numeric.c: introduce `mrb_int_to_cstr()` to dump `mrb_int`.

* refactor `mrb_integer_to_str()`
* refactor `mrb_str_format()`

include/mruby/numeric.h

@@ -35,6 +35,7 @@ MRB_API mrb_value mrb_num_minus(mrb_state *mrb, mrb_value x, mrb_value y);
 MRB_API mrb_value mrb_num_mul(mrb_state *mrb, mrb_value x, mrb_value y);
 
 MRB_API mrb_value mrb_integer_to_str(mrb_state *mrb, mrb_value x, mrb_int base);
+MRB_API char *mrb_int_to_cstr(char *buf, size_t len, mrb_int n, mrb_int base);
 
 /* internal function(s) */
 mrb_int mrb_div_int(mrb_state *mrb, mrb_int x, mrb_int y);

mrbgems/mruby-sprintf/src/sprintf.c

@@ -585,50 +585,6 @@ mrb_f_sprintf(mrb_state *mrb, mrb_value obj)
   }
 }
 
-static int
-mrb_int2str(char *buf, size_t len, mrb_int n)
-{
-#ifdef MRB_NO_STDIO
-  char *bufend = buf + len;
-  char *p = bufend - 1;
-
-  if (len < 1) return -1;
-
-  *p -- = '\0';
-  len --;
-
-  if (n < 0) {
-    if (len < 1) return -1;
-
-    *p -- = '-';
-    len --;
-    n = -n;
-  }
-
-  if (n > 0) {
-    for (; n > 0; len --, n /= 10) {
-      if (len < 1) return -1;
-
-      *p -- = '0' + (n % 10);
-    }
-    p ++;
-  }
-  else if (len > 0) {
-    *p = '0';
-    len --;
-  }
-  else {
-    return -1;
-  }
-
-  memmove(buf, p, bufend - p);
-
-  return bufend - p - 1;
-#else
-  return snprintf(buf, len, "%" MRB_PRId, n);
-#endif /* MRB_NO_STDIO */
-}
-
 mrb_value
 mrb_str_format(mrb_state *mrb, mrb_int argc, const mrb_value *argv, mrb_value fmt)
 {
@@ -983,13 +939,10 @@ retry:
             sc = '-';
             width--;
           }
-          mrb_assert(base == 10);
-          mrb_int2str(nbuf, sizeof(nbuf)-1, v);
-          s = nbuf;
+          s = mrb_int_to_cstr(nbuf, sizeof(nbuf), v, base);
           if (v < 0) s++;       /* skip minus sign */
         }
         else {
-          s = nbuf;
           if (v < 0) {
             dots = 1;
             val = mrb_fix2binstr(mrb, mrb_int_value(mrb, v), base);
@@ -997,7 +950,8 @@ retry:
           else {
             val = mrb_integer_to_str(mrb, mrb_int_value(mrb, v), base);
           }
-          strncpy(++s, RSTRING_PTR(val), sizeof(nbuf)-2);
+          strncpy(nbuf+1, RSTRING_PTR(val), sizeof(nbuf)-2);
+          s = nbuf+1;
         }
         {
           size_t size;

src/numeric.c

@@ -1507,35 +1507,51 @@ int_sub(mrb_state *mrb, mrb_value self)
   return int_minus(mrb, self, other);
 }
 
-
-MRB_API mrb_value
-mrb_integer_to_str(mrb_state *mrb, mrb_value x, mrb_int base)
+MRB_API char*
+mrb_int_to_cstr(char *buf, size_t len, mrb_int n, mrb_int base)
 {
-  char buf[MRB_INT_BIT+1];
-  char *b = buf + sizeof buf;
-  mrb_int val = mrb_integer(x);
-  mrb_value str;
+  char *bufend = buf + len;
+  char *b = bufend-1;
 
-  if (base < 2 || 36 < base) {
-    mrb_raisef(mrb, E_ARGUMENT_ERROR, "invalid radix %i", base);
-  }
+  if (base < 2 || 36 < base) return NULL;
+  if (len < 2) return NULL;
 
-  if (val == 0) {
-    *--b = '0';
+  if (n == 0) {
+    buf[0] = '0';
+    buf[1] = '\0';
+    return buf;
   }
-  else if (val < 0) {
+
+  *b-- = '\0';
+  if (n < 0) {
     do {
-      *--b = mrb_digitmap[-(val % base)];
-    } while (val /= base);
-    *--b = '-';
+      if (b-- == buf) return NULL;
+      *b = mrb_digitmap[-(n % base)];
+    } while (n /= base);
+    if (b-- == buf) return NULL;
+    *b = '-';
   }
   else {
     do {
-      *--b = mrb_digitmap[(int)(val % base)];
-    } while (val /= base);
+      if (b-- == buf) return NULL;
+      *b = mrb_digitmap[(int)(n % base)];
+    } while (n /= base);
   }
+  return b;
+}
+
+MRB_API mrb_value
+mrb_integer_to_str(mrb_state *mrb, mrb_value x, mrb_int base)
+{
+  char buf[MRB_INT_BIT+1];
+  mrb_int val = mrb_integer(x);
 
-  str = mrb_str_new(mrb, b, buf + sizeof(buf) - b);
+  if (base < 2 || 36 < base) {
+    mrb_raisef(mrb, E_ARGUMENT_ERROR, "invalid radix %i", base);
+  }
+  const char *p = mrb_int_to_cstr(buf, sizeof(buf), val, base);
+  mrb_assert(p != NULL);
+  mrb_value str = mrb_str_new_cstr(mrb, p);
   RSTR_SET_ASCII_FLAG(mrb_str_ptr(str));
   return str;
 }