utils/upload: init

utils/upload/upload.go

@@ -0,0 +1,27 @@
+package upload
+
+import (
+	"iter"
+
+	"golang.org/x/exp/constraints"
+)
+
+type Chunk[I constraints.Integer] struct {
+	Offset I
+	Size   I
+}
+
+// Chunks yields a sequence of a part number and a Chunk. The Chunk is the offset
+// and size of the chunk. The last chunk may be smaller than chunkSize if size is
+// not a multiple of chunkSize.
+//
+// The first part number is 1 and increases monotonically.
+func Chunks[I constraints.Integer](size, chunkSize I) iter.Seq2[int, Chunk[I]] {
+	return func(yield func(int, Chunk[I]) bool) {
+		var n int
+		for off := I(0); off < size; off += chunkSize {
+			n++
+			yield(n, Chunk[I]{off, min(chunkSize, size-off)})
+		}
+	}
+}

utils/upload/upload_test.go

@@ -0,0 +1,37 @@
+package upload
+
+import (
+	"testing"
+
+	"kr.dev/diff"
+)
+
+func TestChunks(t *testing.T) {
+	const size = 101
+	const chunkSize = 10
+	var got []Chunk[int]
+	var lastN int
+	for n, c := range Chunks(size, chunkSize) {
+		if n != lastN+1 {
+			t.Errorf("n = %d; want %d", n, lastN+1)
+		}
+		got = append(got, c)
+		lastN = n
+	}
+
+	want := []Chunk[int]{
+		{0, 10},
+		{10, 10},
+		{20, 10},
+		{30, 10},
+		{40, 10},
+		{50, 10},
+		{60, 10},
+		{70, 10},
+		{80, 10},
+		{90, 10},
+		{100, 1},
+	}
+
+	diff.Test(t, t.Errorf, got, want)
+}