diff --git a/str.c b/str.c
index 9b293408..b70a5f67 100644
--- a/str.c
+++ b/str.c
@@ -663,14 +663,29 @@ int str_to_int32(const char *str, unsigned base, int32_t *result, const char **a
 
 int str_to_uint32(const char *str, unsigned base, uint32_t *result, const char **afterp)
 {
-  if (isspace(*str))
-    return 0;
-  const char *end = str;
-  errno = 0;
-  unsigned long value = strtoul(str, (char**)&end, base);
+  return strn_to_uint32(str, 0, base, result, afterp);
+}
+
+int strn_to_uint32(const char *str, size_t strlen, unsigned base, uint32_t *result, const char **afterp)
+{
+  assert(base > 0);
+  assert(base <= 16);
+  uint32_t value = 0;
+  uint32_t newvalue = 0;
+  const char *const end = str + strlen;
+  const char *s;
+  for (s = str; strlen ? s < end : *s; ++s) {
+    int digit = hexvalue(*s);
+    if (digit < 0 || (unsigned)digit >= base)
+      break;
+    newvalue = value * base + digit;
+    if (newvalue < value) // overflow
+      break;
+    value = newvalue;
+  }
   if (afterp)
-    *afterp = end;
-  if (errno == ERANGE || end == str || value > UINT32_MAX || isdigit(*end) || (!afterp && *end))
+    *afterp = s;
+  if (s == str || value > UINT32_MAX || value != newvalue || (!afterp && (strlen ? s != end : *s)))
     return 0;
   if (result)
     *result = value;
diff --git a/str.h b/str.h
index b445e087..08b0ce97 100644
--- a/str.h
+++ b/str.h
@@ -396,6 +396,19 @@ int str_to_uint32(const char *str, unsigned base, uint32_t *result, const char *
 int str_to_int64(const char *str, unsigned base, int64_t *result, const char **afterp);
 int str_to_uint64(const char *str, unsigned base, uint64_t *result, const char **afterp);
 
+/* Parse a length-bound string as an integer in ASCII radix notation in the given 'base' (eg,
+ * base=10 means decimal).
+ *
+ * Returns 1 if a valid integer is parsed, storing the value in *result (unless result is NULL) and
+ * storing a pointer to the immediately succeeding character in *afterp.  If afterp is NULL then
+ * returns 0 unless all 'strlen' characters of the string were consumed.  If no integer is parsed or
+ * if the integer overflows (too many digits), then returns 0, leaving *result unchanged and setting
+ * setting *afterp to point to the character where parsing failed.
+ *
+ * @author Andrew Bettison <andrew@servalproject.com>
+ */
+int strn_to_uint32(const char *str, size_t strlen, unsigned base, uint32_t *result, const char **afterp);
+
 /* Parse a string as an integer in ASCII radix notation in the given 'base' (eg, base=10 means
  * decimal) and scale the result by a factor given by an optional suffix "scaling" character in the
  * set {kKmMgG}: 'k' = 1e3, 'K' = 1<<10, 'm' = 1e6, 'M' = 1<<20, 'g' = 1e9, 'G' = * 1<<30.