1 files changed, 252 insertions, 0 deletions
diff --git a/libpkgconf/version.c b/libpkgconf/version.c
new file mode 100644
index 000000000000..7b597bd721b2
--- /dev/null
+++ b/libpkgconf/version.c
@@ -0,0 +1,252 @@
+/*
+ * version.c
+ * version comparison
+ *
+ * SPDX-License-Identifier: pkgconf
+ *
+ * Copyright (c) 2011-2026 pkgconf authors (see AUTHORS).
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#include <libpkgconf/config.h>
+#include <libpkgconf/stdinc.h>
+#include <libpkgconf/libpkgconf.h>
+
+typedef enum {
+	PKGCONF_VERSION_TOKEN_END = 0,
+	PKGCONF_VERSION_TOKEN_TILDE,
+	PKGCONF_VERSION_TOKEN_NUMERIC,
+	PKGCONF_VERSION_TOKEN_ALPHA,
+	PKGCONF_VERSION_TOKEN_OTHER
+} pkgconf_version_token_kind_t;
+
+typedef struct {
+	pkgconf_version_token_kind_t kind;
+	const char *start;
+	const char *end;
+} pkgconf_version_token_t;
+
+typedef struct {
+	const char *cur;
+} pkgconf_version_iter_t;
+
+static inline bool
+pkgconf_version_is_separator(unsigned char ch)
+{
+	return !isalnum(ch) && ch != '~';
+}
+
+static const char *
+pkgconf_version_skip_separators(const char *s)
+{
+	while (*s && pkgconf_version_is_separator((unsigned char)*s))
+		s++;
+
+	return s;
+}
+
+static pkgconf_version_token_t
+pkgconf_version_next_token(pkgconf_version_iter_t *it)
+{
+	pkgconf_version_token_t tok;
+	const char *s = pkgconf_version_skip_separators(it->cur);
+
+	tok.start = s;
+	tok.end = s;
+	tok.kind = PKGCONF_VERSION_TOKEN_END;
+
+	if (*s == '\0')
+	{
+		it->cur = s;
+		return tok;
+	}
+
+	if (*s == '~')
+	{
+		tok.kind = PKGCONF_VERSION_TOKEN_TILDE;
+		tok.end = s + 1;
+		it->cur = tok.end;
+		return tok;
+	}
+
+	if (isdigit((unsigned char)*s))
+	{
+		tok.kind = PKGCONF_VERSION_TOKEN_NUMERIC;
+		while (*tok.end && isdigit((unsigned char)*tok.end))
+			tok.end++;
+		it->cur = tok.end;
+		return tok;
+	}
+
+	if (isalpha((unsigned char)*s))
+	{
+		tok.kind = PKGCONF_VERSION_TOKEN_ALPHA;
+		while (*tok.end && isalpha((unsigned char)*tok.end))
+			tok.end++;
+		it->cur = tok.end;
+		return tok;
+	}
+
+	tok.kind = PKGCONF_VERSION_TOKEN_OTHER;
+	tok.end = s + 1;
+	it->cur = tok.end;
+
+	return tok;
+}
+
+static int
+pkgconf_version_compare_numeric(const pkgconf_version_token_t *a, const pkgconf_version_token_t *b)
+{
+	const char *ap = a->start;
+	const char *bp = b->start;
+	size_t alen, blen;
+	int ret;
+
+	while (ap < a->end && *ap == '0')
+		ap++;
+
+	while (bp < b->end && *bp == '0')
+		bp++;
+
+	alen = (size_t)(a->end - ap);
+	blen = (size_t)(b->end - bp);
+
+	if (alen > blen)
+		return 1;
+	if (alen < blen)
+		return -1;
+
+	if (alen == 0)
+		return 0;
+
+	ret = strncmp(ap, bp, alen);
+	if (ret < 0)
+		return -1;
+	if (ret > 0)
+		return 1;
+
+	return 0;
+}
+
+static int
+pkgconf_version_compare_alpha(const pkgconf_version_token_t *a, const pkgconf_version_token_t *b)
+{
+	size_t alen = (size_t)(a->end - a->start);
+	size_t blen = (size_t)(b->end - b->start);
+	size_t len = alen < blen ? alen : blen;
+	int ret;
+
+	ret = strncmp(a->start, b->start, len);
+	if (ret < 0)
+		return -1;
+	if (ret > 0)
+		return 1;
+
+	if (alen < blen)
+		return -1;
+	if (alen > blen)
+		return 1;
+
+	return 0;
+}
+
+static int
+pkgconf_version_compare_token(const pkgconf_version_token_t *a, const pkgconf_version_token_t *b)
+{
+	if (a->kind == PKGCONF_VERSION_TOKEN_TILDE || b->kind == PKGCONF_VERSION_TOKEN_TILDE)
+	{
+		if (a->kind != PKGCONF_VERSION_TOKEN_TILDE)
+			return 1;
+		if (b->kind != PKGCONF_VERSION_TOKEN_TILDE)
+			return -1;
+
+		return 0;
+	}
+
+	if (a->kind == PKGCONF_VERSION_TOKEN_END || b->kind == PKGCONF_VERSION_TOKEN_END)
+	{
+		if (a->kind == PKGCONF_VERSION_TOKEN_END && b->kind == PKGCONF_VERSION_TOKEN_END)
+			return 0;
+		if (a->kind == PKGCONF_VERSION_TOKEN_END)
+			return -1;
+
+		return 1;
+	}
+
+	/* left-side is numeric, beats any right-side non-numeric */
+	if (a->kind == PKGCONF_VERSION_TOKEN_NUMERIC)
+	{
+		if (b->kind != PKGCONF_VERSION_TOKEN_NUMERIC)
+			return 1;
+
+		return pkgconf_version_compare_numeric(a, b);
+	}
+
+	/* left-side is alpha, any right-side non-alpha wins */
+	if (a->kind == PKGCONF_VERSION_TOKEN_ALPHA)
+	{
+		if (b->kind != PKGCONF_VERSION_TOKEN_ALPHA)
+			return -1;
+
+		return pkgconf_version_compare_alpha(a, b);
+	}
+
+	if (a->kind < b->kind)
+		return -1;
+	if (a->kind > b->kind)
+		return 1;
+
+	return 0;
+}
+
+/*
+ * !doc
+ *
+ * .. c:function:: int pkgconf_compare_version(const char *a, const char *b)
+ *
+ *    Compare versions using RPM version comparison rules as described in the LSB.
+ *
+ *    :param char* a: The first version to compare in the pair.
+ *    :param char* b: The second version to compare in the pair.
+ *    :return: -1 if the first version is less than, 0 if both versions are equal, 1 if the second version is less than.
+ *    :rtype: int
+ */
+int
+pkgconf_compare_version(const char *a, const char *b)
+{
+	pkgconf_version_iter_t ia, ib;
+
+	if (a == NULL)
+		return -1;
+	if (b == NULL)
+		return 1;
+
+	if (!strcasecmp(a, b))
+		return 0;
+
+	ia.cur = a;
+	ib.cur = b;
+
+	for (;;)
+	{
+		pkgconf_version_token_t ta = pkgconf_version_next_token(&ia);
+		pkgconf_version_token_t tb = pkgconf_version_next_token(&ib);
+		int ret = pkgconf_version_compare_token(&ta, &tb);
+
+		if (ret != 0)
+			return ret;
+
+		if (ta.kind == PKGCONF_VERSION_TOKEN_END &&
+			tb.kind == PKGCONF_VERSION_TOKEN_END)
+		{
+			return 0;
+		}
+	}
+}