Merge aed0a5d626 into ee788ca28f

README.md

@@ -25,7 +25,7 @@ Errors are raised as exceptions.
     2> Doc = {[{foo, [<<"bing">>, 2.3, true]}]}.
     {[{foo,[<<"bing">>,2.3,true]}]}
     3> jiffy:encode(Doc).
-    <<"{\"foo\":[\"bing\",2.2999999999999998224,true]}">>
+    <<"{\"foo\":[\"bing\",2.3,true]}">>
 
 
 Data Format

c_src/encoder.c

@@ -4,12 +4,15 @@
 #include <assert.h>
 #include <stdio.h>
 #include <string.h>
+#include <float.h>
 
 #include "erl_nif.h"
 #include "jiffy.h"
 
 #define BIN_INC_SIZE 2048
 
+#define FLOAT_BUFLEN (LDBL_DIG*2)
+
 #define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
 
 #define MAYBE_PRETTY(e)             \
@@ -393,13 +396,18 @@ enc_double(Encoder* e, double val)
     size_t len;
     size_t i;
 
-    if(!enc_ensure(e, 32)) {
+    if(!enc_ensure(e, FLOAT_BUFLEN)) {
         return 0;
     }
 
     start = &(e->p[e->i]);
 
-    sprintf(start, "%0.20g", val);
+    // try to encode doubles using the fewest digits possible...
+    if (snprintf(start, FLOAT_BUFLEN, "%.*g", DBL_DIG, val) > FLT_DIG)
+    {
+        // ...fall back to full expansion to be safe
+        snprintf(start, FLOAT_BUFLEN, "%.*g", LDBL_DIG, val);
+    }
     len = strlen(start);
 
     // Check if we have a decimal point
@@ -408,7 +416,7 @@ enc_double(Encoder* e, double val)
             goto done;
     }
 
-    if(len > 29) return 0;
+    if(len >= FLOAT_BUFLEN-2) return 0;
 
     // Force a decimal point
     start[len++] = '.';

test/003-numbers.t

@@ -21,30 +21,25 @@ good() ->
         {<<"1234567890123456789012345">>, 1234567890123456789012345},
         {<<"1310050760199">>, 1310050760199},
         {
-            <<"1234567890123456789012345.0">>,
-            1.23456789012345678e24,
-            <<"1.2345678901234568245e+24">>
+            1.23456789012345678e24
         },
         {
-            <<"1234567890123456789012345.0E3">>,
-            1.2345678901234569e27,
-            <<"1.2345678901234568502e+27">>
+            1.2345678901234569e27
         },
         {
             <<"1234567890123456789012345012">>,
-            1234567890123456789012345012,
-            <<"1234567890123456789012345012">>
+            1234567890123456789012345012
         },
         {<<"1.0">>, 1.0},
         {
             <<"0.000000000000000000000000000000000001">>,
             1.0E-36,
-            <<"9.9999999999999994104e-37">>
+            <<"1e-36">>
         },
         {<<"0.75">>, 0.75},
-        {<<"2.0123456789">>, 2.0123456789, <<"2.0123456789000000455">>},
-        {<<"2.4234324E24">>, 2.4234324E24, <<"2.4234323999999998107e+24">>},
-        {<<"-3.1416">>, -3.1416, <<"-3.1415999999999999481">>},
+        {2.0123456789},
+        {2.4234324E24},
+        {-3.1416},
         {<<"1E4">>, 10000.0, <<"10000.0">>},
         {<<"1.0E+01">>, 10.0, <<"10.0">>},
         {<<"1e1">>, 10.0, <<"10.0">>},

test/util.erl

@@ -22,6 +22,8 @@ do_encode(E, Options) ->
 error_mesg(J) ->
     lists:flatten(io_lib:format("Decoding ~p returns an error.", [J])).
 
+check_good({E}, Options) ->
+    check_good({jiffy:encode(E), E}, Options);
 check_good({J, E}, Options) ->
     etap:is(jiffy:decode(J), E, ok_dec(J, E)),
     etap:is(do_encode(E, Options), J, ok_enc(E, J));