75 lines
1.8 KiB
Go
75 lines
1.8 KiB
Go
// Copyright 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// +build !go1.7
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package spanner
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import (
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"reflect"
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"strconv"
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)
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func structTagLookup(tag reflect.StructTag, key string) (string, bool) {
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// from go1.10.2 implementation of StructTag.Lookup.
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for tag != "" {
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// Skip leading space.
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i := 0
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for i < len(tag) && tag[i] == ' ' {
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i++
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}
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tag = tag[i:]
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if tag == "" {
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break
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}
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// Scan to colon. A space, a quote or a control character is a syntax error.
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// Strictly speaking, control chars include the range [0x7f, 0x9f], not just
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// [0x00, 0x1f], but in practice, we ignore the multi-byte control characters
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// as it is simpler to inspect the tag's bytes than the tag's runes.
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i = 0
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for i < len(tag) && tag[i] > ' ' && tag[i] != ':' && tag[i] != '"' && tag[i] != 0x7f {
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i++
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}
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if i == 0 || i+1 >= len(tag) || tag[i] != ':' || tag[i+1] != '"' {
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break
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}
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name := string(tag[:i])
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tag = tag[i+1:]
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// Scan quoted string to find value.
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i = 1
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for i < len(tag) && tag[i] != '"' {
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if tag[i] == '\\' {
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i++
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}
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i++
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}
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if i >= len(tag) {
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break
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}
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qvalue := string(tag[:i+1])
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tag = tag[i+1:]
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if key == name {
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value, err := strconv.Unquote(qvalue)
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if err != nil {
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break
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}
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return value, true
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}
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}
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return "", false
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}
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