示例#1
0
// Alloc allocates storage space for b and returns the handle of the new block
// with content set to b or an error, if any. The returned handle is valid only
// while the block is used - until the block is deallocated. No two valid
// handles share the same value within the same Filer, but any value of a
// handle not referring to any used block may become valid any time as a result
// of Alloc.
//
// Invoking Alloc on an empty Allocator is guaranteed to return handle with
// value 1. The intended use of content of handle 1 is a root "directory" of
// other data held by an Allocator.
//
// Passing handles not obtained initially from Alloc or not anymore valid to
// any other Allocator methods can result in an irreparably corrupted database.
func (a *Allocator) Alloc(b []byte) (handle int64, err error) {
	buf := bufs.GCache.Get(zappy.MaxEncodedLen(len(b)))
	defer bufs.GCache.Put(buf)
	buf, _, cc, err := a.makeUsedBlock(buf, b)
	if err != nil {
		return
	}

	if handle, err = a.alloc(buf, cc); err == nil {
		a.cadd(b, handle)
	}
	return
}
示例#2
0
func (a *Allocator) realloc(handle int64, b []byte) (err error) {
	var dlen, needAtoms0 int

	b8 := bufs.GCache.Get(8)
	defer bufs.GCache.Put(b8)
	dst := bufs.GCache.Get(zappy.MaxEncodedLen(len(b)))
	defer bufs.GCache.Put(dst)
	b, needAtoms0, cc, err := a.makeUsedBlock(dst, b)
	if err != nil {
		return
	}

	needAtoms := int64(needAtoms0)
	off := h2off(handle)
	if err = a.read(b8[:], off); err != nil {
		return
	}

	switch tag := b8[0]; tag {
	default:
		dlen = int(b8[0])
	case tagUsedLong:
		dlen = m2n(int(b8[1])<<8 | int(b8[2]))
	case tagUsedRelocated:
		if err = a.free(b2h(b8[1:]), handle, false); err != nil {
			return err
		}

		dlen = 0
	case tagFreeShort, tagFreeLong:
		return &ErrINVAL{"Allocator.Realloc: invalid handle", handle}
	}

	atoms := int64(n2atoms(dlen))
retry:
	switch {
	case needAtoms < atoms:
		// in place shrink
		if err = a.writeUsedBlock(handle, cc, b); err != nil {
			return
		}

		fh, fa := handle+needAtoms, atoms-needAtoms
		sz, err := a.f.Size()
		if err != nil {
			return err
		}

		if h2off(fh)+16*fa == sz {
			return a.f.Truncate(h2off(fh))
		}

		return a.free2(fh, fa)
	case needAtoms == atoms:
		// in place replace
		return a.writeUsedBlock(handle, cc, b)
	}

	// case needAtoms > atoms:
	// in place extend or relocate
	var sz int64
	if sz, err = a.f.Size(); err != nil {
		return
	}

	off = h2off(handle)
	switch {
	case off+atoms*16 == sz:
		// relocating tail block - shortcut
		return a.writeUsedBlock(handle, cc, b)
	default:
		if off+atoms*16 < sz {
			// handle is not a tail block, check right neighbour
			rh := handle + atoms
			rtag, ratoms, p, n, e := a.nfo(rh)
			if e != nil {
				return e
			}

			if rtag == tagFreeShort || rtag == tagFreeLong {
				// Right neighbour is a free block
				if needAtoms <= atoms+ratoms {
					// can expand in place
					if err = a.unlink(rh, ratoms, p, n); err != nil {
						return
					}

					atoms += ratoms
					goto retry

				}
			}
		}
	}

	if atoms > 1 {
		if err = a.realloc(handle, nil); err != nil {
			return
		}
	}

	var newH int64
	if newH, err = a.alloc(b, cc); err != nil {
		return err
	}

	rb := bufs.GCache.Cget(16)
	defer bufs.GCache.Put(rb)
	rb[0] = tagUsedRelocated
	h2b(rb[1:], newH)
	if err = a.writeAt(rb[:], h2off(handle)); err != nil {
		return
	}

	return a.writeUsedBlock(newH, cc, b)
}