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// Copyright 2015 The Hugo Authors. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package transform
import (
"bytes"
"io"
bp "github.com/gohugoio/hugo/bufferpool"
)
type trans func(rw contentTransformer)
type link trans
type chain []link
// NewChain creates a chained content transformer given the provided transforms.
func NewChain(trs ...link) chain {
return trs
}
// NewEmptyTransforms creates a new slice of transforms with a capacity of 20.
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 {
Path() []byte
Content() []byte
io.Writer
}
// Implements contentTransformer
// Content is read from the from-buffer and rewritten to to the to-buffer.
type fromToBuffer struct {
path []byte
from *bytes.Buffer
to *bytes.Buffer
}
func (ft fromToBuffer) Path() []byte {
return ft.path
}
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, p []byte) error {
b1 := bp.GetBuffer()
defer bp.PutBuffer(b1)
if _, err := b1.ReadFrom(r); err != nil {
return err
}
if len(*c) == 0 {
_, err := b1.WriteTo(w)
return err
}
b2 := bp.GetBuffer()
defer bp.PutBuffer(b2)
fb := &fromToBuffer{path: p, 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)
}
_, err := fb.to.WriteTo(w)
return err
}
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