implements: add implements cli interface

Add a main.go file to complete the `implements` cli tool.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

contrib/implements/main.go

@@ -0,0 +1,95 @@
+package main
+
+// The "implements" tool uses code analysis and the conventions of the go-ceph
+// project to produce a report comparing what go-ceph implements and what
+// exists in the C ceph APIs. Only (lib)cephfs, (lib)rados, and (lib)rbd are
+// and the equilvaent go-ceph packages are supported.
+//
+// Examples:
+//   # generate a full report on cephfs with a function listing
+//   ./implements --list ./cephfs
+//
+//   # generate a brief summary on all packages
+//   ./implements ./cephfs ./rados ./rbd
+//
+//   # generate a comprehensive report on rbd in json
+//   ./implements --list --annotate --json rbd
+
+import (
+	"flag"
+	"log"
+	"os"
+	"path"
+
+	"github.com/ceph/go-ceph/contrib/implements/internal/implements"
+)
+
+var (
+	verbose    bool
+	list       bool
+	annotate   bool
+	reportJSON bool
+
+	// verbose logger
+	logger = log.New(os.Stderr, "(implements/verbose) ", log.LstdFlags)
+)
+
+func abort(msg string) {
+	log.Fatalf("error: %v\n", msg)
+}
+
+func init() {
+	flag.BoolVar(&verbose, "verbose", false, "be more verbose (for debugging)")
+	flag.BoolVar(&list, "list", false, "list functions")
+	flag.BoolVar(&annotate, "annotate", false, "annotate functions")
+	flag.BoolVar(&reportJSON, "json", false, "use JSON output format")
+}
+
+func main() {
+	flag.Parse()
+	args := flag.Args()
+	if len(args) < 1 {
+		abort("missing package(s) to analyze")
+	}
+	if verbose {
+		implements.SetLogger(logger)
+	}
+
+	var r implements.Reporter
+	o := implements.ReportOptions{
+		List:     list,
+		Annotate: annotate,
+	}
+	switch {
+	case reportJSON:
+		r = implements.NewJSONReport(o, os.Stdout)
+	default:
+		r = implements.NewTextReport(o)
+	}
+
+	for _, pkgref := range args[0:] {
+		source, pkg := path.Split(pkgref)
+		switch pkg {
+		case "cephfs", "rados", "rbd":
+			if verbose {
+				logger.Printf("Processing package: %s\n", pkg)
+			}
+		default:
+			abort("unknown package name: " + pkg)
+		}
+		if source == "" {
+			source = "."
+		}
+		ii := implements.NewInspector()
+		if err := implements.CephCFunctions(pkg, ii); err != nil {
+			abort(err.Error())
+		}
+		if err := implements.CephGoFunctions(source, pkg, ii); err != nil {
+			abort(err.Error())
+		}
+		if err := r.Report(pkg, ii); err != nil {
+			abort(err.Error())
+		}
+	}
+	r.Done()
+}