Add convert_to_base_64 function to convert string integer to magnitudes #34
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sahmad98
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faheel
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Thanks, but the logic you've used for conversion isn't right.
test/functions/utility.test.cpp
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| TEST_CASE("Conversion to Base64 magnitudes from String", "[Utility][Helper][Base64]") { | ||
| std::string num = "481482486096808911670147153572883801"; | ||
| // Magnitude should be {11670147153572883801, 4814824860968089} |
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The magnitude is incorrect. It should be {5717256727323176281, 26101217871994095}, since
481482486096808911670147153572883801 = 5717256727323176281⋅(264)0 + 26101217871994095⋅(264)1
include/functions/utility.hpp
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| try { | ||
| std::string num_slice = num.substr(start_it, stop_it); | ||
| component = std::stoull(num_slice); | ||
| } catch (std::out_of_range& e) { //Using out_of_range to determine overflow |
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This logic wouldn't work. What we want is to divide the number by the largest power of 264 that gives a non-zero quotient, push that in an array, use the remainder as the new number and repeat the process with decreasing powers until we reach 1 (0th power). Then return the reversed array.
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I was wondering how can we divide a number even with 264, the dividend will anyway overflow if we are going to do these in the traditional way. So i am thinking it must all be done in strings rather than converting the numbers into integer chunks or something related.
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Yes, we'll need to do string-based division first to convert to base 264. I'm working on removing as much code as possible while still having string division and remainder work. But it'll take some time as I'm busy with exams currently. In the meanwhile, if you have another suggestion, or would like to work on this then let me know.
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Yes, i will modify it to use string divisions instead.
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| magnitude = convert_to_base_2_to_the_64(num_magnitude); | ||
| */ | ||
| magnitude = {0}; | ||
| magnitude = convert_to_base_64(num_magnitude); |
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It seems we have a circular dependency here, because in order to get magnitudes we first need to create a BigInt from string and then get magnitudes by calling a function which returns a magnitude vector, in my case BigInt::to_base64. What are your thoughts on this?
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Added a function to convert
BigIntstring representation into Base64 magnitudes. It starts from back of string and checks for overflow if saved into a 64-bit variable, which means we have reached at a point in string which is a component inmagnitudevector, push this component into the vector and then start over again from the current point in string to check for next component.