Refactor json_decode_integer to not decode the number twice

Author: byroot

ext/json/ext/parser/parser.c

@@ -21,6 +21,16 @@ typedef unsigned char _Bool;
 #endif
 #endif
 
+#if SIZEOF_UINT64_T == SIZEOF_LONG_LONG
+# define INT64T2NUM(x) LL2NUM(x)
+# define UINT64T2NUM(x) ULL2NUM(x)
+#elif SIZEOF_UINT64_T == SIZEOF_LONG
+# define INT64T2NUM(x) LONG2NUM(x)
+# define UINT64T2NUM(x) ULONG2NUM(x)
+#else
+# error No uint64_t conversion
+#endif
+
 #include "../simd/simd.h"
 
 #ifndef RB_UNLIKELY
@@ -756,26 +766,6 @@ static VALUE json_string_unescape(JSON_ParserState *state, const char *string, c
 }
 
 #define MAX_FAST_INTEGER_SIZE 18
-static inline VALUE fast_decode_integer(const char *p, const char *pe)
-{
-    bool negative = false;
-    if (*p == '-') {
-        negative = true;
-        p++;
-    }
-
-    long long memo = 0;
-    while (p < pe) {
-        memo *= 10;
-        memo += *p - '0';
-        p++;
-    }
-
-    if (negative) {
-        memo = -memo;
-    }
-    return LL2NUM(memo);
-}
 
 static VALUE json_decode_large_integer(const char *start, long len)
 {
@@ -789,13 +779,16 @@ static VALUE json_decode_large_integer(const char *start, long len)
 }
 
 static inline VALUE
-json_decode_integer(const char *start, const char *end)
+json_decode_integer(uint64_t mantissa, int mantissa_digits, bool negative, const char *start, const char *end)
 {
-    long len = end - start;
-    if (RB_LIKELY(len < MAX_FAST_INTEGER_SIZE)) {
-        return fast_decode_integer(start, end);
+    if (RB_LIKELY(mantissa_digits < MAX_FAST_INTEGER_SIZE)) {
+        if (negative) {
+            return INT64T2NUM(-((int64_t)mantissa));
+        }
+        return UINT64T2NUM(mantissa);
     }
-    return json_decode_large_integer(start, len);
+
+    return json_decode_large_integer(start, end - start);
 }
 
 static VALUE json_decode_large_float(const char *start, long len)
@@ -1119,12 +1112,9 @@ static VALUE json_parse_any(JSON_ParserState *state, JSON_ParserConfig *config)
                 state->cursor++;
             }
 
-            long integer_length = state->cursor - start;
-            if (negative) integer_length--;  // Don't count the sign
-
-            if (RB_UNLIKELY(start[0] == '0' && integer_length > 1)) {
+            if (RB_UNLIKELY(start[0] == '0' && mantissa_digits > 1)) {
                 raise_parse_error_at("invalid number: %s", state, start);
-            } else if (RB_UNLIKELY(integer_length > 1 && negative && start[1] == '0')) {
+            } else if (RB_UNLIKELY(mantissa_digits > 1 && negative && start[1] == '0')) {
                 raise_parse_error_at("invalid number: %s", state, start);
             }
 
@@ -1171,7 +1161,7 @@ static VALUE json_parse_any(JSON_ParserState *state, JSON_ParserConfig *config)
             }
 
             if (integer) {
-                return json_push_value(state, config, json_decode_integer(start, state->cursor));
+                return json_push_value(state, config, json_decode_integer(mantissa, mantissa_digits, negative, start, state->cursor));
             }
 
             // Adjust exponent based on decimal point position