[llvm] r303011 - [StringExtras] Add llvm::to_integer.

[David Blaikie via llvm-commits]

On Sun, May 14, 2017 at 10:24 AM Zachary Turner via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: zturner
> Date: Sun May 14 12:11:05 2017
> New Revision: 303011
>
> URL: http://llvm.org/viewvc/llvm-project?rev=303011&view=rev
> Log:
> [StringExtras] Add llvm::to_integer.
>
> This is a very thin wrapper around StringRef::getAsInteger.
> It serves three purposes.
>
> 1) It allows a cleaner syntax when you have something other than
>    a StringRef - for example, a std::string or an llvm::SmallString.
>    Previously, in this case you would have to write something like:
>       StringRef(MyStr).getAsInteger(0, Result)
>    by explicitly constructing a temporary StringRef.  This can be
>    done implicitly however with the new function by just writing:
>       to_integer(MyStr, ...).
>

For this ^ it seems like it'd be better, maybe, to remove the member
version and just have the non-member version?


> 2) Correcting the travesty that is getAsInteger's return value.
>    This function returns true on success, and false on failure.
>    While this may cause confusion with people familiar with the
>    getAsInteger API, there seems to be widespread agreement that
>    the return semantics of getAsInteger was a mistake.
>

^ this might be less obvious. LLVM had/has a long history of that
true-on-success return bool in some parts of the codebase... :/

Though I guess there's probably enough inconsistency there these days that
maybe it's fine to lean more heavily towards non-zero (true) on failure.


> 3) It allows the Radix to be deduced as a default argument by
>    putting it last in the parameter list.  Most uses of getAsInteger
>    pass 0 for the first argument.  With this syntax it can just be
>    omitted.
>
> Modified:
>     llvm/trunk/include/llvm/ADT/StringExtras.h
>
> Modified: llvm/trunk/include/llvm/ADT/StringExtras.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/ADT/StringExtras.h?rev=303011&r1=303010&r2=303011&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/ADT/StringExtras.h (original)
> +++ llvm/trunk/include/llvm/ADT/StringExtras.h Sun May 14 12:11:05 2017
> @@ -106,6 +106,13 @@ static inline std::string fromHex(String
>    return Output;
>  }
>
> +/// \brief Convert the string \p S to an integer of the specified type
> using
> +/// the radix \p Base.  If \p Base is 0, auto-detects the radix.
> +/// Returns true if the number was successfully converted, false
> otherwise.
> +template <typename N> bool to_integer(StringRef S, N &Num, unsigned Base
> = 0) {
> +  return !S.getAsInteger(Base, Num);
> +}
> +
>  static inline std::string utostr(uint64_t X, bool isNeg = false) {
>    char Buffer[21];
>    char *BufPtr = std::end(Buffer);
>
>
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