src/cmd/internal/test2json/test2json.go - go - Git at Google

 // Copyright 2017 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 // Package test2json implements conversion of test binary output to JSON.
 // It is used by cmd/test2json and cmd/go.
 //
 // See the cmd/test2json documentation for details of the JSON encoding.
 package test2json

 import (
 	"bytes"
 	"encoding/json"
 	"fmt"
 	"io"
 	"strconv"
 	"strings"
 	"time"
 	"unicode"
 	"unicode/utf8"
 )

 // Mode controls details of the conversion.
 type Mode int

 const (
 	Timestamp Mode = 1 << iota // include Time in events
 )

 // event is the JSON struct we emit.
 type event struct {
 	Time    *time.Time `json:",omitempty"`
 	Action  string
 	Package string     `json:",omitempty"`
 	Test    string     `json:",omitempty"`
 	Elapsed *float64   `json:",omitempty"`
 	Output  *textBytes `json:",omitempty"`
 }

 // textBytes is a hack to get JSON to emit a []byte as a string
 // without actually copying it to a string.
 // It implements encoding.TextMarshaler, which returns its text form as a []byte,
 // and then json encodes that text form as a string (which was our goal).
 type textBytes []byte

 func (b textBytes) MarshalText() ([]byte, error) { return b, nil }

 // A converter holds the state of a test-to-JSON conversion.
 // It implements io.WriteCloser; the caller writes test output in,
 // and the converter writes JSON output to w.
 type converter struct {
 	w        io.Writer  // JSON output stream
 	pkg      string     // package to name in events
 	mode     Mode       // mode bits
 	start    time.Time  // time converter started
 	testName string     // name of current test, for output attribution
 	report   []*event   // pending test result reports (nested for subtests)
 	result   string     // overall test result if seen
 	input    lineBuffer // input buffer
 	output   lineBuffer // output buffer
 }

 // inBuffer and outBuffer are the input and output buffer sizes.
 // They're variables so that they can be reduced during testing.
 //
 // The input buffer needs to be able to hold any single test
 // directive line we want to recognize, like:
 //
 //     <many spaces> --- PASS: very/nested/s/u/b/t/e/s/t
 //
 // If anyone reports a test directive line > 4k not working, it will
 // be defensible to suggest they restructure their test or test names.
 //
 // The output buffer must be >= utf8.UTFMax, so that it can
 // accumulate any single UTF8 sequence. Lines that fit entirely
 // within the output buffer are emitted in single output events.
 // Otherwise they are split into multiple events.
 // The output buffer size therefore limits the size of the encoding
 // of a single JSON output event. 1k seems like a reasonable balance
 // between wanting to avoid splitting an output line and not wanting to
 // generate enormous output events.
 var (
 	inBuffer  = 4096
 	outBuffer = 1024
 )

 // NewConverter returns a "test to json" converter.
 // Writes on the returned writer are written as JSON to w,
 // with minimal delay.
 //
 // The writes to w are whole JSON events ending in \n,
 // so that it is safe to run multiple tests writing to multiple converters
 // writing to a single underlying output stream w.
 // As long as the underlying output w can handle concurrent writes
 // from multiple goroutines, the result will be a JSON stream
 // describing the relative ordering of execution in all the concurrent tests.
 //
 // The mode flag adjusts the behavior of the converter.
 // Passing ModeTime includes event timestamps and elapsed times.
 //
 // The pkg string, if present, specifies the import path to
 // report in the JSON stream.
 func NewConverter(w io.Writer, pkg string, mode Mode) io.WriteCloser {
 	c := new(converter)
 	*c = converter{
 		w:     w,
 		pkg:   pkg,
 		mode:  mode,
 		start: time.Now(),
 		input: lineBuffer{
 			b:    make([]byte, 0, inBuffer),
 			line: c.handleInputLine,
 			part: c.output.write,
 		},
 		output: lineBuffer{
 			b:    make([]byte, 0, outBuffer),
 			line: c.writeOutputEvent,
 			part: c.writeOutputEvent,
 		},
 	}
 	return c
 }

