Added JNumber conversions

[mdedetrich]

This is an implementation which adds various conversions from JNumber to other number types (see https://github.com/mdedetrich/scalajson/issues/37). Unlike the previous implementation, these conversions

• Aren't done by a typeclass but rather by direct methods
• Are correct in that they won't lose precision (i.e. a toDouble will return None if the value inside the JNumber is too big and you will lose data)

To make the various number converter calls as performant as possible, when you construct a JNumber we store a bitFlag (called constructedFlag) which tracks how a JNumber is constructed. This means that if you construct a JNumber as a double with its argument (i.e. JNumber(3446437343d)), we first do a check against this bitflag (which is a single if statement) and immediately return a Some(value.toDouble) (since we know its a double), otherwise we do a more expensive check. This also means that the JNumber has an extra int per instance of JNumber in terms of memory (so we are trading a very small amount of extra memory for a more performant number conversion in typical use cases).

The checks were inspired from argonaut (i.e. https://github.com/argonaut-io/argonaut/blob/master/argonaut/shared/src/main/scala/argonaut/JsonNumber.scala) afaik, these are known to be correct

One note, due to how ast.unsafe.JNumber was constructed (the String constructer by default is public), we now added the a second parameter to the constructor list which is not hidden (i.e. its final case class JNumber(value: String, constructedFlag: Int = 0)) which means the unapply method has been changed. Although this change is breaking, it means the unsafe AST does give you control over specifying the constructedFlag.

