Switch to using the dep tool and update all the dependencies

2017-05-11 15:39:54 +01:00
parent 5135ff73cb
commit 98c2d2c41b
5321 changed files with 4483197 additions and 5918 deletions
@@ -0,0 +1,174 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package breakpoints handles breakpoint requests we get from the user through
+// the Debuglet Controller, and manages corresponding breakpoints set in the code.
+package breakpoints
+
+import (
+	"log"
+	"sync"
+
+	"golang.org/x/debug"
+	cd "google.golang.org/api/clouddebugger/v2"
+)
+
+// BreakpointStore stores the set of breakpoints for a program.
+type BreakpointStore struct {
+	mu sync.Mutex
+	// prog is the program being debugged.
+	prog debug.Program
+	// idToBreakpoint is a map from breakpoint identifier to *cd.Breakpoint.  The
+	// map value is nil if the breakpoint is inactive.  A breakpoint is active if:
+	// - We received it from the Debuglet Controller, and it was active at the time;
+	// - We were able to set code breakpoints for it;
+	// - We have not reached any of those code breakpoints while satisfying the
+	//   breakpoint's conditions, or the breakpoint has action LOG; and
+	// - The Debuglet Controller hasn't informed us the breakpoint has become inactive.
+	idToBreakpoint map[string]*cd.Breakpoint
+	// pcToBps and bpToPCs store the many-to-many relationship between breakpoints we
+	// received from the Debuglet Controller and the code breakpoints we set for them.
+	pcToBps map[uint64][]*cd.Breakpoint
+	bpToPCs map[*cd.Breakpoint][]uint64
+	// errors contains any breakpoints which couldn't be set because they caused an
+	// error.  These are retrieved with ErrorBreakpoints, and the caller is
+	// expected to handle sending updates for them.
+	errors []*cd.Breakpoint
+}
+
+// NewBreakpointStore returns a BreakpointStore for the given program.
+func NewBreakpointStore(prog debug.Program) *BreakpointStore {
+	return &BreakpointStore{
+		idToBreakpoint: make(map[string]*cd.Breakpoint),
+		pcToBps:        make(map[uint64][]*cd.Breakpoint),
+		bpToPCs:        make(map[*cd.Breakpoint][]uint64),
+		prog:           prog,
+	}
+}
+
+// ProcessBreakpointList applies updates received from the Debuglet Controller through a List call.
+func (bs *BreakpointStore) ProcessBreakpointList(bps []*cd.Breakpoint) {
+	bs.mu.Lock()
+	defer bs.mu.Unlock()
+	for _, bp := range bps {
+		if storedBp, ok := bs.idToBreakpoint[bp.Id]; ok {
+			if storedBp != nil && bp.IsFinalState {
+				// IsFinalState indicates that the breakpoint has been made inactive.
+				bs.removeBreakpointLocked(storedBp)
+			}
+		} else {
+			if bp.IsFinalState {
+				// The controller is notifying us that the breakpoint is no longer active,
+				// but we didn't know about it anyway.
+				continue
+			}
+			if bp.Action != "" && bp.Action != "CAPTURE" && bp.Action != "LOG" {
+				bp.IsFinalState = true
+				bp.Status = &cd.StatusMessage{
+					Description: &cd.FormatMessage{Format: "Action is not supported"},
+					IsError:     true,
+				}
+				bs.errors = append(bs.errors, bp)
+				// Note in idToBreakpoint that we've already seen this breakpoint, so that we
+				// don't try to report it as an error multiple times.
+				bs.idToBreakpoint[bp.Id] = nil
+				continue
+			}
+			pcs, err := bs.prog.BreakpointAtLine(bp.Location.Path, uint64(bp.Location.Line))
+			if err != nil {
+				log.Printf("error setting breakpoint at %s:%d: %v", bp.Location.Path, bp.Location.Line, err)
+			}
+			if len(pcs) == 0 {
+				// We can't find a PC for this breakpoint's source line, so don't make it active.
+				// TODO: we could snap the line to a location where we can break, or report an error to the user.
+				bs.idToBreakpoint[bp.Id] = nil
+			} else {
+				bs.idToBreakpoint[bp.Id] = bp
+				for _, pc := range pcs {
+					bs.pcToBps[pc] = append(bs.pcToBps[pc], bp)
+				}
+				bs.bpToPCs[bp] = pcs
+			}
+		}
+	}
+}
+
+// ErrorBreakpoints returns a slice of Breakpoints that caused errors when the
+// BreakpointStore tried to process them, and resets the list of such
+// breakpoints.
+// The caller is expected to send updates to the server to indicate the errors.
+func (bs *BreakpointStore) ErrorBreakpoints() []*cd.Breakpoint {
+	bs.mu.Lock()
+	defer bs.mu.Unlock()
+	bps := bs.errors
+	bs.errors = nil
+	return bps
+}
+
+// BreakpointsAtPC returns all the breakpoints for which we set a code
+// breakpoint at the given address.
+func (bs *BreakpointStore) BreakpointsAtPC(pc uint64) []*cd.Breakpoint {
+	bs.mu.Lock()
+	defer bs.mu.Unlock()
+	return bs.pcToBps[pc]
+}
+
+// RemoveBreakpoint makes the given breakpoint inactive.
+// This is called when either the debugged program hits the breakpoint, or the Debuglet
+// Controller informs us that the breakpoint is now inactive.
+func (bs *BreakpointStore) RemoveBreakpoint(bp *cd.Breakpoint) {
+	bs.mu.Lock()
+	bs.removeBreakpointLocked(bp)
+	bs.mu.Unlock()
+}
+
+func (bs *BreakpointStore) removeBreakpointLocked(bp *cd.Breakpoint) {
+	// Set the ID's corresponding breakpoint to nil, so that we won't activate it
+	// if we see it again.
+	// TODO: we could delete it after a few seconds.
+	bs.idToBreakpoint[bp.Id] = nil
+
+	// Delete bp from the list of cd breakpoints at each of its corresponding
+	// code breakpoint locations, and delete any code breakpoints which no longer
+	// have a corresponding cd breakpoint.
+	var codeBreakpointsToDelete []uint64
+	for _, pc := range bs.bpToPCs[bp] {
+		bps := remove(bs.pcToBps[pc], bp)
+		if len(bps) == 0 {
+			// bp was the last breakpoint set at this PC, so delete the code breakpoint.
+			codeBreakpointsToDelete = append(codeBreakpointsToDelete, pc)
+			delete(bs.pcToBps, pc)
+		} else {
+			bs.pcToBps[pc] = bps
+		}
+	}
+	if len(codeBreakpointsToDelete) > 0 {
+		bs.prog.DeleteBreakpoints(codeBreakpointsToDelete)
+	}
+	delete(bs.bpToPCs, bp)
+}
+
+// remove updates rs by removing r, then returns rs.
+// The mutex in the BreakpointStore which contains rs should be held.
+func remove(rs []*cd.Breakpoint, r *cd.Breakpoint) []*cd.Breakpoint {
+	for i := range rs {
+		if rs[i] == r {
+			rs[i] = rs[len(rs)-1]
+			rs = rs[0 : len(rs)-1]
+			return rs
+		}
+	}
+	// We shouldn't reach here.
