CSHARP-2442: Increase StringBuilder capacity

[Achilles1515]

This StringBuilder object is being created because the string named "value" needs escaping. It is unknown at this point exactly how many characters need escaping, but AT MINIMUM there is one. This means the new escaped string length will be larger than original string length by at least one character, and the StringBuilder constructor capacity parameter should reflect this logic. Without this change, the StringBuilder object is GUARANTEED to allocate and chain together a new StringBuilder object under the hood as it increases it's capacity to handle the larger escaped string.

[jyemin]

Hi @Achilles1515 as per our contributing guide, please open an issue at jira.mongodb.org in the CSHARP project and link it to the pull request.

Thanks,
Jeff

[Achilles1515]

Hi @Achilles1515 as per our contributing guide, please open an issue at jira.mongodb.org in the CSHARP project and link it to the pull request.

Thanks,
Jeff

Done. Sorry about that.

[dnickless]

How about something like this even:

            int replacements = value.Count(c => NeedsEscaping(c));
            if (replacements == 0)
            {
                return value;
            }

            var sb = new StringBuilder(value.Length + replacements);

Also, NeedsEscaping should be made static as we currently have a lambda closure over "this" here which allocates no matter if we end up escaping things or not.

Thinking about it a bit more, I would go as far as suggesting to drop the whole temporary string that gets built using the StringBuilder and have EscapedString write to the _textWriter directly instead. Looking at the current usages of EscapedString this appears justifiable.

[rstam]

This PR was included as part of PR #1290

Thank you for submitting it.