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102 lines
2.1 KiB
102 lines
2.1 KiB
package filetag
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import (
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"bytes"
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"crypto/sha1"
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"encoding/base64"
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"io"
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"mime/multipart"
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"os"
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)
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const (
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_BlockBits = 22 // Indicate that the blockSize is 4M
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_BlockSize = 1 << _BlockBits
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)
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func blockCount(fileSize int64) int {
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return int((fileSize + (_BlockSize -1)) >> _BlockBits)
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}
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// 计算文件SHA1值
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func sha1Value(b []byte, r io.Reader) ([]byte, error) {
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h := sha1.New()
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_, err := io.Copy(h, r)
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if err != nil {
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return nil, err
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}
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return h.Sum(b), nil
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}
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// 依据文件大小将计算出etag值
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func Filename(fn string) (etag string, err error) {
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f, err := os.Open(fn)
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if err != nil {
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return
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}
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defer f.Close()
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fi, err := f.Stat()
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if err != nil {
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return
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}
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fileSize := fi.Size()
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blockCnt := blockCount(fileSize)
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sha1Buf := make([]byte, 0, 21)
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if blockCnt <= 1 { // file size <= 4M
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sha1Buf = append(sha1Buf, 0x16)
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sha1Buf, err = sha1Value(sha1Buf, f)
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if err != nil {
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return
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}
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} else { // file size > 4M
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sha1Buf = append(sha1Buf, 0x96)
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sha1BlockBuf := make([]byte, 0, blockCnt * 20)
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for i := 0; i < blockCnt; i ++ {
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body := io.LimitReader(f, _BlockSize)
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sha1BlockBuf, err = sha1Value(sha1BlockBuf, body)
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if err != nil {
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return
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}
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}
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sha1Buf, _ = sha1Value(sha1Buf, bytes.NewReader(sha1BlockBuf))
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}
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etag = base64.URLEncoding.EncodeToString(sha1Buf)
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return
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}
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// 依据文件大小将计算出etag值
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func Multipart(f *multipart.FileHeader) (etag string, err error) {
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src, err := f.Open()
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if err != nil {
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return
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}
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defer src.Close()
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blockCnt := blockCount(f.Size)
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sha1Buf := make([]byte, 0, 21)
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if blockCnt <= 1 { // file size <= 4M
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sha1Buf = append(sha1Buf, 0x16)
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sha1Buf, err = sha1Value(sha1Buf, src)
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if err != nil {
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return
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}
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} else { // file size > 4M
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sha1Buf = append(sha1Buf, 0x96)
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sha1BlockBuf := make([]byte, 0, blockCnt * 20)
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for i := 0; i < blockCnt; i ++ {
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body := io.LimitReader(src, _BlockSize)
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sha1BlockBuf, err = sha1Value(sha1BlockBuf, body)
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if err != nil {
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return
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}
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}
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sha1Buf, _ = sha1Value(sha1Buf, bytes.NewReader(sha1BlockBuf))
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}
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etag = base64.URLEncoding.EncodeToString(sha1Buf)
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return
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} |