golib/mail/base64.go

/*
 *  MIT License
 *
 *  Copyright (c) 2020 Nicolas JUHEL
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 *
 *  The above copyright notice and this permission notice shall be included in all
 *  copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 *  SOFTWARE.
 *
 */

package mail

import "io"

const maxLineChars = 76

type base64LineWrap struct {
	writer       io.Writer
	numLineChars int
}

func (e *base64LineWrap) Write(p []byte) (n int, err error) {
	n = 0
	// while we have more chars than are allowed
	for len(p)+e.numLineChars > maxLineChars {
		numCharsToWrite := maxLineChars - e.numLineChars
		// write the chars we can
		/* #nosec */
		//nolint #nosec
		_, _ = e.writer.Write(p[:numCharsToWrite])
		// write a line break
		/* #nosec */
		//nolint #nosec
		_, _ = e.writer.Write([]byte("\r\n"))
		// reset the line count
		e.numLineChars = 0
		// remove the chars that have been written
		p = p[numCharsToWrite:]
		// set the num of chars written
		n += numCharsToWrite
	}

	// write what is left
	/* #nosec */
	//nolint #nosec
	_, _ = e.writer.Write(p)
	e.numLineChars += len(p)
	n += len(p)

	return
}