Add docs for backup and blob API.

backup.go

@@ -18,10 +18,23 @@ import (
 	"unsafe"
 )
 
+// Backup/Copy the content of one database (source) to another (destination).
+// Example:
+//	bck, err := sqlite.NewBackup(dst, "main", src, "main")
+//	// check err
+//  defer bck.Close()
+//	cbs := make(chan sqlite.BackupStatus)
+//	go func() {
+//		s := <- cbs
+//		// report progress
+//	}()
+//	err = bck.Run(100, 250000, cbs)
+//	check(err)
+//
 // Calls http://sqlite.org/c3ref/backup_finish.html#sqlite3backupinit
-func NewBackup(dst *Conn, dstTable string, src *Conn, srcTable string) (*Backup, error) {
-	dname := C.CString(dstTable)
-	sname := C.CString(srcTable)
+func NewBackup(dst *Conn, dstDbName string, src *Conn, srcDbName string) (*Backup, error) {
+	dname := C.CString(dstDbName)
+	sname := C.CString(srcDbName)
 	defer C.free(unsafe.Pointer(dname))
 	defer C.free(unsafe.Pointer(sname))
 
@@ -32,6 +45,7 @@ func NewBackup(dst *Conn, dstTable string, src *Conn, srcTable string) (*Backup,
 	return &Backup{sb, dst, src}, nil
 }
 
+// Encapsulates backup API
 type Backup struct {
 	sb       *C.sqlite3_backup
 	dst, src *Conn
@@ -46,6 +60,7 @@ func (b *Backup) Step(npage int) error {
 	return Errno(rv)
 }
 
+// Backup progression
 type BackupStatus struct {
 	Remaining int
 	PageCount int
@@ -67,7 +82,9 @@ func (b *Backup) Run(npage int, sleepNs int64, c chan<- BackupStatus) error {
 		if c != nil {
 			c <- b.Status()
 		}
-		time.Sleep(sleepNs)
+		if sleepNs > 0 {
+			time.Sleep(sleepNs)
+		}
 	}
 	return b.dst.error(C.sqlite3_errcode(b.dst.db))
 }

blob.go

@@ -18,23 +18,43 @@ import (
 )
 
 type BlobReader struct {
-	c  *Conn
-	bl *C.sqlite3_blob
+	c          *Conn
+	bl         *C.sqlite3_blob
+	ReadOffset int
 }
 
 type BlobReadWriter struct {
 	BlobReader
+	WriteOffset int
 }
 
+// Zeroblobs are used to reserve space for a BLOB that is later written.
+// 
+// Example:
+//	s, err := db.Prepare("INSERT INTO test VALUES (?)")
+//	// check err
+//	defer s.Finalize()
+//	err = s.Exec(ZeroBlobLength(10))
+//	// check err
 type ZeroBlobLength int
 
+// Example:
+//	br, err := db.NewBlobReader("db_name", "table_name", "column_name", rowid)
+//  // check err
+//	defer br.Close()
+//	size, err := br.Size()
+//  // check err
+//	content = make([]byte, size)
+//	n, err = br.Read(content)
+//  // check err
+//
 // Calls http://sqlite.org/c3ref/blob_open.html
 func (c *Conn) NewBlobReader(db, table, column string, row int64) (*BlobReader, error) {
 	bl, err := c.blob_open(db, table, column, row, false)
 	if err != nil {
 		return nil, err
 	}
-	return &BlobReader{c, bl}, nil
+	return &BlobReader{c, bl, 0}, nil
 }
 
 // Calls http://sqlite.org/c3ref/blob_open.html
@@ -43,7 +63,7 @@ func (c *Conn) NewBlobReadWriter(db, table, column string, row int64) (*BlobRead
 	if err != nil {
 		return nil, err
 	}
-	return &BlobReadWriter{BlobReader{c, bl}}, nil
+	return &BlobReadWriter{BlobReader{c, bl, 0}, 0}, nil
 }
 
 func (c *Conn) blob_open(db, table, column string, row int64, write bool) (*C.sqlite3_blob, error) {
@@ -83,10 +103,11 @@ func (r *BlobReader) Read(v []byte) (int, error) {
 	if len(v) > 0 {
 		p = &v[0]
 	}
-	rv := C.sqlite3_blob_read(r.bl, unsafe.Pointer(p), C.int(len(v)), 0) // TODO offset
+	rv := C.sqlite3_blob_read(r.bl, unsafe.Pointer(p), C.int(len(v)), C.int(r.ReadOffset))
 	if rv != C.SQLITE_OK {
 		return 0, r.c.error(rv)
 	}
+	r.ReadOffset += len(v)
 	return len(v), nil
 }
 
@@ -102,10 +123,11 @@ func (w *BlobReadWriter) Write(v []byte) (int, error) {
 	if len(v) > 0 {
 		p = &v[0]
 	}
-	rv := C.sqlite3_blob_write(w.bl, unsafe.Pointer(p), C.int(len(v)), 0) // TODO offset
+	rv := C.sqlite3_blob_write(w.bl, unsafe.Pointer(p), C.int(len(v)), C.int(w.WriteOffset))
 	if rv != C.SQLITE_OK {
 		return 0, w.c.error(rv)
 	}
+	w.WriteOffset += len(v)
 	return len(v), nil
 }
 
@@ -115,5 +137,6 @@ func (r *BlobReader) Reopen(rowid int64) error {
 	if rv != C.SQLITE_OK {
 		return r.c.error(rv)
 	}
+	r.ReadOffset = 0
 	return nil
 }