revamp the LargeObject API

I thought about this some more, and I believe the Writer-based approach
in the previous version of the LargeObject API does not scale: It makes
it very hard to write code that uploads segments without resorting to a
buffer the same size as the segments. I don't want gigabyte-scale
buffers filling up my RAM, so this commit switches to a different API
based on Readers. LargeObject.Append() now behaves very similar to
Object.Upload(), which I find quite nice.

1 files changed, 49 insertions, 1 deletions

diff --git a/largeobject_test.go b/largeobject_test.go
index fe781ab..724654a 100644
--- a/largeobject_test.go
+++ b/largeobject_test.go
@@ -18,7 +18,11 @@
 
 package schwift
 
-import "testing"
+import (
+	"bytes"
+	"io/ioutil"
+	"testing"
+)
 
 func TestParseHTTPRange(t *testing.T) {
 	testCases := []struct {
@@ -62,3 +66,47 @@ func TestParseHTTPRange(t *testing.T) {
 		}
 	}
 }
+
+func TestSegmentingReader(t *testing.T) {
+	testCases := []struct {
+		input    string
+		segments []string
+	}{
+		{"abcdefghi", []string{"abc", "def", "ghi"}},
+		{"abcdefgh", []string{"abc", "def", "gh"}},
+		{"abcdefg", []string{"abc", "def", "g"}},
+	}
+
+	for _, tc := range testCases {
+		sr := segmentingReader{
+			Reader:           bytes.NewReader([]byte(tc.input)),
+			SegmentSizeBytes: 3,
+		}
+
+		for _, expected := range tc.segments {
+			segment := sr.NextSegment()
+			if segment == nil {
+				t.Errorf("expected segment %q, but NextSegment() returned nil", expected)
+				break
+			}
+			actual, err := ioutil.ReadAll(segment)
+			if err != nil {
+				t.Errorf("expected segment %q, but got read error %q", expected, err.Error())
+				break
+			}
+			if string(actual) != expected {
+				t.Errorf("expected segment %q, but got %q", expected, string(actual))
+			}
+		}
+
+		segment := sr.NextSegment()
+		if segment != nil {
+			actual, err := ioutil.ReadAll(segment)
+			if err == nil {
+				t.Errorf("expected no more segments, but got segment producing read error %q", err.Error())
+			} else {
+				t.Errorf("expected no more segments, but got %q", string(actual))
+			}
+		}
+	}
+}