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278 lines
6.4 KiB
278 lines
6.4 KiB
<p align="center">
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<img
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src="logo.png"
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width="240" height="78" border="0" alt="SJSON">
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<br>
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<a href="https://travis-ci.org/tidwall/sjson"><img src="https://img.shields.io/travis/tidwall/sjson.svg?style=flat-square" alt="Build Status"></a>
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<a href="https://godoc.org/github.com/tidwall/sjson"><img src="https://img.shields.io/badge/api-reference-blue.svg?style=flat-square" alt="GoDoc"></a>
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</p>
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<p align="center">set a json value quickly</a></p>
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SJSON is a Go package that provides a [very fast](#performance) and simple way to set a value in a json document. The purpose for this library is to provide efficient json updating for the [SummitDB](https://github.com/tidwall/summitdb) project.
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For quickly retrieving json values check out [GJSON](https://github.com/tidwall/gjson).
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For a command line interface check out [JSONed](https://github.com/tidwall/jsoned).
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Getting Started
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===============
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Installing
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----------
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To start using SJSON, install Go and run `go get`:
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```sh
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$ go get -u github.com/tidwall/sjson
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```
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This will retrieve the library.
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Set a value
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-----------
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Set sets the value for the specified path.
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A path is in dot syntax, such as "name.last" or "age".
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This function expects that the json is well-formed and validated.
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Invalid json will not panic, but it may return back unexpected results.
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Invalid paths may return an error.
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```go
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package main
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import "github.com/tidwall/sjson"
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const json = `{"name":{"first":"Janet","last":"Prichard"},"age":47}`
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func main() {
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value, _ := sjson.Set(json, "name.last", "Anderson")
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println(value)
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}
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```
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This will print:
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```json
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{"name":{"first":"Janet","last":"Anderson"},"age":47}
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```
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Path syntax
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-----------
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A path is a series of keys separated by a dot.
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The dot and colon characters can be escaped with '\'.
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```json
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{
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"name": {"first": "Tom", "last": "Anderson"},
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"age":37,
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"children": ["Sara","Alex","Jack"],
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"fav.movie": "Deer Hunter",
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"friends": [
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{"first": "James", "last": "Murphy"},
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{"first": "Roger", "last": "Craig"}
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]
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}
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```
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```
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"name.last" >> "Anderson"
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"age" >> 37
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"children.1" >> "Alex"
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"friends.1.last" >> "Craig"
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```
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The `-1` key can be used to append a value to an existing array:
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```
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"children.-1" >> appends a new value to the end of the children array
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```
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Normally number keys are used to modify arrays, but it's possible to force a numeric object key by using the colon character:
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```json
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{
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"users":{
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"2313":{"name":"Sara"},
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"7839":{"name":"Andy"}
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}
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}
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```
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A colon path would look like:
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```
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"users.:2313.name" >> "Sara"
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```
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Supported types
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---------------
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Pretty much any type is supported:
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```go
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sjson.Set(`{"key":true}`, "key", nil)
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sjson.Set(`{"key":true}`, "key", false)
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sjson.Set(`{"key":true}`, "key", 1)
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sjson.Set(`{"key":true}`, "key", 10.5)
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sjson.Set(`{"key":true}`, "key", "hello")
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sjson.Set(`{"key":true}`, "key", map[string]interface{}{"hello":"world"})
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```
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When a type is not recognized, SJSON will fallback to the `encoding/json` Marshaller.
