mirror of
https://github.com/gohugoio/hugo.git
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125 lines
3.2 KiB
Go
125 lines
3.2 KiB
Go
// Copyright 2018 The Hugo Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package transform
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import (
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"bytes"
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"io"
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"os"
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bp "github.com/gohugoio/hugo/bufferpool"
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"github.com/gohugoio/hugo/common/herrors"
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"github.com/gohugoio/hugo/hugofs"
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)
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// Transformer is the func that needs to be implemented by a transformation step.
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type Transformer func(ft FromTo) error
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// BytesReader wraps the Bytes method, usually implemented by bytes.Buffer, and an
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// io.Reader.
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type BytesReader interface {
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// The slice given by Bytes is valid for use only until the next buffer modification.
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// That is, if you want to use this value outside of the current transformer step,
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// you need to take a copy.
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Bytes() []byte
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io.Reader
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}
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// FromTo is sent to each transformation step in the chain.
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type FromTo interface {
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From() BytesReader
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To() io.Writer
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}
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// Chain is an ordered processing chain. The next transform operation will
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// receive the output from the previous.
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type Chain []Transformer
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// New creates a content transformer chain given the provided transform funcs.
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func New(trs ...Transformer) Chain {
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return trs
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}
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// NewEmpty creates a new slice of transformers with a capacity of 20.
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func NewEmpty() Chain {
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return make(Chain, 0, 20)
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}
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// Implements contentTransformer
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// Content is read from the from-buffer and rewritten to to the to-buffer.
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type fromToBuffer struct {
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from *bytes.Buffer
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to *bytes.Buffer
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}
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func (ft fromToBuffer) From() BytesReader {
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return ft.from
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}
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func (ft fromToBuffer) To() io.Writer {
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return ft.to
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}
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// Apply passes the given from io.Reader through the transformation chain.
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// The result is written to to.
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func (c *Chain) Apply(to io.Writer, from io.Reader) error {
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if len(*c) == 0 {
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_, err := io.Copy(to, from)
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return err
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}
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b1 := bp.GetBuffer()
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defer bp.PutBuffer(b1)
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if _, err := b1.ReadFrom(from); err != nil {
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return err
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}
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b2 := bp.GetBuffer()
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defer bp.PutBuffer(b2)
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fb := &fromToBuffer{from: b1, to: b2}
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for i, tr := range *c {
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if i > 0 {
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if fb.from == b1 {
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fb.from = b2
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fb.to = b1
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fb.to.Reset()
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} else {
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fb.from = b1
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fb.to = b2
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fb.to.Reset()
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}
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}
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if err := tr(fb); err != nil {
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// Write output to a temp file so it can be read by the user for trouble shooting.
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filename := "output.html"
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tempfile, ferr := os.CreateTemp("", "hugo-transform-error")
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if ferr == nil {
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filename = tempfile.Name()
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defer tempfile.Close()
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_, _ = io.Copy(tempfile, fb.from)
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return herrors.NewFileErrorFromFile(err, filename, hugofs.Os, nil)
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}
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return herrors.NewFileErrorFromName(err, filename).UpdateContent(fb.from, nil)
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}
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}
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_, err := fb.to.WriteTo(to)
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return err
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}
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