package transform import ( "bytes" bp "github.com/spf13/hugo/bufferpool" "io" ) type trans func(rw contentTransformer) type link trans type chain []link func NewChain(trs ...link) chain { return trs } func NewEmptyTransforms() []link { return make([]link, 0, 20) } // contentTransformer is an interface that enables rotation of pooled buffers // in the transformer chain. type contentTransformer interface { Content() []byte io.Writer } // Implements contentTransformer // Content is read from the from-buffer and rewritten to to the to-buffer. type fromToBuffer struct { from *bytes.Buffer to *bytes.Buffer } func (ft fromToBuffer) Write(p []byte) (n int, err error) { return ft.to.Write(p) } func (ft fromToBuffer) Content() []byte { return ft.from.Bytes() } func (c *chain) Apply(w io.Writer, r io.Reader) error { b1 := bp.GetBuffer() defer bp.PutBuffer(b1) b1.ReadFrom(r) if len(*c) == 0 { b1.WriteTo(w) return nil } b2 := bp.GetBuffer() defer bp.PutBuffer(b2) fb := &fromToBuffer{from: b1, to: b2} for i, tr := range *c { if i > 0 { if fb.from == b1 { fb.from = b2 fb.to = b1 fb.to.Reset() } else { fb.from = b1 fb.to = b2 fb.to.Reset() } } tr(fb) } fb.to.WriteTo(w) return nil }