Move parsing functions to pkg/parsers and the specific kernel handling

functions to pkg/parsers/kernel, and parsing filters to
pkg/parsers/filter. Adjust imports and package references.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)

parsers/filters/parse.go

@@ -0,0 +1,63 @@
+package filters
+
+import (
+	"encoding/json"
+	"errors"
+	"strings"
+)
+
+type Args map[string][]string
+
+// Parse the argument to the filter flag. Like
+//
+//   `docker ps -f 'created=today' -f 'image.name=ubuntu*'`
+//
+// If prev map is provided, then it is appended to, and returned. By default a new
+// map is created.
+func ParseFlag(arg string, prev Args) (Args, error) {
+	var filters Args = prev
+	if prev == nil {
+		filters = Args{}
+	}
+	if len(arg) == 0 {
+		return filters, nil
+	}
+
+	if !strings.Contains(arg, "=") {
+		return filters, ErrorBadFormat
+	}
+
+	f := strings.SplitN(arg, "=", 2)
+	filters[f[0]] = append(filters[f[0]], f[1])
+
+	return filters, nil
+}
+
+var ErrorBadFormat = errors.New("bad format of filter (expected name=value)")
+
+// packs the Args into an string for easy transport from client to server
+func ToParam(a Args) (string, error) {
+	// this way we don't URL encode {}, just empty space
+	if len(a) == 0 {
+		return "", nil
+	}
+
+	buf, err := json.Marshal(a)
+	if err != nil {
+		return "", err
+	}
+	return string(buf), nil
+}
+
+// unpacks the filter Args
+func FromParam(p string) (Args, error) {
+	args := Args{}
+	if len(p) == 0 {
+		return args, nil
+	}
+	err := json.Unmarshal([]byte(p), &args)
+	if err != nil {
+		return nil, err
+	}
+	return args, nil
+}