+	return rs
+}
@@ -0,0 +1,168 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package breakpoints
+
+import (
+	"reflect"
+	"testing"
+
+	"golang.org/x/debug"
+	cd "google.golang.org/api/clouddebugger/v2"
+)
+
+var (
+	testPC1     uint64 = 0x1234
+	testPC2     uint64 = 0x5678
+	testPC3     uint64 = 0x3333
+	testFile           = "foo.go"
+	testLine    uint64 = 42
+	testLine2   uint64 = 99
+	testLogPC   uint64 = 0x9abc
+	testLogLine uint64 = 43
+	testBadPC   uint64 = 0xdef0
+	testBadLine uint64 = 44
+	testBP             = &cd.Breakpoint{
+		Action:       "CAPTURE",
+		Id:           "TestBreakpoint",
+		IsFinalState: false,
+		Location:     &cd.SourceLocation{Path: testFile, Line: int64(testLine)},
+	}
+	testBP2 = &cd.Breakpoint{
+		Action:       "CAPTURE",
+		Id:           "TestBreakpoint2",
+		IsFinalState: false,
+		Location:     &cd.SourceLocation{Path: testFile, Line: int64(testLine2)},
+	}
+	testLogBP = &cd.Breakpoint{
+		Action:       "LOG",
+		Id:           "TestLogBreakpoint",
+		IsFinalState: false,
+		Location:     &cd.SourceLocation{Path: testFile, Line: int64(testLogLine)},
+	}
+	testBadBP = &cd.Breakpoint{
+		Action:       "BEEP",
+		Id:           "TestBadBreakpoint",
+		IsFinalState: false,
+		Location:     &cd.SourceLocation{Path: testFile, Line: int64(testBadLine)},
+	}
+)
+
+func TestBreakpointStore(t *testing.T) {
+	p := &Program{breakpointPCs: make(map[uint64]bool)}
+	bs := NewBreakpointStore(p)
+	checkPCs := func(expected map[uint64]bool) {
+		if !reflect.DeepEqual(p.breakpointPCs, expected) {
+			t.Errorf("got breakpoint map %v want %v", p.breakpointPCs, expected)
+		}
+	}
+	bs.ProcessBreakpointList([]*cd.Breakpoint{testBP, testBP2, testLogBP, testBadBP})
+	checkPCs(map[uint64]bool{
+		testPC1:   true,
+		testPC2:   true,
+		testPC3:   true,
+		testLogPC: true,
+	})
+	for _, test := range []struct {
+		pc       uint64
+		expected []*cd.Breakpoint
+	}{
+		{testPC1, []*cd.Breakpoint{testBP}},
+		{testPC2, []*cd.Breakpoint{testBP}},
+		{testPC3, []*cd.Breakpoint{testBP2}},
+		{testLogPC, []*cd.Breakpoint{testLogBP}},
+	} {
+		if bps := bs.BreakpointsAtPC(test.pc); !reflect.DeepEqual(bps, test.expected) {
+			t.Errorf("BreakpointsAtPC(%x): got %v want %v", test.pc, bps, test.expected)
+		}
+	}
+	testBP2.IsFinalState = true
+	bs.ProcessBreakpointList([]*cd.Breakpoint{testBP, testBP2, testLogBP, testBadBP})
+	checkPCs(map[uint64]bool{
+		testPC1:   true,
+		testPC2:   true,
+		testPC3:   false,
+		testLogPC: true,
+	})
+	bs.RemoveBreakpoint(testBP)
+	checkPCs(map[uint64]bool{
+		testPC1:   false,
+		testPC2:   false,
+		testPC3:   false,
+		testLogPC: true,
+	})
+	for _, pc := range []uint64{testPC1, testPC2, testPC3} {
+		if bps := bs.BreakpointsAtPC(pc); len(bps) != 0 {
+			t.Errorf("BreakpointsAtPC(%x): got %v want []", pc, bps)
+		}
+	}
+	// bs.ErrorBreakpoints should return testBadBP.
+	errorBps := bs.ErrorBreakpoints()
+	if len(errorBps) != 1 {
+		t.Errorf("ErrorBreakpoints: got %d want 1", len(errorBps))
+	} else {
+		bp := errorBps[0]
+		if bp.Id != testBadBP.Id {
+			t.Errorf("ErrorBreakpoints: got id %q want 1", bp.Id)
+		}
+		if bp.Status == nil || !bp.Status.IsError {
+			t.Errorf("ErrorBreakpoints: got %v, want error", bp.Status)
+		}
+	}
+	// The error should have been removed by the last call to bs.ErrorBreakpoints.
+	errorBps = bs.ErrorBreakpoints()
+	if len(errorBps) != 0 {
+		t.Errorf("ErrorBreakpoints: got %d want 0", len(errorBps))
+	}
+	// Even if testBadBP is sent in a new list, it should not be returned again.
+	bs.ProcessBreakpointList([]*cd.Breakpoint{testBadBP})
+	errorBps = bs.ErrorBreakpoints()
+	if len(errorBps) != 0 {
+		t.Errorf("ErrorBreakpoints: got %d want 0", len(errorBps))
+	}
+}
+
+// Program implements the similarly-named interface in x/debug.
+// ValueCollector should only call its BreakpointAtLine and DeleteBreakpoints methods.
+type Program struct {
+	debug.Program
+	// breakpointPCs contains the state of code breakpoints -- true if the
+	// breakpoint is currently set, false if it has been deleted.
+	breakpointPCs map[uint64]bool
+}
+
+func (p *Program) BreakpointAtLine(file string, line uint64) ([]uint64, error) {
+	var pcs []uint64
+	switch {
+	case file == testFile && line == testLine:
+		pcs = []uint64{testPC1, testPC2}
+	case file == testFile && line == testLine2:
+		pcs = []uint64{testPC3}
+	case file == testFile && line == testLogLine:
+		pcs = []uint64{testLogPC}
+	default:
+		pcs = []uint64{0xbad}
+	}
+	for _, pc := range pcs {
+		p.breakpointPCs[pc] = true
+	}
+	return pcs, nil
+}
+
+func (p *Program) DeleteBreakpoints(pcs []uint64) error {
+	for _, pc := range pcs {
+		p.breakpointPCs[pc] = false
+	}
+	return nil
+}
@@ -0,0 +1,279 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package controller is a library for interacting with the Google Cloud Debugger's Debuglet Controller service.
+package controller
+
+import (
+	"crypto/sha256"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log"
+	"sync"
+
+	"golang.org/x/net/context"
+	"golang.org/x/oauth2"
+	cd "google.golang.org/api/clouddebugger/v2"
+	"google.golang.org/api/googleapi"
+	"google.golang.org/api/option"
+	"google.golang.org/api/transport"
+)
+
+const (
+	// agentVersionString identifies the agent to the service.
+	agentVersionString = "google.com/go-gcp/v0.2"
+	// initWaitToken is the wait token sent in the first Update request to a server.
+	initWaitToken = "init"
+)
+
+var (
+	// ErrListUnchanged is returned by List if the server time limit is reached
+	// before the list of breakpoints changes.
+	ErrListUnchanged = errors.New("breakpoint list unchanged")
+	// ErrDebuggeeDisabled is returned by List or Update if the server has disabled
+	// this Debuggee.  The caller can retry later.
+	ErrDebuggeeDisabled = errors.New("debuglet disabled by server")
+)
+
+// Controller manages a connection to the Debuglet Controller service.
+type Controller struct {
+	s serviceInterface
+	// waitToken is sent with List requests so the server knows which set of
+	// breakpoints this client has already seen. Each successful List request
+	// returns a new waitToken to send in the next request.