 // Write writes the test input to the converter.
 func (c *converter) Write(b []byte) (int, error) {
 	c.input.write(b)
 	return len(b), nil
 }

 var (
 	bigPass = []byte("PASS\n")
 	bigFail = []byte("FAIL\n")

 	updates = [][]byte{
 		[]byte("=== RUN   "),
 		[]byte("=== PAUSE "),
 		[]byte("=== CONT  "),
 	}

 	reports = [][]byte{
 		[]byte("--- PASS: "),
 		[]byte("--- FAIL: "),
 		[]byte("--- SKIP: "),
 		[]byte("--- BENCH: "),
 	}

 	fourSpace = []byte("    ")

 	skipLinePrefix = []byte("?   \t")
 	skipLineSuffix = []byte("\t[no test files]\n")
 )

 // handleInputLine handles a single whole test output line.
 // It must write the line to c.output but may choose to do so
 // before or after emitting other events.
 func (c *converter) handleInputLine(line []byte) {
 	// Final PASS or FAIL.
 	if bytes.Equal(line, bigPass) || bytes.Equal(line, bigFail) {
 		c.flushReport(0)
 		c.output.write(line)
 		if bytes.Equal(line, bigPass) {
 			c.result = "pass"
 		} else {
 			c.result = "fail"
 		}
 		return
 	}

 	// Special case for entirely skipped test binary: "?   \tpkgname\t[no test files]\n" is only line.
 	// Report it as plain output but remember to say skip in the final summary.
 	if bytes.HasPrefix(line, skipLinePrefix) && bytes.HasSuffix(line, skipLineSuffix) && len(c.report) == 0 {
 		c.result = "skip"
 	}

 	// "=== RUN   "
 	// "=== PAUSE "
 	// "=== CONT  "
 	actionColon := false
 	origLine := line
 	ok := false
 	indent := 0
 	for _, magic := range updates {
 		if bytes.HasPrefix(line, magic) {
 			ok = true
 			break
 		}
 	}
 	if !ok {
 		// "--- PASS: "
 		// "--- FAIL: "
 		// "--- SKIP: "
 		// "--- BENCH: "
 		// but possibly indented.
 		for bytes.HasPrefix(line, fourSpace) {
 			line = line[4:]
 			indent++
 		}
 		for _, magic := range reports {
 			if bytes.HasPrefix(line, magic) {
 				actionColon = true
 				ok = true
 				break
 			}
 		}
 	}

 	if !ok {
 		// Not a special test output line.
 		c.output.write(origLine)
 		return
 	}

 	// Parse out action and test name.
 	i := 0
 	if actionColon {
 		i = bytes.IndexByte(line, ':') + 1
 	}
 	if i == 0 {
 		i = len(updates[0])
 	}
 	action := strings.ToLower(strings.TrimSuffix(strings.TrimSpace(string(line[4:i])), ":"))
 	name := strings.TrimSpace(string(line[i:]))

 	e := &event{Action: action}
 	if line[0] == '-' { // PASS or FAIL report
 		// Parse out elapsed time.
 		if i := strings.Index(name, " ("); i >= 0 {
 			if strings.HasSuffix(name, "s)") {
 				t, err := strconv.ParseFloat(name[i+2:len(name)-2], 64)
 				if err == nil {
 					if c.mode&Timestamp != 0 {
 						e.Elapsed = &t
 					}
 				}
 			}
 			name = name[:i]
 		}
 		if len(c.report) < indent {
 			// Nested deeper than expected.
 			// Treat this line as plain output.
 			c.output.write(origLine)
 			return
 		}
 		// Flush reports at this indentation level or deeper.
 		c.flushReport(indent)
 		e.Test = name
 		c.testName = name
 		c.report = append(c.report, e)
 		c.output.write(origLine)
 		return
 	}
 	// === update.
 	// Finish any pending PASS/FAIL reports.
 	c.flushReport(0)
 	c.testName = name

