bundle swiss cross image file to avoid file system dependency
This commit is contained in:
Michael Stapelberg
190
goembed.go
Normal file
190
goembed.go
Normal file
@@ -0,0 +1,190 @@
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// copied from https://github.com/dsymonds/goembed/ with pull requests applied
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// +build ignore
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// goembed generates a Go source file from an input file.
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package main
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import (
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"bufio"
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"bytes"
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"compress/gzip"
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"flag"
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"fmt"
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"io"
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"log"
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"os"
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"text/template"
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"unicode/utf8"
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)
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var (
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packageFlag = flag.String("package", "", "Go package name")
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varFlag = flag.String("var", "", "Go var name")
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gzipFlag = flag.Bool("gzip", false, "Whether to gzip contents")
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)
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func main() {
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flag.Parse()
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fmt.Printf("package %s\n\n", *packageFlag)
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if *gzipFlag {
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err := gzipPrologue.Execute(os.Stdout, map[string]interface{}{
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"Args": flag.Args(),
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"VarName": *varFlag,
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})
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if err != nil {
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log.Fatal(err)
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}
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}
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if flag.NArg() > 0 {
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fmt.Println("// Table of contents")
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fmt.Printf("var %v = map[string][]byte{\n", *varFlag)
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for i, filename := range flag.Args() {
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fmt.Printf("\t%#v: %s_%d,\n", filename, *varFlag, i)
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}
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fmt.Println("}")
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// Using a separate variable for each []byte, instead of
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// combining them into a single map literal, enables a storage
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// optimization: the compiler places the data directly in the
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// program's noptrdata section instead of the heap.
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for i, filename := range flag.Args() {
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if err := oneVar(fmt.Sprintf("%s_%d", *varFlag, i), filename); err != nil {
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log.Fatal(err)
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}
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}
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} else {
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if err := oneVarReader(*varFlag, os.Stdin); err != nil {
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log.Fatal(err)
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}
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}
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}
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func oneVar(varName, filename string) error {
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f, err := os.Open(filename)
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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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return oneVarReader(varName, f)
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}
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func oneVarReader(varName string, r io.Reader) error {
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// Generate []byte(<big string constant>) instead of []byte{<list of byte values>}.
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// The latter causes a memory explosion in the compiler (60 MB of input chews over 9 GB RAM).
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// Doing a string conversion avoids some of that, but incurs a slight startup cost.
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if !*gzipFlag {
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fmt.Printf(`var %s = []byte("`, varName)
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} else {
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var buf bytes.Buffer
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gzw, _ := gzip.NewWriterLevel(&buf, gzip.BestCompression)
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if _, err := io.Copy(gzw, r); err != nil {
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return err
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}
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if err := gzw.Close(); err != nil {
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return err
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}
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fmt.Printf("var %s []byte // set in init\n\n", varName)
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fmt.Printf(`var %s_gzip = []byte("`, varName)
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r = &buf
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}
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bufw := bufio.NewWriter(os.Stdout)
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if _, err := io.Copy(&writer{w: bufw}, r); err != nil {
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return err
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}
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if err := bufw.Flush(); err != nil {
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return err
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}
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fmt.Println(`")`)
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return nil
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}
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type writer struct {
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w io.Writer
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}
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func (w *writer) Write(data []byte) (n int, err error) {
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n = len(data)
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for err == nil && len(data) > 0 {
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// https://golang.org/ref/spec#String_literals: "Within the quotes, any
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// character may appear except newline and unescaped double quote. The
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// text between the quotes forms the value of the literal, with backslash
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// escapes interpreted as they are in rune literals […]."
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switch b := data[0]; b {
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case '\\':
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_, err = w.w.Write([]byte(`\\`))
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case '"':
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_, err = w.w.Write([]byte(`\"`))
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case '\n':
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_, err = w.w.Write([]byte(`\n`))
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case '\x00':
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// https://golang.org/ref/spec#Source_code_representation: "Implementation
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// restriction: For compatibility with other tools, a compiler may
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// disallow the NUL character (U+0000) in the source text."
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_, err = w.w.Write([]byte(`\x00`))
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default:
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// https://golang.org/ref/spec#Source_code_representation: "Implementation
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// restriction: […] A byte order mark may be disallowed anywhere else in
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// the source."
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const byteOrderMark = '\uFEFF'
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if r, size := utf8.DecodeRune(data); r != utf8.RuneError && r != byteOrderMark {
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_, err = w.w.Write(data[:size])
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data = data[size:]
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continue
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}
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_, err = fmt.Fprintf(w.w, `\x%02x`, b)
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}
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data = data[1:]
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}
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return n - len(data), err
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}
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var gzipPrologue = template.Must(template.New("").Parse(`
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import (
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"bytes"
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"compress/gzip"
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"io/ioutil"
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)
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func init() {
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var (
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r *gzip.Reader
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err error
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)
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{{ if gt (len .Args) 0 }}
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{{ range $idx, $var := .Args }}
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{{ $n := printf "%s_%d" $.VarName $idx }}
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r, err = gzip.NewReader(bytes.NewReader({{ $n }}_gzip))
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if err != nil {
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panic(err)
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}
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{{ $n }}, err = ioutil.ReadAll(r)
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r.Close()
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if err != nil {
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panic(err)
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}
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{{ end }}
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{{ else }}
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r, err = gzip.NewReader(bytes.NewReader({{ .VarName }}_gzip))
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if err != nil {
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panic(err)
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}
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{{ .VarName }}, err = ioutil.ReadAll(r)
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r.Close()
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if err != nil {
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panic(err)
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}
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{{ end }}
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}
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`))
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