Commit 25a8766b authored by Kirill Smelkov's avatar Kirill Smelkov

go/xzodb: New package that provides zodb-related utilities shared by drivers (draft)

parent 4fb6bd0a
// Copyright (C) 2017-2021 Nexedi SA and Contributors.
// Kirill Smelkov <kirr@nexedi.com>
//
// This program is free software: you can Use, Study, Modify and Redistribute
// it under the terms of the GNU General Public License version 3, or (at your
// option) any later version, as published by the Free Software Foundation.
//
// You can also Link and Combine this program with other software covered by
// the terms of any of the Free Software licenses or any of the Open Source
// Initiative approved licenses and Convey the resulting work. Corresponding
// source of such a combination shall include the source code for all other
// software used.
//
// This program is distributed WITHOUT ANY WARRANTY; without even the implied
// warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
//
// See COPYING file for full licensing terms.
// See https://www.nexedi.com/licensing for rationale and options.
// Package xzodb complements package zodb.
package xzodb
import (
"lab.nexedi.com/kirr/neo/go/zodb"
)
// At2Before converts at to before for ZODB load semantics taking edge cases into account.
//
// For most values it is
//
// before = at + 1 ; at < ∞
//
// but at ∞ (zodb.TidMax) it is just
//
// before = at ; at = ∞
func At2Before(at zodb.Tid) (before zodb.Tid) {
if at < zodb.TidMax {
return at + 1
} else {
// XXX do we need to care here also for at > zodb.TidMax (zodb.Tid is currently unsigned)
return zodb.TidMax
}
}
// Before2At is the reverse function to At2Before
func Before2At(before zodb.Tid) (at zodb.Tid) {
if before < zodb.TidMax {
// XXX before = 0 ?
return before - 1
} else {
// XXX before > zodb.TidMax (same as in At2Before) ?
return zodb.TidMax
}
}
...@@ -32,6 +32,7 @@ import ( ...@@ -32,6 +32,7 @@ import (
"lab.nexedi.com/kirr/go123/mem" "lab.nexedi.com/kirr/go123/mem"
"lab.nexedi.com/kirr/go123/xerr" "lab.nexedi.com/kirr/go123/xerr"
"lab.nexedi.com/kirr/go123/xnet" "lab.nexedi.com/kirr/go123/xnet"
"lab.nexedi.com/kirr/neo/go/internal/xzodb"
"lab.nexedi.com/kirr/neo/go/zodb" "lab.nexedi.com/kirr/neo/go/zodb"
) )
...@@ -95,7 +96,7 @@ func (z *zeo) Load(ctx context.Context, xid zodb.Xid) (buf *mem.Buf, serial zodb ...@@ -95,7 +96,7 @@ func (z *zeo) Load(ctx context.Context, xid zodb.Xid) (buf *mem.Buf, serial zodb
rpc := z.rpc("loadBefore") rpc := z.rpc("loadBefore")
enc := z.link.enc enc := z.link.enc
xres, err := rpc.call(ctx, enc.Oid(xid.Oid), enc.Tid(xid.At+1)) // XXX at2Before xres, err := rpc.call(ctx, enc.Oid(xid.Oid), enc.Tid(xzodb.At2Before(xid.At)))
if err != nil { if err != nil {
return nil, 0, err return nil, 0, err
} }
......
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