[RFC PATCH 06/11] lib: getopt: Add getopt_pop() helper

[Simon Glass <sjg@chromium.org>]

Callers that consume positional arguments after parsing routinely write
the same shape:

    algo = gs.args[gs.index];
    /* advance past algo */
    return hash_command(algo, ..., gs.nonopts - 1, &gs.args[gs.index + 1]);

Wrap that in a small inline helper that returns the next positional,
advances gs.index, decrements gs.nonopts, and returns NULL when no
positionals remain. The same helper doubles as an iterator:

    while ((arg = getopt_pop(&gs)))
        process(arg);

stddef.h is now included from getopt.h for the NULL macro.

Signed-off-by: Simon Glass <sjg@chromium.org>
---

 include/getopt.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/getopt.h b/include/getopt.h
index 5a9e7802e65..013431807ff 100644
--- a/include/getopt.h
+++ b/include/getopt.h
@@ -10,6 +10,7 @@
 #define __GETOPT_H
 
 #include <stdbool.h>
+#include <stddef.h>
 #include <linux/kconfig.h>
 
 /**
@@ -126,4 +127,26 @@ static inline int getopt_silent(struct getopt_state *gs,
 	return __getopt(gs, optstring, true);
 }
 
+/**
+ * getopt_pop() - Take the next remaining positional argument
+ * @gs: State, after getopt() has returned -1
+ *
+ * Returns the first parked non-option (``gs->args[gs->index]``),
+ * advances the index, and decrements ``gs->nonopts``. Returns NULL
+ * when no positional arguments remain.
+ *
+ * Useful for consuming positionals one at a time after parsing::
+ *
+ *     algo = getopt_pop(&gs);
+ *     return hash_command(algo, ..., gs.nonopts, &gs.args[gs.index]);
+ */
+static inline char *getopt_pop(struct getopt_state *gs)
+{
+	if (gs->index >= gs->argc)
+		return NULL;
+	if (gs->nonopts > 0)
+		gs->nonopts--;
+	return gs->args[gs->index++];
+}
+
 #endif /* __GETOPT_H */
-- 
2.43.0