Integration test fails when read with Range: bytes=-xxx

[JinnyYi]

Expected Behavior

According to COS API doc, when GetObject with Range header:

例如 bytes=0-9，表示下载对象的开头10个字节的数据；bytes=5-9，表示下载对象的第6到第10个字节。此时返回 HTTP 状态码206（Partial Content）及 Content-Range 响应头部。

And also, FormatRangeOptions() was provided to format Range value in cos-go-sdk:

func FormatRangeOptions(opt *RangeOptions) string {
	if opt == nil {
		return ""
	}
	if opt.HasStart && opt.HasEnd {
		return fmt.Sprintf("bytes=%v-%v", opt.Start, opt.End)
	}
	if opt.HasStart {
		return fmt.Sprintf("bytes=%v-", opt.Start)
	}
	if opt.HasEnd {
		return fmt.Sprintf("bytes=-%v", opt.End)
	}
	return ""
}

Based on the above, we envision that when Range: bytes=-9 we should be able to download data from 0 to 9([0-9]).

Current Behavior

• When setting RangeOptions.End as follows, we will get the read size check error.

  rangeOptions := &cos.RangeOptions{}
  if opt.HasSize {
    	rangeOptions.HasEnd = true
    	rangeOptions.End = rangeOptions.Start + opt.Size - 1
  }
  

• When setting RangeOptions.End as follows, we will get the read content check error.

  rangeOptions := &cos.RangeOptions{}
  if opt.HasSize {
    	rangeOptions.HasEnd = true
    	rangeOptions.End = opt.Size
  }
  

Steps to Reproduce

Run integration test after modifying the code as above.

Enviroment

github.com/tencentyun/cos-go-sdk-v5 v0.7.31

[JinnyYi]

Based on the above, we envision that when Range: bytes=-9 we should be able to download data from 0 to 9([0-9]).

Seems that Range: bytes=-9 identifies the final 9 bytes, ref: https://datatracker.ietf.org/doc/html/rfc7233#section-2.1. I'll test and verify it later.

rfc7233

Hypertext Transfer Protocol (HTTP/1.1): Range Requests (RFC )

[JinnyYi]

GetObject with Range: bytes=-5 will get the final 5 bytes. So if Read with only size, we have to set the offset to 0 actively.

[Xuanwo]

Nice work!