// New returns a new File backed by store or an error if any.
// Any existing data in store are discarded.
func New(store storage.Accessor) (f *File, err error) {
f = &File{f: store}
return f, storage.Mutate(store, func() (err error) {
if err = f.f.Truncate(0); err != nil {
return &ECreate{f.f.Name(), err}
}
if _, err = f.Alloc(hdr[1:]); err != nil { //TODO internal panicking versions of the exported fns.
return
}
if _, err = f.Alloc(nil); err != nil { // (empty) root @1
return
}
b := make([]byte, 3856*14)
for i := 1; i <= 3856; i++ {
Handle(i).Put(b[(i-1)*14:])
}
if _, err = f.Alloc(b); err != nil {
return
}
f.canfree = f.atoms
return
})
}
// Alloc stores b in a newly allocated space and returns its handle and an error if any.
func (f *File) Alloc(b []byte) (handle Handle, err error) {
err = storage.Mutate(f.Accessor(), func() (err error) {
rqAtoms := rq2Atoms(len(b))
if rqAtoms > 3856 {
return &EBadRequest{f.f.Name(), len(b)}
}
for foundsize, foundp := range f.freetab[rqAtoms:] {
if foundp != 0 {
// this works only for the current unique sizes list (except the last item!)
size := int64(foundsize) + rqAtoms
handle = Handle(foundp)
if size == 3856 {
buf := make([]byte, 7)
f.read(buf, int64(handle)<<4+15)
(*Handle)(&size).Get(buf)
}
f.delFree(int64(handle), size)
if rqAtoms < size {
f.addFree(int64(handle)+rqAtoms, size-rqAtoms)
}
f.writeUsed(b, int64(handle))
return
}
}
handle = Handle(f.extend(b))
return
})
return
}
// Close closes f and returns an error if any.
func (f *File) Close() (err error) {
return storage.Mutate(f.Accessor(), func() (err error) {
if err = f.f.Close(); err != nil {
err = &EClose{f.f.Name(), err}
}
return
})
}
// Free frees space associated with handle and returns an error if any. Passing an invalid
// handle to Free or reusing handle afterwards will probably corrupt the database or provide
// invalid data on Read. It's like corrupting memory via passing an invalid pointer to C.free()
// or reusing that pointer.
func (f *File) Free(handle Handle) (err error) {
return storage.Mutate(f.Accessor(), func() (err error) {
atom := int64(handle)
atoms, isFree := f.getSize(atom)
if isFree || atom < f.canfree {
return &EHandle{f.f.Name(), handle}
}
leftFree, rightFree := f.checkLeft(atom), f.checkRight(atom, atoms)
switch {
case leftFree != 0 && rightFree != 0:
f.delFree(atom-leftFree, leftFree)
f.delFree(atom+atoms, rightFree)
f.addFree(atom-leftFree, leftFree+atoms+rightFree)
case leftFree != 0 && rightFree == 0:
f.delFree(atom-leftFree, leftFree)
if atom+atoms == f.atoms { // the left free neighbour and this block together are an empy tail
f.atoms = atom - leftFree
f.f.Truncate(f.atoms << 4)
return
}
f.addFree(atom-leftFree, leftFree+atoms)
case leftFree == 0 && rightFree != 0:
f.delFree(atom+atoms, rightFree)
f.addFree(atom, atoms+rightFree)
default: // leftFree == 0 && rightFree == 0
if atom+atoms < f.atoms { // isolated inner block
f.addFree(atom, atoms)
return
}
f.f.Truncate(atom << 4) // isolated tail block, shrink file
f.atoms = atom
}
return
})
}
// Realloc reallocates space associted with handle to acomodate b, returns the newhandle
// newly associated with b and an error if any. If keepHandle == true then Realloc guarantees
// newhandle == handle even if the new data are larger then the previous content associated
// with handle. If !keepHandle && newhandle != handle then reusing handle will probably corrupt
// the database.
// The above effects are like corrupting memory/data via passing an invalid pointer to C.realloc().
func (f *File) Realloc(handle Handle, b []byte, keepHandle bool) (newhandle Handle, err error) {
err = storage.Mutate(f.Accessor(), func() (err error) {
switch handle {
case 0, 2:
return &EHandle{f.f.Name(), handle}
case 1:
keepHandle = true
}
newhandle = handle
atom, newatoms := int64(handle), rq2Atoms(len(b))
if newatoms > 3856 {
return &EBadRequest{f.f.Name(), len(b)}
}
typ, oldatoms := f.getInfo(atom)
switch {
default:
return &ECorrupted{f.f.Name(), atom << 4}
case typ <= 0xfc: // non relocated used block
switch {
case newatoms == oldatoms: // in place replace
f.writeUsed(b, atom)
case newatoms < oldatoms: // in place shrink
rightFree := f.checkRight(atom, oldatoms)
if rightFree > 0 { // right join
f.delFree(atom+oldatoms, rightFree)
}
f.addFree(atom+newatoms, oldatoms+rightFree-newatoms)
f.writeUsed(b, atom)
case newatoms > oldatoms:
if rightFree := f.checkRight(atom, oldatoms); rightFree > 0 && newatoms <= oldatoms+rightFree {
f.delFree(atom+oldatoms, rightFree)
if newatoms < oldatoms+rightFree {
f.addFree(atom+newatoms, oldatoms+rightFree-newatoms)
}
f.writeUsed(b, atom)
return
}
if !keepHandle {
f.Free(Handle(atom))
newhandle, err = f.Alloc(b)
return
}
// reloc
newatom, e := f.Alloc(b)
if e != nil {
return e
}
buf := make([]byte, 16)
buf[0] = 0xfd
Handle(newatom).Put(buf[1:])
f.Realloc(Handle(atom), buf[1:], true)
f.write(buf[:1], atom<<4)
}
case typ == 0xfd: // reloc
var target Handle
buf := make([]byte, 7)
f.read(buf, atom<<4+1)
target.Get(buf)
switch {
case newatoms == 1:
f.writeUsed(b, atom)
f.Free(target)
default:
if rightFree := f.checkRight(atom, 1); rightFree > 0 && newatoms <= 1+rightFree {
f.delFree(atom+1, rightFree)
if newatoms < 1+rightFree {
f.addFree(atom+newatoms, 1+rightFree-newatoms)
}
f.writeUsed(b, atom)
f.Free(target)
return
}
newtarget, e := f.Realloc(Handle(target), b, false)
if e != nil {
return e
}
if newtarget != target {
Handle(newtarget).Put(buf)
f.write(buf, atom<<4+1)
}
}
}
return
})
return
}