FFstrbuf: handles double rounding and zero representation in formatter

Author: CarterLi

src/util/FFstrbuf.c

@@ -2,6 +2,7 @@
 
 #include <ctype.h>
 #include <inttypes.h>
+#include <math.h>
 
 char* CHAR_NULL_PTR = "";
 
@@ -577,9 +578,12 @@ void ffStrbufAppendDouble(FFstrbuf* strbuf, double value, int8_t precision)
     ffStrbufEnsureFree(strbuf, 40); // Required by yyjson_write_number
     char* start = strbuf->chars + strbuf->length;
 
+    if (precision == 0)
+        value = round(value);
     yyjson_val val = {};
     unsafe_yyjson_set_double(&val, value);
-    if (precision >= 0) unsafe_yyjson_set_fp_to_fixed(&val, precision == 0 ? 1 : precision); // yyjson ignores precision == 0
+    if (precision > 0)
+        unsafe_yyjson_set_fp_to_fixed(&val, precision);
 
     // Write at most <precision> digits after the decimal point; doesn't append trailing zeros
     char* end = yyjson_write_number(&val, start);

tests/strbuf.c

@@ -759,6 +759,14 @@ int main(void)
         ffStrbufAppendDouble(&strbuf, 120.123456789, 5);
         VERIFY(ffStrbufEqualS(&strbuf, "120.12346"));
 
+        ffStrbufClear(&strbuf);
+        ffStrbufAppendDouble(&strbuf, 120.888888, 0);
+        VERIFY(ffStrbufEqualS(&strbuf, "121"));
+
+        ffStrbufClear(&strbuf);
+        ffStrbufAppendDouble(&strbuf, 120.999999, 2);
+        VERIFY(ffStrbufEqualS(&strbuf, "121.00"));
+
         ffStrbufClear(&strbuf);
         ffStrbufAppendDouble(&strbuf, 120.123456789, 0);
         VERIFY(ffStrbufEqualS(&strbuf, "120"));
@@ -799,6 +807,14 @@ int main(void)
         ffStrbufAppendDouble(&strbuf, -120.123, 5);
         VERIFY(ffStrbufEqualS(&strbuf, "-120.12300"));
 
+        ffStrbufClear(&strbuf);
+        ffStrbufAppendDouble(&strbuf, -120.888888, 0);
+        VERIFY(ffStrbufEqualS(&strbuf, "-121"));
+
+        ffStrbufClear(&strbuf);
+        ffStrbufAppendDouble(&strbuf, -120.999999, 2);
+        VERIFY(ffStrbufEqualS(&strbuf, "-121.00"));
+
         ffStrbufClear(&strbuf);
         ffStrbufAppendDouble(&strbuf, 1.2345e50, 1);
         VERIFY(ffStrbufEqualS(&strbuf, "1.2345e50"));
@@ -832,12 +848,12 @@ int main(void)
         VERIFY(ffStrbufEqualS(&strbuf, "-123450000000000000000.0"));
 
         ffStrbufClear(&strbuf);
-        ffStrbufAppendDouble(&strbuf, 0, 0);
+        ffStrbufAppendDouble(&strbuf, +0.0, 0);
         VERIFY(ffStrbufEqualS(&strbuf, "0"));
 
         ffStrbufClear(&strbuf);
-        ffStrbufAppendDouble(&strbuf, -0, 0);
-        VERIFY(ffStrbufEqualS(&strbuf, "0"));
+        ffStrbufAppendDouble(&strbuf, -0.0, 0);
+        VERIFY(ffStrbufEqualS(&strbuf, "-0"));
 
         ffStrbufDestroy(&strbuf);
     }