Massively simplify WTF's StringConcatenate

third_party/WebKit/Source/wtf/text/StringConcatenate.cpp

Index: third_party/WebKit/Source/wtf/text/StringConcatenate.cpp
diff --git a/third_party/WebKit/Source/wtf/text/StringConcatenate.cpp b/third_party/WebKit/Source/wtf/text/StringConcatenate.cpp
index 7da90e9cabd9f540cf1519e785f19c5f8f8344ce..cbcd0231c01218f93f834f9ca14902de0286b68c 100644
--- a/third_party/WebKit/Source/wtf/text/StringConcatenate.cpp
+++ b/third_party/WebKit/Source/wtf/text/StringConcatenate.cpp
@@ -6,144 +6,62 @@
 
 #include "wtf/text/StringConcatenate.h"
 
+#include "wtf/CheckedNumeric.h"
+#include "wtf/text/StringImpl.h"
+
+namespace WTF {
+
 // This macro is helpful for testing how many intermediate Strings are created while evaluating an
 // expression containing operator+.
 #ifndef WTF_STRINGTYPEADAPTER_COPIED_WTF_STRING
 #define WTF_STRINGTYPEADAPTER_COPIED_WTF_STRING() ((void)0)
 #endif
 
-void WTF::StringTypeAdapter<char*>::writeTo(LChar* destination)
-{
-    for (unsigned i = 0; i < m_length; ++i)
-        destination[i] = static_cast<LChar>(m_buffer[i]);
-}
-
-void WTF::StringTypeAdapter<char*>::writeTo(UChar* destination)
-{
-    for (unsigned i = 0; i < m_length; ++i) {
-        unsigned char c = m_buffer[i];
-        destination[i] = c;
-    }
-}
+namespace internal {
 
-WTF::StringTypeAdapter<LChar*>::StringTypeAdapter(LChar* buffer)
-    : m_buffer(buffer)
-    , m_length(strlen(reinterpret_cast<char*>(buffer)))
+unsigned checkedAddLength(unsigned a, unsigned b)
 {
+    CheckedNumeric<unsigned> length = a;
+    length += b;
+    return length.ValueOrDie();
 }
 
-void WTF::StringTypeAdapter<LChar*>::writeTo(LChar* destination)
-{
-    memcpy(destination, m_buffer, m_length * sizeof(LChar));
-}
+} // namespace internal
 
-void WTF::StringTypeAdapter<LChar*>::writeTo(UChar* destination)
+void StringTypeAdapter<const UChar*>::writeTo(UChar* destination) const
 {
     StringImpl::copyChars(destination, m_buffer, m_length);
 }
 
-WTF::StringTypeAdapter<const UChar*>::StringTypeAdapter(const UChar* buffer)
-    : m_buffer(buffer)
-{
-    size_t len = 0;
-    while (m_buffer[len] != UChar(0))
-        ++len;
-
-    RELEASE_ASSERT(len <= std::numeric_limits<unsigned>::max());
-
-    m_length = len;
-}
-
-void WTF::StringTypeAdapter<const UChar*>::writeTo(UChar* destination)
-{
-    memcpy(destination, m_buffer, m_length * sizeof(UChar));
-}
-
-WTF::StringTypeAdapter<const char*>::StringTypeAdapter(const char* buffer)
-: m_buffer(buffer)
-, m_length(strlen(buffer))
-{
-}
-
-void WTF::StringTypeAdapter<const char*>::writeTo(LChar* destination)
-{
-    memcpy(destination, m_buffer, static_cast<size_t>(m_length) * sizeof(LChar));
-}
-
-void WTF::StringTypeAdapter<const char*>::writeTo(UChar* destination)
-{
-    for (unsigned i = 0; i < m_length; ++i) {
-        unsigned char c = m_buffer[i];
-        destination[i] = c;
-    }
-}
-
-WTF::StringTypeAdapter<const LChar*>::StringTypeAdapter(const LChar* buffer)
-: m_buffer(buffer)
-, m_length(strlen(reinterpret_cast<const char*>(buffer)))
-{
-}
-
-void WTF::StringTypeAdapter<const LChar*>::writeTo(LChar* destination)
-{
-    memcpy(destination, m_buffer, static_cast<size_t>(m_length) * sizeof(LChar));
-}
-
-void WTF::StringTypeAdapter<const LChar*>::writeTo(UChar* destination)
+void StringTypeAdapter<const LChar*>::writeTo(LChar* destination) const
 {
     StringImpl::copyChars(destination, m_buffer, m_length);
 }
 
-void WTF::StringTypeAdapter<Vector<char>>::writeTo(LChar* destination)
+void StringTypeAdapter<const LChar*>::writeTo(UChar* destination) const
 {
-    for (size_t i = 0; i < m_buffer.size(); ++i)
-        destination[i] = static_cast<unsigned char>(m_buffer[i]);
-}
-
-void WTF::StringTypeAdapter<Vector<char>>::writeTo(UChar* destination)
-{
-    for (size_t i = 0; i < m_buffer.size(); ++i)
-        destination[i] = static_cast<unsigned char>(m_buffer[i]);
-}
-
-void WTF::StringTypeAdapter<Vector<LChar>>::writeTo(LChar* destination)
-{
-    for (size_t i = 0; i < m_buffer.size(); ++i)
-        destination[i] = m_buffer[i];
+    StringImpl::copyChars(destination, m_buffer, m_length);
 }
 
-void WTF::StringTypeAdapter<Vector<LChar>>::writeTo(UChar* destination)
-{
-    for (size_t i = 0; i < m_buffer.size(); ++i)
-        destination[i] = m_buffer[i];
-}
+StringTypeAdapter<const UChar*>::StringTypeAdapter(const UChar* buffer)
+    : m_buffer(buffer)
+    , m_length(lengthOfNullTerminatedString(buffer)) {}
 
-void WTF::StringTypeAdapter<String>::writeTo(LChar* destination)
+void StringTypeAdapter<String>::writeTo(LChar* destination) const
 {
-    unsigned length = m_buffer.length();
-
-    ASSERT(is8Bit());
-    const LChar* data = m_buffer.characters8();
-    for (unsigned i = 0; i < length; ++i)
-        destination[i] = data[i];
-
+    DCHECK(is8Bit());
+    StringImpl::copyChars(destination, m_buffer.characters8(), m_buffer.length());
     WTF_STRINGTYPEADAPTER_COPIED_WTF_STRING();
 }
 
-void WTF::StringTypeAdapter<String>::writeTo(UChar* destination)
+void StringTypeAdapter<String>::writeTo(UChar* destination) const
 {
-    unsigned length = m_buffer.length();
-
-    if (is8Bit()) {
-        const LChar* data = m_buffer.characters8();
-        for (unsigned i = 0; i < length; ++i)
-            destination[i] = data[i];
-    } else {
-        const UChar* data = m_buffer.characters16();
-        for (unsigned i = 0; i < length; ++i)
-            destination[i] = data[i];
-    }
+    if (is8Bit())
+        StringImpl::copyChars(destination, m_buffer.characters8(), m_buffer.length());
+    else
+        StringImpl::copyChars(destination, m_buffer.characters16(), m_buffer.length());
 
     WTF_STRINGTYPEADAPTER_COPIED_WTF_STRING();
 }
 
+} // namespace WTF