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416 lines
12 KiB
Go
416 lines
12 KiB
Go
// Copyright (c) 2016-2019 Daniel Oaks <daniel@danieloaks.net>
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// Copyright (c) 2018-2019 Shivaram Lingamneni <slingamn@cs.stanford.edu>
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// released under the ISC license
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package ircmsg
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import (
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"bytes"
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"errors"
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"strings"
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)
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const (
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// "The size limit for message tags is 8191 bytes, including the leading
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// '@' (0x40) and trailing space ' ' (0x20) characters."
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MaxlenTags = 8191
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// MaxlenTags - ('@' + ' ')
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MaxlenTagData = MaxlenTags - 2
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// "Clients MUST NOT send messages with tag data exceeding 4094 bytes,
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// this includes tags with or without the client-only prefix."
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MaxlenClientTagData = 4094
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// "Servers MUST NOT add tag data exceeding 4094 bytes to messages."
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MaxlenServerTagData = 4094
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// '@' + MaxlenClientTagData + ' '
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// this is the analogue of MaxlenTags when the source of the message is a client
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MaxlenTagsFromClient = MaxlenClientTagData + 2
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)
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var (
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// ErrorLineIsEmpty indicates that the given IRC line was empty.
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ErrorLineIsEmpty = errors.New("Line is empty")
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// ErrorLineContainsBadChar indicates that the line contained invalid characters
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ErrorLineContainsBadChar = errors.New("Line contains invalid characters")
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// ErrorLineTooLong indicates that the message exceeded the maximum tag length
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// (the name references 417 ERR_INPUTTOOLONG; we reserve the right to return it
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// for messages that exceed the non-tag length limit)
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ErrorLineTooLong = errors.New("Line could not be parsed because a specified length limit was exceeded")
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ErrorCommandMissing = errors.New("IRC messages MUST have a command")
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ErrorBadParam = errors.New("Cannot have an empty param, a param with spaces, or a param that starts with ':' before the last parameter")
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)
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// IrcMessage represents an IRC message, as defined by the RFCs and as
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// extended by the IRCv3 Message Tags specification with the introduction
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// of message tags.
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type IrcMessage struct {
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Prefix string
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Command string
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Params []string
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forceTrailing bool
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tags map[string]string
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clientOnlyTags map[string]string
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}
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// ForceTrailing ensures that when the message is serialized, the final parameter
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// will be encoded as a "trailing parameter" (preceded by a colon). This is
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// almost never necessary and should not be used except when having to interact
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// with broken implementations that don't correctly interpret IRC messages.
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func (msg *IrcMessage) ForceTrailing() {
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msg.forceTrailing = true
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}
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// GetTag returns whether a tag is present, and if so, what its value is.
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func (msg *IrcMessage) GetTag(tagName string) (present bool, value string) {
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if len(tagName) == 0 {
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return
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} else if tagName[0] == '+' {
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value, present = msg.clientOnlyTags[tagName]
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return
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} else {
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value, present = msg.tags[tagName]
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return
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}
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}
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// HasTag returns whether a tag is present.
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func (msg *IrcMessage) HasTag(tagName string) (present bool) {
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present, _ = msg.GetTag(tagName)
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return
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}
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// SetTag sets a tag.
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func (msg *IrcMessage) SetTag(tagName, tagValue string) {
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if len(tagName) == 0 {
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return
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} else if tagName[0] == '+' {
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if msg.clientOnlyTags == nil {
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msg.clientOnlyTags = make(map[string]string)
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}
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msg.clientOnlyTags[tagName] = tagValue
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} else {
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if msg.tags == nil {
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msg.tags = make(map[string]string)
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}
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msg.tags[tagName] = tagValue
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}
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}
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// DeleteTag deletes a tag.
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func (msg *IrcMessage) DeleteTag(tagName string) {
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if len(tagName) == 0 {
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return
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} else if tagName[0] == '+' {
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delete(msg.clientOnlyTags, tagName)
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} else {
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delete(msg.tags, tagName)
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}
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}
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// UpdateTags is a convenience to set multiple tags at once.
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func (msg *IrcMessage) UpdateTags(tags map[string]string) {
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for name, value := range tags {
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msg.SetTag(name, value)
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}
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}
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// AllTags returns all tags as a single map.
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func (msg *IrcMessage) AllTags() (result map[string]string) {
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result = make(map[string]string, len(msg.tags)+len(msg.clientOnlyTags))
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for name, value := range msg.tags {
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result[name] = value
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}
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for name, value := range msg.clientOnlyTags {
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result[name] = value
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}
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return
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}
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// ClientOnlyTags returns the client-only tags (the tags with the + prefix).
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// The returned map may be internal storage of the IrcMessage object and
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// should not be modified.
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func (msg *IrcMessage) ClientOnlyTags() map[string]string {
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return msg.clientOnlyTags
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}
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// ParseLine creates and returns a message from the given IRC line.
