util/buffer: rework

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

util/buffer/seeker_buffer_test.go

@@ -0,0 +1,55 @@
+package buffer
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func noErrorT(t *testing.T, err error) {
+	if nil != err {
+		t.Fatalf("%s", err)
+	}
+}
+
+func boolT(t *testing.T, cond bool, s ...string) {
+	if !cond {
+		what := strings.Join(s, ", ")
+		if len(what) > 0 {
+			what = ": " + what
+		}
+		t.Fatalf("assert.Bool failed%s", what)
+	}
+}
+
+func TestSeeking(t *testing.T) {
+	partA := []byte("hello, ")
+	partB := []byte("world!")
+
+	buf := NewSeekerBuffer(partA)
+
+	boolT(t, buf.Len() == len(partA), fmt.Sprintf("on init: have length %d, want length %d", buf.Len(), len(partA)))
+
+	b := make([]byte, 32)
+
+	n, err := buf.Read(b)
+	noErrorT(t, err)
+	boolT(t, buf.Len() == 0, fmt.Sprintf("after reading 1: have length %d, want length 0", buf.Len()))
+	boolT(t, n == len(partA), fmt.Sprintf("after reading 2: have length %d, want length %d", n, len(partA)))
+
+	n, err = buf.Write(partB)
+	noErrorT(t, err)
+	boolT(t, n == len(partB), fmt.Sprintf("after writing: have length %d, want length %d", n, len(partB)))
+
+	n, err = buf.Read(b)
+	noErrorT(t, err)
+	boolT(t, buf.Len() == 0, fmt.Sprintf("after rereading 1: have length %d, want length 0", buf.Len()))
+	boolT(t, n == len(partB), fmt.Sprintf("after rereading 2: have length %d, want length %d", n, len(partB)))
+
+	partsLen := len(partA) + len(partB)
+	_ = buf.Rewind()
+	boolT(t, buf.Len() == partsLen, fmt.Sprintf("after rewinding: have length %d, want length %d", buf.Len(), partsLen))
+
+	buf.Close()
+	boolT(t, buf.Len() == 0, fmt.Sprintf("after closing, have length %d, want length 0", buf.Len()))
+}