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feat: adds efficient move support to Value::get<string>() #980
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Fixes googleapis#422 Changes `Value::get<T>()` to efficiently move `std::string` values out of the proto and directly to the caller. `std::string` is the only type that can do this because it's the only type which is exactly the same in the proto and outside of it. All other types require some type of decoding, which necessarily requires some amount of copying from the proto out to the caller.
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@@ Coverage Diff @@
## master #980 +/- ##
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- Coverage 94.17% 94.16% -0.01%
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Files 158 159 +1
Lines 10704 10753 +49
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+ Hits 10080 10126 +46
- Misses 624 627 +3
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coryan
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Oct 25, 2019
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I would call this a feat: , not a chore: , but in either case
Reviewed 3 of 3 files at r1.
Reviewable status:complete! all files reviewed, all discussions resolved
devjgm
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Yep, changed to |
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…/google-cloud-cpp-spanner#980) Fixes googleapis/google-cloud-cpp-spanner#422 Changes Value::get<T>() to efficiently move std::string values out of the proto and directly to the caller. std::string is the only type that can do this because it's the only type which is exactly the same in the proto and outside of it. All other types require some type of decoding, which necessarily requires some amount of copying from the proto out to the caller. Note: the unit tests verifying this behavior rely on unspecified behavior of std::string. Specifically that a moved-from large string ends up empty. This is not guaranteed, but it appears to the true in all cases that I've seen. So we rely on this behavior in the unit test. If this turns out to not be true on some platform, we'll have to adjust the unit tests. I've commented the tests about this.
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Fixes #422
Changes
Value::get<T>()to efficiently movestd::stringvalues outof the proto and directly to the caller.
std::stringis the only typethat can do this because it's the only type which is exactly the same in
the proto and outside of it. All other types require some type of
decoding, which necessarily requires some amount of copying from the
proto out to the caller.
Note: the unit tests verifying this behavior rely on unspecified behavior of std::string. Specifically that a moved-from large string ends up empty. This is not guaranteed, but it appears to the true in all cases that I've seen. So we rely on this behavior in the unit test. If this turns out to not be true on some platform, we'll have to adjust the unit tests. I've commented the tests about this.
This change is