Fixing CA2014 warnings, and removing suppressions

[creative-cloud]

PR Summary

Fixes #13531 - No longer allocating memory in loops. Removed related suppress warnings.

Moved out the stackalloc statements for 2/3 cases, and removed the loop entirely for the other.

PR Context

Copying context over from the issue -

We currently suppress warnings of CA2014 in parts of the build. stackallocs in loops can cause stack overflows, so we need to refactor our code to fix this.

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    • Issue filed: Fix CA2014: Stackalloc in loops #13531
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[ghost]

All CLA requirements met.

[creative-cloud]

Pinging the original reviewers, to get a few more eyes on the PR.
@anmenaga @adityapatwardhan @daxian-dbw

[iSazonov]

Here we could allocate ~16KB (MaxBufferSize) in stack. That it is not good. I suggest to output the tail before the condition if the tail >= MaxStackAlloc ( MaxStackAlloc = 512).

[creative-cloud]

@iSazonov
I think what you are suggesting is that we should further split the outBuffer into 2 pieces -> MaxBufferSize - 512b and 512b, such that the span that is stacalloc'ed is 512 bytes.
(assuming that the size of the outBuffer is MaxBufferSize, in the worst case)

The first MaxBufferSize - 512b piece will need additional memory. This will also end up going on the stack since we are using spans. This route does not seem any better than allocating the entire MaxBufferSize.

Also, this will mean that we would now need to make two WriteConsole calls to finish writing the contents of the outBuffer, rather than 1.
I don't think the memory allocation issue is significant enough to justify adding the perf of a whole other IO operation.

Let me know if I understood that right.

[iSazonov]

I mean:

        internal static void WriteConsole(ConsoleHandle consoleHandle, ReadOnlySpan<char> output, bool newLine)
        {
            Dbg.Assert(!consoleHandle.IsInvalid, "ConsoleHandle is not valid");
            Dbg.Assert(!consoleHandle.IsClosed, "ConsoleHandle is closed");

            const char MaxStackAlloc = 512;
            Span<char> buffer = stackalloc char[MaxStackAlloc];
            ReadOnlySpan<char> outBuffer;

            // Native WriteConsole doesn't support output buffer longer than 64K.
            // We need to chop the output string if it is too long.
            // This records the chopping position in output string
            int cursor = 0;

            // this is 64K/4 - 1 to account for possible width of each character.
            const int MaxBufferSize = 16383;

            while (cursor <= output.Length - MaxBufferSize)
            {
                outBuffer = output.Slice(cursor, MaxBufferSize);
                cursor += MaxBufferSize;

                WriteConsole(consoleHandle, outBuffer);
            }

            if (cursor == output.Length)
            {
                if (newLine)
                {
                    WriteConsole(consoleHandle, Environment.NewLine);
                }

                return;
            }

            outBuffer = output.Slice(cursor);

            if (!newLine)
            {
                WriteConsole(consoleHandle, outBuffer);

                return;
            }

            if (outBuffer.Length < MaxStackAlloc - 1)
            {
                // We expect it is a hot path.
                var endOfLine = Environment.NewLine.AsSpan();
                var endOfLineLength = endOfLine.Length;
                buffer = buffer.Slice(0, outBuffer.Length + endOfLineLength);            }

                outBuffer.CopyTo(buffer);
                endOfLine.CopyTo(buffer.Slice(buffer.Length - endOfLineLength));

                WriteConsole(consoleHandle, buffer);
            }
            else
            {
                WriteConsole(consoleHandle, outBuffer);

                WriteConsole(consoleHandle, Environment.NewLine);
            }
        }

[iSazonov]

Up.

[daxian-dbw]

@iSazonov I understand your concern here. But the while (cursor + MaxBufferSize < output.Length) comes from the existing if (cursor + MaxBufferSize < output.Length), so it's not a problem introduced by this cleanup change. So, I'm fine merging this PR as is, and submit a new PR to address your concern.

[iSazonov]

@daxian-dbw Agree.

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Total files changed: 3

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.cs : +38 -48

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[daxian-dbw]

LGTM

[iSazonov]

@creative-cloud Thanks for your contribution!