+	waitToken string
+	// verbose determines whether to do some logging
+	verbose bool
+	// options, uniquifier and description are used in register.
+	options     Options
+	uniquifier  string
+	description string
+	// mu protects debuggeeID
+	mu sync.Mutex
+	// debuggeeID is returned from the server on registration, and is passed back
+	// to the server in List and Update requests.
+	debuggeeID string
+}
+
+// Options controls how the Debuglet Controller client identifies itself to the server.
+// See https://cloud.google.com/storage/docs/projects and
+// https://cloud.google.com/tools/cloud-debugger/setting-up-on-compute-engine
+// for further documentation of these parameters.
+type Options struct {
+	ProjectNumber  string              // GCP Project Number.
+	ProjectID      string              // GCP Project ID.
+	AppModule      string              // Module name for the debugged program.
+	AppVersion     string              // Version number for this module.
+	SourceContexts []*cd.SourceContext // Description of source.
+	Verbose        bool
+	TokenSource    oauth2.TokenSource // Source of Credentials used for Stackdriver Debugger.
+}
+
+type serviceInterface interface {
+	Register(ctx context.Context, req *cd.RegisterDebuggeeRequest) (*cd.RegisterDebuggeeResponse, error)
+	Update(ctx context.Context, debuggeeID, breakpointID string, req *cd.UpdateActiveBreakpointRequest) (*cd.UpdateActiveBreakpointResponse, error)
+	List(ctx context.Context, debuggeeID, waitToken string) (*cd.ListActiveBreakpointsResponse, error)
+}
+
+var newService = func(ctx context.Context, tokenSource oauth2.TokenSource) (serviceInterface, error) {
+	httpClient, endpoint, err := transport.NewHTTPClient(ctx, option.WithTokenSource(tokenSource))
+	if err != nil {
+		return nil, err
+	}
+	s, err := cd.New(httpClient)
+	if err != nil {
+		return nil, err
+	}
+	if endpoint != "" {
+		s.BasePath = endpoint
+	}
+	return &service{s: s}, nil
+}
+
+type service struct {
+	s *cd.Service
+}
+
+func (s service) Register(ctx context.Context, req *cd.RegisterDebuggeeRequest) (*cd.RegisterDebuggeeResponse, error) {
+	call := cd.NewControllerDebuggeesService(s.s).Register(req)
+	return call.Context(ctx).Do()
+}
+
+func (s service) Update(ctx context.Context, debuggeeID, breakpointID string, req *cd.UpdateActiveBreakpointRequest) (*cd.UpdateActiveBreakpointResponse, error) {
+	call := cd.NewControllerDebuggeesBreakpointsService(s.s).Update(debuggeeID, breakpointID, req)
+	return call.Context(ctx).Do()
+}
+
+func (s service) List(ctx context.Context, debuggeeID, waitToken string) (*cd.ListActiveBreakpointsResponse, error) {
+	call := cd.NewControllerDebuggeesBreakpointsService(s.s).List(debuggeeID)
+	call.WaitToken(waitToken)
+	return call.Context(ctx).Do()
+}
+
+// NewController connects to the Debuglet Controller server using the given options,
+// and returns a Controller for that connection.
+// Google Application Default Credentials are used to connect to the Debuglet Controller;
+// see https://developers.google.com/identity/protocols/application-default-credentials
+func NewController(ctx context.Context, o Options) (*Controller, error) {
+	// We build a JSON encoding of o.SourceContexts so we can hash it.
+	scJSON, err := json.Marshal(o.SourceContexts)
+	if err != nil {
+		scJSON = nil
+		o.SourceContexts = nil
+	}
+
+	// Compute a uniquifier string by hashing the project number, app module name,
+	// app module version, debuglet version, and source context.
+	// The choice of hash function is arbitrary.
+	h := sha256.Sum256([]byte(fmt.Sprintf("%d %s %d %s %d %s %d %s %d %s",
+		len(o.ProjectNumber), o.ProjectNumber,
+		len(o.AppModule), o.AppModule,
+		len(o.AppVersion), o.AppVersion,
+		len(agentVersionString), agentVersionString,
+		len(scJSON), scJSON)))
+	uniquifier := fmt.Sprintf("%X", h[0:16]) // 32 hex characters
+
+	description := o.ProjectID
+	if o.AppModule != "" {
+		description += "-" + o.AppModule
+	}
+	if o.AppVersion != "" {
+		description += "-" + o.AppVersion
+	}
+
+	s, err := newService(ctx, o.TokenSource)
+	if err != nil {
+		return nil, err
+	}
+
+	// Construct client.
+	c := &Controller{
+		s:           s,
+		waitToken:   initWaitToken,
+		verbose:     o.Verbose,
+		options:     o,
+		uniquifier:  uniquifier,
+		description: description,
+	}
+
+	return c, nil
+}
+
+func (c *Controller) getDebuggeeID(ctx context.Context) (string, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if c.debuggeeID != "" {
+		return c.debuggeeID, nil
+	}
+	// The debuglet hasn't been registered yet, or it is disabled and we should try registering again.
+	if err := c.register(ctx); err != nil {
+		return "", err
+	}
+	return c.debuggeeID, nil
+}
+
+// List retrieves the current list of breakpoints from the server.
+// If the set of breakpoints on the server is the same as the one returned in
+// the previous call to List, the server can delay responding until it changes,
+// and return an error instead if no change occurs before a time limit the
+// server sets.  List can't be called concurrently with itself.
+func (c *Controller) List(ctx context.Context) (*cd.ListActiveBreakpointsResponse, error) {
+	id, err := c.getDebuggeeID(ctx)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := c.s.List(ctx, id, c.waitToken)
+	if err != nil {
+		if isAbortedError(err) {
+			return nil, ErrListUnchanged
+		}
+		// For other errors, the protocol requires that we attempt to re-register.
+		c.mu.Lock()
+		defer c.mu.Unlock()
+		if regError := c.register(ctx); regError != nil {
+			return nil, regError
+		}
+		return nil, err
+	}
+	if resp == nil {
+		return nil, errors.New("no response")
+	}
+	if c.verbose {
+		log.Printf("List response: %v", resp)
+	}
+	c.waitToken = resp.NextWaitToken
+	return resp, nil
+}
+
+// isAbortedError tests if err is a *googleapi.Error, that it contains one error
+// in Errors, and that that error's Reason is "aborted".
+func isAbortedError(err error) bool {
+	e, _ := err.(*googleapi.Error)
+	if e == nil {
+		return false
+	}
+	if len(e.Errors) != 1 {
+		return false
+	}
+	return e.Errors[0].Reason == "aborted"
+}
+
+// Update reports information to the server about a breakpoint that was hit.
+// Update can be called concurrently with List and Update.
+func (c *Controller) Update(ctx context.Context, breakpointID string, bp *cd.Breakpoint) error {
+	req := &cd.UpdateActiveBreakpointRequest{Breakpoint: bp}
+	if c.verbose {
+		log.Printf("sending update for %s: %v", breakpointID, req)
+	}
+	id, err := c.getDebuggeeID(ctx)
+	if err != nil {
+		return err
+	}
+	_, err = c.s.Update(ctx, id, breakpointID, req)
+	return err
+}
+
+// register calls the Debuglet Controller Register method, and sets c.debuggeeID.
