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tag.go
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tag.go
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// Copyright 2019 The ebml-go authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ebml
import (
"errors"
"os"
"strconv"
"strings"
)
type structTag struct {
name string
size uint64
omitEmpty bool
stop bool
}
// ErrEmptyTag means that a tag string has empty item.
var ErrEmptyTag = errors.New("empty tag in tag string")
// ErrInvalidTag means that an invaild tag is specified.
var ErrInvalidTag = errors.New("invalid tag in tag string")
func parseTag(rawtag string) (*structTag, error) {
tag := &structTag{}
ts := strings.Split(rawtag, ",")
for i, t := range ts {
if i == 0 {
tag.name = t
continue
}
kv := strings.SplitN(t, "=", 2)
if len(kv) == 1 {
switch kv[0] {
case "":
return nil, ErrEmptyTag
case "omitempty":
tag.omitEmpty = true
case "inf":
os.Stderr.WriteString("Deprecated: \"inf\" tag is replaced by \"size=unknown\"\n")
tag.size = SizeUnknown
case "stop":
tag.stop = true
default:
return nil, wrapErrorf(ErrInvalidTag, "parsing \"%s\"", t)
}
continue
}
switch kv[0] {
case "":
return nil, ErrEmptyTag
case "size":
if kv[1] == "unknown" {
tag.size = SizeUnknown
} else {
s, err := strconv.Atoi(kv[1])
if err != nil {
return nil, wrapErrorf(err, "parsing \"%s\"", t)
}
tag.size = uint64(s)
}
default:
return nil, wrapErrorf(ErrInvalidTag, "parsing \"%s\"", t)
}
}
return tag, nil
}