Custom number parser to speed up config parsing

The glibc's generic parser is slow due to its versatility. Specialized
parsers for base-10 and base-16 are much faster and we don't use other
bases.

1 files changed, 61 insertions, 0 deletions

diff --git a/lib/strtoul.c b/lib/strtoul.c
new file mode 100644
index 00000000..44a1bb1d
--- /dev/null
+++ b/lib/strtoul.c
@@ -0,0 +1,61 @@
+/*
+ *	BIRD Library -- Parse numbers
+ *
+ *	(c) 2019 Maria Matejka <mq@jmq.cz>
+ *
+ *	Can be freely distributed and used under the terms of the GNU GPL.
+ */
+
+#include "nest/bird.h"
+#include "lib/string.h"
+
+#include <errno.h>
+
+#define ULI_MAX_DIV10 (UINT64_MAX / 10)
+#define ULI_MAX_MOD10 (UINT64_MAX % 10)
+
+u64
+bstrtoul10(const char *str, char **end)
+{
+  u64 out = 0;
+  for (*end = (char *) str; (**end >= '0') && (**end <= '9'); (*end)++) {
+    u64 digit = **end - '0';
+    if ((out > ULI_MAX_DIV10) ||
+	(out == ULI_MAX_DIV10) && (digit > ULI_MAX_MOD10)) {
+      errno = ERANGE;
+      return UINT64_MAX;
+    }
+    
+    out *= 10;
+    out += (**end) - '0';
+  }
+  return out;
+}
+
+u64
+bstrtoul16(const char *str, char **end)
+{
+  u64 out = 0;
+  for (int i=0; i<=(64/4); i++) {
+    switch (str[i]) {
+      case '0' ... '9':
+	out *= 16;
+	out += str[i] - '0';
+	break;
+      case 'a' ... 'f':
+	out *= 16;
+	out += str[i] + 10 - 'a';
+	break;
+      case 'A' ... 'F':
+	out *= 16;
+	out += str[i] + 10 - 'A';
+	break;
+      default:
+	*end = (char *) &(str[i]);
+	return out;
+    }
+  }
+
+  errno = ERANGE;
+  return UINT64_MAX;
+}