Introduce StringBuilder utility around raw_string_ostream

[Yaron Keren]

This looks like a very useful class. It should work for the similar
SmallString pattern, right?

  SmallString<256> OutName;
  llvm::raw_svector_ostream Out(OutName);

cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext()).mangleCXXVTT(RD,
Out);
  Out.flush();
  StringRef Name = OutName.str();

->

  StringBuilder Out;

cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext()).mangleCXXVTT(RD,
Out);
  StringRef Name = Out.str();

Yaron



2014-06-12 8:01 GMT+03:00 Alp Toker <alp at nuanti.com>:

>
> On 12/06/2014 07:41, David Blaikie wrote:
>
>> (would find this a little easier to review if it were in Phab)
>>
>> One off-the-cuff thought: If it's not already documented, you might
>> want to put a comment in raw_string_ostream's ctor that declares that
>> it /really shouldn't/ touch the string (since you're passing in an
>> object in the derived class that won't itself be constructed until
>> after the raw_string_ostream's ctor has finished). Or, better yet, if
>> there's a way to build a raw_string_ostream without a string, then
>> attach it later (in the constructor of StringBuilder) that might be
>> good.
>>
>
> Sure, I'll add a comment. (But I don't think it's a big concern to justify
> any major shuffle -- the ctor is right there inline to see a few lines
> above, and it seems unlikely a stream adapter would ever touch its storage
> unless written to.)
>
>
>> (insert various bikeshedding about the name - though I'm not really
>> sure raw_ostream ever needed to adopt the C++ standard library naming
>> convention in the first place, but I haven't looked closely)
>>
>
> So, I thought about that..
>
> Having tried raw_string_builder_ostream, string_builder_ostream,
> raw_string_builder, I ended up with StringBuilder as the only one that
> looked beautiful in use.
>
> Hard to say why, but it's probably because it has a dual role as storage
> and streaming interface unlike the ostream adapter classes, making the
> distinction significant.
>
> Alp.
>
>
>
>> On Wed, Jun 11, 2014 at 9:25 PM, Alp Toker <alp at nuanti.com> wrote:
>>
>>> Replaces the pattern:
>>>
>>>    std::string buf;
>>>    raw_string_ostream os(buf);
>>>    ...
>>>    os.flush();
>>>    use(buf);
>>>
>>> with:
>>>    StringBuilder os;
>>>    ...
>>>    use (os.str());
>>>
>>> Benefits:
>>>
>>>   * Provides an inherently safe and opaque interface for building
>>> std::string
>>> instances
>>>   * Opens up the possibility of changing the underlying storage in
>>> future.
>>>
>>> Patch also converts various uses, some of which were accessing the
>>> storage
>>> without flushing.
>>>
>>> Alp.
>>>
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