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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// This file implements printing of syntax tree structures.
package syntax
import (
"fmt"
"io"
"reflect"
"unicode"
"unicode/utf8"
)
// Fdump dumps the structure of the syntax tree rooted at n to w.
// It is intended for debugging purposes; no specific output format
// is guaranteed.
func Fdump(w io.Writer, n Node) (err error) {
p := dumper{
output: w,
ptrmap: make(map[Node]int),
last: '\n', // force printing of line number on first line
}
defer func() {
if e := recover(); e != nil {
err = e.(writeError).err // re-panics if it's not a writeError
}
}()
if n == nil {
p.printf("nil\n")
return
}
p.dump(reflect.ValueOf(n), n)
p.printf("\n")
return
}
type dumper struct {
output io.Writer
ptrmap map[Node]int // node -> dump line number
indent int // current indentation level
last byte // last byte processed by Write
line int // current line number
}
var indentBytes = []byte(". ")
func (p *dumper) Write(data []byte) (n int, err error) {
var m int
for i, b := range data {
// invariant: data[0:n] has been written
if b == '\n' {
m, err = p.output.Write(data[n : i+1])
n += m
if err != nil {
return
}
} else if p.last == '\n' {
p.line++
_, err = fmt.Fprintf(p.output, "%6d ", p.line)
if err != nil {
return
}
for j := p.indent; j > 0; j-- {
_, err = p.output.Write(indentBytes)
if err != nil {
return
}
}
}
p.last = b
}
if len(data) > n {
m, err = p.output.Write(data[n:])
n += m
}
return
}
// writeError wraps locally caught write errors so we can distinguish
// them from genuine panics which we don't want to return as errors.
type writeError struct {
err error
}
// printf is a convenience wrapper that takes care of print errors.
func (p *dumper) printf(format string, args ...interface{}) {
if _, err := fmt.Fprintf(p, format, args...); err != nil {
panic(writeError{err})
}
}
// dump prints the contents of x.
// If x is the reflect.Value of a struct s, where &s
// implements Node, then &s should be passed for n -
// this permits printing of the unexported span and
// comments fields of the embedded isNode field by
// calling the Span() and Comment() instead of using
// reflection.
func (p *dumper) dump(x reflect.Value, n Node) {
switch x.Kind() {
case reflect.Interface:
if x.IsNil() {
p.printf("nil")
return
}
p.dump(x.Elem(), nil)
case reflect.Ptr:
if x.IsNil() {
p.printf("nil")
return
}
// special cases for identifiers w/o attached comments (common case)
if x, ok := x.Interface().(*Name); ok {
p.printf("%s @ %v", x.Value, x.Pos())
return
}
p.printf("*")
// Fields may share type expressions, and declarations
// may share the same group - use ptrmap to keep track
// of nodes that have been printed already.
if ptr, ok := x.Interface().(Node); ok {
if line, exists := p.ptrmap[ptr]; exists {
p.printf("(Node @ %d)", line)
return
}
p.ptrmap[ptr] = p.line
n = ptr
}
p.dump(x.Elem(), n)
case reflect.Slice:
if x.IsNil() {
p.printf("nil")
return
}
p.printf("%s (%d entries) {", x.Type(), x.Len())
if x.Len() > 0 {
p.indent++
p.printf("\n")
for i, n := 0, x.Len(); i < n; i++ {
p.printf("%d: ", i)
p.dump(x.Index(i), nil)
p.printf("\n")
}
p.indent--
}
p.printf("}")
case reflect.Struct:
typ := x.Type()
// if span, ok := x.Interface().(lexical.Span); ok {
// p.printf("%s", &span)
// return
// }
p.printf("%s {", typ)
p.indent++
first := true
if n != nil {
p.printf("\n")
first = false
// p.printf("Span: %s\n", n.Span())
// if c := *n.Comments(); c != nil {
// p.printf("Comments: ")
// p.dump(reflect.ValueOf(c), nil) // a Comment is not a Node
// p.printf("\n")
// }
}
for i, n := 0, typ.NumField(); i < n; i++ {
// Exclude non-exported fields because their
// values cannot be accessed via reflection.
if name := typ.Field(i).Name; isExported(name) {
if first {
p.printf("\n")
first = false
}
p.printf("%s: ", name)
p.dump(x.Field(i), nil)
p.printf("\n")
}
}
p.indent--
p.printf("}")
default:
switch x := x.Interface().(type) {
case string:
// print strings in quotes
p.printf("%q", x)
default:
p.printf("%v", x)
}
}
}
func isExported(name string) bool {
ch, _ := utf8.DecodeRuneInString(name)
return unicode.IsUpper(ch)
}
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