mirror of
https://github.com/octoleo/restic.git
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370 lines
9.7 KiB
Go
370 lines
9.7 KiB
Go
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// Copyright 2015 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package gen
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import (
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"bytes"
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"encoding/gob"
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"fmt"
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"hash"
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"hash/fnv"
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"io"
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"log"
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"os"
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"reflect"
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"strings"
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"unicode"
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"unicode/utf8"
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)
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// This file contains utilities for generating code.
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// TODO: other write methods like:
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// - slices, maps, types, etc.
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// CodeWriter is a utility for writing structured code. It computes the content
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// hash and size of written content. It ensures there are newlines between
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// written code blocks.
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type CodeWriter struct {
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buf bytes.Buffer
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Size int
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Hash hash.Hash32 // content hash
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gob *gob.Encoder
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// For comments we skip the usual one-line separator if they are followed by
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// a code block.
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skipSep bool
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}
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func (w *CodeWriter) Write(p []byte) (n int, err error) {
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return w.buf.Write(p)
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}
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// NewCodeWriter returns a new CodeWriter.
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func NewCodeWriter() *CodeWriter {
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h := fnv.New32()
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return &CodeWriter{Hash: h, gob: gob.NewEncoder(h)}
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}
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// WriteGoFile appends the buffer with the total size of all created structures
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// and writes it as a Go file to the the given file with the given package name.
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func (w *CodeWriter) WriteGoFile(filename, pkg string) {
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f, err := os.Create(filename)
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if err != nil {
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log.Fatalf("Could not create file %s: %v", filename, err)
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}
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defer f.Close()
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if _, err = w.WriteGo(f, pkg, ""); err != nil {
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log.Fatalf("Error writing file %s: %v", filename, err)
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}
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}
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// WriteVersionedGoFile appends the buffer with the total size of all created
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// structures and writes it as a Go file to the the given file with the given
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// package name and build tags for the current Unicode version,
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func (w *CodeWriter) WriteVersionedGoFile(filename, pkg string) {
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tags := buildTags()
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if tags != "" {
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filename = insertVersion(filename, UnicodeVersion())
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}
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f, err := os.Create(filename)
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if err != nil {
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log.Fatalf("Could not create file %s: %v", filename, err)
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}
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defer f.Close()
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if _, err = w.WriteGo(f, pkg, tags); err != nil {
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log.Fatalf("Error writing file %s: %v", filename, err)
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}
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}
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// WriteGo appends the buffer with the total size of all created structures and
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// writes it as a Go file to the the given writer with the given package name.
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func (w *CodeWriter) WriteGo(out io.Writer, pkg, tags string) (n int, err error) {
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sz := w.Size
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w.WriteComment("Total table size %d bytes (%dKiB); checksum: %X\n", sz, sz/1024, w.Hash.Sum32())
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defer w.buf.Reset()
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return WriteGo(out, pkg, tags, w.buf.Bytes())
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}
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func (w *CodeWriter) printf(f string, x ...interface{}) {
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fmt.Fprintf(w, f, x...)
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}
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func (w *CodeWriter) insertSep() {
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if w.skipSep {
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w.skipSep = false
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return
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}
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// Use at least two newlines to ensure a blank space between the previous
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// block. WriteGoFile will remove extraneous newlines.
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w.printf("\n\n")
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}
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// WriteComment writes a comment block. All line starts are prefixed with "//".
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// Initial empty lines are gobbled. The indentation for the first line is
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// stripped from consecutive lines.
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func (w *CodeWriter) WriteComment(comment string, args ...interface{}) {
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s := fmt.Sprintf(comment, args...)
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s = strings.Trim(s, "\n")
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// Use at least two newlines to ensure a blank space between the previous
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// block. WriteGoFile will remove extraneous newlines.
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w.printf("\n\n// ")
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w.skipSep = true
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// strip first indent level.
