mox/imapclient/prefixconn.go
Mechiel Lukkien f40f94670e
implement IMAP extension COMPRESS=DEFLATE, rfc 4978
to compress the entire IMAP connection. tested with thunderbird, meli, k9, ios
mail. the initial implementation had interoperability issues with some of these
clients: if they write the deflate stream and flush in "partial mode", the go
stdlib flate reader does not return any data (until there is an explicit
zero-length "sync flush" block, or until the history/sliding window is full),
blocking progress, resulting in clients closing the seemingly stuck connection
after considering the connection timed out. this includes a coy of the flate
package with a new reader that returns partially flushed blocks earlier.

this also adds imap trace logging to imapclient.Conn, which was useful for
debugging.
2025-02-21 14:56:17 +01:00

45 lines
983 B
Go

package imapclient
import (
"io"
"net"
)
// prefixConn is a net.Conn with a buffer from which the first reads are satisfied.
// used for STARTTLS where already did a buffered read of initial TLS data.
type prefixConn struct {
prefix []byte
net.Conn
}
func (c *prefixConn) Read(buf []byte) (int, error) {
if len(c.prefix) > 0 {
n := len(buf)
if n > len(c.prefix) {
n = len(c.prefix)
}
copy(buf[:n], c.prefix[:n])
c.prefix = c.prefix[n:]
if len(c.prefix) == 0 {
c.prefix = nil
}
return n, nil
}
return c.Conn.Read(buf)
}
// xprefixConn checks if there are any buffered unconsumed reads. If not, it
// returns c.conn. Otherwise, it returns a *prefixConn from which the buffered data
// can be read followed by data from c.conn.
func (c *Conn) xprefixConn() net.Conn {
n := c.br.Buffered()
if n == 0 {
return c.conn
}
buf := make([]byte, n)
_, err := io.ReadFull(c.br, buf)
c.xcheckf(err, "get buffered data")
return &prefixConn{buf, c.conn}
}