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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:23:18 +0000 |
commit | 43a123c1ae6613b3efeed291fa552ecd909d3acf (patch) | |
tree | fd92518b7024bc74031f78a1cf9e454b65e73665 /src/mime/quotedprintable/writer.go | |
parent | Initial commit. (diff) | |
download | golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.tar.xz golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.zip |
Adding upstream version 1.20.14.upstream/1.20.14upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/mime/quotedprintable/writer.go')
-rw-r--r-- | src/mime/quotedprintable/writer.go | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/src/mime/quotedprintable/writer.go b/src/mime/quotedprintable/writer.go new file mode 100644 index 0000000..16ea0bf --- /dev/null +++ b/src/mime/quotedprintable/writer.go @@ -0,0 +1,172 @@ +// Copyright 2015 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package quotedprintable + +import "io" + +const lineMaxLen = 76 + +// A Writer is a quoted-printable writer that implements io.WriteCloser. +type Writer struct { + // Binary mode treats the writer's input as pure binary and processes end of + // line bytes as binary data. + Binary bool + + w io.Writer + i int + line [78]byte + cr bool +} + +// NewWriter returns a new Writer that writes to w. +func NewWriter(w io.Writer) *Writer { + return &Writer{w: w} +} + +// Write encodes p using quoted-printable encoding and writes it to the +// underlying io.Writer. It limits line length to 76 characters. The encoded +// bytes are not necessarily flushed until the Writer is closed. +func (w *Writer) Write(p []byte) (n int, err error) { + for i, b := range p { + switch { + // Simple writes are done in batch. + case b >= '!' && b <= '~' && b != '=': + continue + case isWhitespace(b) || !w.Binary && (b == '\n' || b == '\r'): + continue + } + + if i > n { + if err := w.write(p[n:i]); err != nil { + return n, err + } + n = i + } + + if err := w.encode(b); err != nil { + return n, err + } + n++ + } + + if n == len(p) { + return n, nil + } + + if err := w.write(p[n:]); err != nil { + return n, err + } + + return len(p), nil +} + +// Close closes the Writer, flushing any unwritten data to the underlying +// io.Writer, but does not close the underlying io.Writer. +func (w *Writer) Close() error { + if err := w.checkLastByte(); err != nil { + return err + } + + return w.flush() +} + +// write limits text encoded in quoted-printable to 76 characters per line. +func (w *Writer) write(p []byte) error { + for _, b := range p { + if b == '\n' || b == '\r' { + // If the previous byte was \r, the CRLF has already been inserted. + if w.cr && b == '\n' { + w.cr = false + continue + } + + if b == '\r' { + w.cr = true + } + + if err := w.checkLastByte(); err != nil { + return err + } + if err := w.insertCRLF(); err != nil { + return err + } + continue + } + + if w.i == lineMaxLen-1 { + if err := w.insertSoftLineBreak(); err != nil { + return err + } + } + + w.line[w.i] = b + w.i++ + w.cr = false + } + + return nil +} + +func (w *Writer) encode(b byte) error { + if lineMaxLen-1-w.i < 3 { + if err := w.insertSoftLineBreak(); err != nil { + return err + } + } + + w.line[w.i] = '=' + w.line[w.i+1] = upperhex[b>>4] + w.line[w.i+2] = upperhex[b&0x0f] + w.i += 3 + + return nil +} + +const upperhex = "0123456789ABCDEF" + +// checkLastByte encodes the last buffered byte if it is a space or a tab. +func (w *Writer) checkLastByte() error { + if w.i == 0 { + return nil + } + + b := w.line[w.i-1] + if isWhitespace(b) { + w.i-- + if err := w.encode(b); err != nil { + return err + } + } + + return nil +} + +func (w *Writer) insertSoftLineBreak() error { + w.line[w.i] = '=' + w.i++ + + return w.insertCRLF() +} + +func (w *Writer) insertCRLF() error { + w.line[w.i] = '\r' + w.line[w.i+1] = '\n' + w.i += 2 + + return w.flush() +} + +func (w *Writer) flush() error { + if _, err := w.w.Write(w.line[:w.i]); err != nil { + return err + } + + w.i = 0 + return nil +} + +func isWhitespace(b byte) bool { + return b == ' ' || b == '\t' +} |