Golang上传文件的Mime类型检查

Question

我正在尝试获取上传到我的服务器中的mime类型的文件。

.xlsx和.docx文件mime类型出现在application/zip中。我尝试解压缩文件并读取"_rels/.rels“类型的文件。我的疑问是，在读取这个特定的文件时，我应该为读取文件保留的最大大小是多少，如果Target是"xl/workbook.xml“，我可以假定它是xlsx类型的吗？

我的代码如下

 file, fileHeader, err := r.FormFile("file")

buffer := make([]byte, 512)
_, err = file.Read(buffer)
if err != nil {
    fmt.Println(err)
}

contentType := http.DetectContentType(buffer)
if contentType == "application/zip" {
    r, err := zip.NewReader(file, fileHeader.Size)
    if err != nil {
        fmt.Println(err)
    }
    for _, zf := range r.File {
        if zf.Name == "_rels/.rels" {
            fmt.Println("rels")
            rc, err := zf.Open()
            if err != nil {
                fmt.Println("Rels errors")
            }
            const BufferSize = 1000
            buffer := make([]byte, BufferSize)
            defer rc.Close()
            bytesread, err := rc.Read(buffer)
            if err != nil {
                if err != io.EOF {
                    fmt.Println(err)
                }
            }

            fmt.Println("bytes read: ", bytesread)
            fmt.Println("bytestream to string: ", string(buffer[:bytesread]))
            fmt.Println(rc)
        }
    }
}


var arr []byte
w.Header().Set("Content-Type", "application/json")
w.Write(arr)

}

我得到的输出是

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<Relationships     xmlns="http://schemas.openxmlformats.org/package/2006/relationships"><Relationship Id="rId3" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/extended-properties" Target="docProps/app.xml"/><Relationship Id="rId2" Type="http://schemas.openxmlformats.org/package/2006/relationships/metadata/core-properties" Target="docProps/core.xml"/><Relationship Id="rId1" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument" Target="xl/workbook.xml"/></Relationships>

关于如何阅读.doc或.xls有什么建议吗？

Answer 1

不幸的是，html包中的DetectContentType仅限于它可以检测到的mime类型。

你只要检查文件签名就行了。file signatures是一个很好的文件签名资源

免责声明:我是mimetype的作者。

• filetype

- pure go, no c bindings
- can be extented to detect new mime types
- has issues with files which pass as more than one mime type (ex: xlsx and docx passing as zip) because it stores matching functions in a map, thus it does not guarantee the order of traversal

• magicmime

- needs libmagic-dev installed
- can be extended, albeit harder... `man magic`

• mimetype

- pure go, no c bindings
- higher number of detected mime types than `filetype`
- is thread safe
- can be extended