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range.go
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range.go
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// Copyright 2020 The searKing Author. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package http
import (
"errors"
"net/textproto"
"strconv"
"strings"
)
// httpRange specifies the byte range to be sent to the client.
type httpRange struct {
start, length int64
}
func (r httpRange) contentRange(size int64) string {
cr := &httpContentRange{
firstBytePos: r.start,
lastBytePos: r.start + r.length - 1,
completeLength: size,
}
return cr.String()
}
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 7233.
// errNoOverlap is returned if none of the ranges overlap.
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
noOverlap := false
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 < 0 {
return nil, errors.New("invalid range")
}
if i >= size {
// If the range begins after the size of the content,
// then it does not overlap.
noOverlap = true
continue
}
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)
}
if noOverlap && len(ranges) == 0 {
// The specified ranges did not overlap with the content.
return nil, errNoOverlap
}
return ranges, nil
}