func (h *dbCorruptHarness) corrupt(ft storage.FileType, offset, n int) {
p := &h.dbHarness
t := p.t
var file storage.File
for _, f := range p.stor.GetFiles(ft) {
if file == nil || f.Num() > file.Num() {
file = f
}
}
if file == nil {
t.Fatalf("no such file with type %q", ft)
}
r, err := file.Open()
if err != nil {
t.Fatal("cannot open file: ", err)
}
x, err := file.Size()
if err != nil {
t.Fatal("cannot query file size: ", err)
}
m := int(x)
if offset < 0 {
if -offset > m {
offset = 0
} else {
offset = m + offset
}
}
if offset > m {
offset = m
}
if offset+n > m {
n = m - offset
}
buf := make([]byte, m)
_, err = io.ReadFull(r, buf)
if err != nil {
t.Fatal("cannot read file: ", err)
}
r.Close()
for i := 0; i < n; i++ {
buf[offset+i] ^= 0x80
}
err = file.Remove()
if err != nil {
t.Fatal("cannot remove old file: ", err)
}
w, err := file.Create()
if err != nil {
t.Fatal("cannot create new file: ", err)
}
_, err = w.Write(buf)
if err != nil {
t.Fatal("cannot write new file: ", err)
}
w.Close()
}