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sep := "\n"
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for ; len(s) > 0 && (s[0] == '\t' || s[0] == ' '); s = s[1:] {
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sep += s[:1]
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}
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strings.NewReplacer(sep, "\n// ", "\n", "\n// ").WriteString(w, s)
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w.printf("\n")
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}
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func (w *CodeWriter) writeSizeInfo(size int) {
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w.printf("// Size: %d bytes\n", size)
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}
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// WriteConst writes a constant of the given name and value.
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func (w *CodeWriter) WriteConst(name string, x interface{}) {
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w.insertSep()
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v := reflect.ValueOf(x)
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switch v.Type().Kind() {
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case reflect.String:
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w.printf("const %s %s = ", name, typeName(x))
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w.WriteString(v.String())
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w.printf("\n")
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default:
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w.printf("const %s = %#v\n", name, x)
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}
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}
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// WriteVar writes a variable of the given name and value.
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func (w *CodeWriter) WriteVar(name string, x interface{}) {
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w.insertSep()
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v := reflect.ValueOf(x)
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oldSize := w.Size
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sz := int(v.Type().Size())
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w.Size += sz
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switch v.Type().Kind() {
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case reflect.String:
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w.printf("var %s %s = ", name, typeName(x))
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w.WriteString(v.String())
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case reflect.Struct:
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w.gob.Encode(x)
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fallthrough
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case reflect.Slice, reflect.Array:
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w.printf("var %s = ", name)
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w.writeValue(v)
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w.writeSizeInfo(w.Size - oldSize)
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default:
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w.printf("var %s %s = ", name, typeName(x))
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w.gob.Encode(x)
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w.writeValue(v)
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w.writeSizeInfo(w.Size - oldSize)
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}
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w.printf("\n")
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}
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func (w *CodeWriter) writeValue(v reflect.Value) {
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x := v.Interface()
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switch v.Kind() {
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case reflect.String:
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w.WriteString(v.String())
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case reflect.Array:
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// Don't double count: callers of WriteArray count on the size being
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// added, so we need to discount it here.
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w.Size -= int(v.Type().Size())
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w.writeSlice(x, true)
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case reflect.Slice:
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w.writeSlice(x, false)
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case reflect.Struct:
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w.printf("%s{\n", typeName(v.Interface()))
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t := v.Type()
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for i := 0; i < v.NumField(); i++ {
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w.printf("%s: ", t.Field(i).Name)
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w.writeValue(v.Field(i))
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w.printf(",\n")
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}
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w.printf("}")
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default:
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w.printf("%#v", x)
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}
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}
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// WriteString writes a string literal.
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func (w *CodeWriter) WriteString(s string) {
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s = strings.Replace(s, `\`, `\\`, -1)
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io.WriteString(w.Hash, s) // content hash
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w.Size += len(s)
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const maxInline = 40
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if len(s) <= maxInline {
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w.printf("%q", s)
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return
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}
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// We will render the string as a multi-line string.
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const maxWidth = 80 - 4 - len(`"`) - len(`" +`)
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// When starting on its own line, go fmt indents line 2+ an extra level.
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n, max := maxWidth, maxWidth-4
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// As per https://golang.org/issue/18078, the compiler has trouble
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// compiling the concatenation of many strings, s0 + s1 + s2 + ... + sN,
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// for large N. We insert redundant, explicit parentheses to work around
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// that, lowering the N at any given step: (s0 + s1 + ... + s63) + (s64 +
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// ... + s127) + etc + (etc + ... + sN).
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explicitParens, extraComment := len(s) > 128*1024, ""
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if explicitParens {
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w.printf(`(`)
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extraComment = "; the redundant, explicit parens are for https://golang.org/issue/18078"
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}
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// Print "" +\n, if a string does not start on its own line.