+// c.mu should be locked while calling this function.  List and Update can't
+// make progress until it returns.
+func (c *Controller) register(ctx context.Context) error {
+	req := cd.RegisterDebuggeeRequest{
+		Debuggee: &cd.Debuggee{
+			AgentVersion:   agentVersionString,
+			Description:    c.description,
+			Project:        c.options.ProjectNumber,
+			SourceContexts: c.options.SourceContexts,
+			Uniquifier:     c.uniquifier,
+		},
+	}
+	resp, err := c.s.Register(ctx, &req)
+	if err != nil {
+		return err
+	}
+	if resp == nil {
+		return errors.New("register: no response")
+	}
+	if resp.Debuggee.IsDisabled {
+		// Setting c.debuggeeID to empty makes sure future List and Update calls
+		// will call register first.
+		c.debuggeeID = ""
+	} else {
+		c.debuggeeID = resp.Debuggee.Id
+	}
+	if c.debuggeeID == "" {
+		return ErrDebuggeeDisabled
+	}
+	return nil
+}
@@ -0,0 +1,218 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package controller
+
+import (
+	"testing"
+
+	"golang.org/x/net/context"
+	"golang.org/x/oauth2"
+
+	cd "google.golang.org/api/clouddebugger/v2"
+	"google.golang.org/api/googleapi"
+)
+
+const (
+	testDebuggeeID   = "d12345"
+	testBreakpointID = "bp12345"
+)
+
+var (
+	// The sequence of wait tokens in List requests and responses.
+	expectedWaitToken = []string{"init", "token1", "token2", "token1", "token1"}
+	// The set of breakpoints returned from each List call.
+	expectedBreakpoints = [][]*cd.Breakpoint{
+		nil,
+		{
+			&cd.Breakpoint{
+				Id:           testBreakpointID,
+				IsFinalState: false,
+				Location:     &cd.SourceLocation{Line: 42, Path: "foo.go"},
+			},
+		},
+		nil,
+	}
+	abortedError error = &googleapi.Error{
+		Code:    409,
+		Message: "Conflict",
+		Body: `{
+		 "error": {
+		  "errors": [
+		   {
+		    "domain": "global",
+		    "reason": "aborted",
+		    "message": "Conflict"
+		   }
+		  ],
+		  "code": 409,
+		  "message": "Conflict"
+		 }
+		}`,
+		Errors: []googleapi.ErrorItem{
+			{Reason: "aborted", Message: "Conflict"},
+		},
+	}
+	backendError error = &googleapi.Error{
+		Code:    503,
+		Message: "Backend Error",
+		Body: `{
+		 "error": {
+		  "errors": [
+		   {
+		    "domain": "global",
+		    "reason": "backendError",
+		    "message": "Backend Error"
+		   }
+		  ],
+		  "code": 503,
+		  "message": "Backend Error"
+		 }
+		}`,
+		Errors: []googleapi.ErrorItem{
+			{Reason: "backendError", Message: "Backend Error"},
+		},
+	}
+)
+
+type mockService struct {
+	t                 *testing.T
+	listCallsSeen     int
+	registerCallsSeen int
+}
+
+func (s *mockService) Register(ctx context.Context, req *cd.RegisterDebuggeeRequest) (*cd.RegisterDebuggeeResponse, error) {
+	s.registerCallsSeen++
+	if req.Debuggee == nil {
+		s.t.Errorf("missing debuggee")
+		return nil, nil
+	}
+	if req.Debuggee.AgentVersion == "" {
+		s.t.Errorf("missing agent version")
+	}
+	if req.Debuggee.Description == "" {
+		s.t.Errorf("missing debuglet description")
+	}
+	if req.Debuggee.Project == "" {
+		s.t.Errorf("missing project id")
+	}
+	if req.Debuggee.Uniquifier == "" {
+		s.t.Errorf("missing uniquifier")
+	}
+	return &cd.RegisterDebuggeeResponse{
+		Debuggee: &cd.Debuggee{Id: testDebuggeeID},
+	}, nil
+}
+
+func (s *mockService) Update(ctx context.Context, id, breakpointID string, req *cd.UpdateActiveBreakpointRequest) (*cd.UpdateActiveBreakpointResponse, error) {
+	if id != testDebuggeeID {
+		s.t.Errorf("got debuggee ID %s want %s", id, testDebuggeeID)
+	}
+	if breakpointID != testBreakpointID {
+		s.t.Errorf("got breakpoint ID %s want %s", breakpointID, testBreakpointID)
+	}
+	if !req.Breakpoint.IsFinalState {
+		s.t.Errorf("got IsFinalState = false, want true")
+	}
+	return nil, nil
+}
+
+func (s *mockService) List(ctx context.Context, id, waitToken string) (*cd.ListActiveBreakpointsResponse, error) {
+	if id != testDebuggeeID {
+		s.t.Errorf("got debuggee ID %s want %s", id, testDebuggeeID)
+	}
+	if waitToken != expectedWaitToken[s.listCallsSeen] {
+		s.t.Errorf("got wait token %s want %s", waitToken, expectedWaitToken[s.listCallsSeen])
+	}
+	s.listCallsSeen++
+	if s.listCallsSeen == 4 {
+		return nil, backendError
+	}
+	if s.listCallsSeen == 5 {
+		return nil, abortedError
+	}
+	resp := &cd.ListActiveBreakpointsResponse{
+		Breakpoints:   expectedBreakpoints[s.listCallsSeen-1],
+		NextWaitToken: expectedWaitToken[s.listCallsSeen],
+	}
+	return resp, nil
+}
+
+func TestDebugletControllerClientLibrary(t *testing.T) {
+	var (
+		m    *mockService
+		c    *Controller
+		list *cd.ListActiveBreakpointsResponse
+		err  error
+	)
+	m = &mockService{t: t}
+	newService = func(context.Context, oauth2.TokenSource) (serviceInterface, error) { return m, nil }
+	opts := Options{
+		ProjectNumber: "5",
+		ProjectID:     "p1",
+		AppModule:     "mod1",
+		AppVersion:    "v1",
+	}
+	ctx := context.Background()
+	if c, err = NewController(ctx, opts); err != nil {
+		t.Fatal("Initializing Controller client:", err)
+	}
+	if list, err = c.List(ctx); err != nil {
+		t.Fatal("List:", err)
+	}
+	if m.registerCallsSeen != 1 {
+		t.Errorf("saw %d Register calls, want 1", m.registerCallsSeen)
+	}
+	if list, err = c.List(ctx); err != nil {
+		t.Fatal("List:", err)
+	}
+	if len(list.Breakpoints) != 1 {
+		t.Fatalf("got %d breakpoints, want 1", len(list.Breakpoints))
+	}
+	if err = c.Update(ctx, list.Breakpoints[0].Id, &cd.Breakpoint{Id: testBreakpointID, IsFinalState: true}); err != nil {
+		t.Fatal("Update:", err)
+	}
+	if list, err = c.List(ctx); err != nil {
+		t.Fatal("List:", err)
+	}
+	if m.registerCallsSeen != 1 {
+		t.Errorf("saw %d Register calls, want 1", m.registerCallsSeen)
+	}
+	// The next List call produces an error that should cause a Register call.
+	if list, err = c.List(ctx); err == nil {
+		t.Fatal("List should have returned an error")
+	}
+	if m.registerCallsSeen != 2 {
+		t.Errorf("saw %d Register calls, want 2", m.registerCallsSeen)
+	}
+	// The next List call produces an error that should not cause a Register call.
