refactor: centralize formatting helpers and harden out-plutil

1 files changed, 100 insertions, 0 deletions

diff --git a/src/common.c b/src/common.c
new file mode 100644
index 0000000..0b11d57
--- /dev/null
+++ b/src/common.c
@@ -0,0 +1,100 @@
+/*
+ * common.c
+ * contains some common functions
+ *
+ * Copyright (c) 2026 Nikias Bassen, All Rights Reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+#include <math.h>
+#include <stdio.h>
+#include <stdint.h>
+#include "common.h"
+
+size_t dtostr(char *buf, size_t bufsize, double realval)
+{
+    int slen = 0;
+    if (isnan(realval)) {
+        slen = snprintf(buf, bufsize, "nan");
+    } else if (isinf(realval)) {
+        slen = snprintf(buf, bufsize, "%cinfinity", (realval > 0.0) ? '+' : '-');
+    } else if (realval == 0.0f) {
+        slen = snprintf(buf, bufsize, "0.0");
+    } else {
+        slen = snprintf(buf, bufsize, "%.*g", 17, realval);
+        if (slen < 0) {
+            return 0;
+        }
+        if (!buf || bufsize == 0) {
+            return (size_t)slen;
+        }
+        size_t len = (size_t)slen;
+        if (len >= bufsize) {
+            len = bufsize - 1;
+        }
+        size_t i = 0;
+        for (i = 0; i < len; i++) {
+            if (buf[i] == ',') {
+                buf[i] = '.';
+                break;
+            } else if (buf[i] == '.') {
+                break;
+            }
+        }
+        return len;
+    }
+    if (slen < 0) {
+        return 0;
+    }
+    return (size_t)slen;
+}
+
+/* based on https://stackoverflow.com/a/4143288 */
+#define PO10i_LIMIT (INT64_MAX/10)
+int num_digits_i(int64_t i)
+{
+    int n;
+    int64_t po10;
+    n=1;
+    if (i < 0) {
+        i = (i == INT64_MIN) ? INT64_MAX : -i;
+        n++;
+    }
+    po10=10;
+    while (i>=po10) {
+        n++;
+        if (po10 > PO10i_LIMIT) break;
+        po10*=10;
+    }
+    return n;
+}
+#undef PO10i_LIMIT
+
+/* based on https://stackoverflow.com/a/4143288 */
+#define PO10u_LIMIT (UINT64_MAX/10)
+int num_digits_u(uint64_t i)
+{
+    int n;
+    uint64_t po10;
+    n=1;
+    po10=10;
+    while (i>=po10) {
+        n++;
+        if (po10 > PO10u_LIMIT) break;
+        po10*=10;
+    }
+    return n;
+}
+#undef PO10u_LIMIT