Windows path limitation tests

.gitignore

*.exe
*.pdb
*.ilk

longpathtest.d

// Warning: this program creates and deletes files and directories on C:\.
// Run at your own risk! (Better use a VM)

import std.array;
import std.file;
import std.range;
import std.stdio;

import ae.sys.file : longPath;

void main()
{
	for (int chars = 1; ; chars++)
	{
		auto path = `C:\` ~ replicate("a", chars);
		if (path.longPath.exists) path.longPath.rmdirRecurse();
		scope(exit) if (path.longPath.exists) path.longPath.rmdirRecurse();
		try
			mkdir(path);
		catch (Exception e)
		{
			writefln("mkdir (%d chars) absolute limit: %s chars: %s", chars, path.length, e.msg.replace(path, "[path]"));
			break;
		}
	}

	foreach (chars; 1..3+1)
	{
		auto root = (`C:\` ~ replicate("a", chars)).longPath;
		if (root.exists) root.rmdirRecurse;
		scope(exit) root.rmdirRecurse();
		for (int n = 1; ; n++)
		{
			auto path = `C:\` ~ replicate(replicate("a", chars) ~ `\`, n);
			try
				mkdir(path);
			catch (Exception e)
			{
				writefln("nested mkdir (%d chars) absolute limit: %s chars (%d dirs): %s", chars, path.length, n, e.msg.replace(path, "[path]"));
				break;
			}
		}
	}

	foreach (chars; 1..3+1)
	{
		auto root = (`C:\` ~ replicate("a", chars)).longPath;
		if (root.exists) root.rmdirRecurse;
		scope(exit) root.rmdirRecurse();
		chdir(`C:\`);
		scope(exit) chdir(`C:\`);
		for (int n = 0; ; n++)
		{
			auto path = replicate("a", chars);
			string op;
			try
			{
				op = "mkdir"; mkdir(path);
				op = "chdir"; chdir(path);
			}
			catch (Exception e)
			{
				writefln("descending mkdir (%d chars) absolute limit (%s): %s chars (%d dirs): %s", chars, op, path.length, n, e.msg);
				break;
			}
		}
	}

	foreach (chars; 1..3+1)
	{
		auto dir = replicate("a", chars);
		auto root = (`C:\` ~ dir).longPath;
		if (root.exists) root.rmdirRecurse;
		scope(exit) root.rmdirRecurse();

		// Make arena
		mkdirRecurse(longPath(`C:\` ~ replicate(dir ~ `\`, 1000)));

		writeln;

		enum step = 10;

		foreach (start; iota(0, 300, step))
		{
			auto cwd = `C:\` ~ replicate(dir ~ `\`, start);
			try
				chdir(cwd);
			catch (Exception e)
				continue;
			scope(exit) chdir(`C:\`);

			writef("relative write (%d chars, CWD at %s dirs / %d chars):", chars, start, cwd.length);
			foreach (back; iota(0, start+1, step))
			{
				bool found;
				foreach (forward; iota(0, 300, step))
				{
					auto path = replicate(`..\`, back) ~ replicate(dir ~ `\`, forward) ~ `f`;
					try
						std.file.write(path, "");
					catch (Exception e)
					{
						writef(" -%d+%d", back, forward);
						found = true;
						break;
					}
				}
				if (!found)
					writef(" -%d+∞", back);
			}
			writeln;
		}
	}
}

output.txt

mkdir (245 chars) absolute limit: 248 chars: [path]: The filename or extension is too long. (error 206)
nested mkdir (1 chars) absolute limit: 249 chars (123 dirs): [path]: The filename or extension is too long. (error 206)
nested mkdir (2 chars) absolute limit: 249 chars (82 dirs): [path]: The filename or extension is too long. (error 206)
nested mkdir (3 chars) absolute limit: 251 chars (62 dirs): [path]: The filename or extension is too long. (error 206)
descending mkdir (1 chars) absolute limit (mkdir): 1 chars (122 dirs): a: The filename or extension is too long. (error 206)
descending mkdir (2 chars) absolute limit (mkdir): 2 chars (81 dirs): aa: The filename or extension is too long. (error 206)
descending mkdir (3 chars) absolute limit (mkdir): 3 chars (61 dirs): aaa: The filename or extension is too long. (error 206)