+	if list, err = c.List(ctx); err == nil {
+		t.Fatal("List should have returned an error")
+	}
+	if m.registerCallsSeen != 2 {
+		t.Errorf("saw %d Register calls, want 2", m.registerCallsSeen)
+	}
+	if m.listCallsSeen != 5 {
+		t.Errorf("saw %d list calls, want 5", m.listCallsSeen)
+	}
+}
+
+func TestIsAbortedError(t *testing.T) {
+	if !isAbortedError(abortedError) {
+		t.Errorf("isAborted(%+v): got false, want true", abortedError)
+	}
+	if isAbortedError(backendError) {
+		t.Errorf("isAborted(%+v): got true, want false", backendError)
+	}
+}
@@ -0,0 +1,460 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package valuecollector is used to collect the values of variables in a program.
+package valuecollector
+
+import (
+	"bytes"
+	"fmt"
+	"strconv"
+	"strings"
+
+	"golang.org/x/debug"
+	cd "google.golang.org/api/clouddebugger/v2"
+)
+
+const (
+	maxArrayLength = 50
+	maxMapLength   = 20
+)
+
+// Collector is given references to variables from a program being debugged
+// using AddVariable. Then when ReadValues is called, the Collector will fetch
+// the values of those variables. Any variables referred to by those values
+// will also be fetched; e.g. the targets of pointers, members of structs,
+// elements of slices, etc. This continues iteratively, building a graph of
+// values, until all the reachable values are fetched, or a size limit is
+// reached.
+//
+// Variables are passed to the Collector as debug.Var, which is used by x/debug
+// to represent references to variables. Values are returned as cd.Variable,
+// which is used by the Debuglet Controller to represent the graph of values.
+//
+// For example, if the program has a struct variable:
+//
+//	foo := SomeStruct{a:42, b:"xyz"}
+//
+// and we call AddVariable with a reference to foo, we will get back a result
+// like:
+//
+//	cd.Variable{Name:"foo", VarTableIndex:10}
+//
+// which denotes a variable named "foo" which will have its value stored in
+// element 10 of the table that will later be returned by ReadValues. That
+// element might be:
+//
+//	out[10] = &cd.Variable{Members:{{Name:"a", VarTableIndex:11},{Name:"b", VarTableIndex:12}}}
+//
+// which denotes a struct with two members a and b, whose values are in elements
+// 11 and 12 of the output table:
+//
+//	out[11] = &cd.Variable{Value:"42"}
+//	out[12] = &cd.Variable{Value:"xyz"}
+type Collector struct {
+	// prog is the program being debugged.
+	prog debug.Program
+	// limit is the maximum size of the output slice of values.
+	limit int
+	// index is a map from references (variables and map elements) to their
+	// locations in the table.
+	index map[reference]int
+	// table contains the references, including those given to the
+	// Collector directly and those the Collector itself found.
+	// If VarTableIndex is set to 0 in a cd.Variable, it is ignored, so the first entry
+	// of table can't be used. On initialization we put a dummy value there.
+	table []reference
+}
+
+// reference represents a value which is in the queue to be read by the
+// collector.  It is either a debug.Var, or a mapElement.
+type reference interface{}
+
+// mapElement represents an element of a map in the debugged program's memory.
+type mapElement struct {
+	debug.Map
+	index uint64
+}
+
+// NewCollector returns a Collector for the given program and size limit.
+// The limit is the maximum size of the slice of values returned by ReadValues.
+func NewCollector(prog debug.Program, limit int) *Collector {
+	return &Collector{
+		prog:  prog,
+		limit: limit,
+		index: make(map[reference]int),
+		table: []reference{debug.Var{}},
+	}
+}
+
+// AddVariable adds another variable to be collected.
+// The Collector doesn't get the value immediately; it returns a cd.Variable
+// that contains an index into the table which will later be returned by
+// ReadValues.
+func (c *Collector) AddVariable(lv debug.LocalVar) *cd.Variable {
+	ret := &cd.Variable{Name: lv.Name}
+	if index, ok := c.add(lv.Var); !ok {
+		// If the add call failed, it's because we reached the size limit.
+		// The Debuglet Controller's convention is to pass it a "Not Captured" error
+		// in this case.
+		ret.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
+	} else {
+		ret.VarTableIndex = int64(index)
+	}
+	return ret
+}
+
+// add adds a reference to the set of values to be read from the
+// program. It returns the index in the output table that will contain the
+// corresponding value. It fails if the table has reached the size limit.
+// It deduplicates references, so the index may be the same as one that was
+// returned from an earlier add call.
+func (c *Collector) add(r reference) (outputIndex int, ok bool) {
+	if i, ok := c.index[r]; ok {
+		return i, true
+	}
+	i := len(c.table)
+	if i >= c.limit {
+		return 0, false
+	}
+	c.index[r] = i
+	c.table = append(c.table, r)
+	return i, true
+}
+
+func addMember(v *cd.Variable, name string) *cd.Variable {
+	v2 := &cd.Variable{Name: name}
+	v.Members = append(v.Members, v2)
+	return v2
+}
+
+// ReadValues fetches values of the variables that were passed to the Collector
+// with AddVariable. The values of any new variables found are also fetched,
+// e.g. the targets of pointers or the members of structs, until we reach the
+// size limit or we run out of values to fetch.
+// The results are output as a []*cd.Variable, which is the type we need to send
+// to the Debuglet Controller after we trigger a breakpoint.
+func (c *Collector) ReadValues() (out []*cd.Variable) {
+	for i := 0; i < len(c.table); i++ {
+		// Create a new cd.Variable for this value, and append it to the output.
+		dcv := new(cd.Variable)
+		out = append(out, dcv)
+		if i == 0 {
+			// The first element is unused.
+			continue
+		}
+		switch x := c.table[i].(type) {
+		case mapElement:
+			key, value, err := c.prog.MapElement(x.Map, x.index)
+			if err != nil {
+				dcv.Status = statusMessage(err.Error(), true, refersToVariableValue)
+				continue
+			}
+			// Add a member for the key.
+			member := addMember(dcv, "key")
+			if index, ok := c.add(key); !ok {
+				// The table is full.
+				member.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
+				continue
+			} else {
+				member.VarTableIndex = int64(index)
+			}
+			// Add a member for the value.
+			member = addMember(dcv, "value")
+			if index, ok := c.add(value); !ok {
+				// The table is full.
+				member.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
+			} else {
+				member.VarTableIndex = int64(index)
+			}
+		case debug.Var:
+			if v, err := c.prog.Value(x); err != nil {
+				dcv.Status = statusMessage(err.Error(), true, refersToVariableValue)
+			} else {
+				c.FillValue(v, dcv)
+			}
+		}
+	}
+	return out
+}
+
+// indexable is an interface for arrays, slices and channels.
+type indexable interface {
+	Len() uint64
+	Element(uint64) debug.Var
+}
+
+// channel implements indexable.
+type channel struct {
+	debug.Channel
+}
+
+func (c channel) Len() uint64 {
+	return c.Length
+}
+
+var (
+	_ indexable = debug.Array{}
+	_ indexable = debug.Slice{}
+	_ indexable = channel{}
+)
+
+// FillValue copies a value into a cd.Variable.  Any variables referred to by
+// that value, e.g. struct members and pointer targets, are added to the
+// collector's queue, to be fetched later by ReadValues.
