Clean-up multiselect code

Allocate memory for the multiselect buffer in chunks, similar to how the
`choices` buffer is resized. This results in potentially more unused
(i.e. wasted) memory, but in fewer invocations of `malloc`/`realloc`,
which is probably more important, considering the size of the
multiselect array will never be that large.

src/choices.c

@@ -15,6 +15,9 @@
 /* Initial size of choices array */
 #define INITIAL_CHOICE_CAPACITY 128
 
+/* Initial size of multi-selection buffer */
+#define INITIAL_SELECTIONS_CAPACITY 8
+
 static int cmpchoice(const void *_idx1, const void *_idx2) {
 	const struct scored_result *a = _idx1;
 	const struct scored_result *b = _idx2;
@@ -92,6 +95,11 @@ static void choices_resize(choices_t *c, size_t new_capacity) {
 	c->capacity = new_capacity;
 }
 
+static void choices_resize_selections(choices_t *c, size_t new_capacity) {
+	c->selections.strings = safe_realloc(c->selections.strings, new_capacity * sizeof(const char *));
+	c->selections.capacity = new_capacity;
+}
+
 static void choices_reset_search(choices_t *c) {
 	free(c->results);
 	c->results = NULL;
@@ -101,8 +109,8 @@ static void choices_reset_search(choices_t *c) {
 void choices_init(choices_t *c, options_t *options) {
 	c->strings = NULL;
 	c->results = NULL;
-	c->selections = NULL;
-	c->num_selections = 0;
+	c->selections.strings = NULL;
+	c->selections.capacity = c->selections.size = 0;
 
 	c->buffer_size = 0;
 	c->buffer = NULL;
@@ -132,9 +140,9 @@ void choices_destroy(choices_t *c) {
 	c->results = NULL;
 	c->available = c->selection = 0;
 
-	free(c->selections);
-	c->selections = NULL;
-	c->num_selections = 0;
+	free(c->selections.strings);
+	c->selections.strings = NULL;
+	c->selections.capacity = c->selections.size = 0;
 }
 
 void choices_add(choices_t *c, const char *choice) {
@@ -148,30 +156,37 @@ void choices_add(choices_t *c, const char *choice) {
 }
 
 void choices_select(choices_t *c, const char *choice) {
-	if (!c->selections) {
-		c->num_selections = 1;
-		c->selections = malloc(sizeof(char *));
-		c->selections[0] = choice;
-	} else if (!choices_selected(c, choice)) {
-		c->num_selections++;
-		c->selections = realloc(c->selections, c->num_selections * sizeof(char *));
-		c->selections[c->num_selections - 1] = choice;
+	if (c->selections.size == c->selections.capacity) {
+		if (c->selections.capacity == 0) {
+			choices_resize_selections(c, INITIAL_SELECTIONS_CAPACITY);
+		} else {
+			choices_resize_selections(c, c->selections.capacity * 2);
+		}
+	}
+
+	if (!choices_selected(c, choice)) {
+		c->selections.strings[c->selections.size++] = choice;
 	}
 }
 
 void choices_deselect(choices_t *c, const char *choice) {
-	for (size_t i = 0; i < c->num_selections; i++) {
-		if (c->selections[i] == choice) {
-			c->selections[i] = NULL;
-			c->num_selections--;
+	size_t index = c->selections.size;
+	for (size_t i = 0; i < c->selections.size; i++) {
+		if (c->selections.strings[i] == choice) {
+			c->selections.size--;
+			index = i;
 			break;
 		}
 	}
+
+	for (size_t i = index; i < c->selections.size; i++) {
+		c->selections.strings[i] = c->selections.strings[i+1];
+	}
 }
 
 bool choices_selected(choices_t *c, const char *choice) {
-	for (size_t i = 0; i < c->num_selections; i++) {
-		if (c->selections[i] == choice) {
+	for (size_t i = 0; i < c->selections.size; i++) {
+		if (c->selections.strings[i] == choice) {
 			return true;
 		}
 	}

src/choices.h

@@ -25,8 +25,12 @@ typedef struct {
 	size_t available;
 	size_t selection;
 
