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Winni Neessen
946d9888d6
Switched ErrNoOutWriter from a string constant to an error object for improved error handling consistency. This change enhances clarity and reduces the risk of error handling inconsistencies in the future.
94 lines
2.6 KiB
Go
94 lines
2.6 KiB
Go
// SPDX-FileCopyrightText: 2022-2023 The go-mail Authors
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//
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// SPDX-License-Identifier: MIT
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package mail
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import (
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"errors"
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"io"
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)
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// newlineBytes is a byte slice representation of the SingleNewLine constant used for line breaking
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// in encoding processes.
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var newlineBytes = []byte(SingleNewLine)
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// ErrNoOutWriter is the error returned when no io.Writer is set for Base64LineBreaker.
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var ErrNoOutWriter = errors.New("no io.Writer set for Base64LineBreaker")
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// Base64LineBreaker handles base64 encoding with the insertion of new lines after a certain number
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// of characters.
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//
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// This struct is used to manage base64 encoding while ensuring that new lines are inserted after
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// reaching a specific line length. It satisfies the io.WriteCloser interface.
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//
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// References:
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// - https://datatracker.ietf.org/doc/html/rfc2045 (Base64 and line length limitations)
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type Base64LineBreaker struct {
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line [MaxBodyLength]byte
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used int
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out io.Writer
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}
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// Write writes data to the Base64LineBreaker, ensuring lines do not exceed MaxBodyLength.
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//
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// This method writes the provided data to the Base64LineBreaker. It ensures that the written
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// lines do not exceed the MaxBodyLength. If the data exceeds the limit, it handles the
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// continuation by splitting the data and writing new lines as necessary.
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//
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// Parameters:
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// - data: A byte slice containing the data to be written.
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//
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// Returns:
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// - numBytes: The number of bytes written.
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// - err: An error if one occurred during the write operation.
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func (l *Base64LineBreaker) Write(data []byte) (numBytes int, err error) {
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if l.out == nil {
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err = ErrNoOutWriter
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return
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}
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if l.used+len(data) < MaxBodyLength {
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copy(l.line[l.used:], data)
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l.used += len(data)
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return len(data), nil
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}
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numBytes, err = l.out.Write(l.line[0:l.used])
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if err != nil {
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return
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}
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excess := MaxBodyLength - l.used
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l.used = 0
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numBytes, err = l.out.Write(data[0:excess])
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if err != nil {
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return
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}
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numBytes, err = l.out.Write(newlineBytes)
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if err != nil {
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return
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}
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return l.Write(data[excess:])
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}
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// Close finalizes the Base64LineBreaker, writing any remaining buffered data and appending a newline.
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//
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// This method ensures that any remaining data in the buffer is written to the output and appends
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// a newline. It is used to finalize the Base64LineBreaker and should be called when no more data
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// is expected to be written.
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//
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// Returns:
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// - err: An error if one occurred during the final write operation.
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func (l *Base64LineBreaker) Close() (err error) {
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if l.used > 0 {
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_, err = l.out.Write(l.line[0:l.used])
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if err != nil {
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return
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}
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_, err = l.out.Write(newlineBytes)
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}
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return
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}
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