+func (c *Collector) FillValue(v debug.Value, dcv *cd.Variable) {
+	if c, ok := v.(debug.Channel); ok {
+		// Convert to channel, which implements indexable.
+		v = channel{c}
+	}
+	// Fill in dcv in a manner depending on the type of the value we got.
+	switch val := v.(type) {
+	case int8, int16, int32, int64, bool, uint8, uint16, uint32, uint64, float32, float64, complex64, complex128:
+		// For simple types, we just print the value to dcv.Value.
+		dcv.Value = fmt.Sprint(val)
+	case string:
+		// Put double quotes around strings.
+		dcv.Value = strconv.Quote(val)
+	case debug.String:
+		if uint64(len(val.String)) < val.Length {
+			// This string value was truncated.
+			dcv.Value = strconv.Quote(val.String + "...")
+		} else {
+			dcv.Value = strconv.Quote(val.String)
+		}
+	case debug.Struct:
+		// For structs, we add an entry to dcv.Members for each field in the
+		// struct.
+		// Each member will contain the name of the field, and the index in the
+		// output table which will contain the value of that field.
+		for _, f := range val.Fields {
+			member := addMember(dcv, f.Name)
+			if index, ok := c.add(f.Var); !ok {
+				// The table is full.
+				member.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
+			} else {
+				member.VarTableIndex = int64(index)
+			}
+		}
+	case debug.Map:
+		dcv.Value = fmt.Sprintf("len = %d", val.Length)
+		for i := uint64(0); i < val.Length; i++ {
+			field := addMember(dcv, `⚫`)
+			if i == maxMapLength {
+				field.Name = "..."
+				field.Status = statusMessage(messageTruncated, true, refersToVariableName)
+				break
+			}
+			if index, ok := c.add(mapElement{val, i}); !ok {
+				// The value table is full; add a member to contain the error message.
+				field.Name = "..."
+				field.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
+				break
+			} else {
+				field.VarTableIndex = int64(index)
+			}
+		}
+	case debug.Pointer:
+		if val.Address == 0 {
+			dcv.Value = "<nil>"
+		} else if val.TypeID == 0 {
+			// We don't know the type of the pointer, so just output the address as
+			// the value.
+			dcv.Value = fmt.Sprintf("0x%X", val.Address)
+			dcv.Status = statusMessage(messageUnknownPointerType, false, refersToVariableName)
+		} else {
+			// Adds the pointed-to variable to the table, and links this value to
+			// that table entry through VarTableIndex.
+			dcv.Value = fmt.Sprintf("0x%X", val.Address)
+			target := addMember(dcv, "")
+			if index, ok := c.add(debug.Var(val)); !ok {
+				target.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
+			} else {
+				target.VarTableIndex = int64(index)
+			}
+		}
+	case indexable:
+		// Arrays, slices and channels.
+		dcv.Value = "len = " + fmt.Sprint(val.Len())
+		for j := uint64(0); j < val.Len(); j++ {
+			field := addMember(dcv, fmt.Sprint(`[`, j, `]`))
+			if j == maxArrayLength {
+				field.Name = "..."
+				field.Status = statusMessage(messageTruncated, true, refersToVariableName)
+				break
+			}
+			vr := val.Element(j)
+			if index, ok := c.add(vr); !ok {
+				// The value table is full; add a member to contain the error message.
+				field.Name = "..."
+				field.Status = statusMessage(messageNotCaptured, true, refersToVariableName)
+				break
+			} else {
+				// Add a member with the index as the name.
+				field.VarTableIndex = int64(index)
+			}
+		}
+	default:
+		dcv.Status = statusMessage(messageUnknownType, false, refersToVariableName)
+	}
+}
+
+// statusMessage returns a *cd.StatusMessage with the given message, IsError
+// field and refersTo field.
+func statusMessage(msg string, isError bool, refersTo int) *cd.StatusMessage {
+	return &cd.StatusMessage{
+		Description: &cd.FormatMessage{Format: "$0", Parameters: []string{msg}},
+		IsError:     isError,
+		RefersTo:    refersToString[refersTo],
+	}
+}
+
+// LogString produces a string for a logpoint, substituting in variable values
+// using evaluatedExpressions and varTable.
+func LogString(s string, evaluatedExpressions []*cd.Variable, varTable []*cd.Variable) string {
+	var buf bytes.Buffer
+	fmt.Fprintf(&buf, "LOGPOINT: ")
+	seen := make(map[*cd.Variable]bool)
+	for i := 0; i < len(s); {
+		if s[i] == '$' {
+			i++
+			if num, n, ok := parseToken(s[i:], len(evaluatedExpressions)-1); ok {
+				// This token is one of $0, $1, etc.  Write the corresponding expression.
+				writeExpression(&buf, evaluatedExpressions[num], false, varTable, seen)
+				i += n
+			} else {
+				// Something else, like $$.
+				buf.WriteByte(s[i])
+				i++
+			}
+		} else {
+			buf.WriteByte(s[i])
+			i++
+		}
+	}
+	return buf.String()
+}
+
+func parseToken(s string, max int) (num int, bytesRead int, ok bool) {
+	var i int
+	for i < len(s) && s[i] >= '0' && s[i] <= '9' {
+		i++
+	}
+	num, err := strconv.Atoi(s[:i])
+	return num, i, err == nil && num <= max
+}
+
+// writeExpression recursively writes variables to buf, in a format suitable
+// for logging.  If printName is true, writes the name of the variable.
+func writeExpression(buf *bytes.Buffer, v *cd.Variable, printName bool, varTable []*cd.Variable, seen map[*cd.Variable]bool) {
+	if v == nil {
+		// Shouldn't happen.
+		return
+	}
+	name, value, status, members := v.Name, v.Value, v.Status, v.Members
+
+	// If v.VarTableIndex is not zero, it refers to an element of varTable.
+	// We merge its fields with the fields we got from v.
+	var other *cd.Variable
+	if idx := int(v.VarTableIndex); idx > 0 && idx < len(varTable) {
+		other = varTable[idx]
+	}
+	if other != nil {
+		if name == "" {
+			name = other.Name
+		}
+		if value == "" {
+			value = other.Value
+		}
+		if status == nil {
+			status = other.Status
+		}
+		if len(members) == 0 {
+			members = other.Members
+		}
+	}
+	if printName && name != "" {
+		buf.WriteString(name)
+		buf.WriteByte(':')
+	}
+
+	// If we have seen this value before, write "..." rather than repeating it.
+	if seen[v] {
+		buf.WriteString("...")
+		return
+	}
+	seen[v] = true
+	if other != nil {
+		if seen[other] {
+			buf.WriteString("...")
+			return
+		}
+		seen[other] = true
+	}
+
+	if value != "" && !strings.HasPrefix(value, "len = ") {
+		// A plain value.
+		buf.WriteString(value)
+	} else if status != nil && status.Description != nil {
+		// An error.
+		for _, p := range status.Description.Parameters {
+			buf.WriteByte('(')
+			buf.WriteString(p)
+			buf.WriteByte(')')
+		}
+	} else if name == `⚫` {
+		// A map element.
+		first := true
+		for _, member := range members {
+			if first {
+				first = false
+			} else {
+				buf.WriteByte(':')
+			}
+			writeExpression(buf, member, false, varTable, seen)
+		}
+	} else {
+		// A map, array, slice, channel, or struct.
