1 files changed, 93 insertions, 0 deletions
diff --git a/objects/properties.go b/objects/properties.go
new file mode 100644
index 0000000..6b4acc1
--- /dev/null
+++ b/objects/properties.go
@@ -0,0 +1,93 @@
+package objects
+
+import (
+	"encoding/hex"
+	"fmt"
+	"net/url"
+	"sort"
+)
+
+// properties are mappings from strings to strings that are encoded as a restricted version of URL query strings
+// (only the characters [a-zA-Z0-9.:_-] are allowed, values are ordered by their key)
+type properties map[string]string
+
+// escapePropertyString escapes all bytes not in [a-zA-Z0-9.:_-] as %XX, where XX represents the hexadecimal value of the byte.
+// Compatible with URL query strings
+func escapePropertyString(s string) []byte {
+	out := []byte{}
+	esc := []byte("%XX")
+
+	for _, b := range []byte(s) {
+		if (b >= 'a' && b <= 'z') || (b >= 'A' && b <= 'Z') || (b >= '0' && b <= '9') || b == '.' || b == ':' || b == '_' || b == '-' {
+			out = append(out, b)
+		} else {
+			hex.Encode(esc[1:], []byte{b})
+			out = append(out, esc...)
+		}
+	}
+
+	return out
+}
+
+func (p properties) MarshalText() ([]byte, error) { // Guaranteed to not fail, error is only here to satisfy encoding.TextMarshaler
+	keys := make([]string, len(p))
+	i := 0
+	for k := range p {
+		keys[i] = k
+		i++
+	}
+
+	sort.Strings(keys)
+
+	out := []byte{}
+
+	first := true
+	for _, k := range keys {
+		if first {
+			first = false
+		} else {
+			out = append(out, '&')
+		}
+
+		out = append(out, escapePropertyString(k)...)
+		out = append(out, '=')
+		out = append(out, escapePropertyString(p[k])...)
+	}
+
+	return out, nil
+}
+
+func (p properties) UnmarshalText(text []byte) error {
+	vals, err := url.ParseQuery(string(text))
+	if err != nil {
+		return err
+	}
+
+	for k, v := range vals {
+		if len(v) != 1 {
+			return fmt.Errorf("Got %d values for key %s, expected 1", len(v), k)
+		}
+
+		p[k] = v[0]
+	}
+
+	return nil
+}
+
+func (a properties) Equals(b properties) bool {
+	for k, va := range a {
+		vb, ok := b[k]
+		if !ok || vb != va {
+			return false
+		}
+	}
+
+	for k := range b {
+		_, ok := a[k]
+		if !ok {
+			return false
+		}
+	}
+
+	return true
+}