/*
* Copyright (c) 2013 Dave Collins <dave@davec.name>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
package spew
import (
"bytes"
"fmt"
"io"
"reflect"
"sort"
"strconv"
)
// Some constants in the form of bytes to avoid string overhead. This mirrors
// the technique used in the fmt package.
var (
panicBytes = []byte("(PANIC=")
plusBytes = []byte("+")
iBytes = []byte("i")
trueBytes = []byte("true")
falseBytes = []byte("false")
interfaceBytes = []byte("(interface {})")
commaNewlineBytes = []byte(",\n")
newlineBytes = []byte("\n")
openBraceBytes = []byte("{")
openBraceNewlineBytes = []byte("{\n")
closeBraceBytes = []byte("}")
asteriskBytes = []byte("*")
colonBytes = []byte(":")
colonSpaceBytes = []byte(": ")
openParenBytes = []byte("(")
closeParenBytes = []byte(")")
spaceBytes = []byte(" ")
pointerChainBytes = []byte("->")
nilAngleBytes = []byte("<nil>")
maxNewlineBytes = []byte("<max depth reached>\n")
maxShortBytes = []byte("<max>")
circularBytes = []byte("<already shown>")
circularShortBytes = []byte("<shown>")
invalidAngleBytes = []byte("<invalid>")
openBracketBytes = []byte("[")
closeBracketBytes = []byte("]")
percentBytes = []byte("%")
precisionBytes = []byte(".")
openAngleBytes = []byte("<")
closeAngleBytes = []byte(">")
openMapBytes = []byte("map[")
closeMapBytes = []byte("]")
lenEqualsBytes = []byte("len=")
capEqualsBytes = []byte("cap=")
)
// hexDigits is used to map a decimal value to a hex digit.
var hexDigits = "0123456789abcdef"
// catchPanic handles any panics that might occur during the handleMethods
// calls.
func catchPanic(w io.Writer, v reflect.Value) {
if err := recover(); err != nil {
w.Write(panicBytes)
fmt.Fprintf(w, "%v", err)
w.Write(closeParenBytes)
}
}
// handleMethods attempts to call the Error and String methods on the underlying
// type the passed reflect.Value represents and outputes the result to Writer w.
//
// It handles panics in any called methods by catching and displaying the error
// as the formatted value.
func handleMethods(cs *ConfigState, w io.Writer, v reflect.Value) (handled bool) {
// We need an interface to check if the type implements the error or
// Stringer interface. However, the reflect package won't give us an
// interface on certain things like unexported struct fields in order
// to enforce visibility rules. We use unsafe, when it's available,
// to bypass these restrictions since this package does not mutate the
// values.
if !v.CanInterface() {
if UnsafeDisabled {
return false
}
v = unsafeReflectValue(v)
}
// Choose whether or not to do error and Stringer interface lookups against
// the base type or a pointer to the base type depending on settings.
// Technically calling one of these methods with a pointer receiver can
// mutate the value, however, types which choose to satisify an error or
// Stringer interface with a pointer receiver should not be mutating their
// state inside these interface methods.
if !cs.DisablePointerMethods && !UnsafeDisabled && !v.CanAddr() {
v = unsafeReflectValue(v)
}
if v.CanAddr() {
v = v.Addr()
}
// Is it an error or Stringer?
switch iface := v.Interface().(type) {
case error:
defer catchPanic(w, v)
if cs.ContinueOnMethod {
w.Write(openParenBytes)
w.Write([]byte(iface.Error()))
w.Write(closeParenBytes)
w.Write(spaceBytes)
return false
}
w.Write([]byte(iface.Error()))
return true
case fmt.Stringer:
defer catchPanic(w, v)
if cs.ContinueOnMethod {
w.Write(openParenBytes)
w.Write([]byte(iface.String()))
w.Write(closeParenBytes)
w.Write(spaceBytes)
return false
}
w.Write([]byte(iface.String()))
return true
}
return false
}
// printBool outputs a boolean value as true or false to Writer w.
func printBool(w io.Writer, val bool) {
if val {
w.Write(trueBytes)
} else {
w.Write(falseBytes)
}
}
// printInt outputs a signed integer value to Writer w.
func printInt(w io.Writer, val int64, base int) {
w.Write([]byte(strconv.FormatInt(val, base)))
}
// printUint outputs an unsigned integer value to Writer w.
func printUint(w io.Writer, val uint64, base int) {
w.Write([]byte(strconv.FormatUint(val, base)))
}
// printFloat outputs a floating point value using the specified precision,
// which is expected to be 32 or 64bit, to Writer w.
func printFloat(w io.Writer, val float64, precision int) {
w.Write([]byte(strconv.FormatFloat(val, 'g', -1, precision)))
}
// printComplex outputs a complex value using the specified float precision
// for the real and imaginary parts to Writer w.