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Examples
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--------
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Set a value from empty document:
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```go
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value, _ := sjson.Set("", "name", "Tom")
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println(value)
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// Output:
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// {"name":"Tom"}
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```
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Set a nested value from empty document:
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```go
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value, _ := sjson.Set("", "name.last", "Anderson")
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println(value)
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// Output:
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// {"name":{"last":"Anderson"}}
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```
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Set a new value:
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```go
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value, _ := sjson.Set(`{"name":{"last":"Anderson"}}`, "name.first", "Sara")
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println(value)
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// Output:
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// {"name":{"first":"Sara","last":"Anderson"}}
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```
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Update an existing value:
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```go
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value, _ := sjson.Set(`{"name":{"last":"Anderson"}}`, "name.last", "Smith")
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println(value)
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// Output:
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// {"name":{"last":"Smith"}}
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```
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Set a new array value:
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```go
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value, _ := sjson.Set(`{"friends":["Andy","Carol"]}`, "friends.2", "Sara")
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println(value)
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// Output:
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// {"friends":["Andy","Carol","Sara"]
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```
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Append an array value by using the `-1` key in a path:
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```go
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value, _ := sjson.Set(`{"friends":["Andy","Carol"]}`, "friends.-1", "Sara")
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println(value)
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// Output:
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// {"friends":["Andy","Carol","Sara"]
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```
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Append an array value that is past the end:
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```go
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value, _ := sjson.Set(`{"friends":["Andy","Carol"]}`, "friends.4", "Sara")
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println(value)
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// Output:
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// {"friends":["Andy","Carol",null,null,"Sara"]
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```
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Delete a value:
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```go
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value, _ := sjson.Delete(`{"name":{"first":"Sara","last":"Anderson"}}`, "name.first")
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println(value)
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// Output:
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// {"name":{"last":"Anderson"}}
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```
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Delete an array value:
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```go
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value, _ := sjson.Delete(`{"friends":["Andy","Carol"]}`, "friends.1")
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println(value)
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// Output:
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// {"friends":["Andy"]}
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```
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Delete the last array value:
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```go
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value, _ := sjson.Delete(`{"friends":["Andy","Carol"]}`, "friends.-1")
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println(value)
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// Output:
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// {"friends":["Andy"]}
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```
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## Performance
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Benchmarks of SJSON alongside [encoding/json](https://golang.org/pkg/encoding/json/),
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[ffjson](https://github.com/pquerna/ffjson),
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[EasyJSON](https://github.com/mailru/easyjson),
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and [Gabs](https://github.com/Jeffail/gabs)
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```
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Benchmark_SJSON-8 3000000 805 ns/op 1077 B/op 3 allocs/op
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Benchmark_SJSON_ReplaceInPlace-8 3000000 449 ns/op 0 B/op 0 allocs/op
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Benchmark_JSON_Map-8 300000 21236 ns/op 6392 B/op 150 allocs/op
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Benchmark_JSON_Struct-8 300000 14691 ns/op 1789 B/op 24 allocs/op
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Benchmark_Gabs-8 300000 21311 ns/op 6752 B/op 150 allocs/op
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Benchmark_FFJSON-8 300000 17673 ns/op 3589 B/op 47 allocs/op
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Benchmark_EasyJSON-8 1500000 3119 ns/op 1061 B/op 13 allocs/op
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```
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JSON document used:
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```json
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{
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"widget": {
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"debug": "on",
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"window": {
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"title": "Sample Konfabulator Widget",
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"name": "main_window",
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"width": 500,
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"height": 500
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},
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"image": {
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"src": "Images/Sun.png",
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"hOffset": 250,
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"vOffset": 250,
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"alignment": "center"
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},
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"text": {
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"data": "Click Here",
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"size": 36,
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"style": "bold",
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"vOffset": 100,
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"alignment": "center",
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"onMouseUp": "sun1.opacity = (sun1.opacity / 100) * 90;"
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}
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}
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}
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```
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Each operation was rotated though one of the following search paths:
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```
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widget.window.name
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widget.image.hOffset
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widget.text.onMouseUp
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```
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*These benchmarks were run on a MacBook Pro 15" 2.8 GHz Intel Core i7 using Go 1.7.*
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## Contact
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Josh Baker [@tidwall](http://twitter.com/tidwall)
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## License
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SJSON source code is available under the MIT [License](/LICENSE).
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