add type-safe accessors for most container headers

1 files changed, 71 insertions, 0 deletions

diff --git a/headers/time.go b/headers/time.go
new file mode 100644
index 0000000..5f9209f
--- /dev/null
+++ b/headers/time.go
@@ -0,0 +1,71 @@
+/******************************************************************************
+*
+*  Copyright 2018 Stefan Majewsky <majewsky@gmx.net>
+*
+*  Licensed under the Apache License, Version 2.0 (the "License");
+*  you may not use this file except in compliance with the License.
+*  You may obtain a copy of the License at
+*
+*      http://www.apache.org/licenses/LICENSE-2.0
+*
+*  Unless required by applicable law or agreed to in writing, software
+*  distributed under the License is distributed on an "AS IS" BASIS,
+*  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+*  See the License for the specific language governing permissions and
+*  limitations under the License.
+*
+******************************************************************************/
+
+package headers
+
+import (
+	"math"
+	"strconv"
+	"time"
+)
+
+//UnixTimeReadonly is a helper type that provides type-safe access to a Swift
+//header whose value is a UNIX timestamp. It cannot be directly constructed,
+//but some subtypes of schwift.Headers have fields of this type. For example:
+//
+//    var hdr AccountHeaders
+//    //hdr.Timestamp is a headers.UnixTimeReadonly instance
+//    hdr.Timestamp.Get()    //returns a time.Time
+//    hdr.Get("X-Timestamp") //returns a string containing a UNIX timestamp
+//                           //refering to the same point in time
+type UnixTimeReadonly struct {
+	Base
+}
+
+//Exists checks whether there is a value for this header.
+func (f UnixTimeReadonly) Exists() bool {
+	return f.H.Get(f.K) != ""
+}
+
+//Get returns the value for this header, or the zero value if there is no value
+//(or if it is not a valid timestamp).
+func (f UnixTimeReadonly) Get() time.Time {
+	v, err := strconv.ParseFloat(f.H.Get(f.K), 64)
+	if err != nil {
+		return time.Time{}
+	}
+	seconds := math.Floor(v)
+	return time.Unix(
+		int64(seconds),
+		int64(1e9*(v-seconds)),
+	)
+}
+
+//Validate is only used internally, but needs to be exported to cross package
+//boundaries.
+func (f UnixTimeReadonly) Validate() error {
+	val := f.H.Get(f.K)
+	if val == "" {
+		return nil
+	}
+	_, err := strconv.ParseFloat(val, 64)
+	if err == nil {
+		return nil
+	}
+	return MalformedHeaderError{f.K, err}
+}