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fs: Adjust RangeOption.Decode to return -1 for read to end

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A Range request can never request 0 bytes however this change was made
to make a clearer signal that the limit means read to the end.

Add test and more documentation and fixup uses
This commit is contained in:
Nick Craig-Wood 2018-01-27 10:07:17 +00:00
parent 9a73688e3a
commit fe52502f19
7 changed files with 42 additions and 14 deletions
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4
backend/cache/object.go vendored
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@ -220,11 +220,11 @@ func (o *Object) Open(options ...fs.OpenOption) (io.ReadCloser, error) {
var err error
cacheReader := NewObjectHandle(o)
var offset, limit int64
var offset, limit int64 = 0, -1
for _, option := range options {
switch x := option.(type) {
case *fs.SeekOption:
offset, limit = x.Offset, 0
offset = x.Offset
case *fs.RangeOption:
offset, limit = x.Decode(o.Size())
}

4
backend/ftp/ftp.go
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@ -634,11 +634,11 @@ func (f *ftpReadCloser) Close() error {
func (o *Object) Open(options ...fs.OpenOption) (rc io.ReadCloser, err error) {
// defer fs.Trace(o, "")("rc=%v, err=%v", &rc, &err)
path := path.Join(o.fs.root, o.remote)
var offset, limit int64
var offset, limit int64 = 0, -1
for _, option := range options {
switch x := option.(type) {
case *fs.SeekOption:
offset, limit = x.Offset, 0
offset = x.Offset
case *fs.RangeOption:
offset, limit = x.Decode(o.Size())
default:

5
backend/local/local.go
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@ -676,13 +676,12 @@ func (file *localOpenFile) Close() (err error) {
// Open an object for read
func (o *Object) Open(options ...fs.OpenOption) (in io.ReadCloser, err error) {
var offset int64
var limit int64
var offset, limit int64 = 0, -1
hashes := hash.Supported
for _, option := range options {
switch x := option.(type) {
case *fs.SeekOption:
offset, limit = x.Offset, 0
offset = x.Offset
case *fs.RangeOption:
offset, limit = x.Decode(o.size)
case *fs.HashesOption:

4
backend/sftp/sftp.go
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@ -855,11 +855,11 @@ func (file *ObjectReader) Close() (err error) {
// Open a remote sftp file object for reading. Seek is supported
func (o *Object) Open(options ...fs.OpenOption) (in io.ReadCloser, err error) {
var offset, limit int64
var offset, limit int64 = 0, -1
for _, option := range options {
switch x := option.(type) {
case *fs.SeekOption:
offset, limit = x.Offset, 0
offset = x.Offset
case *fs.RangeOption:
offset, limit = x.Decode(o.Size())
default:

14
fs/options.go
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@ -97,17 +97,25 @@ func (o *RangeOption) Mandatory() bool {
}
// Decode interprets the RangeOption into an offset and a limit
//
// The offset is the start of the stream and the limit is how many
// bytes should be read from it. If the limit is -1 then the stream
// should be read to the end.
func (o *RangeOption) Decode(size int64) (offset, limit int64) {
if o.Start >= 0 {
offset = o.Start
if o.End >= 0 {
limit = o.End - o.Start + 1
} else {
limit = 0
limit = -1
}
} else {
offset = size - o.End
limit = 0
if o.End >= 0 {
offset = size - o.End
} else {
offset = 0
}
limit = -1
}
return offset, limit
}

21
fs/options_test.go
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@ -37,3 +37,24 @@ func TestParseRangeOption(t *testing.T) {
}
}
}
func TestRangeOptionDecode(t *testing.T) {
for _, test := range []struct {
in RangeOption
size int64
wantOffset int64
wantLimit int64
}{
{in: RangeOption{Start: 1, End: 10}, size: 100, wantOffset: 1, wantLimit: 10},
{in: RangeOption{Start: 10, End: 10}, size: 100, wantOffset: 10, wantLimit: 1},
{in: RangeOption{Start: 10, End: 9}, size: 100, wantOffset: 10, wantLimit: 0},
{in: RangeOption{Start: 1, End: -1}, size: 100, wantOffset: 1, wantLimit: -1},
{in: RangeOption{Start: -1, End: 90}, size: 100, wantOffset: 10, wantLimit: -1},
{in: RangeOption{Start: -1, End: -1}, size: 100, wantOffset: 0, wantLimit: -1},
} {
gotOffset, gotLimit := test.in.Decode(test.size)
what := fmt.Sprintf("%+v size=%d", test.in, test.size)
assert.Equal(t, test.wantOffset, gotOffset, "offset "+what)
assert.Equal(t, test.wantLimit, gotLimit, "limit "+what)
}
}

4
lib/readers/limited.go
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@ -9,10 +9,10 @@ type LimitedReadCloser struct {
}
// NewLimitedReadCloser returns a LimitedReadCloser wrapping rc to
// limit it to reading limit bytes. If limit == 0 then it does not
// limit it to reading limit bytes. If limit < 0 then it does not
// wrap rc, it just returns it.
func NewLimitedReadCloser(rc io.ReadCloser, limit int64) (lrc io.ReadCloser) {
if limit == 0 {
if limit < 0 {
return rc
}
return &LimitedReadCloser{