 	if action == "pause" {
 		// For a pause, we want to write the pause notification before
 		// delivering the pause event, just so it doesn't look like the test
 		// is generating output immediately after being paused.
 		c.output.write(origLine)
 	}
 	c.writeEvent(e)
 	if action != "pause" {
 		c.output.write(origLine)
 	}

 	return
 }

 // flushReport flushes all pending PASS/FAIL reports at levels >= depth.
 func (c *converter) flushReport(depth int) {
 	c.testName = ""
 	for len(c.report) > depth {
 		e := c.report[len(c.report)-1]
 		c.report = c.report[:len(c.report)-1]
 		c.writeEvent(e)
 	}
 }

 // Close marks the end of the go test output.
 // It flushes any pending input and then output (only partial lines at this point)
 // and then emits the final overall package-level pass/fail event.
 func (c *converter) Close() error {
 	c.input.flush()
 	c.output.flush()
 	e := &event{Action: "pass"}
 	if c.result != "" {
 		e.Action = c.result
 	}
 	if c.mode&Timestamp != 0 {
 		dt := time.Since(c.start).Round(1 * time.Millisecond).Seconds()
 		e.Elapsed = &dt
 	}
 	c.writeEvent(e)
 	return nil
 }

 // writeOutputEvent writes a single output event with the given bytes.
 func (c *converter) writeOutputEvent(out []byte) {
 	c.writeEvent(&event{
 		Action: "output",
 		Output: (*textBytes)(&out),
 	})
 }

 // writeEvent writes a single event.
 // It adds the package, time (if requested), and test name (if needed).
 func (c *converter) writeEvent(e *event) {
 	e.Package = c.pkg
 	if c.mode&Timestamp != 0 {
 		t := time.Now()
 		e.Time = &t
 	}
 	if e.Test == "" {
 		e.Test = c.testName
 	}
 	js, err := json.Marshal(e)
 	if err != nil {
 		// Should not happen - event is valid for json.Marshal.
 		c.w.Write([]byte(fmt.Sprintf("testjson internal error: %v\n", err)))
 		return
 	}
 	js = append(js, '\n')
 	c.w.Write(js)
 }

 // A lineBuffer is an I/O buffer that reacts to writes by invoking
 // input-processing callbacks on whole lines or (for long lines that
 // have been split) line fragments.
 //
 // It should be initialized with b set to a buffer of length 0 but non-zero capacity,
 // and line and part set to the desired input processors.
 // The lineBuffer will call line(x) for any whole line x (including the final newline)
 // that fits entirely in cap(b). It will handle input lines longer than cap(b) by
 // calling part(x) for sections of the line. The line will be split at UTF8 boundaries,
 // and the final call to part for a long line includes the final newline.
 type lineBuffer struct {
 	b    []byte       // buffer
 	mid  bool         // whether we're in the middle of a long line
 	line func([]byte) // line callback
 	part func([]byte) // partial line callback
 }

 // write writes b to the buffer.
 func (l *lineBuffer) write(b []byte) {
 	for len(b) > 0 {
 		// Copy what we can into b.
 		m := copy(l.b[len(l.b):cap(l.b)], b)
 		l.b = l.b[:len(l.b)+m]
 		b = b[m:]

 		// Process lines in b.
 		i := 0
 		for i < len(l.b) {
 			j := bytes.IndexByte(l.b[i:], '\n')
 			if j < 0 {
 				if !l.mid {
 					if j := bytes.IndexByte(l.b[i:], '\t'); j >= 0 {
 						if isBenchmarkName(bytes.TrimRight(l.b[i:i+j], " ")) {
 							l.part(l.b[i : i+j+1])
 							l.mid = true
 							i += j + 1
 						}
 					}
 				}
 				break
 			}
 			e := i + j + 1
 			if l.mid {
 				// Found the end of a partial line.
 				l.part(l.b[i:e])
 				l.mid = false
 			} else {
 				// Found a whole line.
 				l.line(l.b[i:e])
 			}
 			i = e
 		}

