/
ranges.go
133 lines (122 loc) · 3.37 KB
/
ranges.go
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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package servecontent
import (
"errors"
"fmt"
"mime/multipart"
"net/textproto"
"strconv"
"strings"
)
// ErrNoOverlap is returned by ParseRange if first-byte-pos of
// all of the byte-range-spec values is greater than the content size.
var ErrNoOverlap = errors.New("invalid range: failed to overlap")
// 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 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
}
// 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
}
// RangesMIMESize returns the number of bytes it takes to encode the
// 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
}