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func ParseLine(line string) (ircmsg IrcMessage, err error) {
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return parseLine(line, 0, 0)
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}
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// ParseLineStrict creates and returns an IrcMessage from the given IRC line,
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// taking the maximum length into account and truncating the message as appropriate.
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// If fromClient is true, it enforces the client limit on tag data length (4094 bytes),
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// allowing the server to return ERR_INPUTTOOLONG as appropriate. If truncateLen is
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// nonzero, it is the length at which the non-tag portion of the message is truncated.
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func ParseLineStrict(line string, fromClient bool, truncateLen int) (ircmsg IrcMessage, err error) {
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maxTagDataLength := MaxlenTagData
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if fromClient {
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maxTagDataLength = MaxlenClientTagData
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}
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return parseLine(line, maxTagDataLength, truncateLen)
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}
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// slice off any amount of ' ' from the front of the string
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func trimInitialSpaces(str string) string {
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var i int
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for i = 0; i < len(str) && str[i] == ' '; i += 1 {
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}
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return str[i:]
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}
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func parseLine(line string, maxTagDataLength int, truncateLen int) (ircmsg IrcMessage, err error) {
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if strings.IndexByte(line, '\x00') != -1 {
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err = ErrorLineContainsBadChar
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return
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}
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// trim to the first appearance of either '\r' or '\n':
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lineEnd := strings.IndexByte(line, '\r')
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newlineIndex := strings.IndexByte(line, '\n')
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if newlineIndex != -1 && (lineEnd == -1 || newlineIndex < lineEnd) {
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lineEnd = newlineIndex
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}
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if lineEnd != -1 {
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line = line[:lineEnd]
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}
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if len(line) < 1 {
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return ircmsg, ErrorLineIsEmpty
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}
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// tags
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if line[0] == '@' {
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tagEnd := strings.IndexByte(line, ' ')
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if tagEnd == -1 {
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return ircmsg, ErrorLineIsEmpty
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}
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tags := line[1:tagEnd]
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if 0 < maxTagDataLength && maxTagDataLength < len(tags) {
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return ircmsg, ErrorLineTooLong
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}
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err = ircmsg.parseTags(tags)
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if err != nil {
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return
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}
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// skip over the tags and the separating space
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line = line[tagEnd+1:]
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}
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// truncate if desired
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if 0 < truncateLen && truncateLen < len(line) {
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line = line[:truncateLen]
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}
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// modern: "These message parts, and parameters themselves, are separated
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// by one or more ASCII SPACE characters"
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line = trimInitialSpaces(line)
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// prefix
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if 0 < len(line) && line[0] == ':' {
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prefixEnd := strings.IndexByte(line, ' ')
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if prefixEnd == -1 {
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return ircmsg, ErrorLineIsEmpty
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}
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ircmsg.Prefix = line[1:prefixEnd]
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// skip over the prefix and the separating space
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line = line[prefixEnd+1:]
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}
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line = trimInitialSpaces(line)
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// command
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commandEnd := strings.IndexByte(line, ' ')
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paramStart := commandEnd + 1
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if commandEnd == -1 {
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commandEnd = len(line)
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paramStart = len(line)
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}
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// normalize command to uppercase:
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ircmsg.Command = strings.ToUpper(line[:commandEnd])
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if len(ircmsg.Command) == 0 {
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return ircmsg, ErrorLineIsEmpty
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}
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line = line[paramStart:]
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for {
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line = trimInitialSpaces(line)
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if len(line) == 0 {
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break
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}
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// handle trailing
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if line[0] == ':' {
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ircmsg.Params = append(ircmsg.Params, line[1:])
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break
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}
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paramEnd := strings.IndexByte(line, ' ')
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if paramEnd == -1 {
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ircmsg.Params = append(ircmsg.Params, line)
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break
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}
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ircmsg.Params = append(ircmsg.Params, line[:paramEnd])
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line = line[paramEnd+1:]
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}
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return ircmsg, nil
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}
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// helper to parse tags
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func (ircmsg *IrcMessage) parseTags(tags string) (err error) {
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for 0 < len(tags) {
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tagEnd := strings.IndexByte(tags, ';')
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endPos := tagEnd
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nextPos := tagEnd + 1
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if tagEnd == -1 {
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endPos = len(tags)
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nextPos = len(tags)
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}
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tagPair := tags[:endPos]
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equalsIndex := strings.IndexByte(tagPair, '=')
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var tagName, tagValue string
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if equalsIndex == -1 {
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// tag with no value
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tagName = tagPair
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} else {
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tagName, tagValue = tagPair[:equalsIndex], tagPair[equalsIndex+1:]
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}
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ircmsg.SetTag(tagName, UnescapeTagValue(tagValue))
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// skip over the tag just processed, plus the delimiting ; if any
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tags = tags[nextPos:]
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}
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return nil
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}
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// MakeMessage provides a simple way to create a new IrcMessage.
