std.array.Appender needs a way to set/get the length

[dlangBugzillaToGithub]

johnnymarler (@marler8997) reported this on 2018-09-22T22:25:15Z

Transfered from https://issues.dlang.org/show_bug.cgi?id=19259

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Description

std.array.Appender needs a way to extend/add to the length of `data`.  See the following use case:

```
uint tryAppendFullPathNameImpl(const(wchar)* nullTerminatedPath, Appender!(wchar[]) builder)
{
    import core.sys.windows.winbase : GetFullPathNameW;
    auto prefixLength = builder.data.length;
    for (;;)
    {
        const result = GetFullPathNameW(nullTerminatedPath, builder.capacity - prefixLength,
            builder.data.ptr + prefixLength, null);
        if (result <= (builder.capacity - prefixLength))
        {
            // NO WAY TO DO THIS:
            //builder.overrideDataLength(prefixLength + result);
            return result;
        }
        builder.reserve(prefixLength + result);
    }
}
```

What's happening here is we are passing the Appender array to a C function that populates the array with our resuling "full path".  Note that this implementation is taken from .NET CoreFX:

https://github.com/dotnet/corefx/blob/1bff7880bfa949e8c5e46039808ec412640bbb5e/src/Common/src/CoreLib/System/IO/PathHelper.Windows.cs#L72

The problem is that once it's populated, we have no way of extending the length of the array after it was populated by the C function.

[dlangBugzillaToGithub]

dlang-bot commented on 2022-04-16T14:09:39Z

@ljmf00 updated dlang/phobos pull request #8432 "feat(array): add .length property" fixing this issue:

- feat(array): add .length property
  
  This patch adds a .length property to either get and set the length of the
  managed array.
  
  Fix issue 19259.
  
  Reference: https://issues.dlang.org/show_bug.cgi?id=19259
  Signed-off-by: Luís Ferreira <contact@lsferreira.net>

https://github.com/dlang/phobos/pull/8432