seaweedfs/go/weed/weed_server/volume_server_handlers_helper.go

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2014-05-27 04:15:05 +00:00
package weed_server
import (
"errors"
"fmt"
"mime/multipart"
"net/textproto"
"strconv"
"strings"
)
// copied from src/pkg/net/http/fs.go
// httpRange specifies the byte range to be sent to the client.
type httpRange struct {
start, length int64
}
func (r httpRange) contentRange(size int64) string {
return fmt.Sprintf("bytes %d-%d/%d", r.start, r.start+r.length-1, size)
}
func (r httpRange) mimeHeader(contentType string, size int64) textproto.MIMEHeader {
return textproto.MIMEHeader{
"Content-Range": {r.contentRange(size)},
"Content-Type": {contentType},
}
}
// parseRange parses a Range header string as per RFC 2616.
func parseRange(s string, size int64) ([]httpRange, error) {
if s == "" {
return nil, nil // header not present
}
const b = "bytes="
if !strings.HasPrefix(s, b) {
return nil, errors.New("invalid range")
}
var ranges []httpRange
for _, ra := range strings.Split(s[len(b):], ",") {
ra = strings.TrimSpace(ra)
if ra == "" {
continue
}
i := strings.Index(ra, "-")
if i < 0 {
return nil, errors.New("invalid range")
}
start, end := strings.TrimSpace(ra[:i]), strings.TrimSpace(ra[i+1:])
var r httpRange
if start == "" {
// If no start is specified, end specifies the
// range start relative to the end of the file.
i, err := strconv.ParseInt(end, 10, 64)
if err != nil {
return nil, errors.New("invalid range")
}
if i > size {
i = size
}
r.start = size - i
r.length = size - r.start
} else {
i, err := strconv.ParseInt(start, 10, 64)
if err != nil || i > size || i < 0 {
return nil, errors.New("invalid range")
}
r.start = i
if end == "" {
// If no end is specified, range extends to end of the file.
r.length = size - r.start
} else {
i, err := strconv.ParseInt(end, 10, 64)
if err != nil || r.start > i {
return nil, errors.New("invalid range")
}
if i >= size {
i = size - 1
}
r.length = i - r.start + 1
}
}
ranges = append(ranges, r)
}
return ranges, nil
}
// countingWriter counts how many bytes have been written to it.
type countingWriter int64
func (w *countingWriter) Write(p []byte) (n int, err error) {
*w += countingWriter(len(p))
return len(p), nil
}
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// rangesMIMESize returns the number of bytes it takes to encode the
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// provided ranges as a multipart response.
func rangesMIMESize(ranges []httpRange, contentType string, contentSize int64) (encSize int64) {
var w countingWriter
mw := multipart.NewWriter(&w)
for _, ra := range ranges {
mw.CreatePart(ra.mimeHeader(contentType, contentSize))
encSize += ra.length
}
mw.Close()
encSize += int64(w)
return
}
func sumRangesSize(ranges []httpRange) (size int64) {
for _, ra := range ranges {
size += ra.length
}
return
}