 		// Whatever's left in l.b is a line fragment.
 		if i == 0 && len(l.b) == cap(l.b) {
 			// The whole buffer is a fragment.
 			// Emit it as the beginning (or continuation) of a partial line.
 			t := trimUTF8(l.b)
 			l.part(l.b[:t])
 			l.b = l.b[:copy(l.b, l.b[t:])]
 			l.mid = true
 		}

 		// There's room for more input.
 		// Slide it down in hope of completing the line.
 		if i > 0 {
 			l.b = l.b[:copy(l.b, l.b[i:])]
 		}
 	}
 }

 // flush flushes the line buffer.
 func (l *lineBuffer) flush() {
 	if len(l.b) > 0 {
 		// Must be a line without a \n, so a partial line.
 		l.part(l.b)
 		l.b = l.b[:0]
 	}
 }

 var benchmark = []byte("Benchmark")

 // isBenchmarkName reports whether b is a valid benchmark name
 // that might appear as the first field in a benchmark result line.
 func isBenchmarkName(b []byte) bool {
 	if !bytes.HasPrefix(b, benchmark) {
 		return false
 	}
 	if len(b) == len(benchmark) { // just "Benchmark"
 		return true
 	}
 	r, _ := utf8.DecodeRune(b[len(benchmark):])
 	return !unicode.IsLower(r)
 }

 // trimUTF8 returns a length t as close to len(b) as possible such that b[:t]
 // does not end in the middle of a possibly-valid UTF-8 sequence.
 //
 // If a large text buffer must be split before position i at the latest,
 // splitting at position trimUTF(b[:i]) avoids splitting a UTF-8 sequence.
 func trimUTF8(b []byte) int {
 	// Scan backward to find non-continuation byte.
 	for i := 1; i < utf8.UTFMax && i <= len(b); i++ {
 		if c := b[len(b)-i]; c&0xc0 != 0x80 {
 			switch {
 			case c&0xe0 == 0xc0:
 				if i < 2 {
 					return len(b) - i
 				}
 			case c&0xf0 == 0xe0:
 				if i < 3 {
 					return len(b) - i
 				}
 			case c&0xf8 == 0xf0:
 				if i < 4 {
 					return len(b) - i
 				}
 			}
 			break
 		}
 	}
 	return len(b)
 }
	// Copyright 2017 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	// Package test2json implements conversion of test binary output to JSON.
	// It is used by cmd/test2json and cmd/go.
	//
	// See the cmd/test2json documentation for details of the JSON encoding.
	package test2json

	import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"strconv"
	"strings"
	"time"
	"unicode"
	"unicode/utf8"
	)

	// Mode controls details of the conversion.
	type Mode int

	const (
	Timestamp Mode = 1 << iota // include Time in events
	)

	// event is the JSON struct we emit.
	type event struct {
	Time *time.Time `json:",omitempty"`
	Action string
	Package string `json:",omitempty"`
	Test string `json:",omitempty"`
	Elapsed *float64 `json:",omitempty"`
	Output *textBytes `json:",omitempty"`
	}

	// textBytes is a hack to get JSON to emit a []byte as a string
	// without actually copying it to a string.
	// It implements encoding.TextMarshaler, which returns its text form as a []byte,
	// and then json encodes that text form as a string (which was our goal).
	type textBytes []byte

	func (b textBytes) MarshalText() ([]byte, error) { return b, nil }

	// A converter holds the state of a test-to-JSON conversion.
	// It implements io.WriteCloser; the caller writes test output in,
	// and the converter writes JSON output to w.
	type converter struct {
	w io.Writer // JSON output stream
	pkg string // package to name in events
	mode Mode // mode bits
	start time.Time // time converter started
	testName string // name of current test, for output attribution
	report []*event // pending test result reports (nested for subtests)
	result string // overall test result if seen
	input lineBuffer // input buffer
	output lineBuffer // output buffer
	}

