Refactor: String#to_i to avoid future overflow #7172
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asterite
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Dec 10, 2018
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@asterite done |
asterite
approved these changes
Dec 10, 2018
vladfaust
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Dec 11, 2018
| @@ -497,7 +497,7 @@ class String | |||
| if info.negative | |||
| {% if max_negative %} | |||
| return yield if info.value > {{max_negative}} | |||
| -info.value.to_{{method}} | |||
| (~info.value &+ 1).unsafe_as(Int64).to_{{method}} | |||
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@vladfaust it's inverting bits to perform https://en.wikipedia.org/wiki/Two%27s_complement
Sample:
00000011 ( 3. info.value)
11111100 (-4. ~info.value)
11111101 (-3. ~info.value &+ 1)
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This method could use some API docs.
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This is a small refactor on
String#to_imethods.Before this PR when parsing the minimum negative value (eg:
-128forInt8) the code will first convert theUInt64absolute value to aInt8and then return it with opposite sign.The positive
128is not a validInt8so we should change the conversion to use 2's complement.First compute the binary
Int64representation of negative number to return, cast it asInt64and then narrow its type to the expected one.