cborpretty.c: Implement numeric encoding indicators for floating point

RFC 7049 section 6 has an encoding mechanism that I had not noticed
before. It says:

   An underscore followed by a decimal digit n indicates that the
   preceding item [...] was encoded with an additional
   information value of 24+n.  For example, 1.5_1 is a half-precision
   floating-point number, while 1.5_3 is encoded as double precision.

This flag only changes the suffix used by floating point. We don't show
the encoding indicator in other contexts, including that for double
precision. That's a job for another flag.

Signed-off-by: Thiago Macieira <[email protected]>

Author: thiagomacieira

src/cbor.h

@@ -484,6 +484,9 @@ CBOR_INLINE_API CborError cbor_value_get_double(const CborValue *value, double *
 /* Human-readable (dump) API */
 
 enum CborPrettyFlags {
+    CborPrettyNumericEncodingIndicators     = 0x01,
+    CborPrettyTextualEncodingIndicators     = 0,
+
     CborPrettyDefaultFlags          = 0
 };
 

src/cborpretty.c

@@ -99,8 +99,11 @@
  *      \c true or \c false
  * \par Floating point:
  *      If NaN or infinite, the actual words \c NaN or \c infinite.
- *      Otherwise, the decimal representation with as many digits as necessary to ensure no loss of information,
- *      with float values suffixed by "f" and half-float values suffixed by "f16" (doubles have no suffix). A dot is always present.
+ *      Otherwise, the decimal representation with as many digits as necessary to ensure no loss of information.
+ *      By default, float values are suffixed by "f" and half-float values suffixed by "f16" (doubles have no suffix).
+ *      If the CborPrettyNumericEncodingIndicators flag is active, the values instead are encoded following the
+ *      Section 6 recommended encoding indicators: float values are suffixed with "_2" and half-float with "_1".
+ *      A dot is always present.
  * \par Arrays:
  *      Comma-separated list of elements, enclosed in square brackets ("[" and "]").
  *     If the array length is indeterminate, an underscore ("_") appears immediately after the opening bracket.
@@ -114,6 +117,8 @@
  * \enum CborPrettyFlags
  * The CborPrettyFlags enum contains flags that control the conversion of CBOR to text format.
  *
+ * \value CborPrettyNumericEncodingIndicators   Use numeric encoding indicators instead of textual for float and half-float.
+ * \value CborPrettyTextualEncodingIndicators   Use textual encoding indicators for float ("f") and half-float ("f16").
  * \value CborPrettyDefaultFlags       Default conversion flags.
  */
 
@@ -404,26 +409,29 @@ static CborError value_to_pretty(FILE *out, CborValue *it, int flags)
     case CborDoubleType: {
         const char *suffix;
         double val;
+        int r;
         if (false) {
             float f;
     case CborFloatType:
             cbor_value_get_float(it, &f);
             val = f;
-            suffix = "f";
+            suffix = flags & CborPrettyNumericEncodingIndicators ? "_2" : "f";
         } else if (false) {
             uint16_t f16;
     case CborHalfFloatType:
             cbor_value_get_half_float(it, &f16);
             val = decode_half(f16);
-            suffix = "f16";
+            suffix = flags & CborPrettyNumericEncodingIndicators ? "_1" : "f16";
         } else {
             cbor_value_get_double(it, &val);
             suffix = "";
         }
 
-        int r = fpclassify(val);
-        if (r == FP_NAN || r == FP_INFINITE)
-            suffix = "";
+        if ((flags & CborPrettyNumericEncodingIndicators) == 0) {
+            r = fpclassify(val);
+            if (r == FP_NAN || r == FP_INFINITE)
+                suffix = "";
+        }
 
         uint64_t ival = (uint64_t)fabs(val);
         if (ival == fabs(val)) {