	// inBuffer and outBuffer are the input and output buffer sizes.
	// They're variables so that they can be reduced during testing.
	//
	// The input buffer needs to be able to hold any single test
	// directive line we want to recognize, like:
	//
	// <many spaces> --- PASS: very/nested/s/u/b/t/e/s/t
	//
	// If anyone reports a test directive line > 4k not working, it will
	// be defensible to suggest they restructure their test or test names.
	//
	// The output buffer must be >= utf8.UTFMax, so that it can
	// accumulate any single UTF8 sequence. Lines that fit entirely
	// within the output buffer are emitted in single output events.
	// Otherwise they are split into multiple events.
	// The output buffer size therefore limits the size of the encoding
	// of a single JSON output event. 1k seems like a reasonable balance
	// between wanting to avoid splitting an output line and not wanting to
	// generate enormous output events.
	var (
	inBuffer = 4096
	outBuffer = 1024
	)

	// NewConverter returns a "test to json" converter.
	// Writes on the returned writer are written as JSON to w,
	// with minimal delay.
	//
	// The writes to w are whole JSON events ending in \n,
	// so that it is safe to run multiple tests writing to multiple converters
	// writing to a single underlying output stream w.
	// As long as the underlying output w can handle concurrent writes
	// from multiple goroutines, the result will be a JSON stream
	// describing the relative ordering of execution in all the concurrent tests.
	//
	// The mode flag adjusts the behavior of the converter.
	// Passing ModeTime includes event timestamps and elapsed times.
	//
	// The pkg string, if present, specifies the import path to
	// report in the JSON stream.
	func NewConverter(w io.Writer, pkg string, mode Mode) io.WriteCloser {
	c := new(converter)
	*c = converter{
	w: w,
	pkg: pkg,
	mode: mode,
	start: time.Now(),
	input: lineBuffer{
	b: make([]byte, 0, inBuffer),
	line: c.handleInputLine,
	part: c.output.write,
	},
	output: lineBuffer{
	b: make([]byte, 0, outBuffer),
	line: c.writeOutputEvent,
	part: c.writeOutputEvent,
	},
	}
	return c
	}

	// Write writes the test input to the converter.
	func (c *converter) Write(b []byte) (int, error) {
	c.input.write(b)
	return len(b), nil
	}

	var (
	bigPass = []byte("PASS\n")
	bigFail = []byte("FAIL\n")

	updates = [][]byte{
	[]byte("=== RUN "),
	[]byte("=== PAUSE "),
	[]byte("=== CONT "),
	}

	reports = [][]byte{
	[]byte("--- PASS: "),
	[]byte("--- FAIL: "),
	[]byte("--- SKIP: "),
	[]byte("--- BENCH: "),
	}

	fourSpace = []byte(" ")

	skipLinePrefix = []byte("? \t")
	skipLineSuffix = []byte("\t[no test files]\n")
	)

	// handleInputLine handles a single whole test output line.
	// It must write the line to c.output but may choose to do so
	// before or after emitting other events.
	func (c *converter) handleInputLine(line []byte) {
	// Final PASS or FAIL.
	if bytes.Equal(line, bigPass) \|\| bytes.Equal(line, bigFail) {
	c.flushReport(0)
	c.output.write(line)
	if bytes.Equal(line, bigPass) {
	c.result = "pass"
	} else {
	c.result = "fail"
	}
	return
	}

	// Special case for entirely skipped test binary: "? \tpkgname\t[no test files]\n" is only line.
	// Report it as plain output but remember to say skip in the final summary.
	if bytes.HasPrefix(line, skipLinePrefix) && bytes.HasSuffix(line, skipLineSuffix) && len(c.report) == 0 {
	c.result = "skip"
	}

