420 lines
11 KiB
Go
420 lines
11 KiB
Go
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/*
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* Copyright (c) 2013 Dave Collins <dave@davec.name>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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package spew
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import (
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"bytes"
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"fmt"
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"reflect"
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"strconv"
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"strings"
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)
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// supportedFlags is a list of all the character flags supported by fmt package.
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const supportedFlags = "0-+# "
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// formatState implements the fmt.Formatter interface and contains information
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// about the state of a formatting operation. The NewFormatter function can
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// be used to get a new Formatter which can be used directly as arguments
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// in standard fmt package printing calls.
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type formatState struct {
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value interface{}
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fs fmt.State
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depth int
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pointers map[uintptr]int
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ignoreNextType bool
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cs *ConfigState
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}
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// buildDefaultFormat recreates the original format string without precision
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// and width information to pass in to fmt.Sprintf in the case of an
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// unrecognized type. Unless new types are added to the language, this
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// function won't ever be called.
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func (f *formatState) buildDefaultFormat() (format string) {
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buf := bytes.NewBuffer(percentBytes)
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for _, flag := range supportedFlags {
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if f.fs.Flag(int(flag)) {
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buf.WriteRune(flag)
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}
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}
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buf.WriteRune('v')
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format = buf.String()
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return format
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}
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// constructOrigFormat recreates the original format string including precision
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// and width information to pass along to the standard fmt package. This allows
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// automatic deferral of all format strings this package doesn't support.
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func (f *formatState) constructOrigFormat(verb rune) (format string) {
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buf := bytes.NewBuffer(percentBytes)
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for _, flag := range supportedFlags {
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if f.fs.Flag(int(flag)) {
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buf.WriteRune(flag)
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}
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}
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if width, ok := f.fs.Width(); ok {
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buf.WriteString(strconv.Itoa(width))
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}
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if precision, ok := f.fs.Precision(); ok {
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buf.Write(precisionBytes)
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buf.WriteString(strconv.Itoa(precision))
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}
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buf.WriteRune(verb)
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format = buf.String()
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return format
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}
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// unpackValue returns values inside of non-nil interfaces when possible and
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// ensures that types for values which have been unpacked from an interface
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// are displayed when the show types flag is also set.
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// This is useful for data types like structs, arrays, slices, and maps which
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// can contain varying types packed inside an interface.
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func (f *formatState) unpackValue(v reflect.Value) reflect.Value {
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if v.Kind() == reflect.Interface {
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f.ignoreNextType = false
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if !v.IsNil() {
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v = v.Elem()
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}
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}
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return v
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}
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// formatPtr handles formatting of pointers by indirecting them as necessary.
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func (f *formatState) formatPtr(v reflect.Value) {
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// Display nil if top level pointer is nil.
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showTypes := f.fs.Flag('#')
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if v.IsNil() && (!showTypes || f.ignoreNextType) {
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f.fs.Write(nilAngleBytes)
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return
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}
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// Remove pointers at or below the current depth from map used to detect
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// circular refs.
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for k, depth := range f.pointers {
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if depth >= f.depth {
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delete(f.pointers, k)
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}
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}
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// Keep list of all dereferenced pointers to possibly show later.
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pointerChain := make([]uintptr, 0)
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// Figure out how many levels of indirection there are by derferencing
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// pointers and unpacking interfaces down the chain while detecting circular
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// references.
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nilFound := false
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cycleFound := false
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indirects := 0
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ve := v
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for ve.Kind() == reflect.Ptr {
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if ve.IsNil() {
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nilFound = true
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break
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}
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indirects++
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addr := ve.Pointer()
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pointerChain = append(pointerChain, addr)
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if pd, ok := f.pointers[addr]; ok && pd < f.depth {
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cycleFound = true
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indirects--
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break
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}
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f.pointers[addr] = f.depth
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ve = ve.Elem()
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if ve.Kind() == reflect.Interface {
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if ve.IsNil() {
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nilFound = true
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break
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}
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ve = ve.Elem()
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}
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}
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// Display type or indirection level depending on flags.