relative write (1 chars, CWD at 0 dirs / 3 chars): -0+0
relative write (1 chars, CWD at 10 dirs / 23 chars): -0+120 -10+0
relative write (1 chars, CWD at 20 dirs / 43 chars): -0+110 -10+100 -20+0
relative write (1 chars, CWD at 30 dirs / 63 chars): -0+100 -10+90 -20+70 -30+0
relative write (1 chars, CWD at 40 dirs / 83 chars): -0+90 -10+80 -20+60 -30+50 -40+0
relative write (1 chars, CWD at 50 dirs / 103 chars): -0+80 -10+70 -20+50 -30+40 -40+20 -50+0
relative write (1 chars, CWD at 60 dirs / 123 chars): -0+70 -10+60 -20+40 -30+30 -40+10 -50+0 -60+0
relative write (1 chars, CWD at 70 dirs / 143 chars): -0+60 -10+50 -20+30 -30+20 -40+0 -50+0 -60+0 -70+0
relative write (1 chars, CWD at 80 dirs / 163 chars): -0+50 -10+40 -20+20 -30+10 -40+0 -50+0 -60+0 -70+0 -80+0
relative write (1 chars, CWD at 90 dirs / 183 chars): -0+40 -10+30 -20+10 -30+0 -40+0 -50+0 -60+0 -70+0 -80+0 -90+0
relative write (1 chars, CWD at 100 dirs / 203 chars): -0+30 -10+20 -20+0 -30+0 -40+0 -50+0 -60+0 -70+0 -80+0 -90+0 -100+0
relative write (1 chars, CWD at 110 dirs / 223 chars): -0+20 -10+10 -20+0 -30+0 -40+0 -50+0 -60+0 -70+0 -80+0 -90+0 -100+0 -110+0
relative write (1 chars, CWD at 120 dirs / 243 chars): -0+10 -10+0 -20+0 -30+0 -40+0 -50+0 -60+0 -70+0 -80+0 -90+0 -100+0 -110+0 -120+0

relative write (2 chars, CWD at 0 dirs / 3 chars): -0+0
relative write (2 chars, CWD at 10 dirs / 33 chars): -0+80 -10+0
relative write (2 chars, CWD at 20 dirs / 63 chars): -0+70 -10+60 -20+0
relative write (2 chars, CWD at 30 dirs / 93 chars): -0+60 -10+50 -20+40 -30+0
relative write (2 chars, CWD at 40 dirs / 123 chars): -0+50 -10+40 -20+30 -30+20 -40+0
relative write (2 chars, CWD at 50 dirs / 153 chars): -0+40 -10+30 -20+20 -30+10 -40+0 -50+0
relative write (2 chars, CWD at 60 dirs / 183 chars): -0+30 -10+20 -20+10 -30+0 -40+0 -50+0 -60+0
relative write (2 chars, CWD at 70 dirs / 213 chars): -0+20 -10+10 -20+0 -30+0 -40+0 -50+0 -60+0 -70+0
relative write (2 chars, CWD at 80 dirs / 243 chars): -0+10 -10+0 -20+0 -30+0 -40+0 -50+0 -60+0 -70+0 -80+0

relative write (3 chars, CWD at 0 dirs / 3 chars): -0+0
relative write (3 chars, CWD at 10 dirs / 43 chars): -0+60 -10+0
relative write (3 chars, CWD at 20 dirs / 83 chars): -0+50 -10+40 -20+0
relative write (3 chars, CWD at 30 dirs / 123 chars): -0+40 -10+30 -20+20 -30+0
relative write (3 chars, CWD at 40 dirs / 163 chars): -0+30 -10+20 -20+10 -30+10 -40+0
relative write (3 chars, CWD at 50 dirs / 203 chars): -0+20 -10+10 -20+0 -30+0 -40+0 -50+0
relative write (3 chars, CWD at 60 dirs / 243 chars): -0+10 -10+0 -20+0 -30+0 -40+0 -50+0 -60+0