.

t/neo/storage/fs1/cmd/fstail/fstail.go

@@ -24,55 +24,96 @@ package main
 import (
 	"crypto/sha1"
 	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+
+	"../../../../storage/fs1"
 )
 
-fsDump(w io.Writer, path string, ntxn int) error {
+func fsDump(w io.Writer, path string, ntxn int) (err error) {
+	// path & fsdump on error context
+	defer func() {
+		if err != nil {
+			err = fmt.Errorf("%s: fsdump: %v", err)
+		}
+	}()
+
 	// we are not using fs1.Open here, since the file could be e.g. corrupt
 	// (same logic as in fstail/py)
 	f, err := os.Open(path)
-	// XXX err
+	if err != nil {
+		return err
+	}
 
-	// TODO get fSize
+	// get file size as topPos
+	fi, err := f.Stat()
+	if err != nil {
+		return err
+	}
+	topPos := fi.Size()
 
+	// txn header & data buffer for iterating
 	txnh := fs1.TxnHeader{}
+	data := []byte{}
 
 	// start iterating at tail.
 	// this should get EOF but read txnh.LenPrev ok.
-	err = txnh.Load(f, fSize, LoadAll)
+	err = txnh.Load(f, topPos, fs1.LoadAll)
 	if err != io.EOF {
 		if err == nil {
 			// XXX or allow this?
 			// though then, if we start not from a txn boundary - there are
 			// high chances further iteration will go wrong.
-			err = fmt.Errorf("%s @%v: reading past file end was unexpectedly successful: probably the file is being modified simultaneously",
-				path, fSize)
+			err = fmt.Errorf("@%v: reading past file end was unexpectedly successful: probably the file is being modified simultaneously", topPos)
 		}
 		// otherwise err already has the context
 		return err
 	}
 	if txnh.LenPrev <= 0 {
-		return fmt.Errorf("%s @%v: previous record could not be read", path, fSize)
+		return fmt.Errorf("@%v: previous record could not be read", topPos)
 	}
 
 	// now loop loading previous txn until EOF / ntxn limit
-	for {
-		err = txnh.LoadPrev(fs1.LoadAll)
+	for i := ntxn; i > 0; i-- {
+		err = txnh.LoadPrev(f, fs1.LoadAll)
 		if err != nil {
 			if err == io.EOF {
-				err = nil
+				err = nil	// XXX -> okEOF(err)
 			}
 			break
 		}
 
-		// TODO read raw data	(get_raw_data) -> sha1
-		// txnh.Tid.TimeStamp() ?  XXX -> PerTimeStamp ? (get_timestamp)
+		// read raw data inside transaction record
+		dataLen := txnh.DataLen()
+		if int64(cap(data)) < dataLen {
+			data = make([]byte, dataLen)
+		} else {
+			data = data[:dataLen]
+		}
 
-		//"user=%'q description=%'q length=%d offset=%d (+%d)", txnh.User, txnh.Description, // .Len, .offset ...
+		_, err = f.ReadAt(data, txnh.DataPos())
+		if err != nil {
+			// XXX -> txnh.Err(...) ?
+			// XXX err = noEOF(err)
+			err = &fs1.ErrTxnRecord{txnh.Pos, "read data payload", err}
+			break
 		}
 
+		// print information about read txn record
+		_, err = fmt.Fprintf(w, "%s: hash=%x\nuser=%q description=%q length=%d offset=%d (+%d)\n\n",
+				txnh.Tid.Time(), sha1.Sum(data),
+				txnh.User, txnh.Description,
+				// NOTE in zodb/py .length is len - 8, in zodb/go - whole txn record length
+				txnh.Len - 8,
+				txnh.Pos, txnh.HeaderLen())
 		if err != nil {
-		// TODO
+			break
+		}
 	}
+
+	return err
 }
 
 func usage() {
@@ -101,7 +142,7 @@ func main() {
 	}
 	storPath := argv[0]
 
-	err = fsDump(os.Stdout, storPath, n)
+	err := fsDump(os.Stdout, storPath, n)
 	if err != nil {
 		log.Fatal(err)
 	}

t/neo/storage/fs1/filestorage.go

@@ -174,6 +174,16 @@ func (txnh *TxnHeader) HeaderLen() int64 {
 	return TxnHeaderFixSize + int64(len(txnh.workMem))
 }
 
+// DataPos returns start position of data inside transaction record
+func (txnh *TxnHeader) DataPos() int64 {
+	return txnh.Pos + txnh.HeaderLen()
+}
+
+// DataLen returns length of all data inside transaction record container
+func (txnh *TxnHeader) DataLen() int64 {
+	return txnh.Len - txnh.HeaderLen() - 8 /* trailer redundant length */
+}
+
 // CloneFrom copies txnh2 to txnh making sure underlying slices (.workMem .User
 // .Desc ...) are not shared.
 func (txnh *TxnHeader) CloneFrom(txnh2 *TxnHeader) {
@@ -899,7 +909,7 @@ func (fsi *iterator) NextTxn() (*zodb.TxnInfo, zodb.IStorageRecordIterator, erro
 	}
 
 	// set .dataIter to iterate over .txnIter.Txnh
-	fsi.dataIter.Datah.Pos = fsi.txnIter.Txnh.Pos + fsi.txnIter.Txnh.HeaderLen()
+	fsi.dataIter.Datah.Pos = fsi.txnIter.Txnh.DataPos()
 	fsi.dataIter.Datah.DataLen = -DataHeaderSize // first iteration will go to first data record
 
 	return &fsi.txnIter.Txnh.TxnInfo, &fsi.dataIter, nil