Reland of Add a library for running external commands, providing timeouts and test injection.

go/util/util.go

 package util
 
 import (
         "crypto/rand"
         "crypto/sha256"
         "fmt"
         "io"
         mathrand "math/rand"
         "os"
+        "reflect"
         "regexp"
         "runtime"
         "sort"
         "strings"
         "time"
 
         "github.com/skia-dev/glog"
 )
 
 const (
@@ skipping 418 matching lines @@
 
 // AnyMatch returns true iff the given string matches any regexp in the slice.
 func AnyMatch(re []*regexp.Regexp, s string) bool {
         for _, r := range re {
                 if r.MatchString(s) {
                         return true
                 }
         }
         return false
 }
+
+// Returns true if i is nil or is an interface containing a nil or invalid value.
+func IsNil(i interface{}) bool {
+        if i == nil {
+                return true
+        }
+        v := reflect.ValueOf(i)
+        if !v.IsValid() {
+                return true
+        }
+        switch v.Kind() {
+        case reflect.Chan, reflect.Func, reflect.Map, reflect.Slice:
+                return v.IsNil()
+        case reflect.Interface, reflect.Ptr:
+                if v.IsNil() {
+                        return true
+                }
+                inner := v.Elem()
+                if !inner.IsValid() {
+                        return true
+                }
+                if inner.CanInterface() {
+                        return IsNil(inner.Interface())
+                }
+                return false
+        default:
+                return false
+        }
+}