Vendor dependencies for GCS

vendor/cloud.google.com/go/cmd/go-cloud-debug-agent/internal/breakpoints/breakpoints.go

@@ -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
+}