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63 lines
2.2 KiB
Go
63 lines
2.2 KiB
Go
// SPDX-FileCopyrightText: Copyright The Miniflux Authors. All rights reserved.
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// SPDX-License-Identifier: Apache-2.0
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package encoding // import "miniflux.app/v2/internal/reader/encoding"
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import (
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"bytes"
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"fmt"
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"io"
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"unicode/utf8"
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"golang.org/x/net/html/charset"
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)
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// CharsetReader is used when the XML encoding is specified for the input document.
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//
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// The document is converted in UTF-8 only if a different encoding is specified
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// and the document is not already UTF-8.
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//
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// Several edge cases could exists:
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//
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// - Feeds with encoding specified only in Content-Type header and not in XML document
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// - Feeds with encoding specified in both places
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// - Feeds with encoding specified only in XML document and not in HTTP header
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// - Feeds with wrong encoding defined and already in UTF-8
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func CharsetReader(charsetLabel string, input io.Reader) (io.Reader, error) {
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buffer, err := io.ReadAll(input)
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if err != nil {
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return nil, fmt.Errorf(`encoding: unable to read input: %w`, err)
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}
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r := bytes.NewReader(buffer)
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// The document is already UTF-8, do not do anything (avoid double-encoding).
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// That means the specified encoding in XML prolog is wrong.
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if utf8.Valid(buffer) {
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return r, nil
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}
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// Transform document to UTF-8 from the specified encoding in XML prolog.
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return charset.NewReaderLabel(charsetLabel, r)
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}
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// NewCharsetReader returns an io.Reader that converts the content of r to UTF-8.
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func NewCharsetReader(r io.Reader, contentType string) (io.Reader, error) {
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buffer, err := io.ReadAll(r)
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if err != nil {
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return nil, fmt.Errorf(`encoding: unable to read input: %w`, err)
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}
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internalReader := bytes.NewReader(buffer)
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// The document is already UTF-8, do not do anything.
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if utf8.Valid(buffer) {
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return internalReader, nil
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}
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// Transform document to UTF-8 from the specified encoding in Content-Type header.
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// Note that only the first 1024 bytes are used to detect the encoding.
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// If the <meta charset> tag is not found in the first 1024 bytes, charset.DetermineEncoding returns "windows-1252" resulting in encoding issues.
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// See https://html.spec.whatwg.org/multipage/parsing.html#determining-the-character-encoding
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return charset.NewReader(internalReader, contentType)
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}
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