[PATCH v3 1/4] scripts: include: Add string_util.h for strsep_unescaped

[Jonas Rebmann]

lib/string.c has strsep_unescaped() that will be useful for the keytoc
host tool to split ENV specs at spaces not preceded by a backslash in a
future commit.

In preparation, create scripts/include/string_util.h with a copy of that
function as to have it available in host tools.

Signed-off-by: Jonas Rebmann <jre at pengutronix.de>
---
 scripts/include/string_util.h | 65 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/scripts/include/string_util.h b/scripts/include/string_util.h
new file mode 100644
index 0000000000..e71aa60d26
--- /dev/null
+++ b/scripts/include/string_util.h
@@ -0,0 +1,65 @@
+#ifndef _TOOLS_STRING_UTIL_H_
+#define _TOOLS_STRING_UTIL_H_
+
+#include <linux/types.h>
+#include <stddef.h>
+
+// SPDX-SnippetBegin
+// SPDX-Snippet-Comment: Origin-URL: https://git.pengutronix.de/cgit/barebox/tree/lib/string.c?id=dfcf686f94a5a5387660f2afab79a714baab828a
+
+/**
+ * strsep_unescaped - Split a string into tokens, while ignoring escaped delimiters
+ * @s: The string to be searched
+ * @ct: The delimiter characters to search for
+ * @delim: optional pointer to store found delimiter into
+ *
+ * strsep_unescaped() behaves like strsep unless it meets an escaped delimiter.
+ * In that case, it shifts the string back in memory to overwrite the escape's
+ * backslash then continues the search until an unescaped delimiter is found.
+ *
+ * On end of string, this function returns NULL. As long as a non-NULL
+ * value is returned and @delim is not NULL, the found delimiter will
+ * be stored into *@delim.
+ */
+static char *strsep_unescaped(char **s, const char *ct, char *delim)
+{
+	char *sbegin = *s, *hay;
+	const char *needle;
+	size_t shift = 0;
+
+	if (sbegin == NULL)
+		return NULL;
+
+	for (hay = sbegin; *hay != '\0'; ++hay) {
+		*hay = hay[shift];
+
+		if (*hay == '\\') {
+			*hay = hay[++shift];
+			if (*hay != '\\')
+				continue;
+		}
+
+		for (needle = ct; *needle != '\0'; ++needle) {
+			if (*hay == *needle)
+				goto match;
+		}
+	}
+
+	*s = NULL;
+	if (delim)
+		*delim = '\0';
+	return sbegin;
+
+match:
+	if (delim)
+		*delim = *hay;
+	*hay = '\0';
+	*s = &hay[shift + 1];
+
+	return sbegin;
+}
+
+// SPDX-SnippetEnd
+
+
+#endif /* _TOOLS_STRING_UTIL_H_ */

-- 
2.53.0.308.g50d063e335