Introduce StringImpl::createPreallocatedStatic

third_party/WebKit/Source/build/scripts/templates/MakeNames.cpp.tmpl

 {% from "macros.tmpl" import license %}
 {{ license() }}
 
 #include "config.h"
 
 #include "{{namespace}}{{suffix}}Names.h"
 
 #include "wtf/StdLibExtras.h"
 
 // Generated from:
 {% for entry in in_files|sort %}
 // - {{entry}}
 {% endfor %}
 
 namespace blink {
 namespace {{namespace}}Names {
 
 using namespace WTF;
 
 void* {{suffix}}NamesStorage[{{namespace}}{{suffix}}NamesCount * ((sizeof(AtomicString) + sizeof(void *) - 1) / sizeof(void *))];
 
 {% for entry in entries|sort(attribute='name', case_sensitive=True) %}
 {% filter enable_conditional(entry.Conditional) %}
 const AtomicString& {{entry|symbol}} = reinterpret_cast<AtomicString*>(&{{suffix}}NamesStorage)[{{loop.index0}}];
 {% endfilter %}
 {% endfor %}
 
 void init{{suffix}}()
 {
+    const int kMaxNameLength = {{entries|map(attribute='name')|map('length')|max}} + 1;
     struct NameEntry {
-        const char* name;
+        char string_impl_storage[sizeof(StringImpl)];

[tkent, 2015/10/21 03:19:33]

* Need a comment that the layout should be matched StringImpl, and an assertion
that |name| is next to |string_impl_storrage|.

* style error: |string_impl_storage| should be |stringImplStorage| or something.

[Daniel Bratell, 2015/10/21 09:51:25]

This looks like it could make the Names array rather large in the binary. There
are quite a lot of NameEntry objects right. Not sure why the const char* name
pointer was bad?

Also, can you move the string_impl_storage array out of this object because
while NameEntry objects need to be setup statically, string_impl_storage is just
a preallocated memory buffer and much cheaper to setup. Mixing them brings the
worse of both together.

[tzik, 2015/10/28 14:33:31]

Done.

[tzik, 2015/10/28 14:33:31]

|name| needs to be an array instead of char* to match memory layout requirement
of StringImpl. And stringImplStorage also needs to here.
Though single kMaxNameLength makes some gap between strings, but that seems not
significant.

+        char name[kMaxNameLength];
         unsigned hash;
         unsigned char length;
     };
 
-    static const NameEntry kNames[] = {
+    static NameEntry Names[] = {

[tkent, 2015/10/21 03:19:33]

You don't need to rename kNames to Names, which doesn't match to the coding
style.

[tzik, 2015/10/28 14:33:31]

Done.

     {% for entry in entries|sort(attribute='name', case_sensitive=True) %}
-        { "{{entry|cpp_name}}", {{entry|cpp_name|hash}}, {{entry|cpp_name|length}} },
+        { "", "{{entry|cpp_name}}", {{entry|cpp_name|hash}}, {{entry|cpp_name|length}} },
     {% endfor %}
     };
 
-    for (size_t i = 0; i < WTF_ARRAY_LENGTH(kNames); i++) {
-        StringImpl* stringImpl = StringImpl::createStatic(kNames[i].name, kNames[i].length, kNames[i].hash);
+    for (size_t i = 0; i < WTF_ARRAY_LENGTH(Names); i++) {
+        StringImpl* stringImpl = StringImpl::createPreallocatedStatic(Names[i].string_impl_storage, Names[i].length, Names[i].hash);
         void* address = reinterpret_cast<AtomicString*>(&{{suffix}}NamesStorage) + i;
         new (address) AtomicString(stringImpl);
     }
 }
 
 } // {{namespace}}Names
 } // namespace blink