1 files changed, 277 insertions, 0 deletions
diff --git a/src/cmd/internal/cov/readcovdata.go b/src/cmd/internal/cov/readcovdata.go
new file mode 100644
index 0000000..086be40
--- /dev/null
+++ b/src/cmd/internal/cov/readcovdata.go
@@ -0,0 +1,277 @@
+// Copyright 2022 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 cov
+
+import (
+	"cmd/internal/bio"
+	"fmt"
+	"internal/coverage"
+	"internal/coverage/decodecounter"
+	"internal/coverage/decodemeta"
+	"internal/coverage/pods"
+	"io"
+	"os"
+)
+
+// CovDataReader is a general-purpose helper/visitor object for
+// reading coverage data files in a structured way. Clients create a
+// CovDataReader to process a given collection of coverage data file
+// directories, then pass in a visitor object with methods that get
+// invoked at various important points. CovDataReader is intended
+// to facilitate common coverage data file operations such as
+// merging or intersecting data files, analyzing data files, or
+// dumping data files.
+type CovDataReader struct {
+	vis            CovDataVisitor
+	indirs         []string
+	matchpkg       func(name string) bool
+	flags          CovDataReaderFlags
+	err            error
+	verbosityLevel int
+}
+
+// MakeCovDataReader creates a CovDataReader object to process the
+// given set of input directories. Here 'vis' is a visitor object
+// providing methods to be invoked as we walk through the data,
+// 'indirs' is the set of coverage data directories to examine,
+// 'verbosityLevel' controls the level of debugging trace messages
+// (zero for off, higher for more output), 'flags' stores flags that
+// indicate what to do if errors are detected, and 'matchpkg' is a
+// caller-provided function that can be used to select specific
+// packages by name (if nil, then all packages are included).
+func MakeCovDataReader(vis CovDataVisitor, indirs []string, verbosityLevel int, flags CovDataReaderFlags, matchpkg func(name string) bool) *CovDataReader {
+	return &CovDataReader{
+		vis:            vis,
+		indirs:         indirs,
+		matchpkg:       matchpkg,
+		verbosityLevel: verbosityLevel,
+		flags:          flags,
+	}
+}
+
+// CovDataVisitor defines hooks for clients of CovDataReader. When the
+// coverage data reader makes its way through a coverage meta-data
+// file and counter data files, it will invoke the methods below to
+// hand off info to the client. The normal sequence of expected
+// visitor method invocations is:
+//
+//	for each pod P {
+//		BeginPod(p)
+//		let MF be the meta-data file for P
+//		VisitMetaDataFile(MF)
+//		for each counter data file D in P {
+//			BeginCounterDataFile(D)
+//			for each live function F in D {
+//				VisitFuncCounterData(F)
+//			}
+//			EndCounterDataFile(D)
+//		}
+//		EndCounters(MF)
+//		for each package PK in MF {
+//			BeginPackage(PK)
+//			if <PK matched according to package pattern and/or modpath> {
+//				for each function PF in PK {
+//					VisitFunc(PF)
+//				}
+//			}
+//			EndPackage(PK)
+//		}
+//		EndPod(p)
+//	}
+//	Finish()
+
+type CovDataVisitor interface {
+	// Invoked at the start and end of a given pod (a pod here is a
+	// specific coverage meta-data files with the counter data files
+	// that correspond to it).
+	BeginPod(p pods.Pod)
+	EndPod(p pods.Pod)
+
+	// Invoked when the reader is starting to examine the meta-data
+	// file for a pod. Here 'mdf' is the path of the file, and 'mfr'
+	// is an open meta-data reader.
+	VisitMetaDataFile(mdf string, mfr *decodemeta.CoverageMetaFileReader)
+
+	// Invoked when the reader processes a counter data file, first
+	// the 'begin' method at the start, then the 'end' method when
+	// we're done with the file.
+	BeginCounterDataFile(cdf string, cdr *decodecounter.CounterDataReader, dirIdx int)
+	EndCounterDataFile(cdf string, cdr *decodecounter.CounterDataReader, dirIdx int)
+
+	// Invoked once for each live function in the counter data file.
+	VisitFuncCounterData(payload decodecounter.FuncPayload)
+
+	// Invoked when we've finished processing the counter files in a
+	// POD (e.g. no more calls to VisitFuncCounterData).
+	EndCounters()
+
+	// Invoked for each package in the meta-data file for the pod,
+	// first the 'begin' method when processing of the package starts,
+	// then the 'end' method when we're done
+	BeginPackage(pd *decodemeta.CoverageMetaDataDecoder, pkgIdx uint32)
+	EndPackage(pd *decodemeta.CoverageMetaDataDecoder, pkgIdx uint32)
+
+	// Invoked for each function  the package being visited.
+	VisitFunc(pkgIdx uint32, fnIdx uint32, fd *coverage.FuncDesc)
+
+	// Invoked when all counter + meta-data file processing is complete.
+	Finish()
+}
+
+type CovDataReaderFlags uint32
+
+const (
+	CovDataReaderNoFlags CovDataReaderFlags = 0
+	PanicOnError                            = 1 << iota
+	PanicOnWarning
+)
+
+func (r *CovDataReader) Visit() error {
+	podlist, err := pods.CollectPods(r.indirs, false)
+	if err != nil {
+		return fmt.Errorf("reading inputs: %v", err)
+	}
+	if len(podlist) == 0 {
+		r.warn("no applicable files found in input directories")
+	}
+	for _, p := range podlist {
+		if err := r.visitPod(p); err != nil {
+			return err
+		}
+	}
+	r.vis.Finish()
+	return nil
+}
+
+func (r *CovDataReader) verb(vlevel int, s string, a ...interface{}) {
+	if r.verbosityLevel >= vlevel {
+		fmt.Fprintf(os.Stderr, s, a...)