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if showTypes && !f.ignoreNextType {
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f.fs.Write(openParenBytes)
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f.fs.Write(bytes.Repeat(asteriskBytes, indirects))
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f.fs.Write([]byte(ve.Type().String()))
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f.fs.Write(closeParenBytes)
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} else {
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if nilFound || cycleFound {
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indirects += strings.Count(ve.Type().String(), "*")
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}
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f.fs.Write(openAngleBytes)
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f.fs.Write([]byte(strings.Repeat("*", indirects)))
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f.fs.Write(closeAngleBytes)
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}
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// Display pointer information depending on flags.
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if f.fs.Flag('+') && (len(pointerChain) > 0) {
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f.fs.Write(openParenBytes)
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for i, addr := range pointerChain {
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if i > 0 {
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f.fs.Write(pointerChainBytes)
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}
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printHexPtr(f.fs, addr)
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}
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f.fs.Write(closeParenBytes)
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}
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// Display dereferenced value.
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switch {
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case nilFound == true:
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f.fs.Write(nilAngleBytes)
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case cycleFound == true:
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f.fs.Write(circularShortBytes)
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default:
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f.ignoreNextType = true
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f.format(ve)
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}
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}
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// format is the main workhorse for providing the Formatter interface. It
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// uses the passed reflect value to figure out what kind of object we are
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// dealing with and formats it appropriately. It is a recursive function,
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// however circular data structures are detected and handled properly.
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func (f *formatState) format(v reflect.Value) {
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// Handle invalid reflect values immediately.
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kind := v.Kind()
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if kind == reflect.Invalid {
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f.fs.Write(invalidAngleBytes)
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return
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}
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// Handle pointers specially.
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if kind == reflect.Ptr {
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f.formatPtr(v)
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return
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}
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// Print type information unless already handled elsewhere.
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if !f.ignoreNextType && f.fs.Flag('#') {
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f.fs.Write(openParenBytes)
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f.fs.Write([]byte(v.Type().String()))
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f.fs.Write(closeParenBytes)
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}
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f.ignoreNextType = false
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// Call Stringer/error interfaces if they exist and the handle methods
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// flag is enabled.
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if !f.cs.DisableMethods {
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if (kind != reflect.Invalid) && (kind != reflect.Interface) {
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if handled := handleMethods(f.cs, f.fs, v); handled {
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return
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}
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}
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}
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switch kind {
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case reflect.Invalid:
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// Do nothing. We should never get here since invalid has already
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// been handled above.
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case reflect.Bool:
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printBool(f.fs, v.Bool())
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case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int:
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printInt(f.fs, v.Int(), 10)
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case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint:
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printUint(f.fs, v.Uint(), 10)
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case reflect.Float32:
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printFloat(f.fs, v.Float(), 32)
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case reflect.Float64:
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printFloat(f.fs, v.Float(), 64)
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case reflect.Complex64:
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printComplex(f.fs, v.Complex(), 32)
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case reflect.Complex128:
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printComplex(f.fs, v.Complex(), 64)
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case reflect.Slice:
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if v.IsNil() {
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f.fs.Write(nilAngleBytes)
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break
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}
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fallthrough
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case reflect.Array:
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f.fs.Write(openBracketBytes)
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f.depth++
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if (f.cs.MaxDepth != 0) && (f.depth > f.cs.MaxDepth) {
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f.fs.Write(maxShortBytes)
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} else {
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numEntries := v.Len()
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for i := 0; i < numEntries; i++ {
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if i > 0 {
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f.fs.Write(spaceBytes)
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}
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f.ignoreNextType = true
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f.format(f.unpackValue(v.Index(i)))
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}
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}
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f.depth--
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f.fs.Write(closeBracketBytes)
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case reflect.String:
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f.fs.Write([]byte(v.String()))
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case reflect.Interface:
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// The only time we should get here is for nil interfaces due to
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// unpackValue calls.
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if v.IsNil() {
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f.fs.Write(nilAngleBytes)
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}
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case reflect.Ptr:
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// Do nothing. We should never get here since pointers have already
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// been handled above.
