private void AddStringsWithSameHashCode(int numberOfStrings)
{
string[] cachedStrings = new string[numberOfStrings];
int[] hashCodes = new int[numberOfStrings];
for (int i = 0; i < numberOfStrings; i++)
{
string strPart2 = "1" + String.Concat(Enumerable.Repeat("4428939786", i));
hashCodes[i] = AddString("Random string ", strPart2, (string cachedString) =>
{
_cache.GetDebugInfo().ShouldBe(new WeakStringCache.DebugInfo()
{
LiveStringCount = 1,
CollectedStringCount = 0,
});
cachedStrings[i] = cachedString;
});
if (i > 0)
{
// The strings have been carefully constructed to have the same hash code.
hashCodes[i].ShouldBe(hashCodes[i - 1]);
}
}
// There are no cache hits when iterating over our strings again because the last one always wins and steals the slot.
for (int i = 0; i < numberOfStrings; i++)
{
InternableString stringCopy = new InternableString(new string(cachedStrings[i].ToCharArray()));
string cachedStringFromCache = _cache.GetOrCreateEntry(ref stringCopy, out bool cacheHit);
cacheHit.ShouldBeFalse();
cachedStringFromCache.ShouldNotBeSameAs(cachedStrings[i]);
}
}
private int AddString(string strPart1, string strPart2, Action <string> callbackToRunWithTheStringAlive)
{
// Compose the string with SB so it doesn't get interned by the runtime.
string testString = new StringBuilder(strPart1).Append(strPart2).ToString();
InternableString testStringTarget = new InternableString(testString);
int hashCode = testStringTarget.GetHashCode();
string cachedString = _cache.GetOrCreateEntry(ref testStringTarget, out bool cacheHit);
cacheHit.ShouldBeFalse();
cachedString.ShouldBeSameAs(testString);
callbackToRunWithTheStringAlive(cachedString);
// Verify that the string is really in the cache and the cache returns the interned instance.
string testStringCopy = new StringBuilder(strPart1).Append(strPart2).ToString();
InternableString testStringCopyTarget = new InternableString(testStringCopy);
cachedString = _cache.GetOrCreateEntry(ref testStringCopyTarget, out cacheHit);
cacheHit.ShouldBeTrue();
cachedString.ShouldBeSameAs(testString);
// Trigger full GC and verify that nothing has changed since we're still keeping testString alive.
GC.Collect();
callbackToRunWithTheStringAlive(cachedString);
testStringCopyTarget = new InternableString(testStringCopy);
cachedString = _cache.GetOrCreateEntry(ref testStringCopyTarget, out cacheHit);
cacheHit.ShouldBeTrue();
cachedString.ShouldBeSameAs(testString);
return(hashCode);
}
public void ReferenceEqualsReturnsExpectedValue()
{
string str = "Test";
InternableString internableString = new InternableString(str);
internableString.ReferenceEquals(str).ShouldBeTrue();
internableString = new InternableString(new string(str.ToCharArray()));
internableString.ReferenceEquals(str).ShouldBeFalse();
}
[InlineData("0123456789")] // even number of characters
public void GetHashCodeIsStableRegardlessOfSpanLength(string testString)
{
int hashCode = new InternableString(testString).GetHashCode();
// Chop the string into 2-3 parts and verify that the hash code is unchanged.
for (int i = 0; i < testString.Length - 1; i++)
{
for (int j = i + 1; j < testString.Length; j++)
{
SpanBasedStringBuilder stringBuilder = new SpanBasedStringBuilder();
stringBuilder.Append(testString.Substring(0, i));
stringBuilder.Append(testString.Substring(i, j - i));
stringBuilder.Append(testString.Substring(j));
InternableString internableString = new InternableString(stringBuilder);
internableString.GetHashCode().ShouldBe(hashCode);
}
}
}
public void EqualsReturnsExpectedValue(InterningTestData.TestDatum datum)
{
InternableString internableString = new InternableString(MakeSpanBasedStringBuilder(datum));
internableString.Equals(string.Empty).ShouldBe(internableString.Length == 0);
string substr = datum.Fragments[0] ?? string.Empty;
internableString.Equals(substr).ShouldBe(substr.Length == internableString.Length);
if (datum.Fragments.Length > 1)
{
substr += datum.Fragments[1];
internableString.Equals(substr).ShouldBe(substr.Length == internableString.Length);
internableString.Equals(datum.ToString()).ShouldBeTrue();
}
internableString.Equals("Things").ShouldBeFalse();
}
