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Unit tests are not built by default, and the option to enable them was changed by this commit: google@8ae0ac6 Also add some documentation that the gflags and gtest submodules don't need to be initialized if you don't want to build the binary or unit tests, or if you want to use system libraries instead.
Instead of increasing `address` every iteration of the loop, we can just keep
it fixed and double the number of bytes copied every iteration. This works
because the string to be generated is periodic.
For example, if we want to copy 9 bytes starting 2 bytes back:
|-------| size 9
abc.........
^ ^
| |
| target_bytes_decoded: 3
address: 1
Then the old version of the code would generate these intermediate states:
abc.........
^ ^
abcbc....... (1)
^ ^
abcbcbc..... (2)
^ ^
abcbcbcbc... (3)
^ ^
abcbcbcbcbc. (4)
^ ^
abcbcbcbcbcb (5, outside the loop)
While the new version would double the range to be copied every time:
abc.........
^ ^
abcbc.......(1)
^ ^
abcbcbcbc.. (2)
^ ^
abcbcbcbcbc (3, outside the loop)
In general, if s = size and d = (target_bytes_decoded - address), then the
number of calls to CopyBytes is reduced from (s/d + 1) to log(s/d)/log(2) + 1.
The total time complexity is still O(s) because CopyBytes is presumably linear
in the number of bytes copied, but we end up doing fewer calls in total, which
is likely to be faster in practice.
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Unit tests are not built by default, and the option to enable them was changed
by this commit:
8ae0ac6
Also add some documentation that the gflags and gtest submodules don't need to
be initialized if you don't want to build the binary or unit tests, or if you
want to use system libraries instead.