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