	// "=== RUN "
	// "=== PAUSE "
	// "=== CONT "
	actionColon := false
	origLine := line
	ok := false
	indent := 0
	for _, magic := range updates {
	if bytes.HasPrefix(line, magic) {
	ok = true
	break
	}
	}
	if !ok {
	// "--- PASS: "
	// "--- FAIL: "
	// "--- SKIP: "
	// "--- BENCH: "
	// but possibly indented.
	for bytes.HasPrefix(line, fourSpace) {
	line = line[4:]
	indent++
	}
	for _, magic := range reports {
	if bytes.HasPrefix(line, magic) {
	actionColon = true
	ok = true
	break
	}
	}
	}

	if !ok {
	// Not a special test output line.
	c.output.write(origLine)
	return
	}

	// Parse out action and test name.
	i := 0
	if actionColon {
	i = bytes.IndexByte(line, ':') + 1
	}
	if i == 0 {
	i = len(updates[0])
	}
	action := strings.ToLower(strings.TrimSuffix(strings.TrimSpace(string(line[4:i])), ":"))
	name := strings.TrimSpace(string(line[i:]))

	e := &event{Action: action}
	if line[0] == '-' { // PASS or FAIL report
	// Parse out elapsed time.
	if i := strings.Index(name, " ("); i >= 0 {
	if strings.HasSuffix(name, "s)") {
	t, err := strconv.ParseFloat(name[i+2:len(name)-2], 64)
	if err == nil {
	if c.mode&Timestamp != 0 {
	e.Elapsed = &t
	}
	}
	}
	name = name[:i]
	}
	if len(c.report) < indent {
	// Nested deeper than expected.
	// Treat this line as plain output.
	c.output.write(origLine)
	return
	}
	// Flush reports at this indentation level or deeper.
	c.flushReport(indent)
	e.Test = name
	c.testName = name
	c.report = append(c.report, e)
	c.output.write(origLine)
	return
	}
	// === update.
	// Finish any pending PASS/FAIL reports.
	c.flushReport(0)
	c.testName = name

	if action == "pause" {
	// For a pause, we want to write the pause notification before
	// delivering the pause event, just so it doesn't look like the test
	// is generating output immediately after being paused.
	c.output.write(origLine)
	}
	c.writeEvent(e)
	if action != "pause" {
	c.output.write(origLine)
	}

	return
	}

	// flushReport flushes all pending PASS/FAIL reports at levels >= depth.
	func (c *converter) flushReport(depth int) {
	c.testName = ""
	for len(c.report) > depth {
	e := c.report[len(c.report)-1]
	c.report = c.report[:len(c.report)-1]
	c.writeEvent(e)
	}
	}

	// Close marks the end of the go test output.
	// It flushes any pending input and then output (only partial lines at this point)
	// and then emits the final overall package-level pass/fail event.
	func (c *converter) Close() error {
	c.input.flush()
	c.output.flush()
	e := &event{Action: "pass"}
	if c.result != "" {
	e.Action = c.result
	}
	if c.mode&Timestamp != 0 {
	dt := time.Since(c.start).Round(1 * time.Millisecond).Seconds()
	e.Elapsed = &dt
	}
	c.writeEvent(e)
	return nil
	}

	// writeOutputEvent writes a single output event with the given bytes.
	func (c *converter) writeOutputEvent(out []byte) {
	c.writeEvent(&event{
	Action: "output",
	Output: (*textBytes)(&out),
	})
	}

	// writeEvent writes a single event.
	// It adds the package, time (if requested), and test name (if needed).
	func (c converter) writeEvent(e event) {
	e.Package = c.pkg
	if c.mode&Timestamp != 0 {
	t := time.Now()
	e.Time = &t
	}
	if e.Test == "" {
	e.Test = c.testName
	}
	js, err := json.Marshal(e)
	if err != nil {
	// Should not happen - event is valid for json.Marshal.
	c.w.Write([]byte(fmt.Sprintf("testjson internal error: %v\n", err)))
	return
	}
	js = append(js, '\n')
	c.w.Write(js)
	}