To be done

• [ ] Proper tests
• [ ] More benchmarks for other number types

Here is the current results for the benchmarks

> benchmarkJVM/testOnly scalajson.ast.JNumberConversionBenchmark
[info] ::Benchmark intBitFlagCheckSuccess::
[info] cores: 8
[info] hostname: Matthews-MacBook-Pro.local
[info] name: Java HotSpot(TM) 64-Bit Server VM
[info] osArch: x86_64
[info] osName: Mac OS X
[info] vendor: Oracle Corporation
[info] version: 25.111-b14
[info] Parameters(seed -> 300000): 0.004583
[info] Parameters(seed -> 600000): 0.004508
[info] Parameters(seed -> 900000): 0.00365
[info] Parameters(seed -> 1200000): 0.003651
[info] Parameters(seed -> 1500000): 0.003779
[info]
[info] ::Benchmark intManualCheckSuccess::
[info] cores: 8
[info] hostname: Matthews-MacBook-Pro.local
[info] name: Java HotSpot(TM) 64-Bit Server VM
[info] osArch: x86_64
[info] osName: Mac OS X
[info] vendor: Oracle Corporation
[info] version: 25.111-b14
[info] Parameters(seed -> 300000): 0.008185
[info] Parameters(seed -> 600000): 0.007592
[info] Parameters(seed -> 900000): 0.007627
[info] Parameters(seed -> 1200000): 0.007783
[info] Parameters(seed -> 1500000): 0.007503
[info]
[info] ::Benchmark floatBitFlagCheckSuccess::
[info] cores: 8
[info] hostname: Matthews-MacBook-Pro.local
[info] name: Java HotSpot(TM) 64-Bit Server VM
[info] osArch: x86_64
[info] osName: Mac OS X
[info] vendor: Oracle Corporation
[info] version: 25.111-b14
[info] Parameters(seed -> 300000): 0.004514
[info] Parameters(seed -> 600000): 0.004442
[info] Parameters(seed -> 900000): 0.00447
[info] Parameters(seed -> 1200000): 0.010328
[info] Parameters(seed -> 1500000): 0.010266
[info] Parameters(seed -> 300000): 0.004446
[info] Parameters(seed -> 600000): 0.004409
[info] Parameters(seed -> 900000): 0.004563
[info] Parameters(seed -> 1200000): 0.010455
[info] Parameters(seed -> 1500000): 0.010432
[info] Parameters(seed -> 300000): 0.004532
[info] Parameters(seed -> 600000): 0.004559
[info] Parameters(seed -> 900000): 0.004381
[info] Parameters(seed -> 1200000): 0.010438
[info] Parameters(seed -> 1500000): 0.01039
[info] Parameters(seed -> 300000): 0.004513
[info] Parameters(seed -> 600000): 0.004333
[info] Parameters(seed -> 900000): 0.004222
[info] Parameters(seed -> 1200000): 0.010413
[info] Parameters(seed -> 1500000): 0.010087
[info] Parameters(seed -> 300000): 0.004332
[info] Parameters(seed -> 600000): 0.004259
[info] Parameters(seed -> 900000): 0.004153
[info] Parameters(seed -> 1200000): 0.010197
[info] Parameters(seed -> 1500000): 0.010366
[info]
[info] ::Benchmark floatManualCheckSuccess::
[info] cores: 8
[info] hostname: Matthews-MacBook-Pro.local
[info] name: Java HotSpot(TM) 64-Bit Server VM
[info] osArch: x86_64
[info] osName: Mac OS X
[info] vendor: Oracle Corporation
[info] version: 25.111-b14
[info] Parameters(seed -> 300000): 0.016463
[info] Parameters(seed -> 600000): 0.016133
[info] Parameters(seed -> 900000): 0.015968
[info] Parameters(seed -> 1200000): 0.02228
[info] Parameters(seed -> 1500000): 0.022384
[info] Parameters(seed -> 300000): 0.016113
[info] Parameters(seed -> 600000): 0.016185
[info] Parameters(seed -> 900000): 0.0167
[info] Parameters(seed -> 1200000): 0.023496
[info] Parameters(seed -> 1500000): 0.022714
[info] Parameters(seed -> 300000): 0.016185
[info] Parameters(seed -> 600000): 0.016222
[info] Parameters(seed -> 900000): 0.016077
[info] Parameters(seed -> 1200000): 0.022478
[info] Parameters(seed -> 1500000): 0.022686
[info] Parameters(seed -> 300000): 0.016302
[info] Parameters(seed -> 600000): 0.016113
[info] Parameters(seed -> 900000): 0.015989
[info] Parameters(seed -> 1200000): 0.022411
[info] Parameters(seed -> 1500000): 0.022288
[info] Parameters(seed -> 300000): 0.016191
[info] Parameters(seed -> 600000): 0.016106
[info] Parameters(seed -> 900000): 0.015932
[info] Parameters(seed -> 1200000): 0.022691
[info] Parameters(seed -> 1500000): 0.022319
[info]
[info] Passed: Total 0, Failed 0, Errors 0, Passed 0

@ktoso @travisbrown @Ichoran @eed3si9n @sirthias Thoughts?

[codecov-io]

Codecov Report

Merging #38 into master will decrease coverage by 9.25%. The diff coverage is 17.58%.

@@            Coverage Diff             @@
##           master      #38      +/-   ##
==========================================
- Coverage   44.68%   35.43%   -9.26%     
==========================================
  Files           5        5              
  Lines         687      906     +219     
  Branches      133      194      +61     
==========================================
+ Hits          307      321      +14     
- Misses        380      585     +205

Impacted Files	Coverage Δ
...s/src/main/scala/scalajson/ast/unsafe/JValue.scala	0% <0%> (ø)	:arrow_up:
js/src/main/scala/scalajson/ast/JValue.scala	0% <0%> (ø)	:arrow_up:
shared/src/main/scala/scalajson/ast/package.scala	59.91% <100%> (+2.13%)	:arrow_up:
...m/src/main/scala/scalajson/ast/unsafe/JValue.scala	42.79% <22.97%> (-16.72%)	:arrow_down:
jvm/src/main/scala/scalajson/ast/JValue.scala	47.36% <25.67%> (-26.03%)	:arrow_down:

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