Add utf8_hop functions that return error detection #22689
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Prior to this commit these were illegal. This allows it when there is no pesky thread context in the way. This causes embed.fnc to generate macro 'Perl_foo' #defined to be macro 'foo'. This could be used to easily convert existing macros into having long names should that become a name space pollution problem. But more immediately, we have scattered around, various one line functions that simply call something else. Those were typically created to preserve the pre-existing API should someone be using the long name, and the implementation changed. This commit allows those (that don't use thread context) to be conveniently replaced by a macro. The next couple commits will do that for a couple of them.
This is like plain utf8_hop_back() except it returns how many characters the request would have overshot the edge if it had been allowed to go beyond the edge. This allows the caller to do error handling. The code has to be changed to be more careful (than before this commit) with counting the actual number of characters consumed in the hop.
There is a subtle difference here with existing behavior. Most of the time a zero hop already does nothing; but if the initial conditions were that we were starting the hop past the edge, a runtime error was raised, even though the action was a no-op. Its arguable what to do in this case, but I believe the new behavior is more correct, and it paves the way for future commits where it is more clearly more correct. This adds a conditional and indents the code within the new block, removing now-redundant conditionals.
This is in preparation for a future commit where we will need to do finish-up work before returning.
This is like plain utf8_hop_forward() except it returns how many characters the request would have overshot the edge if it had been allowed to go beyond the edge. This allows the caller to do error handling. The code has to be changed to be more careful (than before this commit) with counting the actual number of characters consumed in the hop.
This is like utf8_hop_safe(), but also returns the number of characters that would have overshot the edge if it had been allowed to go beyond the edge
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These commits add versions of the utf8_hop functions that return extra information that can tell the caller if the request could not be completely filled. This will help simplify several portions of the perl core.
The function names end with
_overshootthat indicate to return how far the function call would have overshot the edge of the string if that had been allowed to happen. I'm open to a better name, but I didn't find one in a thesaurus.Once this is settled, I can write the perldelta