[PATCH v12 03/13] ref-filter: introduce the ref_formatting_state stack machinery

[Karthik Nayak <karthik.188@gmail.com>]

Introduce a stack machinery for ref_formatting_state, this allows us
to push and pop states. Whenever we pop a state the strbuf from that
state is appended into the next state on the stack, this will allow us
to support nesting of modifier atoms.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Matthieu Moy <matthieu.moy@grenoble-inp.fr>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
---
 ref-filter.c | 42 +++++++++++++++++++++++++++++++++---------
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/ref-filter.c b/ref-filter.c
index dd62640..74532d3 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -56,6 +56,7 @@ static struct {
 };
 
 struct ref_formatting_state {
+	struct ref_formatting_state *prev;
 	struct strbuf output;
 	int quote_style;
 };
@@ -134,6 +135,27 @@ int parse_ref_filter_atom(const char *atom, const char *ep)
 	return at;
 }
 
+static void push_new_state(struct ref_formatting_state **stack)
+{
+	struct ref_formatting_state *s = xcalloc(1, sizeof(struct ref_formatting_state));
+
+	strbuf_init(&s->output, 0);
+	s->prev = *stack;
+	*stack = s;
+}
+
+static void pop_state(struct ref_formatting_state **stack)
+{
+	struct ref_formatting_state *current = *stack;
+	struct ref_formatting_state *prev = current->prev;
+
+	if (prev)
+		strbuf_addbuf(&prev->output, &current->output);
+	strbuf_release(&current->output);
+	free(current);
+	*stack = prev;
+}
+
 /*
  * In a format string, find the next occurrence of %(atom).
  */
@@ -1262,23 +1284,24 @@ static void append_literal(const char *cp, const char *ep, struct ref_formatting
 void show_ref_array_item(struct ref_array_item *info, const char *format, int quote_style)
 {
 	const char *cp, *sp, *ep;
-	struct ref_formatting_state state;
+	struct strbuf *final_buf;
+	struct ref_formatting_state *state = NULL;
 
-	strbuf_init(&state.output, 0);
-	state.quote_style = quote_style;
+	push_new_state(&state);
+	state->quote_style = quote_style;
 
 	for (cp = format; *cp && (sp = find_next(cp)); cp = ep + 1) {
 		struct atom_value *atomv;
 
 		ep = strchr(sp, ')');
 		if (cp < sp)
-			append_literal(cp, sp, &state);
+			append_literal(cp, sp, state);
 		get_ref_atom_value(info, parse_ref_filter_atom(sp + 2, ep), &atomv);
-		append_atom(atomv, &state);
+		append_atom(atomv, state);
 	}
 	if (*cp) {
 		sp = cp + strlen(cp);
-		append_literal(cp, sp, &state);
+		append_literal(cp, sp, state);
 	}
 	if (need_color_reset_at_eol) {
 		struct atom_value resetv;
@@ -1287,11 +1310,12 @@ void show_ref_array_item(struct ref_array_item *info, const char *format, int qu
 		if (color_parse("reset", color) < 0)
 			die("BUG: couldn't parse 'reset' as a color");
 		resetv.s = color;
-		append_atom(&resetv, &state);
+		append_atom(&resetv, state);
 	}
-	fwrite(state.output.buf, 1, state.output.len, stdout);
+	final_buf = &state->output;
+	fwrite(final_buf->buf, 1, final_buf->len, stdout);
+	pop_state(&state);
 	putchar('\n');
-	strbuf_release(&state.output);
 }
 
 /*  If no sorting option is given, use refname to sort as default */
-- 
2.5.0