From 4abab5ad6c8465a7528ccdd5f49367da05f78bbd Mon Sep 17 00:00:00 2001
From: Vladimir Azarov <avm@intermediate-node.net>
Date: Tue, 1 Oct 2024 15:47:05 +0200
Subject: Initial version

---
 src/string/strverscmp.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 src/string/strverscmp.c

(limited to 'src/string/strverscmp.c')

diff --git a/src/string/strverscmp.c b/src/string/strverscmp.c
new file mode 100644
index 0000000..16c1da2
--- /dev/null
+++ b/src/string/strverscmp.c
@@ -0,0 +1,34 @@
+#define _GNU_SOURCE
+#include <ctype.h>
+#include <string.h>
+
+int strverscmp(const char *l0, const char *r0)
+{
+	const unsigned char *l = (const void *)l0;
+	const unsigned char *r = (const void *)r0;
+	size_t i, dp, j;
+	int z = 1;
+
+	/* Find maximal matching prefix and track its maximal digit
+	 * suffix and whether those digits are all zeros. */
+	for (dp=i=0; l[i]==r[i]; i++) {
+		int c = l[i];
+		if (!c) return 0;
+		if (!isdigit(c)) dp=i+1, z=1;
+		else if (c!='0') z=0;
+	}
+
+	if (l[dp]-'1'<9U && r[dp]-'1'<9U) {
+		/* If we're looking at non-degenerate digit sequences starting
+		 * with nonzero digits, longest digit string is greater. */
+		for (j=i; isdigit(l[j]); j++)
+			if (!isdigit(r[j])) return 1;
+		if (isdigit(r[j])) return -1;
+	} else if (z && dp<i && (isdigit(l[i]) || isdigit(r[i]))) {
+		/* Otherwise, if common prefix of digit sequence is
+		 * all zeros, digits order less than non-digits. */
+		return (unsigned char)(l[i]-'0') - (unsigned char)(r[i]-'0');
+	}
+
+	return l[i] - r[i];
+}
-- 
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