+		isStruct := value == ""
+		first := true
+		buf.WriteByte('{')
+		for _, member := range members {
+			if first {
+				first = false
+			} else {
+				buf.WriteString(", ")
+			}
+			writeExpression(buf, member, isStruct, varTable, seen)
+		}
+		buf.WriteByte('}')
+	}
+}
+
+const (
+	// Error messages for cd.StatusMessage
+	messageNotCaptured        = "Not captured"
+	messageTruncated          = "Truncated"
+	messageUnknownPointerType = "Unknown pointer type"
+	messageUnknownType        = "Unknown type"
+	// RefersTo values for cd.StatusMessage.
+	refersToVariableName = iota
+	refersToVariableValue
+)
+
+// refersToString contains the strings for each refersTo value.
+// See the definition of StatusMessage in the v2/clouddebugger package.
+var refersToString = map[int]string{
+	refersToVariableName:  "VARIABLE_NAME",
+	refersToVariableValue: "VARIABLE_VALUE",
+}
@@ -0,0 +1,418 @@
+// Copyright 2016 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package valuecollector
+
+import (
+	"fmt"
+	"reflect"
+	"testing"
+
+	"golang.org/x/debug"
+	cd "google.golang.org/api/clouddebugger/v2"
+)
+
+const (
+	// Some arbitrary type IDs for the test, for use in debug.Var's TypeID field.
+	// A TypeID of 0 means the type is unknown, so we start at 1.
+	int16Type = iota + 1
+	stringType
+	structType
+	pointerType
+	arrayType
+	int32Type
+	debugStringType
+	mapType
+	channelType
+	sliceType
+)
+
+func TestValueCollector(t *testing.T) {
+	// Construct the collector.
+	c := NewCollector(&Program{}, 26)
+	// Add some variables of various types, whose values we want the collector to read.
+	variablesToAdd := []debug.LocalVar{
+		{Name: "a", Var: debug.Var{int16Type, 0x1}},
+		{Name: "b", Var: debug.Var{stringType, 0x2}},
+		{Name: "c", Var: debug.Var{structType, 0x3}},
+		{Name: "d", Var: debug.Var{pointerType, 0x4}},
+		{Name: "e", Var: debug.Var{arrayType, 0x5}},
+		{Name: "f", Var: debug.Var{debugStringType, 0x6}},
+		{Name: "g", Var: debug.Var{mapType, 0x7}},
+		{Name: "h", Var: debug.Var{channelType, 0x8}},
+		{Name: "i", Var: debug.Var{sliceType, 0x9}},
+	}
+	expectedResults := []*cd.Variable{
+		&cd.Variable{Name: "a", VarTableIndex: 1},
+		&cd.Variable{Name: "b", VarTableIndex: 2},
+		&cd.Variable{Name: "c", VarTableIndex: 3},
+		&cd.Variable{Name: "d", VarTableIndex: 4},
+		&cd.Variable{Name: "e", VarTableIndex: 5},
+		&cd.Variable{Name: "f", VarTableIndex: 6},
+		&cd.Variable{Name: "g", VarTableIndex: 7},
+		&cd.Variable{Name: "h", VarTableIndex: 8},
+		&cd.Variable{Name: "i", VarTableIndex: 9},
+	}
+	for i, v := range variablesToAdd {
+		added := c.AddVariable(v)
+		if !reflect.DeepEqual(added, expectedResults[i]) {
+			t.Errorf("AddVariable: got %+v want %+v", *added, *expectedResults[i])
+		}
+	}
+	// Read the values, compare the output to what we expect.
+	v := c.ReadValues()
+	expectedValues := []*cd.Variable{
+		&cd.Variable{},
+		&cd.Variable{Value: "1"},
+		&cd.Variable{Value: `"hello"`},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "x", VarTableIndex: 1},
+				&cd.Variable{Name: "y", VarTableIndex: 2},
+			},
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{VarTableIndex: 1},
+			},
+			Value: "0x1",
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "[0]", VarTableIndex: 10},
+				&cd.Variable{Name: "[1]", VarTableIndex: 11},
+				&cd.Variable{Name: "[2]", VarTableIndex: 12},
+				&cd.Variable{Name: "[3]", VarTableIndex: 13},
+			},
+			Value: "len = 4",
+		},
+		&cd.Variable{Value: `"world"`},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "⚫", VarTableIndex: 14},
+				&cd.Variable{Name: "⚫", VarTableIndex: 15},
+				&cd.Variable{Name: "⚫", VarTableIndex: 16},
+			},
+			Value: "len = 3",
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "[0]", VarTableIndex: 17},
+				&cd.Variable{Name: "[1]", VarTableIndex: 18},
+			},
+			Value: "len = 2",
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "[0]", VarTableIndex: 19},
+				&cd.Variable{Name: "[1]", VarTableIndex: 20},
+			},
+			Value: "len = 2",
+		},
+		&cd.Variable{Value: "100"},
+		&cd.Variable{Value: "104"},
+		&cd.Variable{Value: "108"},
+		&cd.Variable{Value: "112"},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "key", VarTableIndex: 21},
+				&cd.Variable{Name: "value", VarTableIndex: 22},
+			},
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "key", VarTableIndex: 23},
+				&cd.Variable{Name: "value", VarTableIndex: 24},
+			},
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "key", VarTableIndex: 25},
+				&cd.Variable{
+					Name: "value",
+					Status: &cd.StatusMessage{
+						Description: &cd.FormatMessage{
+							Format:     "$0",
+							Parameters: []string{"Not captured"},
+						},
+						IsError:  true,
+						RefersTo: "VARIABLE_NAME",
+					},
+				},
+			},
+		},
+		&cd.Variable{Value: "246"},
+		&cd.Variable{Value: "210"},
+		&cd.Variable{Value: "300"},
+		&cd.Variable{Value: "304"},
+		&cd.Variable{Value: "400"},
+		&cd.Variable{Value: "404"},
+		&cd.Variable{Value: "1400"},
+		&cd.Variable{Value: "1404"},
+		&cd.Variable{Value: "2400"},
+	}
+	if !reflect.DeepEqual(v, expectedValues) {
+		t.Errorf("ReadValues: got %v want %v", v, expectedValues)
+		// Do element-by-element comparisons, for more useful error messages.
+		for i := range v {
+			if i < len(expectedValues) && !reflect.DeepEqual(v[i], expectedValues[i]) {
+				t.Errorf("element %d: got %+v want %+v", i, *v[i], *expectedValues[i])
+			}
+		}
+	}
+}
+
+// Program implements the similarly-named interface in x/debug.
+// ValueCollector should only call its Value and MapElement methods.
+type Program struct {
+	debug.Program
+}
+
+func (p *Program) Value(v debug.Var) (debug.Value, error) {
+	// We determine what to return using v.TypeID.
+	switch v.TypeID {
+	case int16Type:
+		// We use the address as the value, so that we're testing whether the right
+		// address was calculated.
+		return int16(v.Address), nil
+	case stringType:
+		// A string.
+		return "hello", nil
+	case structType:
+		// A struct with two elements.
+		return debug.Struct{
+			Fields: []debug.StructField{
+				{
+					Name: "x",
+					Var:  debug.Var{int16Type, 0x1},
+				},
+				{
+					Name: "y",
+					Var:  debug.Var{stringType, 0x2},
+				},
+			},
+		}, nil
+	case pointerType:
+		// A pointer to the first variable above.
