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a3e82eaad3
DeprecatedString (formerly String) has been with us since the start, and it has served us well. However, it has a number of shortcomings that I'd like to address. Some of these issues are hard if not impossible to solve incrementally inside of DeprecatedString, so instead of doing that, let's build a new String class and then incrementally move over to it instead. Problems in DeprecatedString: - It assumes string allocation never fails. This makes it impossible to use in allocation-sensitive contexts, and is the reason we had to ban DeprecatedString from the kernel entirely. - The awkward null state. DeprecatedString can be null. It's different from the empty state, although null strings are considered empty. All code is immediately nicer when using Optional<DeprecatedString> but DeprecatedString came before Optional, which is how we ended up like this. - The encoding of the underlying data is ambiguous. For the most part, we use it as if it's always UTF-8, but there have been cases where we pass around strings in other encodings (e.g ISO8859-1) - operator[] and length() are used to iterate over DeprecatedString one byte at a time. This is done all over the codebase, and will *not* give the right results unless the string is all ASCII. How we solve these issues in the new String: - Functions that may allocate now return ErrorOr<String> so that ENOMEM errors can be passed to the caller. - String has no null state. Use Optional<String> when needed. - String is always UTF-8. This is validated when constructing a String. We may need to add a bypass for this in the future, for cases where you have a known-good string, but for now: validate all the things! - There is no operator[] or length(). You can get the underlying data with bytes(), but for iterating over code points, you should be using an UTF-8 iterator. Furthermore, it has two nifty new features: - String implements a small string optimization (SSO) for strings that can fit entirely within a pointer. This means up to 3 bytes on 32-bit platforms, and 7 bytes on 64-bit platforms. Such small strings will not be heap-allocated. - String can create substrings without making a deep copy of the substring. Instead, the superstring gets +1 refcount from the substring, and it acts like a view into the superstring. To make substrings like this, use the substring_with_shared_superstring() API. One caveat: - String does not guarantee that the underlying data is null-terminated like DeprecatedString does today. While this was nifty in a handful of places where we were calling C functions, it did stand in the way of shared-superstring substrings. |
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| .. | ||
| CMakeLists.txt | ||
| TestAllOf.cpp | ||
| TestAnyOf.cpp | ||
| TestArbitrarySizedEnum.cpp | ||
| TestArray.cpp | ||
| TestAtomic.cpp | ||
| TestBadge.cpp | ||
| TestBase64.cpp | ||
| TestBinaryHeap.cpp | ||
| TestBinarySearch.cpp | ||
| TestBitCast.cpp | ||
| TestBitmap.cpp | ||
| TestBuiltinWrappers.cpp | ||
| TestByteBuffer.cpp | ||
| TestCharacterTypes.cpp | ||
| TestChecked.cpp | ||
| TestCircularDeque.cpp | ||
| TestCircularDuplexStream.cpp | ||
| TestCircularQueue.cpp | ||
| TestComplex.cpp | ||
| TestDeprecatedString.cpp | ||
| TestDisjointChunks.cpp | ||
| TestDistinctNumeric.cpp | ||
| TestDoublyLinkedList.cpp | ||
| TestEndian.cpp | ||
| TestEnumBits.cpp | ||
| TestFind.cpp | ||
| TestFixedArray.cpp | ||
| TestFixedPoint.cpp | ||
| TestFloatingPoint.cpp | ||
| TestFloatingPointParsing.cpp | ||
| TestFormat.cpp | ||
| TestGenericLexer.cpp | ||
| TestHashFunctions.cpp | ||
| TestHashMap.cpp | ||
| TestHashTable.cpp | ||
| TestHex.cpp | ||
| TestIndexSequence.cpp | ||
| TestIntegerMath.cpp | ||
| TestIntrusiveList.cpp | ||
| TestIntrusiveRedBlackTree.cpp | ||
| TestIPv4Address.cpp | ||
| TestIPv6Address.cpp | ||
| TestJSON.cpp | ||
| TestLEB128.cpp | ||
| TestLexicalPath.cpp | ||
| TestMACAddress.cpp | ||
| TestMemory.cpp | ||
| TestMemoryStream.cpp | ||
| TestNeverDestroyed.cpp | ||
| TestNonnullRefPtr.cpp | ||
| TestNumberFormat.cpp | ||
| TestOptional.cpp | ||
| TestPrint.cpp | ||
| TestQueue.cpp | ||
| TestQuickSort.cpp | ||
| TestRedBlackTree.cpp | ||
| TestRefPtr.cpp | ||
| TestSinglyLinkedList.cpp | ||
| TestSourceGenerator.cpp | ||
| TestSourceLocation.cpp | ||
| TestSpan.cpp | ||
| TestStack.cpp | ||
| TestStdLibExtras.cpp | ||
| TestString.cpp | ||
| TestStringFloatingPointConversions.cpp | ||
| TestStringUtils.cpp | ||
| TestStringView.cpp | ||
| TestTime.cpp | ||
| TestTrie.cpp | ||
| TestTuple.cpp | ||
| TestTypedTransfer.cpp | ||
| TestTypeTraits.cpp | ||
| TestUFixedBigInt.cpp | ||
| TestURL.cpp | ||
| TestUtf8.cpp | ||
| TestUtf16.cpp | ||
| TestVariant.cpp | ||
| TestVector.cpp | ||
| TestWeakPtr.cpp | ||