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func MakeMessage(tags map[string]string, prefix string, command string, params ...string) (ircmsg IrcMessage) {
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ircmsg.Prefix = prefix
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ircmsg.Command = command
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ircmsg.Params = params
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ircmsg.UpdateTags(tags)
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return ircmsg
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}
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// Line returns a sendable line created from an IrcMessage.
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func (ircmsg *IrcMessage) Line() (result string, err error) {
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bytes, err := ircmsg.line(0, 0, 0, 0)
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if err == nil {
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result = string(bytes)
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}
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return
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}
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// LineBytes returns a sendable line created from an IrcMessage.
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func (ircmsg *IrcMessage) LineBytes() (result []byte, err error) {
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result, err = ircmsg.line(0, 0, 0, 0)
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return
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}
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// LineBytesStrict returns a sendable line, as a []byte, created from an IrcMessage.
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// fromClient controls whether the server-side or client-side tag length limit
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// is enforced. If truncateLen is nonzero, it is the length at which the
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// non-tag portion of the message is truncated.
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func (ircmsg *IrcMessage) LineBytesStrict(fromClient bool, truncateLen int) ([]byte, error) {
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var tagLimit, clientOnlyTagDataLimit, serverAddedTagDataLimit int
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if fromClient {
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// enforce client max tags:
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// <client_max> (4096) :: '@' <tag_data 4094> ' '
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tagLimit = MaxlenTagsFromClient
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} else {
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// on the server side, enforce separate client-only and server-added tag budgets:
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// "Servers MUST NOT add tag data exceeding 4094 bytes to messages."
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// <combined_max> (8191) :: '@' <tag_data 4094> ';' <tag_data 4094> ' '
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clientOnlyTagDataLimit = MaxlenClientTagData
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serverAddedTagDataLimit = MaxlenServerTagData
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}
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return ircmsg.line(tagLimit, clientOnlyTagDataLimit, serverAddedTagDataLimit, truncateLen)
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}
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func paramRequiresTrailing(param string) bool {
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return len(param) == 0 || strings.IndexByte(param, ' ') != -1 || param[0] == ':'
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}
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// line returns a sendable line created from an IrcMessage.
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func (ircmsg *IrcMessage) line(tagLimit, clientOnlyTagDataLimit, serverAddedTagDataLimit, truncateLen int) ([]byte, error) {
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if len(ircmsg.Command) < 1 {
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return nil, ErrorCommandMissing
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}
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var buf bytes.Buffer
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// write the tags, computing the budgets for client-only tags and regular tags
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var lenRegularTags, lenClientOnlyTags, lenTags int
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if 0 < len(ircmsg.tags) || 0 < len(ircmsg.clientOnlyTags) {
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buf.WriteByte('@')
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firstTag := true
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writeTags := func(tags map[string]string) {
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for tag, val := range tags {
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if !firstTag {
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buf.WriteByte(';') // delimiter
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}
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buf.WriteString(tag)
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if val != "" {
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buf.WriteByte('=')
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buf.WriteString(EscapeTagValue(val))
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}
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firstTag = false
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}
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}
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writeTags(ircmsg.tags)
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lenRegularTags = buf.Len() - 1 // '@' is not counted
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writeTags(ircmsg.clientOnlyTags)
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lenClientOnlyTags = (buf.Len() - 1) - lenRegularTags // '@' is not counted
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if lenRegularTags != 0 {
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// semicolon between regular and client-only tags is not counted
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lenClientOnlyTags -= 1
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}
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buf.WriteByte(' ')
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}
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lenTags = buf.Len()
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if 0 < tagLimit && tagLimit < buf.Len() {
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return nil, ErrorLineTooLong
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}
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if (0 < clientOnlyTagDataLimit && clientOnlyTagDataLimit < lenClientOnlyTags) || (0 < serverAddedTagDataLimit && serverAddedTagDataLimit < lenRegularTags) {
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return nil, ErrorLineTooLong
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}
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if len(ircmsg.Prefix) > 0 {
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buf.WriteByte(':')
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buf.WriteString(ircmsg.Prefix)
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buf.WriteByte(' ')
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}
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buf.WriteString(ircmsg.Command)
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for i, param := range ircmsg.Params {
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buf.WriteByte(' ')
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requiresTrailing := paramRequiresTrailing(param)
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lastParam := i == len(ircmsg.Params)-1
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if (requiresTrailing || ircmsg.forceTrailing) && lastParam {
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buf.WriteByte(':')
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} else if requiresTrailing && !lastParam {
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return nil, ErrorBadParam
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}
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buf.WriteString(param)
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}
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// truncate if desired
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// -2 for \r\n
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restLen := buf.Len() - lenTags
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if 0 < truncateLen && (truncateLen-2) < restLen {
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buf.Truncate(lenTags + (truncateLen - 2))
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}
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buf.WriteString("\r\n")
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result := buf.Bytes()
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if bytes.IndexByte(result, '\x00') != -1 {
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return nil, ErrorLineContainsBadChar
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}
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return result, nil
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}
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