db/simple/Directory: optimize GetName() using the parent's path

This method gets called a lot during MPD startup, via FindChild() and
directory_load_subdir(), so this is worth optimizing at the expense of
code readability.

This speeds up MPD startup by 10%.
This commit is contained in:
Max Kellermann 2020-04-02 15:36:58 +02:00
parent b267ba5f0a
commit cdddaf21b0

View File

@ -32,6 +32,7 @@
#include "fs/Traits.hxx"
#include "util/Alloc.hxx"
#include "util/DeleteDisposer.hxx"
#include "util/StringCompare.hxx"
#include <assert.h>
#include <string.h>
@ -69,7 +70,15 @@ Directory::GetName() const noexcept
{
assert(!IsRoot());
return PathTraitsUTF8::GetBase(path.c_str());
if (parent->IsRoot())
return path.c_str();
assert(StringAfterPrefix(path.c_str(), parent->path.c_str()) != nullptr);
assert(*StringAfterPrefix(path.c_str(), parent->path.c_str()) == PathTraitsUTF8::SEPARATOR);
/* strip the parent directory path and the slash separator
from this directory's path, and the base name remains */
return path.c_str() + parent->path.length() + 1;
}
Directory *