Ejemplo n.º 1
0
// Get returns the data content of a block referred to by handle or an error if
// any.  The returned slice may be a sub-slice of buf if buf was large enough
// to hold the entire content.  Otherwise, a newly allocated slice will be
// returned.  It is valid to pass a nil buf.
//
// If the content was stored using compression then it is transparently
// returned decompressed.
//
// Handle must have been obtained initially from Alloc and must be still valid,
// otherwise invalid data may be returned without detecting the error.
func (a *Allocator) Get(buf []byte, handle int64) (b []byte, err error) {
	buf = buf[:cap(buf)]
	if n, ok := a.m[handle]; ok {
		a.lru.moveToFront(n)
		b = need(len(n.b), buf)
		copy(b, n.b)
		a.expHit++
		a.hit++
		return
	}

	a.expMiss++
	a.miss++
	if a.miss > 10 && len(a.m) < 500 {
		if 100*a.hit/a.miss < 95 {
			a.cacheSz++
		}
		a.hit, a.miss = 0, 0
	}
	defer func(h int64) {
		if err == nil {
			a.cadd(b, h)
		}
	}(handle)

	first := bufs.GCache.Get(16)
	defer bufs.GCache.Put(first)
	relocated := false
	relocSrc := handle
reloc:
	if handle <= 0 || handle > maxHandle {
		return nil, &ErrINVAL{"Allocator.Get: handle out of limits", handle}
	}

	off := h2off(handle)
	if err = a.read(first, off); err != nil {
		return
	}

	switch tag := first[0]; tag {
	default:
		dlen := int(tag)
		atoms := n2atoms(dlen)
		switch atoms {
		case 1:
			switch tag := first[15]; tag {
			default:
				return nil, &ErrILSEQ{Type: ErrTailTag, Off: off, Arg: int64(tag)}
			case tagNotCompressed:
				b = need(dlen, buf)
				copy(b, first[1:])
				return
			case tagCompressed:
				return zappy.Decode(buf, first[1:dlen+1])
			}
		default:
			cc := bufs.GCache.Get(1)
			defer bufs.GCache.Put(cc)
			dlen := int(tag)
			atoms := n2atoms(dlen)
			tailOff := off + 16*int64(atoms) - 1
			if err = a.read(cc, tailOff); err != nil {
				return
			}

			switch tag := cc[0]; tag {
			default:
				return nil, &ErrILSEQ{Type: ErrTailTag, Off: off, Arg: int64(tag)}
			case tagNotCompressed:
				b = need(dlen, buf)
				off += 1
				if err = a.read(b, off); err != nil {
					b = buf[:0]
				}
				return
			case tagCompressed:
				zbuf := bufs.GCache.Get(dlen)
				defer bufs.GCache.Put(zbuf)
				off += 1
				if err = a.read(zbuf, off); err != nil {
					return buf[:0], err
				}

				return zappy.Decode(buf, zbuf)
			}
		}
	case 0:
		return buf[:0], nil
	case tagUsedLong:
		cc := bufs.GCache.Get(1)
		defer bufs.GCache.Put(cc)
		dlen := m2n(int(first[1])<<8 | int(first[2]))
		atoms := n2atoms(dlen)
		tailOff := off + 16*int64(atoms) - 1
		if err = a.read(cc, tailOff); err != nil {
			return
		}

		switch tag := cc[0]; tag {
		default:
			return nil, &ErrILSEQ{Type: ErrTailTag, Off: off, Arg: int64(tag)}
		case tagNotCompressed:
			b = need(dlen, buf)
			off += 3
			if err = a.read(b, off); err != nil {
				b = buf[:0]
			}
			return
		case tagCompressed:
			zbuf := bufs.GCache.Get(dlen)
			defer bufs.GCache.Put(zbuf)
			off += 3
			if err = a.read(zbuf, off); err != nil {
				return buf[:0], err
			}

			return zappy.Decode(buf, zbuf)
		}
	case tagFreeShort, tagFreeLong:
		return nil, &ErrILSEQ{Type: ErrExpUsedTag, Off: off, Arg: int64(tag)}
	case tagUsedRelocated:
		if relocated {
			return nil, &ErrILSEQ{Type: ErrUnexpReloc, Off: off, Arg: relocSrc}
		}

		handle = b2h(first[1:])
		relocated = true
		goto reloc
	}
}
Ejemplo n.º 2
0
func (a *Allocator) verifyUsed(h, totalAtoms int64, tag byte, buf, ubuf []byte, log func(error) bool, fast bool) (compressed bool, dlen int, atoms, link int64, err error) {
	var (
		padding  int
		doff     int64
		padZeros [15]byte
		tailBuf  [16]byte
	)

	switch tag {
	default: // Short used
		dlen = int(tag)
		atoms = int64((dlen+1)/16) + 1
		padding = 15 - (dlen+1)%16
		doff = h2off(h) + 1
	case tagUsedLong:
		off := h2off(h) + 1
		var b2 [2]byte
		if err = a.read(b2[:], off); err != nil {
			return
		}

		dlen = m2n(int(b2[0])<<8 | int(b2[1]))
		atoms = int64((dlen+3)/16) + 1
		padding = 15 - (dlen+3)%16
		doff = h2off(h) + 3
	case tagUsedRelocated:
		dlen = 7
		atoms = 1
		padding = 7
		doff = h2off(h) + 1
	case tagFreeShort, tagFreeLong:
		panic("internal error")
	}

	if fast {
		if tag == tagUsedRelocated {
			dlen = 0
			if err = a.read(buf[:7], doff); err != nil {
				return
			}

			link = b2h(buf)
		}

		return false, dlen, atoms, link, nil
	}

	if ok := h+atoms-1 <= totalAtoms; !ok { // invalid last block
		err = &ErrILSEQ{Type: ErrVerifyUsedSpan, Off: h2off(h), Arg: atoms}
		log(err)
		return
	}

	tailsz := 1 + padding
	off := h2off(h) + 16*atoms - int64(tailsz)
	if err = a.read(tailBuf[:tailsz], off); err != nil {
		return false, 0, 0, 0, err
	}

	if ok := bytes.Equal(padZeros[:padding], tailBuf[:padding]); !ok {
		err = &ErrILSEQ{Type: ErrVerifyPadding, Off: h2off(h)}
		log(err)
		return
	}

	var cc byte
	switch cc = tailBuf[padding]; cc {
	default:
		err = &ErrILSEQ{Type: ErrTailTag, Off: h2off(h)}
		log(err)
		return
	case tagCompressed:
		compressed = true
		if tag == tagUsedRelocated {
			err = &ErrILSEQ{Type: ErrTailTag, Off: h2off(h)}
			log(err)
			return
		}

		fallthrough
	case tagNotCompressed:
		if err = a.read(buf[:dlen], doff); err != nil {
			return false, 0, 0, 0, err
		}
	}

	if cc == tagCompressed {
		if ubuf, err = zappy.Decode(ubuf, buf[:dlen]); err != nil || len(ubuf) > maxRq {
			err = &ErrILSEQ{Type: ErrDecompress, Off: h2off(h)}
			log(err)
			return
		}

		dlen = len(ubuf)
	}

	if tag == tagUsedRelocated {
		link = b2h(buf)
		if link == 0 {
			err = &ErrILSEQ{Type: ErrNullReloc, Off: h2off(h)}
			log(err)
			return
		}

		if link > totalAtoms { // invalid last block
			err = &ErrILSEQ{Type: ErrRelocBeyondEOF, Off: h2off(h), Arg: link}
			log(err)
			return
		}
	}

	return
}