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5b20cba50a
we don't want external software to include internal details like mlog. slog.Logger is/will be the standard. we still have mlog for its helper functions, and its handler that logs in concise logfmt used by mox. packages that are not meant for reuse still pass around mlog.Log for convenience. we use golang.org/x/exp/slog because we also support the previous Go toolchain version. with the next Go release, we'll switch to the builtin slog.
103 lines
2.7 KiB
Go
103 lines
2.7 KiB
Go
package moxio
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import (
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"bufio"
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"errors"
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"fmt"
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"io"
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"golang.org/x/exp/slog"
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"github.com/mjl-/mox/mlog"
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)
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// todo: instead of a bufpool, should maybe just make an alternative to bufio.Reader with a big enough buffer that we can fully use to read a line.
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var ErrLineTooLong = errors.New("line from remote too long") // Returned by Bufpool.Readline.
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// Bufpool caches byte slices for reuse during parsing of line-terminated commands.
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type Bufpool struct {
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c chan []byte
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size int
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}
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// NewBufpool makes a new pool, initially empty, but holding at most "max" buffers of "size" bytes each.
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func NewBufpool(max, size int) *Bufpool {
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return &Bufpool{
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c: make(chan []byte, max),
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size: size,
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}
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}
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// get returns a buffer from the pool if available, otherwise allocates a new buffer.
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// The buffer should be returned with a call to put.
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func (b *Bufpool) get() []byte {
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var buf []byte
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// Attempt to get buffer from pool. Otherwise create new buffer.
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select {
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case buf = <-b.c:
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default:
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}
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if buf == nil {
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buf = make([]byte, b.size)
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}
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return buf
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}
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// put puts a "buf" back in the pool. Put clears the first "n" bytes, which should
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// be all the bytes that have been read in the buffer. If the pool is full, the
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// buffer is discarded, and will be cleaned up by the garbage collector.
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// The caller should no longer reference "buf" after a call to put.
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func (b *Bufpool) put(log mlog.Log, buf []byte, n int) {
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if len(buf) != b.size {
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log.Error("buffer with bad size returned, ignoring", slog.Int("badsize", len(buf)), slog.Int("expsize", b.size))
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return
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}
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for i := 0; i < n; i++ {
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buf[i] = 0
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}
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select {
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case b.c <- buf:
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default:
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}
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}
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// Readline reads a \n- or \r\n-terminated line. Line is returned without \n or \r\n.
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// If the line was too long, ErrLineTooLong is returned.
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// If an EOF is encountered before a \n, io.ErrUnexpectedEOF is returned.
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func (b *Bufpool) Readline(log mlog.Log, r *bufio.Reader) (line string, rerr error) {
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var nread int
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buf := b.get()
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defer func() {
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b.put(log, buf, nread)
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}()
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// Read until newline. If we reach the end of the buffer first, we write back an
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// error and abort the connection because our protocols cannot be recovered. We
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// don't want to consume data until we finally see a newline, which may be never.
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for {
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if nread >= len(buf) {
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return "", fmt.Errorf("%w: no newline after all %d bytes", ErrLineTooLong, nread)
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}
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c, err := r.ReadByte()
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if err == io.EOF {
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return "", io.ErrUnexpectedEOF
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} else if err != nil {
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return "", fmt.Errorf("reading line from remote: %w", err)
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}
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if c == '\n' {
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var s string
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if nread > 0 && buf[nread-1] == '\r' {
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s = string(buf[:nread-1])
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} else {
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s = string(buf[:nread])
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}
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nread++
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return s, nil
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}
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buf[nread] = c
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nread++
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}
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}
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