	// A lineBuffer is an I/O buffer that reacts to writes by invoking
	// input-processing callbacks on whole lines or (for long lines that
	// have been split) line fragments.
	//
	// It should be initialized with b set to a buffer of length 0 but non-zero capacity,
	// and line and part set to the desired input processors.
	// The lineBuffer will call line(x) for any whole line x (including the final newline)
	// that fits entirely in cap(b). It will handle input lines longer than cap(b) by
	// calling part(x) for sections of the line. The line will be split at UTF8 boundaries,
	// and the final call to part for a long line includes the final newline.
	type lineBuffer struct {
	b []byte // buffer
	mid bool // whether we're in the middle of a long line
	line func([]byte) // line callback
	part func([]byte) // partial line callback
	}

	// write writes b to the buffer.
	func (l *lineBuffer) write(b []byte) {
	for len(b) > 0 {
	// Copy what we can into b.
	m := copy(l.b[len(l.b):cap(l.b)], b)
	l.b = l.b[:len(l.b)+m]
	b = b[m:]

	// Process lines in b.
	i := 0
	for i < len(l.b) {
	j := bytes.IndexByte(l.b[i:], '\n')
	if j < 0 {
	if !l.mid {
	if j := bytes.IndexByte(l.b[i:], '\t'); j >= 0 {
	if isBenchmarkName(bytes.TrimRight(l.b[i:i+j], " ")) {
	l.part(l.b[i : i+j+1])
	l.mid = true
	i += j + 1
	}
	}
	}
	break
	}
	e := i + j + 1
	if l.mid {
	// Found the end of a partial line.
	l.part(l.b[i:e])
	l.mid = false
	} else {
	// Found a whole line.
	l.line(l.b[i:e])
	}
	i = e
	}

	// Whatever's left in l.b is a line fragment.
	if i == 0 && len(l.b) == cap(l.b) {
	// The whole buffer is a fragment.
	// Emit it as the beginning (or continuation) of a partial line.
	t := trimUTF8(l.b)
	l.part(l.b[:t])
	l.b = l.b[:copy(l.b, l.b[t:])]
	l.mid = true
	}

	// There's room for more input.
	// Slide it down in hope of completing the line.
	if i > 0 {
	l.b = l.b[:copy(l.b, l.b[i:])]
	}
	}
	}

	// flush flushes the line buffer.
	func (l *lineBuffer) flush() {
	if len(l.b) > 0 {
	// Must be a line without a \n, so a partial line.
	l.part(l.b)
	l.b = l.b[:0]
	}
	}

	var benchmark = []byte("Benchmark")

	// isBenchmarkName reports whether b is a valid benchmark name
	// that might appear as the first field in a benchmark result line.
	func isBenchmarkName(b []byte) bool {
	if !bytes.HasPrefix(b, benchmark) {
	return false
	}
	if len(b) == len(benchmark) { // just "Benchmark"
	return true
	}
	r, _ := utf8.DecodeRune(b[len(benchmark):])
	return !unicode.IsLower(r)
	}

	// trimUTF8 returns a length t as close to len(b) as possible such that b[:t]
	// does not end in the middle of a possibly-valid UTF-8 sequence.
	//
	// If a large text buffer must be split before position i at the latest,
	// splitting at position trimUTF(b[:i]) avoids splitting a UTF-8 sequence.
	func trimUTF8(b []byte) int {
	// Scan backward to find non-continuation byte.
	for i := 1; i < utf8.UTFMax && i <= len(b); i++ {
	if c := b[len(b)-i]; c&0xc0 != 0x80 {
	switch {
	case c&0xe0 == 0xc0:
	if i < 2 {
	return len(b) - i
	}
	case c&0xf0 == 0xe0:
	if i < 3 {
	return len(b) - i
	}
	case c&0xf8 == 0xf0:
	if i < 4 {
	return len(b) - i
	}
	}
	break
	}
	}
	return len(b)
	}