[#96] Support ranges for GetObject

Signed-off-by: Denis Kirillov <denis@nspcc.ru>

api/handler/get_test.go

@@ -0,0 +1,41 @@
+package handler
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/nspcc-dev/neofs-s3-gw/api/layer"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFetchRangeHeader(t *testing.T) {
+	for _, tc := range []struct {
+		header   string
+		expected *layer.RangeParams
+		fullSize uint64
+		err      bool
+	}{
+		{header: "bytes=0-256", expected: &layer.RangeParams{Start: 0, End: 256}, err: false},
+		{header: "bytes=0-0", expected: &layer.RangeParams{Start: 0, End: 0}, err: false},
+		{header: "bytes=0-", expected: &layer.RangeParams{Start: 0, End: 99}, fullSize: 100, err: false},
+		{header: "bytes=-10", expected: &layer.RangeParams{Start: 90, End: 99}, fullSize: 100, err: false},
+		{header: "", err: false},
+		{header: "bytes=-1-256", err: true},
+		{header: "bytes=256-0", err: true},
+		{header: "bytes=string-0", err: true},
+		{header: "bytes=0-string", err: true},
+		{header: "bytes:0-256", err: true},
+		{header: "bytes:-", err: true},
+	} {
+		h := make(http.Header)
+		h.Add("Range", tc.header)
+		params, err := fetchRangeHeader(h, tc.fullSize)
+		if tc.err {
+			require.Error(t, err)
+			continue
+		}
+
+		require.NoError(t, err)
+		require.Equal(t, tc.expected, params)
+	}
+}