defer to GenericCataloger instances for pkg catalogers

Signed-off-by: Alex Goodman <alex.goodman@anchore.com>

syft/cataloger/deb/parse_dpkg_status.go

@@ -0,0 +1,105 @@
+package deb
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"strings"
+
+	"github.com/anchore/syft/syft/cataloger/common"
+	"github.com/anchore/syft/syft/pkg"
+	"github.com/mitchellh/mapstructure"
+)
+
+// integrity check
+var _ common.ParserFn = parseDpkgStatus
+
+var errEndOfPackages = fmt.Errorf("no more packages to read")
+
+// parseDpkgStatus is a parser function for Debian DB status contents, returning all Debian packages listed.
+func parseDpkgStatus(_ string, reader io.Reader) ([]pkg.Package, error) {
+	buffedReader := bufio.NewReader(reader)
+	var packages = make([]pkg.Package, 0)
+
+	for {
+		entry, err := parseDpkgStatusEntry(buffedReader)
+		if err != nil {
+			if err == errEndOfPackages {
+				break
+			}
+			return nil, err
+		}
+		packages = append(packages, pkg.Package{
+			Name:     entry.Package,
+			Version:  entry.Version,
+			Type:     pkg.DebPkg,
+			Metadata: entry,
+		})
+	}
+
+	return packages, nil
+}
+
+// parseDpkgStatusEntry returns an individual Dpkg entry, or returns errEndOfPackages if there are no more packages to parse from the reader.
+func parseDpkgStatusEntry(reader *bufio.Reader) (entry pkg.DpkgMetadata, err error) {
+	dpkgFields := make(map[string]string)
+	var key string
+
+	for {
+		line, err := reader.ReadString('\n')
+		if err != nil {
+			if err == io.EOF {
+				return pkg.DpkgMetadata{}, errEndOfPackages
+			}
+			return pkg.DpkgMetadata{}, err
+		}
+
+		line = strings.TrimRight(line, "\n")
+
+		// empty line indicates end of entry
+		if len(line) == 0 {
+			// if the entry has not started, keep parsing lines
+			if len(dpkgFields) == 0 {
+				continue
+			}
+			break
+		}
+
+		switch {
+		case strings.HasPrefix(line, " "):
+			// a field-body continuation
+			if len(key) == 0 {
+				return pkg.DpkgMetadata{}, fmt.Errorf("no match for continuation: line: '%s'", line)
+			}
+
+			val, ok := dpkgFields[key]
+			if !ok {
+				return pkg.DpkgMetadata{}, fmt.Errorf("no previous key exists, expecting: %s", key)
+			}
+			// concatenate onto previous value
+			val = fmt.Sprintf("%s\n %s", val, strings.TrimSpace(line))
+			dpkgFields[key] = val
+		default:
+			// parse a new key
+			if i := strings.Index(line, ":"); i > 0 {
+				key = strings.TrimSpace(line[0:i])
+				val := strings.TrimSpace(line[i+1:])
+
+				if _, ok := dpkgFields[key]; ok {
+					return pkg.DpkgMetadata{}, fmt.Errorf("duplicate key discovered: %s", key)
+				}
+
+				dpkgFields[key] = val
+			} else {
+				return pkg.DpkgMetadata{}, fmt.Errorf("cannot parse field from line: '%s'", line)
+			}
+		}
+	}
+
+	err = mapstructure.Decode(dpkgFields, &entry)
+	if err != nil {
+		return pkg.DpkgMetadata{}, err
+	}
+
+	return entry, nil
+}