+		fmt.Fprintf(os.Stderr, "\n")
+	}
+}
+
+func (r *CovDataReader) warn(s string, a ...interface{}) {
+	fmt.Fprintf(os.Stderr, "warning: ")
+	fmt.Fprintf(os.Stderr, s, a...)
+	fmt.Fprintf(os.Stderr, "\n")
+	if (r.flags & PanicOnWarning) != 0 {
+		panic("unexpected warning")
+	}
+}
+
+func (r *CovDataReader) fatal(s string, a ...interface{}) error {
+	if r.err != nil {
+		return nil
+	}
+	errstr := "error: " + fmt.Sprintf(s, a...) + "\n"
+	if (r.flags & PanicOnError) != 0 {
+		fmt.Fprintf(os.Stderr, "%s", errstr)
+		panic("fatal error")
+	}
+	r.err = fmt.Errorf("%s", errstr)
+	return r.err
+}
+
+// visitPod examines a coverage data 'pod', that is, a meta-data file and
+// zero or more counter data files that refer to that meta-data file.
+func (r *CovDataReader) visitPod(p pods.Pod) error {
+	r.verb(1, "visiting pod: metafile %s with %d counter files",
+		p.MetaFile, len(p.CounterDataFiles))
+	r.vis.BeginPod(p)
+
+	// Open meta-file
+	f, err := os.Open(p.MetaFile)
+	if err != nil {
+		return r.fatal("unable to open meta-file %s", p.MetaFile)
+	}
+	defer f.Close()
+	br := bio.NewReader(f)
+	fi, err := f.Stat()
+	if err != nil {
+		return r.fatal("unable to stat metafile %s: %v", p.MetaFile, err)
+	}
+	fileView := br.SliceRO(uint64(fi.Size()))
+	br.MustSeek(0, io.SeekStart)
+
+	r.verb(1, "fileView for pod is length %d", len(fileView))
+
+	var mfr *decodemeta.CoverageMetaFileReader
+	mfr, err = decodemeta.NewCoverageMetaFileReader(f, fileView)
+	if err != nil {
+		return r.fatal("decoding meta-file %s: %s", p.MetaFile, err)
+	}
+	r.vis.VisitMetaDataFile(p.MetaFile, mfr)
+
+	// Read counter data files.
+	for k, cdf := range p.CounterDataFiles {
+		cf, err := os.Open(cdf)
+		if err != nil {
+			return r.fatal("opening counter data file %s: %s", cdf, err)
+		}
+		defer func(f *os.File) {
+			f.Close()
+		}(cf)
+		var mr *MReader
+		mr, err = NewMreader(cf)
+		if err != nil {
+			return r.fatal("creating reader for counter data file %s: %s", cdf, err)
+		}
+		var cdr *decodecounter.CounterDataReader
+		cdr, err = decodecounter.NewCounterDataReader(cdf, mr)
+		if err != nil {
+			return r.fatal("reading counter data file %s: %s", cdf, err)
+		}
+		r.vis.BeginCounterDataFile(cdf, cdr, p.Origins[k])
+		var data decodecounter.FuncPayload
+		for {
+			ok, err := cdr.NextFunc(&data)
+			if err != nil {
+				return r.fatal("reading counter data file %s: %v", cdf, err)
+			}
+			if !ok {
+				break
+			}
+			r.vis.VisitFuncCounterData(data)
+		}
+		r.vis.EndCounterDataFile(cdf, cdr, p.Origins[k])
+	}
+	r.vis.EndCounters()
+
+	// NB: packages in the meta-file will be in dependency order (basically
+	// the order in which init files execute). Do we want an additional sort
+	// pass here, say by packagepath?
+	np := uint32(mfr.NumPackages())
+	payload := []byte{}
+	for pkIdx := uint32(0); pkIdx < np; pkIdx++ {
+		var pd *decodemeta.CoverageMetaDataDecoder
+		pd, payload, err = mfr.GetPackageDecoder(pkIdx, payload)
+		if err != nil {
+			return r.fatal("reading pkg %d from meta-file %s: %s", pkIdx, p.MetaFile, err)
+		}
+		r.processPackage(p.MetaFile, pd, pkIdx)
+	}
+	r.vis.EndPod(p)
+
+	return nil
+}
+
+func (r *CovDataReader) processPackage(mfname string, pd *decodemeta.CoverageMetaDataDecoder, pkgIdx uint32) error {
+	if r.matchpkg != nil {
+		if !r.matchpkg(pd.PackagePath()) {
+			return nil
+		}
+	}
+	r.vis.BeginPackage(pd, pkgIdx)
+	nf := pd.NumFuncs()
+	var fd coverage.FuncDesc
+	for fidx := uint32(0); fidx < nf; fidx++ {
+		if err := pd.ReadFunc(fidx, &fd); err != nil {
+			return r.fatal("reading meta-data file %s: %v", mfname, err)
+		}
+		r.vis.VisitFunc(pkgIdx, fidx, &fd)
+	}
+	r.vis.EndPackage(pd, pkgIdx)
+	return nil
+}