FFstrbuf: improve performance of copying static strings

Author: CarterLi

src/util/FFstrbuf.c

@@ -225,12 +225,6 @@ void ffStrbufSetNS(FFstrbuf* strbuf, uint32_t length, const char* value)
     ffStrbufAppendNS(strbuf, length, value);
 }
 
-void ffStrbufSet(FFstrbuf* strbuf, const FFstrbuf* value)
-{
-    ffStrbufClear(strbuf);
-    ffStrbufAppendNS(strbuf, value->length, value->chars);
-}
-
 void ffStrbufTrimLeft(FFstrbuf* strbuf, char c)
 {
     if(strbuf->length == 0)

src/util/FFstrbuf.h

@@ -49,7 +49,6 @@ void ffStrbufPrependC(FFstrbuf* strbuf, char c);
 void ffStrbufInsertNC(FFstrbuf* strbuf, uint32_t index, uint32_t num, char c);
 
 void ffStrbufSetNS(FFstrbuf* strbuf, uint32_t length, const char* value);
-void ffStrbufSet(FFstrbuf* strbuf, const FFstrbuf* value);
 FF_C_PRINTF(2, 3) void ffStrbufSetF(FFstrbuf* strbuf, const char* format, ...);
 
 void ffStrbufTrimLeft(FFstrbuf* strbuf, char c);
@@ -102,8 +101,13 @@ FF_C_NODISCARD static inline FFstrbuf ffStrbufCreateA(uint32_t allocate)
 
 static inline void ffStrbufInitCopy(FFstrbuf* __restrict strbuf, const FFstrbuf* __restrict src)
 {
-    ffStrbufInitA(strbuf, src->allocated);
-    ffStrbufAppend(strbuf, src);
+    if (src->allocated == 0) // static string
+        memcpy(strbuf, src, sizeof(FFstrbuf));
+    else
+    {
+        ffStrbufInitA(strbuf, src->allocated);
+        ffStrbufAppend(strbuf, src);
+    }
 }
 
 FF_C_NODISCARD static inline FFstrbuf ffStrbufCreateCopy(const FFstrbuf* src)
@@ -209,6 +213,17 @@ static inline void ffStrbufSetS(FFstrbuf* strbuf, const char* value)
         ffStrbufAppendNS(strbuf, (uint32_t) strlen(value), value);
 }
 
+static inline void ffStrbufSet(FFstrbuf* strbuf, const FFstrbuf* value)
+{
+    assert(value && value != strbuf);
+    if (strbuf->allocated == 0 && value->allocated == 0)
+    {
+        memcpy(strbuf, value, sizeof(FFstrbuf));
+        return;
+    }
+    ffStrbufSetNS(strbuf, value->length, value->chars);
+}
+
 static inline void ffStrbufInit(FFstrbuf* strbuf)
 {
     extern char* CHAR_NULL_PTR;

tests/strbuf.c

@@ -593,6 +593,48 @@ int main(void)
     VERIFY(ffStrbufRemoveDupWhitespaces(&strbuf) == false);
     VERIFY(strcmp(strbuf.chars, "   ") == 0);
 
+    {
+        ffStrbufSetStatic(&strbuf, "abcdef");
+        FF_STRBUF_AUTO_DESTROY newStr = ffStrbufCreateCopy(&strbuf);
+        VERIFY(newStr.allocated == 0);
+        VERIFY(newStr.chars == strbuf.chars);
+    }
+
+    {
+        ffStrbufSetStatic(&strbuf, "abcdef");
+        FF_STRBUF_AUTO_DESTROY newStr = ffStrbufCreateS("123456");
+        ffStrbufSet(&newStr, &strbuf);
+        VERIFY(newStr.allocated > 0);
+        VERIFY(newStr.chars != strbuf.chars);
+        VERIFY(ffStrbufEqualS(&newStr, "abcdef"));
+    }
+
+    {
+        ffStrbufSetStatic(&strbuf, "abcdefghijkl");
+        FF_STRBUF_AUTO_DESTROY newStr = ffStrbufCreateS("123456");
+        ffStrbufSet(&newStr, &strbuf);
+        VERIFY(newStr.allocated > 0);
+        VERIFY(newStr.chars != strbuf.chars);
+        VERIFY(ffStrbufEqualS(&newStr, "abcdefghijkl"));
+    }
+
+    {
+        ffStrbufClear(&strbuf);
+        FF_STRBUF_AUTO_DESTROY newStr = ffStrbufCreateCopy(&strbuf);
+        VERIFY(newStr.allocated == 0);
+        VERIFY(newStr.chars == strbuf.chars);
+        VERIFY(newStr.chars[0] == '\0');
+    }
+
+    {
+        ffStrbufClear(&strbuf);
+        FF_STRBUF_AUTO_DESTROY newStr = ffStrbufCreateS("123456");
+        ffStrbufSet(&newStr, &strbuf);
+        VERIFY(newStr.allocated > 0);
+        VERIFY(newStr.chars != strbuf.chars);
+        VERIFY(ffStrbufEqualS(&newStr, ""));
+    }
+
     //Success
     puts("\e[32mAll tests passed!" FASTFETCH_TEXT_MODIFIER_RESET);
 }