Reorganize the new map key sorting functionality.

This commit moves the new code related to sorting reflect.Value items into
common.go since it is accessed by both the formatter and the dumper.  It
also adds comments to the new functions and unexports SortValues since it
should be an internal function only.

1 files changed, 49 insertions, 0 deletions

diff --git a/spew/common.go b/spew/common.go
index 11b6d56..3a3a2b0 100644
--- a/spew/common.go
+++ b/spew/common.go
@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"io"
 	"reflect"
+	"sort"
 	"strconv"
 	"unsafe"
 )
@@ -249,3 +250,51 @@ func printHexPtr(w io.Writer, p uintptr) {
 	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
+}
+
+// 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]
+}
+
+// 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 {
+	switch s.values[i].Kind() {
+	case reflect.Bool:
+		return !s.values[i].Bool() && s.values[j].Bool()
+	case reflect.Float32, reflect.Float64:
+		return s.values[i].Float() < s.values[j].Float()
+	case reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Int:
+		return s.values[i].Int() < s.values[j].Int()
+	case reflect.String:
+		return s.values[i].String() < s.values[j].String()
+	case reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uint:
+		return s.values[i].Uint() < s.values[j].Uint()
+	case reflect.Uintptr:
+		return s.values[i].UnsafeAddr() < s.values[j].UnsafeAddr()
+	}
+	return s.values[i].String() < s.values[j].String()
+}
+
+// sortValues is a generic sort function for native types: int, uint, bool,
+// string and uintptr.  Other inputs are sorted according to their
+// Value.String() value to ensure display stability.
+func sortValues(values []reflect.Value) {
+	if len(values) == 0 {
+		return
+	}
+	sort.Sort(&valuesSorter{values})
+}