Add folded stacks output format

Fixes google#658

doc/README.md

@@ -171,6 +171,8 @@ pprof text reports show the location hierarchy in text format.
 * **-peek= _regex_:** Print the location entry with all its predecessors and
   successors, without trimming any entries.
 * **-traces:** Prints each sample with a location per line.
+* **-folded:** Prints each sample in [Brendan Gregg's Folded Stacks
+  format](https://queue.acm.org/detail.cfm?id=2927301#:~:text=The%20folded%20stack%2Dtrace%20format,trace%2C%20followed%20by%20a%20semicolon.).
 
 ## Graphical reports
 

internal/driver/commands.go

@@ -93,6 +93,7 @@ var pprofCommands = commands{
 	"top":      {report.Text, nil, nil, false, "Outputs top entries in text form", reportHelp("top", true, true)},
 	"traces":   {report.Traces, nil, nil, false, "Outputs all profile samples in text form", ""},
 	"tree":     {report.Tree, nil, nil, false, "Outputs a text rendering of call graph", reportHelp("tree", true, true)},
+	"folded":   {report.Folded, nil, nil, false, "Outputs entries in folded stack form", reportHelp("folded", false, true)},
 
 	// Save binary formats to a file
 	"callgrind": {report.Callgrind, nil, awayFromTTY("callgraph.out"), false, "Outputs a graph in callgrind format", reportHelp("callgrind", false, true)},

internal/report/report.go

@@ -48,6 +48,7 @@ const (
 	Traces
 	Tree
 	WebList
+	Folded
 )
 
 // Options are the formatting and filtering options used to generate a
@@ -94,6 +95,8 @@ func Generate(w io.Writer, rpt *Report, obj plugin.ObjTool) error {
 		return printDOT(w, rpt)
 	case Tree:
 		return printTree(w, rpt)
+	case Folded:
+		return printFolded(w, rpt)
 	case Text:
 		return printText(w, rpt)
 	case Traces:
@@ -828,6 +831,50 @@ func printText(w io.Writer, rpt *Report) error {
 	return nil
 }
 
+//
+func printFolded(w io.Writer, rpt *Report) error {
+	prof := rpt.prof
+	o := rpt.options
+
+	_, locations := graph.CreateNodes(prof, &graph.Options{})
+	for _, sample := range prof.Sample {
+		var stack []*graph.NodeInfo
+		for _, loc := range sample.Location {
+			nodes := locations[loc.ID]
+			for _, n := range nodes {
+				stack = append(stack, &n.Info)
+			}
+		}
+
+		if len(stack) == 0 {
+			continue
+		}
+
+		var d, v int64
+		v = o.SampleValue(sample.Value)
+		if o.SampleMeanDivisor != nil {
+			d = o.SampleMeanDivisor(sample.Value)
+		}
+		if d != 0 {
+			v = v / d
+		}
+		// Print call stack.
+		for i := range stack {
+			s := stack[len(stack)-i-1]
+			if i > 0 {
+				fmt.Fprint(w, ";")
+			}
+			// TODO: escape semicolons and newlines and maybe spaces in printable name?
+			// not sure if we need to do spaces.
+			// TODO: should we print more than just name? fmt.Fprintf(w, "%s%s", s.PrintableName(), inline)
+			fmt.Fprint(w, s.Name)
+		}
+		vs := rpt.formatValue(v)
+		fmt.Fprintf(w, " %s\n", vs)
+	}
+	return nil
+}
+
 // printTraces prints all traces from a profile.
 func printTraces(w io.Writer, rpt *Report) error {
 	fmt.Fprintln(w, strings.Join(ProfileLabels(rpt), "\n"))

internal/report/report_test.go

@@ -70,6 +70,18 @@ func TestTextReports(t *testing.T) {
 			),
 			want: path + "report.dot",
 		},
+		{
+			rpt: New(
+				testProfile.Copy(),
+				&Options{
+					OutputFormat: Folded,
+
+					SampleValue: sampleValue1,
+					SampleUnit:  testProfile.SampleType[1].Unit,
+				},
+			),
+			want: path + "report.folded",
+		},
 	} {
 		var b bytes.Buffer
 		if err := Generate(&b, tc.rpt, &binutils.Binutils{}); err != nil {

internal/report/testdata/report.folded

@@ -0,0 +1,5 @@
+main 1
+main;foo;bar 10
+main;bar;tee 100
+main;tee 1000
+main;tee;tee 10000