AK: Rename StringImpl to ByteStringImpl

StringImpl is very specific to ByteString. Let's rename it to match, to
avoid confusion with the StringBase and StringData classes.

AK/ByteStringImpl.cpp

@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <andreas@ladybird.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/ByteStringImpl.h>
+#include <AK/CharacterTypes.h>
+#include <AK/StringHash.h>
+#include <AK/kmalloc.h>
+
+namespace AK {
+
+static ByteStringImpl* s_the_empty_stringimpl = nullptr;
+
+ByteStringImpl& ByteStringImpl::the_empty_stringimpl()
+{
+    if (!s_the_empty_stringimpl) {
+        void* slot = kmalloc(sizeof(ByteStringImpl) + sizeof(char));
+        s_the_empty_stringimpl = new (slot) ByteStringImpl(ConstructTheEmptyStringImpl);
+    }
+    return *s_the_empty_stringimpl;
+}
+
+ByteStringImpl::ByteStringImpl(ConstructWithInlineBufferTag, size_t length)
+    : m_length(length)
+{
+}
+
+ByteStringImpl::~ByteStringImpl() = default;
+
+NonnullRefPtr<ByteStringImpl const> ByteStringImpl::create_uninitialized(size_t length, char*& buffer)
+{
+    VERIFY(length);
+    void* slot = kmalloc(allocation_size_for_stringimpl(length));
+    VERIFY(slot);
+    auto new_stringimpl = adopt_ref(*new (slot) ByteStringImpl(ConstructWithInlineBuffer, length));
+    buffer = const_cast<char*>(new_stringimpl->characters());
+    buffer[length] = '\0';
+    return new_stringimpl;
+}
+
+NonnullRefPtr<ByteStringImpl const> ByteStringImpl::create(char const* cstring, size_t length, ShouldChomp should_chomp)
+{
+    if (should_chomp) {
+        while (length) {
+            char last_ch = cstring[length - 1];
+            if (!last_ch || last_ch == '\n' || last_ch == '\r')
+                --length;
+            else
+                break;
+        }
+    }
+
+    if (!length)
+        return the_empty_stringimpl();
+
+    char* buffer;
+    auto new_stringimpl = create_uninitialized(length, buffer);
+    memcpy(buffer, cstring, length * sizeof(char));
+
+    return new_stringimpl;
+}
+
+NonnullRefPtr<ByteStringImpl const> ByteStringImpl::create(char const* cstring, ShouldChomp shouldChomp)
+{
+    if (!cstring || !*cstring)
+        return the_empty_stringimpl();
+
+    return create(cstring, strlen(cstring), shouldChomp);
+}
+
+NonnullRefPtr<ByteStringImpl const> ByteStringImpl::create(ReadonlyBytes bytes, ShouldChomp shouldChomp)
+{
+    return ByteStringImpl::create(reinterpret_cast<char const*>(bytes.data()), bytes.size(), shouldChomp);
+}
+
+unsigned ByteStringImpl::case_insensitive_hash() const
+{
+    return case_insensitive_string_hash(characters(), length());
+}
+
+void ByteStringImpl::compute_hash() const
+{
+    if (!length())
+        m_hash = 0;
+    else
+        m_hash = string_hash(characters(), m_length);
+    m_has_hash = true;
+}
+
+}