Add HW 3

homework/03-http-server/tests/compare_reader_test.go

@@ -0,0 +1,60 @@
+package hw3test
+
+import (
+	"bytes"
+	"io"
+	"math/rand"
+	"testing"
+)
+
+func TestComparisonReaderMatchesEnvFile(t *testing.T) {
+	for _, seed := range []int64{-7824, 0, 1, 7824, 9223372036854775807} {
+		for _, chunkSize := range []int{1, 6, 7, 8, 13, 64 * 1024, 131071} {
+			const total = 1024*1024 + 19
+			expected := make([]byte, total)
+			actual := make([]byte, total)
+			_, err := io.ReadFull(rand.New(rand.NewSource(seed)), expected)
+			if err != nil {
+				t.Fatal(err)
+			}
+			reader := newComparisonReader(seed)
+			for offset := 0; offset < total; {
+				end := offset + chunkSize
+				if end > total {
+					end = total
+				}
+				if _, err := io.ReadFull(reader, actual[offset:end]); err != nil {
+					t.Fatal(err)
+				}
+				offset = end
+			}
+			if !bytes.Equal(actual, expected) {
+				t.Fatalf("different bytes for seed %d and chunk size %d", seed, chunkSize)
+			}
+		}
+	}
+}
+
+func BenchmarkComparisonReaders(b *testing.B) {
+	const size = 128 * 1024 * 1024
+	buffer := make([]byte, 64*1024)
+	for _, candidate := range []struct {
+		name string
+		open func() io.Reader
+	}{
+		{"math/rand", func() io.Reader { return rand.New(rand.NewSource(7824)) }},
+		{"comparison", func() io.Reader { return newComparisonReader(7824) }},
+	} {
+		b.Run(candidate.name, func(b *testing.B) {
+			b.SetBytes(size)
+			for i := 0; i < b.N; i++ {
+				reader := candidate.open()
+				for remaining := size; remaining > 0; remaining -= len(buffer) {
+					if _, err := io.ReadFull(reader, buffer); err != nil {
+						b.Fatal(err)
+					}
+				}
+			}
+		})
+	}
+}