public_handers.go

package manager

import (

    "net/http"

    "regexp"

    "strconv"

    "io"

    "strings"

    "fmt"

    "time"

)

var publicUrlRegex *regexp.Regexp

func init() {

    var err error

    publicUrlRegex, err = regexp.Compile("/([0-9]*)/([0-9]*)/(.*)")

    if err != nil {

        panic(err)

    }

}

//公共资源处理器

func (vm *VolumeManager)publicEntry(w http.ResponseWriter, r *http.Request) {

    switch r.Method {

    case http.MethodGet, http.MethodHead:

        if publicUrlRegex.MatchString(r.URL.Path) {

            vm.publicReadFile(w, r)

        } else {

            http.NotFound(w, r)

        }

    default:

        w.WriteHeader(http.StatusMethodNotAllowed)

    }

}

//读取公共资源文件

func (vm *VolumeManager)publicReadFile(w http.ResponseWriter, r *http.Request) {

    match := publicUrlRegex.FindStringSubmatch(r.URL.Path)

    vid, _ := strconv.ParseUint(match[1], 10, 64)

    volume := vm.Volumes[vid]

    if volume == nil {

        http.Error(w, "can't find volume", http.StatusNotFound)

        return

    }

    fid, _ := strconv.ParseUint(match[2], 10, 64)

    file, err := volume.Get(fid)

    if err != nil || file.Info.FileName != match[3] {

        http.NotFound(w, r)

        return

    }

    w.Header().Set("Content-Type", get_content_type(file.Info.FileName))

    w.Header().Set("Accept-Ranges", "bytes")

    w.Header().Set("ETag", fmt.Sprintf("\"%d\"", fid))

    //暂时不使用Last-Modified,用ETag即可

    //w.Header().Set("Last-Modified", file.Info.Mtime.Format(http.TimeFormat))

    w.Header().Set("Expires", time.Now().In(time.UTC).Add(DefaultExpires).Format(http.TimeFormat))

    etagMatch := false

    if r.Header.Get("If-None-Match") != "" {

        s := r.Header.Get("If-None-Match")

        if etag, err := strconv.ParseUint(s[1:len(s) - 1], 10, 64); err == nil && etag == fid {

            etagMatch = true

        }

    }

    if r.Header.Get("Range") != "" {

        ranges := strings.Split(r.Header.Get("Range")[6:], "-")

        start, err := strconv.ParseUint(ranges[0], 10, 64)

        if err != nil {

            http.Error(w, err.Error(), http.StatusInternalServerError)

            return

        }

        length := uint64(0)

        if start > file.Info.Size {

            start = file.Info.Size

        } else if ranges[1] != "" {

            end, err := strconv.ParseUint(ranges[1], 10, 64)

            if err != nil {

                http.Error(w, err.Error(), http.StatusInternalServerError)

                return

            }

            end += 1

            if end > file.Info.Size {

                end = file.Info.Size

            }

            length = end - start

        } else {

            length = file.Info.Size - start

        }

        w.Header().Set("Content-Length", strconv.FormatUint(length, 10))

        if length == 0 {

            w.WriteHeader(http.StatusRequestedRangeNotSatisfiable)

            return

        }

        w.Header().Set("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, start + length - 1, file.Info.Size))

        if etagMatch {

            w.WriteHeader(http.StatusNotModified)

            return

        }

        w.WriteHeader(http.StatusPartialContent)

        if r.Method != http.MethodHead {

            file.Seek(int64(start), 0)

            io.CopyN(w, file, int64(length))

        }

    } else {

        w.Header().Set("Content-Length", strconv.FormatUint(file.Info.Size, 10))

        if etagMatch {

            w.WriteHeader(http.StatusNotModified)

        } else if r.Method != http.MethodHead {

            io.Copy(w, file)

        }

    }

}