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// Copyright 2010 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 textproto implements generic support for text-based request/response
// protocols in the style of HTTP, NNTP, and SMTP.
//
// The package provides:
//
// [Error], which represents a numeric error response from
// a server.
//
// [Pipeline], to manage pipelined requests and responses
// in a client.
//
// [Reader], to read numeric response code lines,
// key: value headers, lines wrapped with leading spaces
// on continuation lines, and whole text blocks ending
// with a dot on a line by itself.
//
// [Writer], to write dot-encoded text blocks.
//
// [Conn], a convenient packaging of [Reader], [Writer], and [Pipeline] for use
// with a single network connection.
package textproto
import (
"bufio"
"fmt"
"io"
"net"
)
// An Error represents a numeric error response from a server.
type Error struct {
Code int
Msg string
}
func (e *Error) Error() string {
return fmt.Sprintf("%03d %s", e.Code, e.Msg)
}
// A ProtocolError describes a protocol violation such
// as an invalid response or a hung-up connection.
type ProtocolError string
func (p ProtocolError) Error() string {
return string(p)
}
// A Conn represents a textual network protocol connection.
// It consists of a [Reader] and [Writer] to manage I/O
// and a [Pipeline] to sequence concurrent requests on the connection.
// These embedded types carry methods with them;
// see the documentation of those types for details.
type Conn struct {
Reader
Writer
Pipeline
conn io.ReadWriteCloser
}
// NewConn returns a new [Conn] using conn for I/O.
func NewConn(conn io.ReadWriteCloser) *Conn {
return &Conn{
Reader: Reader{R: bufio.NewReader(conn)},
Writer: Writer{W: bufio.NewWriter(conn)},
conn: conn,
}
}
// Close closes the connection.
func (c *Conn) Close() error {
return c.conn.Close()
}
// Dial connects to the given address on the given network using [net.Dial]
// and then returns a new [Conn] for the connection.
func Dial(network, addr string) (*Conn, error) {
c, err := net.Dial(network, addr)
if err != nil {
return nil, err
}
return NewConn(c), nil
}
// Cmd is a convenience method that sends a command after
// waiting its turn in the pipeline. The command text is the
// result of formatting format with args and appending \r\n.
// Cmd returns the id of the command, for use with StartResponse and EndResponse.
//
// For example, a client might run a HELP command that returns a dot-body
// by using:
//
// id, err := c.Cmd("HELP")
// if err != nil {
// return nil, err
// }
//
// c.StartResponse(id)
// defer c.EndResponse(id)
//
// if _, _, err = c.ReadCodeLine(110); err != nil {
// return nil, err
// }
// text, err := c.ReadDotBytes()
// if err != nil {
// return nil, err
// }
// return c.ReadCodeLine(250)
func (c *Conn) Cmd(format string, args ...any) (id uint, err error) {
id = c.Next()
c.StartRequest(id)
err = c.PrintfLine(format, args...)
c.EndRequest(id)
if err != nil {
return 0, err
}
return id, nil
}
// TrimString returns s without leading and trailing ASCII space.
func TrimString(s string) string {
for len(s) > 0 && isASCIISpace(s[0]) {
s = s[1:]
}
for len(s) > 0 && isASCIISpace(s[len(s)-1]) {
s = s[:len(s)-1]
}
return s
}
// TrimBytes returns b without leading and trailing ASCII space.
func TrimBytes(b []byte) []byte {
for len(b) > 0 && isASCIISpace(b[0]) {
b = b[1:]
}
for len(b) > 0 && isASCIISpace(b[len(b)-1]) {
b = b[:len(b)-1]
}
return b
}
func isASCIISpace(b byte) bool {
return b == ' ' || b == '\t' || b == '\n' || b == '\r'
}
func isASCIILetter(b byte) bool {
b |= 0x20 // make lower case
return 'a' <= b && b <= 'z'
}
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