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[perf] JSON encoding can be faster by skipping string building. #2393

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Merged
merged 1 commit into from
Jul 17, 2019
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[perf] JSON encoding can be faster by skipping string building. #2393

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10 changes: 4 additions & 6 deletions Foundation/JSONSerialization.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -123,14 +123,14 @@ open class JSONSerialization : NSObject {
/* Generate JSON data from a Foundation object. If the object will not produce valid JSON then an exception will be thrown. Setting the NSJSONWritingPrettyPrinted option will generate JSON with whitespace designed to make the output more readable. If that option is not set, the most compact possible JSON will be generated. If an error occurs, the error parameter will be set and the return value will be nil. The resulting data is a encoded in UTF-8.
*/
internal class func _data(withJSONObject value: Any, options opt: WritingOptions, stream: Bool) throws -> Data {
var jsonStr = String()
var jsonStr = [UInt8]()

var writer = JSONWriter(
pretty: opt.contains(.prettyPrinted),
sortedKeys: opt.contains(.sortedKeys),
writer: { (str: String?) in
if let str = str {
jsonStr.append(str)
jsonStr.append(contentsOf: Array(str.utf8))
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I missed this when I scanned this earlier but you could be able to avoid the array allocation by just doing jsonStr.append(contentsOf: str.utf8) right?

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Yes, it seems it should work. I will prepare a follow up. Thanks for pointing it out!

}
}
)
Expand All @@ -147,10 +147,8 @@ open class JSONSerialization : NSObject {
fatalError("Top-level object was not NSArray or NSDictionary") // This is a fatal error in objective-c too (it is an NSInvalidArgumentException)
}

let count = jsonStr.utf8.count
return jsonStr.withCString {
Data(bytes: $0, count: count)
}
let count = jsonStr.count
return Data(bytes: &jsonStr, count: count)
}

open class func data(withJSONObject value: Any, options opt: WritingOptions = []) throws -> Data {
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