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b := w.buf.Bytes()
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if p := len(bytes.TrimRight(b, " \t")); p > 0 && b[p-1] != '\n' {
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w.printf("\"\" + // Size: %d bytes%s\n", len(s), extraComment)
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n, max = maxWidth, maxWidth
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}
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w.printf(`"`)
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for sz, p, nLines := 0, 0, 0; p < len(s); {
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var r rune
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r, sz = utf8.DecodeRuneInString(s[p:])
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out := s[p : p+sz]
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chars := 1
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if !unicode.IsPrint(r) || r == utf8.RuneError || r == '"' {
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switch sz {
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case 1:
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out = fmt.Sprintf("\\x%02x", s[p])
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case 2, 3:
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out = fmt.Sprintf("\\u%04x", r)
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case 4:
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out = fmt.Sprintf("\\U%08x", r)
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}
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chars = len(out)
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}
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if n -= chars; n < 0 {
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nLines++
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if explicitParens && nLines&63 == 63 {
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w.printf("\") + (\"")
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}
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w.printf("\" +\n\"")
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n = max - len(out)
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}
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w.printf("%s", out)
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p += sz
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}
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w.printf(`"`)
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if explicitParens {
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w.printf(`)`)
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}
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}
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// WriteSlice writes a slice value.
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func (w *CodeWriter) WriteSlice(x interface{}) {
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w.writeSlice(x, false)
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}
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// WriteArray writes an array value.
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func (w *CodeWriter) WriteArray(x interface{}) {
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w.writeSlice(x, true)
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}
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func (w *CodeWriter) writeSlice(x interface{}, isArray bool) {
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v := reflect.ValueOf(x)
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w.gob.Encode(v.Len())
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w.Size += v.Len() * int(v.Type().Elem().Size())
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name := typeName(x)
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if isArray {
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name = fmt.Sprintf("[%d]%s", v.Len(), name[strings.Index(name, "]")+1:])
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}
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if isArray {
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w.printf("%s{\n", name)
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} else {
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w.printf("%s{ // %d elements\n", name, v.Len())
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}
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switch kind := v.Type().Elem().Kind(); kind {
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case reflect.String:
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for _, s := range x.([]string) {
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w.WriteString(s)
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w.printf(",\n")
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}
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case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
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reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
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// nLine and nBlock are the number of elements per line and block.
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nLine, nBlock, format := 8, 64, "%d,"
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switch kind {
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case reflect.Uint8:
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format = "%#02x,"
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case reflect.Uint16:
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format = "%#04x,"
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case reflect.Uint32:
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nLine, nBlock, format = 4, 32, "%#08x,"
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case reflect.Uint, reflect.Uint64:
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nLine, nBlock, format = 4, 32, "%#016x,"
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case reflect.Int8:
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nLine = 16
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}
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n := nLine
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for i := 0; i < v.Len(); i++ {
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if i%nBlock == 0 && v.Len() > nBlock {
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w.printf("// Entry %X - %X\n", i, i+nBlock-1)
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}
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x := v.Index(i).Interface()
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w.gob.Encode(x)
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w.printf(format, x)
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if n--; n == 0 {
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n = nLine
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w.printf("\n")
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}
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}
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w.printf("\n")
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case reflect.Struct:
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zero := reflect.Zero(v.Type().Elem()).Interface()
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for i := 0; i < v.Len(); i++ {
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x := v.Index(i).Interface()
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w.gob.EncodeValue(v)
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if !reflect.DeepEqual(zero, x) {
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line := fmt.Sprintf("%#v,\n", x)
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line = line[strings.IndexByte(line, '{'):]
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w.printf("%d: ", i)
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w.printf(line)
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}
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}
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case reflect.Array:
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for i := 0; i < v.Len(); i++ {
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w.printf("%d: %#v,\n", i, v.Index(i).Interface())
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}
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default:
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panic("gen: slice elem type not supported")
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}
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w.printf("}")
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}
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// WriteType writes a definition of the type of the given value and returns the
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// type name.
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func (w *CodeWriter) WriteType(x interface{}) string {
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t := reflect.TypeOf(x)
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w.printf("type %s struct {\n", t.Name())
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for i := 0; i < t.NumField(); i++ {
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w.printf("\t%s %s\n", t.Field(i).Name, t.Field(i).Type)
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}
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w.printf("}\n")
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return t.Name()
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}
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// typeName returns the name of the go type of x.
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func typeName(x interface{}) string {
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t := reflect.ValueOf(x).Type()
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return strings.Replace(fmt.Sprint(t), "main.", "", 1)
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}
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