78 lines
1.7 KiB
Go
78 lines
1.7 KiB
Go
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package metainfo
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import (
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"encoding/base32"
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"encoding/hex"
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"fmt"
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"net/url"
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"strings"
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)
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// Magnet link components.
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type Magnet struct {
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InfoHash Hash
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Trackers []string
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DisplayName string
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}
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const xtPrefix = "urn:btih:"
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func (m Magnet) String() string {
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// net.URL likes to assume //, and encodes ':' on us, so we do most of
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// this manually.
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ret := "magnet:?xt="
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ret += xtPrefix + hex.EncodeToString(m.InfoHash[:])
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if m.DisplayName != "" {
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ret += "&dn=" + url.QueryEscape(m.DisplayName)
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}
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for _, tr := range m.Trackers {
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ret += "&tr=" + url.QueryEscape(tr)
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}
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return ret
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}
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// ParseMagnetURI parses Magnet-formatted URIs into a Magnet instance
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func ParseMagnetURI(uri string) (m Magnet, err error) {
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u, err := url.Parse(uri)
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if err != nil {
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err = fmt.Errorf("error parsing uri: %s", err)
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return
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}
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if u.Scheme != "magnet" {
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err = fmt.Errorf("unexpected scheme: %q", u.Scheme)
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return
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}
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xt := u.Query().Get("xt")
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if !strings.HasPrefix(xt, xtPrefix) {
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err = fmt.Errorf("bad xt parameter")
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return
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}
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infoHash := xt[len(xtPrefix):]
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// BTIH hash can be in HEX or BASE32 encoding
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// will assign appropriate func judging from symbol length
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var decode func(dst, src []byte) (int, error)
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switch len(infoHash) {
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case 40:
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decode = hex.Decode
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case 32:
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decode = base32.StdEncoding.Decode
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}
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if decode == nil {
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err = fmt.Errorf("unhandled xt parameter encoding: encoded length %d", len(infoHash))
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return
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}
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n, err := decode(m.InfoHash[:], []byte(infoHash))
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if err != nil {
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err = fmt.Errorf("error decoding xt: %s", err)
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return
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}
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if n != 20 {
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panic(n)
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}
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m.DisplayName = u.Query().Get("dn")
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m.Trackers = u.Query()["tr"]
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return
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}
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