+		return debug.Pointer{int16Type, 0x1}, nil
+	case arrayType:
+		// An array of 4 32-bit-wide elements.
+		return debug.Array{
+			ElementTypeID: int32Type,
+			Address:       0x64,
+			Length:        4,
+			StrideBits:    32,
+		}, nil
+	case debugStringType:
+		return debug.String{
+			Length: 5,
+			String: "world",
+		}, nil
+	case mapType:
+		return debug.Map{
+			TypeID:  99,
+			Address: 0x100,
+			Length:  3,
+		}, nil
+	case channelType:
+		return debug.Channel{
+			ElementTypeID: int32Type,
+			Address:       200,
+			Buffer:        210,
+			Length:        2,
+			Capacity:      10,
+			Stride:        4,
+			BufferStart:   9,
+		}, nil
+	case sliceType:
+		// A slice of 2 32-bit-wide elements.
+		return debug.Slice{
+			Array: debug.Array{
+				ElementTypeID: int32Type,
+				Address:       300,
+				Length:        2,
+				StrideBits:    32,
+			},
+			Capacity: 50,
+		}, nil
+	case int32Type:
+		// We use the address as the value, so that we're testing whether the right
+		// address was calculated.
+		return int32(v.Address), nil
+	}
+	return nil, fmt.Errorf("unexpected Value request")
+}
+
+func (p *Program) MapElement(m debug.Map, index uint64) (debug.Var, debug.Var, error) {
+	return debug.Var{TypeID: int16Type, Address: 1000*index + 400},
+		debug.Var{TypeID: int32Type, Address: 1000*index + 404},
+		nil
+}
+
+func TestLogString(t *testing.T) {
+	bp := cd.Breakpoint{
+		Action:           "LOG",
+		LogMessageFormat: "$0 hello, $$7world! $1 $2 $3 $4 $5$6 $7 $8",
+		EvaluatedExpressions: []*cd.Variable{
+			&cd.Variable{Name: "a", VarTableIndex: 1},
+			&cd.Variable{Name: "b", VarTableIndex: 2},
+			&cd.Variable{Name: "c", VarTableIndex: 3},
+			&cd.Variable{Name: "d", VarTableIndex: 4},
+			&cd.Variable{Name: "e", VarTableIndex: 5},
+			&cd.Variable{Name: "f", VarTableIndex: 6},
+			&cd.Variable{Name: "g", VarTableIndex: 7},
+			&cd.Variable{Name: "h", VarTableIndex: 8},
+			&cd.Variable{Name: "i", VarTableIndex: 9},
+		},
+	}
+	varTable := []*cd.Variable{
+		&cd.Variable{},
+		&cd.Variable{Value: "1"},
+		&cd.Variable{Value: `"hello"`},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "x", Value: "1"},
+				&cd.Variable{Name: "y", Value: `"hello"`},
+				&cd.Variable{Name: "z", VarTableIndex: 3},
+			},
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{VarTableIndex: 1},
+			},
+			Value: "0x1",
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "[0]", VarTableIndex: 10},
+				&cd.Variable{Name: "[1]", VarTableIndex: 11},
+				&cd.Variable{Name: "[2]", VarTableIndex: 12},
+				&cd.Variable{Name: "[3]", VarTableIndex: 13},
+			},
+			Value: "len = 4",
+		},
+		&cd.Variable{Value: `"world"`},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "⚫", VarTableIndex: 14},
+				&cd.Variable{Name: "⚫", VarTableIndex: 15},
+				&cd.Variable{Name: "⚫", VarTableIndex: 16},
+			},
+			Value: "len = 3",
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "[0]", VarTableIndex: 17},
+				&cd.Variable{Name: "[1]", VarTableIndex: 18},
+			},
+			Value: "len = 2",
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "[0]", VarTableIndex: 19},
+				&cd.Variable{Name: "[1]", VarTableIndex: 20},
+			},
+			Value: "len = 2",
+		},
+		&cd.Variable{Value: "100"},
+		&cd.Variable{Value: "104"},
+		&cd.Variable{Value: "108"},
+		&cd.Variable{Value: "112"},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "key", VarTableIndex: 21},
+				&cd.Variable{Name: "value", VarTableIndex: 22},
+			},
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "key", VarTableIndex: 23},
+				&cd.Variable{Name: "value", VarTableIndex: 24},
+			},
+		},
+		&cd.Variable{
+			Members: []*cd.Variable{
+				&cd.Variable{Name: "key", VarTableIndex: 25},
+				&cd.Variable{
+					Name: "value",
+					Status: &cd.StatusMessage{
+						Description: &cd.FormatMessage{
+							Format:     "$0",
+							Parameters: []string{"Not captured"},
+						},
+						IsError:  true,
+						RefersTo: "VARIABLE_NAME",
+					},
+				},
+			},
+		},
+		&cd.Variable{Value: "246"},
+		&cd.Variable{Value: "210"},
+		&cd.Variable{Value: "300"},
+		&cd.Variable{Value: "304"},
+		&cd.Variable{Value: "400"},
+		&cd.Variable{Value: "404"},
+		&cd.Variable{Value: "1400"},
+		&cd.Variable{Value: "1404"},
+		&cd.Variable{Value: "2400"},
+	}
+	s := LogString(bp.LogMessageFormat, bp.EvaluatedExpressions, varTable)
+	expected := `LOGPOINT: 1 hello, $7world! "hello" {x:1, y:"hello", z:...} ` +
+		`0x1 {100, 104, 108, 112} "world"{400:404, 1400:1404, 2400:(Not captured)} ` +
+		`{246, 210} {300, 304}`
+	if s != expected {
+		t.Errorf("LogString: got %q want %q", s, expected)
+	}
+}
+
+func TestParseToken(t *testing.T) {
+	for _, c := range []struct {
+		s   string
+		max int
+		num int
+		n   int
+		ok  bool
+	}{
+		{"", 0, 0, 0, false},
+		{".", 0, 0, 0, false},
+		{"0", 0, 0, 1, true},
+		{"0", 1, 0, 1, true},
+		{"00", 0, 0, 2, true},
+		{"1.", 1, 1, 1, true},
+		{"1.", 0, 0, 0, false},
+		{"10", 10, 10, 2, true},
+		{"10..", 10, 10, 2, true},
+		{"10", 11, 10, 2, true},
+		{"10..", 11, 10, 2, true},
+		{"10", 9, 0, 0, false},
+		{"10..", 9, 0, 0, false},
+		{" 10", 10, 0, 0, false},
+		{"010", 10, 10, 3, true},
+		{"123456789", 123456789, 123456789, 9, true},
+		{"123456789", 123456788, 0, 0, false},
+		{"123456789123456789123456789", 999999999, 0, 0, false},
+	} {
+		num, n, ok := parseToken(c.s, c.max)
+		if ok != c.ok {
+			t.Errorf("parseToken(%q, %d): got ok=%t want ok=%t", c.s, c.max, ok, c.ok)
+			continue
+		}
+		if !ok {
+			continue
+		}
+		if num != c.num || n != c.n {
+			t.Errorf("parseToken(%q, %d): got %d,%d,%t want %d,%d,%t", c.s, c.max, num, n, ok, c.num, c.n, c.ok)
+		}
+	}
+}