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@@ -8,12 +8,14 @@
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package version
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import (
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+ "bytes"
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+ "encoding/hex"
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+ "errors"
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+ "io"
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"os"
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"path"
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"path/filepath"
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"strings"
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-
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- "rsc.io/goversion/version"
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)
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// CmdName returns either the base name of the current binary
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@@ -30,13 +32,13 @@ func CmdName() string {
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fallbackName := filepath.Base(strings.TrimSuffix(strings.ToLower(e), ".exe"))
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var ret string
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- v, err := version.ReadExe(e)
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+ info, err := findModuleInfo(e)
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if err != nil {
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return fallbackName
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}
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// v is like:
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// "path\ttailscale.com/cmd/tailscale\nmod\ttailscale.com\t(devel)\t\ndep\tgithub.com/apenwarr/fixconsole\tv0.0.0-20191012055117-5a9f6489cc29\th1:muXWUcay7DDy1/hEQWrYlBy+g0EuwT70sBHg65SeUc4=\ndep\tgithub....
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- for _, line := range strings.Split(v.ModuleInfo, "\n") {
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+ for _, line := range strings.Split(info, "\n") {
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if strings.HasPrefix(line, "path\t") {
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goPkg := strings.TrimPrefix(line, "path\t") // like "tailscale.com/cmd/tailscale"
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ret = path.Base(goPkg) // goPkg is always forward slashes; use path, not filepath
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@@ -48,3 +50,84 @@ func CmdName() string {
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}
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return ret
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}
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+
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+// findModuleInfo returns the Go module info from the executable file.
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+func findModuleInfo(file string) (s string, err error) {
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+ f, err := os.Open(file)
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+ if err != nil {
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+ return "", err
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+ }
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+ defer f.Close()
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+ // Scan through f until we find infoStart.
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+ buf := make([]byte, 65536)
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+ start, err := findOffset(f, buf, infoStart)
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+ if err != nil {
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+ return "", err
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+ }
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+ start += int64(len(infoStart))
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+ // Seek to the end of infoStart and scan for infoEnd.
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+ _, err = f.Seek(start, io.SeekStart)
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+ if err != nil {
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+ return "", err
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+ }
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+ end, err := findOffset(f, buf, infoEnd)
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+ if err != nil {
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+ return "", err
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+ }
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+ length := end - start
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+ // As of Aug 2021, tailscaled's mod info was about 2k.
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+ if length > int64(len(buf)) {
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+ return "", errors.New("mod info too large")
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+ }
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+ // We have located modinfo. Read it into buf.
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+ buf = buf[:length]
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+ _, err = f.Seek(start, io.SeekStart)
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+ if err != nil {
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+ return "", err
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+ }
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+ _, err = io.ReadFull(f, buf)
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+ if err != nil {
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+ return "", err
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+ }
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+ return string(buf), nil
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+}
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+
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+// findOffset finds the absolute offset of needle in f,
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+// starting at f's current read position,
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+// using temporary buffer buf.
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+func findOffset(f *os.File, buf, needle []byte) (int64, error) {
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+ for {
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+ // Fill buf and look within it.
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+ n, err := f.Read(buf)
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+ if err != nil {
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+ return -1, err
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+ }
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+ i := bytes.Index(buf[:n], needle)
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+ if i < 0 {
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+ // Not found. Rewind a little bit in case we happened to end halfway through needle.
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+ rewind, err := f.Seek(int64(-len(needle)), io.SeekCurrent)
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+ if err != nil {
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+ return -1, err
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+ }
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+ // If we're at EOF and rewound exactly len(needle) bytes, return io.EOF.
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+ _, err = f.ReadAt(buf[:1], rewind+int64(len(needle)))
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+ if err == io.EOF {
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+ return -1, err
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+ }
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+ continue
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+ }
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+ // Found! Figure out exactly where.
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+ cur, err := f.Seek(0, io.SeekCurrent)
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+ if err != nil {
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+ return -1, err
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+ }
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+ return cur - int64(n) + int64(i), nil
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+ }
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+}
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+
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+// These constants are taken from rsc.io/goversion.
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+
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+var (
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+ infoStart, _ = hex.DecodeString("3077af0c9274080241e1c107e6d618e6")
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+ infoEnd, _ = hex.DecodeString("f932433186182072008242104116d8f2")
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+)
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Josh Bleecher Snyder