mremap.go

     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  
     7  package unix
     8  
     9  import "unsafe"
    10  
    11  type mremapMmapper struct {
    12  	mmapper
    13  	mremap func(oldaddr uintptr, oldlength uintptr, newlength uintptr, flags int, newaddr uintptr) (xaddr uintptr, err error)
    14  }
    15  
    16  var mapper = &mremapMmapper{
    17  	mmapper: mmapper{
    18  		active: make(map[*byte][]byte),
    19  		mmap:   mmap,
    20  		munmap: munmap,
    21  	},
    22  	mremap: mremap,
    23  }
    24  
    25  func (m *mremapMmapper) Mremap(oldData []byte, newLength int, flags int) (data []byte, err error) {
    26  	if newLength <= 0 || len(oldData) == 0 || len(oldData) != cap(oldData) || flags&mremapFixed != 0 {
    27  		return nil, EINVAL
    28  	}
    29  
    30  	pOld := &oldData[cap(oldData)-1]
    31  	m.Lock()
    32  	defer m.Unlock()
    33  	bOld := m.active[pOld]
    34  	if bOld == nil || &bOld[0] != &oldData[0] {
    35  		return nil, EINVAL
    36  	}
    37  	newAddr, errno := m.mremap(uintptr(unsafe.Pointer(&bOld[0])), uintptr(len(bOld)), uintptr(newLength), flags, 0)
    38  	if errno != nil {
    39  		return nil, errno
    40  	}
    41  	bNew := unsafe.Slice((*byte)(unsafe.Pointer(newAddr)), newLength)
    42  	pNew := &bNew[cap(bNew)-1]
    43  	if flags&mremapDontunmap == 0 {
    44  		delete(m.active, pOld)
    45  	}
    46  	m.active[pNew] = bNew
    47  	return bNew, nil
    48  }
    49  
    50  func Mremap(oldData []byte, newLength int, flags int) (data []byte, err error) {
    51  	return mapper.Mremap(oldData, newLength, flags)
    52  }
    53  
    54  func MremapPtr(oldAddr unsafe.Pointer, oldSize uintptr, newAddr unsafe.Pointer, newSize uintptr, flags int) (ret unsafe.Pointer, err error) {
    55  	xaddr, err := mapper.mremap(uintptr(oldAddr), oldSize, newSize, flags, uintptr(newAddr))
    56  	return unsafe.Pointer(xaddr), err
    57  }
    58
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