  
     8  package unix
     9  
    10  import "unsafe"
    11  
    12  type mremapMmapper struct {
    13  	mmapper
    14  	mremap func(oldaddr uintptr, oldlength uintptr, newlength uintptr, flags int, newaddr uintptr) (xaddr uintptr, err error)
    15  }
    16  
    17  var mapper = &mremapMmapper{
    18  	mmapper: mmapper{
    19  		active: make(map[*byte][]byte),
    20  		mmap:   mmap,
    21  		munmap: munmap,
    22  	},
    23  	mremap: mremap,
    24  }
    25  
    26  func (m *mremapMmapper) Mremap(oldData []byte, newLength int, flags int) (data []byte, err error) {
    27  	if newLength <= 0 || len(oldData) == 0 || len(oldData) != cap(oldData) || flags&mremapFixed != 0 {
    28  		return nil, EINVAL
    29  	}
    30  
    31  	pOld := &oldData[cap(oldData)-1]
    32  	m.Lock()
    33  	defer m.Unlock()
    34  	bOld := m.active[pOld]
    35  	if bOld == nil || &bOld[0] != &oldData[0] {
    36  		return nil, EINVAL
    37  	}
    38  	newAddr, errno := m.mremap(uintptr(unsafe.Pointer(&bOld[0])), uintptr(len(bOld)), uintptr(newLength), flags, 0)
    39  	if errno != nil {
    40  		return nil, errno
    41  	}
    42  	bNew := unsafe.Slice((*byte)(unsafe.Pointer(newAddr)), newLength)
    43  	pNew := &bNew[cap(bNew)-1]
    44  	if flags&mremapDontunmap == 0 {
    45  		delete(m.active, pOld)
    46  	}
    47  	m.active[pNew] = bNew
    48  	return bNew, nil
    49  }
    50  
    51  func Mremap(oldData []byte, newLength int, flags int) (data []byte, err error) {
    52  	return mapper.Mremap(oldData, newLength, flags)
    53  }