func printComplex(w io.Writer, c complex128, floatPrecision int) {
r := real(c)
w.Write(openParenBytes)
w.Write([]byte(strconv.FormatFloat(r, 'g', -1, floatPrecision)))
i := imag(c)
if i >= 0 {
w.Write(plusBytes)
}
w.Write([]byte(strconv.FormatFloat(i, 'g', -1, floatPrecision)))
w.Write(iBytes)
w.Write(closeParenBytes)
}
// printHexPtr outputs a uintptr formatted as hexidecimal with a leading '0x'
// prefix to Writer w.
func printHexPtr(w io.Writer, p uintptr) {
// Null pointer.
num := uint64(p)
if num == 0 {
w.Write(nilAngleBytes)
return
}
// Max uint64 is 16 bytes in hex + 2 bytes for '0x' prefix
buf := make([]byte, 18)
// It's simpler to construct the hex string right to left.
base := uint64(16)
i := len(buf) - 1
for num >= base {
buf[i] = hexDigits[num%base]
num /= base
i--
}
buf[i] = hexDigits[num]
// Add '0x' prefix.
i--
buf[i] = 'x'
i--
buf[i] = '0'
// Strip unused leading bytes.
buf = buf[i:]
w.Write(buf)
}
// valuesSorter implements sort.Interface to allow a slice of reflect.Value
// elements to be sorted.
type valuesSorter struct {
values []reflect.Value
strings []string // either nil or same len and values
cs *ConfigState
}
// newValuesSorter initializes a valuesSorter instance, which holds a set of
// surrogate keys on which the data should be sorted. It uses flags in
// ConfigState to decide if and how to populate those surrogate keys.
func newValuesSorter(values []reflect.Value, cs *ConfigState) sort.Interface {
vs := &valuesSorter{values: values, cs: cs}
if canSortSimply(vs.values[0].Kind()) {
return vs
}
if !cs.DisableMethods {
vs.strings = make([]string, len(values))
for i := range vs.values {
b := bytes.Buffer{}
if !handleMethods(cs, &b, vs.values[i]) {
vs.strings = nil
break
}
vs.strings[i] = b.String()
}
}
if vs.strings == nil && cs.SpewKeys {
vs.strings = make([]string, len(values))
for i := range vs.values {
vs.strings[i] = Sprintf("%#v", vs.values[i].Interface())
}
}
return vs
}
// canSortSimply tests whether a reflect.Kind is a primitive that can be sorted
// directly, or whether it should be considered for sorting by surrogate keys
// (if the ConfigState allows it).
func canSortSimply(kind reflect.Kind) bool {
// This switch parallels valueSortLess, except for the default case.
switch kind {
case reflect.Bool:
return true
case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int:
return true
case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint:
return true
case reflect.Float32, reflect.Float64:
return true
case reflect.String:
return true
case reflect.Uintptr:
return true
case reflect.Array:
return true
}
return false
}
// Len returns the number of values in the slice. It is part of the
// sort.Interface implementation.
func (s *valuesSorter) Len() int {
return len(s.values)
}
// Swap swaps the values at the passed indices. It is part of the
// sort.Interface implementation.
func (s *valuesSorter) Swap(i, j int) {
s.values[i], s.values[j] = s.values[j], s.values[i]
if s.strings != nil {
s.strings[i], s.strings[j] = s.strings[j], s.strings[i]
}
}
// valueSortLess returns whether the first value should sort before the second
// value. It is used by valueSorter.Less as part of the sort.Interface
// implementation.
func valueSortLess(a, b reflect.Value) bool {
switch a.Kind() {
case reflect.Bool:
return !a.Bool() && b.Bool()
case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int:
return a.Int() < b.Int()
case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint:
return a.Uint() < b.Uint()
case reflect.Float32, reflect.Float64:
return a.Float() < b.Float()
case reflect.String:
return a.String() < b.String()
case reflect.Uintptr:
return a.Uint() < b.Uint()
case reflect.Array:
// Compare the contents of both arrays.
l := a.Len()
for i := 0; i < l; i++ {
av := a.Index(i)
bv := b.Index(i)
if av.Interface() == bv.Interface() {
continue
}
return valueSortLess(av, bv)
}
}
return a.String() < b.String()
}
// Less returns whether the value at index i should sort before the
// value at index j. It is part of the sort.Interface implementation.
func (s *valuesSorter) Less(i, j int) bool {
if s.strings == nil {
return valueSortLess(s.values[i], s.values[j])
}
return s.strings[i] < s.strings[j]
}
// sortValues is a sort function that handles both native types and any type that
// can be converted to error or Stringer. Other inputs are sorted according to
// their Value.String() value to ensure display stability.
func sortValues(values []reflect.Value, cs *ConfigState) {
if len(values) == 0 {
return
}
sort.Sort(newValuesSorter(values, cs))
}