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case reflect.Map:
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// nil maps should be indicated as different than empty maps
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if v.IsNil() {
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f.fs.Write(nilAngleBytes)
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break
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}
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f.fs.Write(openMapBytes)
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f.depth++
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if (f.cs.MaxDepth != 0) && (f.depth > f.cs.MaxDepth) {
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f.fs.Write(maxShortBytes)
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} else {
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keys := v.MapKeys()
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if f.cs.SortKeys {
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sortValues(keys, f.cs)
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}
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for i, key := range keys {
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if i > 0 {
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f.fs.Write(spaceBytes)
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}
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f.ignoreNextType = true
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f.format(f.unpackValue(key))
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f.fs.Write(colonBytes)
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f.ignoreNextType = true
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f.format(f.unpackValue(v.MapIndex(key)))
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}
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}
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f.depth--
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f.fs.Write(closeMapBytes)
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case reflect.Struct:
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numFields := v.NumField()
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f.fs.Write(openBraceBytes)
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f.depth++
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if (f.cs.MaxDepth != 0) && (f.depth > f.cs.MaxDepth) {
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f.fs.Write(maxShortBytes)
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} else {
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vt := v.Type()
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for i := 0; i < numFields; i++ {
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if i > 0 {
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f.fs.Write(spaceBytes)
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}
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vtf := vt.Field(i)
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if f.fs.Flag('+') || f.fs.Flag('#') {
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f.fs.Write([]byte(vtf.Name))
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f.fs.Write(colonBytes)
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}
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f.format(f.unpackValue(v.Field(i)))
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}
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}
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f.depth--
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f.fs.Write(closeBraceBytes)
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case reflect.Uintptr:
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printHexPtr(f.fs, uintptr(v.Uint()))
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case reflect.UnsafePointer, reflect.Chan, reflect.Func:
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printHexPtr(f.fs, v.Pointer())
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// There were not any other types at the time this code was written, but
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// fall back to letting the default fmt package handle it if any get added.
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default:
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format := f.buildDefaultFormat()
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if v.CanInterface() {
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fmt.Fprintf(f.fs, format, v.Interface())
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} else {
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fmt.Fprintf(f.fs, format, v.String())
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}
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}
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}
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// Format satisfies the fmt.Formatter interface. See NewFormatter for usage
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// details.
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func (f *formatState) Format(fs fmt.State, verb rune) {
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f.fs = fs
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// Use standard formatting for verbs that are not v.
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if verb != 'v' {
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format := f.constructOrigFormat(verb)
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fmt.Fprintf(fs, format, f.value)
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return
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}
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if f.value == nil {
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if fs.Flag('#') {
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fs.Write(interfaceBytes)
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}
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fs.Write(nilAngleBytes)
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return
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}
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f.format(reflect.ValueOf(f.value))
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}
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// newFormatter is a helper function to consolidate the logic from the various
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||
|
|
// public methods which take varying config states.
|
||
|
|
func newFormatter(cs *ConfigState, v interface{}) fmt.Formatter {
|
||
|
|
fs := &formatState{value: v, cs: cs}
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||
|
|
fs.pointers = make(map[uintptr]int)
|
||
|
|
return fs
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
NewFormatter returns a custom formatter that satisfies the fmt.Formatter
|
||
|
|
interface. As a result, it integrates cleanly with standard fmt package
|
||
|
|
printing functions. The formatter is useful for inline printing of smaller data
|
||
|
|
types similar to the standard %v format specifier.
|
||
|
|
|
||
|
|
The custom formatter only responds to the %v (most compact), %+v (adds pointer
|
||
|
|
addresses), %#v (adds types), or %#+v (adds types and pointer addresses) verb
|
||
|
|
combinations. Any other verbs such as %x and %q will be sent to the the
|
||
|
|
standard fmt package for formatting. In addition, the custom formatter ignores
|
||
|
|
the width and precision arguments (however they will still work on the format
|
||
|
|
specifiers not handled by the custom formatter).
|
||
|
|
|
||
|
|
Typically this function shouldn't be called directly. It is much easier to make
|
||
|
|
use of the custom formatter by calling one of the convenience functions such as
|
||
|
|
Printf, Println, or Fprintf.
|
||
|
|
*/
|
||
|
|
func NewFormatter(v interface{}) fmt.Formatter {
|
||
|
|
return newFormatter(&Config, v)
|
||
|
|
}
|