-        const char **selections;
-        size_t num_selections;
+	struct {
+		const char **strings;
+
+		size_t capacity;
+		size_t size;
+	} selections;
 
 	unsigned int worker_count;
 } choices_t;

src/tty_interface.c

@@ -150,7 +150,7 @@ static void action_emit(tty_interface_t *state) {
 
 	/* If no choices were selected with multi-select, use the choice under
 	 * the cursor */
-	if (!state->choices->num_selections) {
+	if (!state->choices->selections.size) {
 		const char *selection = choices_get(state->choices, state->choices->selection);
 		if (selection) {
 			/* output the result */
@@ -160,8 +160,8 @@ static void action_emit(tty_interface_t *state) {
 			printf("%s\n", state->search);
 		}
 	} else {
-		for (size_t i = 0; i < state->choices->num_selections; i++) {
-			printf("%s\n", state->choices->selections[i]);
+		for (size_t i = 0; i < state->choices->selections.size; i++) {
+			printf("%s\n", state->choices->selections.strings[i]);
 		}
 	}
 

test/test_choices.c

@@ -9,27 +9,28 @@
 #include "greatest/greatest.h"
 
 #define ASSERT_SIZE_T_EQ(a,b) ASSERT_EQ_FMT((size_t)(a), (b), "%zu")
+#define ASSERT_TRUE(cond) ASSERT_FALSE(!cond)
 
 static options_t default_options;
 static choices_t choices;
 
 static void setup(void *udata) {
-    (void)udata;
+	(void)udata;
 
-    options_init(&default_options);
-    choices_init(&choices, &default_options);
+	options_init(&default_options);
+	choices_init(&choices, &default_options);
 }
 
 static void teardown(void *udata) {
-    (void)udata;
-    choices_destroy(&choices);
+	(void)udata;
+	choices_destroy(&choices);
 }
 
 TEST test_choices_empty() {
 	ASSERT_SIZE_T_EQ(0, choices.size);
 	ASSERT_SIZE_T_EQ(0, choices.available);
 	ASSERT_SIZE_T_EQ(0, choices.selection);
-	ASSERT_SIZE_T_EQ(0, choices.num_selections);
+	ASSERT_SIZE_T_EQ(0, choices.selections.size);
 
 	choices_prev(&choices);
 	ASSERT_SIZE_T_EQ(0, choices.selection);
@@ -166,18 +167,18 @@ TEST test_choices_multi_select() {
 	const char *first_choice = choices_get(&choices, 0);
 	ASSERT_FALSE(choices_selected(&choices, first_choice));
 	choices_select(&choices, first_choice);
-	ASSERT_FALSE(!choices_selected(&choices, first_choice));
-	ASSERT_SIZE_T_EQ(1, choices.num_selections);
+	ASSERT_TRUE(choices_selected(&choices, first_choice));
+	ASSERT_SIZE_T_EQ(1, choices.selections.size);
 
 	const char *second_choice = choices_get(&choices, 1);
 	ASSERT_FALSE(choices_selected(&choices, second_choice));
 	choices_select(&choices, second_choice);
-	ASSERT_FALSE(!choices_selected(&choices, second_choice));
-	ASSERT_SIZE_T_EQ(2, choices.num_selections);
+	ASSERT_TRUE(choices_selected(&choices, second_choice));
+	ASSERT_SIZE_T_EQ(2, choices.selections.size);
 
 	choices_deselect(&choices, second_choice);
 	ASSERT_FALSE(choices_selected(&choices, second_choice));
-	ASSERT_SIZE_T_EQ(1, choices.num_selections);
+	ASSERT_SIZE_T_EQ(1, choices.selections.size);
 
 	PASS();
 }