Speed up offset calculation #24
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per_page parameter was not working as parameters would get passed to Ratios as strings, which means we'd always fail to calculte the offset. Tests were passing because all of them used the first page, which uses offset 0 independently of the configured ratios. With strings, and any other page > 1, a `TypeError: String can't be coerced into Integer` would be raised as we'd try to perform arithmetic operations on strings.
Switch from O(2^n) (where n is the number of bits used to
represent the page number) to O(1).
Before:
```
portion = GearedPagination::PortionAtOffset.new(page_number: 100000000, per_page: GearedPagination::Ratios.new)
Benchmark.bm do |x|
x.report { portion.offset }
end
user system total real
11.741485 0.296831 12.038316 ( 12.049057)
```
After:
```
portion = GearedPagination::PortionAtOffset.new(page_number: 100000000, per_page: GearedPagination::Ratios.new)
Benchmark.bm do |x|
x.report { portion.offset }
end
user system total real
0.000027 0.000007 0.000034 ( 0.000030)
```
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This PR switches offset calculation from a O(2^n) implementation (where n is the number of bits used to
represent the page number) to O(1).
Before:
After:
Apart from this, this also includes a small fix for the
per_pageparameter, as it was not working due to values there being passed toRatiosas strings, which means we'd always fail to calculate the offset. Tests were passing because all of them used the first page, which uses offset 0 independently of the configured ratios. With strings, and any other page > 1, aTypeError: String can't be coerced into Integerwould be raised as we'd try to perform arithmetic operations on strings.