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package transform
import (
"bytes"
bp "github.com/spf13/hugo/bufferpool"
"io"
)
type trans func(rw contentRewriter)
type link trans
type chain []link
func NewChain(trs ...link) chain {
return trs
}
func NewEmptyTransforms() []link {
return make([]link, 0, 20)
}
// contentRewriter is an interface that enables rotation
// of pooled buffers in the transformer chain.
type contentRewriter interface {
Content() []byte
io.Writer
}
// Implements contentRewriter
// 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
}
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