实现基础的206 partial content缓存

internal/utils/ranges/range.go

@@ -0,0 +1,53 @@
+// Copyright 2022 Liuxiangchao iwind.liu@gmail.com. All rights reserved.
+
+package rangeutils
+
+import "strconv"
+
+type Range [2]int64
+
+func NewRange(start int64, end int64) Range {
+	return [2]int64{start, end}
+}
+
+func (this Range) Start() int64 {
+	return this[0]
+}
+
+func (this Range) End() int64 {
+	return this[1]
+}
+
+func (this Range) Length() int64 {
+	return this[1] - this[0] + 1
+}
+
+func (this Range) Convert(total int64) (newRange Range, ok bool) {
+	if total <= 0 {
+		return this, false
+	}
+	if this[0] < 0 {
+		this[0] += total
+		if this[0] < 0 {
+			return this, false
+		}
+		this[1] = total - 1
+	}
+	if this[1] < 0 {
+		this[1] = total - 1
+	}
+	if this[1] > total-1 {
+		this[1] = total - 1
+	}
+	if this[0] > this[1] {
+		return this, false
+	}
+
+	return this, true
+}
+
+// ComposeContentRangeHeader 组合Content-Range Header
+// totalSize 可能是一个数字，也可能是一个星号（*）
+func (this Range) ComposeContentRangeHeader(totalSize string) string {
+	return "bytes " + strconv.FormatInt(this[0], 10) + "-" + strconv.FormatInt(this[1], 10) + "/" + totalSize
+}