feat(cron): some bug fixes & formatting

.editorconfig

@@ -5,6 +5,5 @@ root = true
 end_of_line = lf
 insert_final_newline = true
 
-[*.v]
+[*.{v,c,h}]
-# vfmt wants it :(
 indent_style = tab

src/cron/expression/c/expression.c

@@ -85,6 +85,7 @@ int ce_next(struct cron_simple_time *out, struct cron_expression *ce, struct cro
 		while (out->day > month_days[ce->months[month_index % ce->month_count] - 1]) {
 			month_index++;
 
+			// TODO find out if this can happen
 			if (month_index == 2 * ce->month_count) {
 				return 1;
 			}

src/cron/expression/c/parse.c

@@ -1,8 +1,11 @@
 #include "expression.h"
 
+// Allowed value ranges for the minute, hour, day and month field
 const uint8_t min[4] = {0, 0, 1, 1};
 const uint8_t max[4] = {59, 23, 31, 12};
 
+// Convert a string a uint8_t value by parsing it using atoi and checking
+// whether it's contained within the given range
 #define SAFE_ATOI(v,s,min,max) \
 	int _##v = atoi(s); \
 	if ((_##v) == 0 && strcmp((s), "0") != 0) { \
@@ -15,11 +18,11 @@ const uint8_t max[4] = {59, 23, 31, 12};
 
 /**
  * Given a range expression, produce a bit field defining what numbers in the
- * min-max range the expression represents. The first bit (starting from the
+ * min-max range the expression represents. Bit 0 (starting from the
- * right) corresponds to min, the max - min + 1'th bit to max. All trailing bits
+ * right) corresponds to min, the bit max - min to max. All trailing bits
  * after this should be ignored. The given bitfield is modified in-place, so
  * multiple calls of this function can be performed on the same value to create
- * the effect of ORing their values:
+ * the effect of ORing their values.
  *
  * A range expression has one of the following forms:
  *
@@ -65,7 +68,7 @@ enum cron_parse_error ce_parse_range(uint64_t *out, char *s, uint8_t min, uint8_
 
 	// Parse the three possible numbers in the pattern
 	uint8_t start = 0;
-    uint8_t end = 0;
+	uint8_t end = max;
 	uint8_t interval = 1;
 
 	SAFE_ATOI(start, s, min, max);
@@ -78,11 +81,10 @@ enum cron_parse_error ce_parse_range(uint64_t *out, char *s, uint8_t min, uint8_
 		SAFE_ATOI(interval, &s[slash_index + 1], 1, max - min);
 	}
 
-    // Single number doesn't need to loop
+	if (dash_index == 0 && slash_index == 0) {
-    if (end == 0 && slash_index == 0) {
 		*out |= ((uint64_t) 1) << (start - min);
 	} else {
-        for (;start <= end; start += interval) {
+		while (start <= end) {
 			*out |= ((uint64_t) 1) << (start - min);
 			start += interval;
 		}
@@ -91,6 +93,11 @@ enum cron_parse_error ce_parse_range(uint64_t *out, char *s, uint8_t min, uint8_
 	return CPEParseOk;
 }
 
+/*
+ * Given an expression part, produce a bitfield defining what numbers in the
+ * min-max range the part represents. A part consists of one or more range
+ * expressions, separated by commas.
+ */
 enum cron_parse_error ce_parse_part(uint64_t *out, char *s, uint8_t min, uint8_t max) {
 	*out = 0;
 
@@ -112,28 +119,47 @@ enum cron_parse_error ce_parse_part(uint64_t *out, char *s, uint8_t min, uint8_t
 	return ce_parse_range(out, s, min, max);
 }
 
+/*
+ * Return how many bits are set in the bitfield, better known as popcount. I
+ * added my own implementation (taken from my algorithms course) as I don't want
+ * to be dependent on GCC-specific extensions.
+ */
+uint8_t uint64_t_popcount(uint64_t n) {
+	uint8_t c = 0;
+
+	while (n != 0) {
+		// This sets the least significant bit to zero (very cool)
+		n &= n - 1;
+		c++;
+	}
+
+	return c;
+}
+
+/*
+ * Convert a bitfield into an array containing the numbers in the min-max range
+ * it represents.
+ */
 uint8_t bf_to_nums(uint8_t **out, uint64_t bf, uint8_t min, uint8_t max) {
-    uint8_t capacity = 8;
+	// Each bit field only has `max - min + 1` meaningful bits. All other bits
-    uint8_t size = 0;
+	// should be ignored, and can be any value. By shifting the bit field back and
+	// forth, we set these excessive bits to zero, ensuring popcount returns the
+	// correct value.
+	uint8_t excess_bits = 64 - (max - min + 1);
+	bf = (bf << excess_bits) >> excess_bits;
+	uint8_t size = uint64_t_popcount(bf);
+	uint8_t *buf = malloc(size * sizeof(uint8_t));
 
-    uint8_t *buf = malloc(capacity * sizeof(uint8_t));
+	uint8_t i = 0, j = 0;
 
-    for (uint8_t i = 0; i <= max - min; i++) {
+	while (j < size && i <= max - min) {
 		if (((uint64_t)1 << i) & bf) {
 			// Resize buffer if needed
-            if (size == capacity) {
+			buf[j] = min + i;
-                capacity *= 2;
+			j++;
-                buf = realloc(buf, capacity * sizeof(uint8_t));
 		}
 
-            buf[size] = min + i;
+		i++;
-            size++;
-        }
-    }
-
-    // Resize buffer once more to remove any trailing unused bytes
-    if (size < capacity) {
-        buf = realloc(buf, size * sizeof(uint8_t));
 	}
 
 	*out = buf;
@@ -141,6 +167,9 @@ uint8_t bf_to_nums(uint8_t **out, uint64_t bf, uint8_t min, uint8_t max) {
 	return size;
 }
 
+/*
+ * Parse a cron expression string into a cron_expression struct.
+ */
 enum cron_parse_error ce_parse_expression(struct cron_expression *out, char *s) {
 	// The parsing functions modify the input string in-place
 	s = strdup(s);
@@ -178,7 +207,6 @@ enum cron_parse_error ce_parse_expression(struct cron_expression *out, char *s)
 
 	// Parse final trailing part
 	if (part_count < 4 && s[0] != '\0') {
-        // Make sure to parse the final range as well
 		res = ce_parse_part(&bfs[part_count], s, min[part_count], max[part_count]);
 
 		if (res != CPEParseOk) {

src/cron/expression/expression_test.v

@@ -26,11 +26,11 @@ fn test_next_simple() ! {
 	util_test_time(exp, '2002-01-01 03:00:00', '2002-01-02 03:00:00')!
 	util_test_time(exp, '2002-01-01 04:00:00', '2002-01-02 03:00:00')!
 
-	/* util_test_time('0 3/4', '2002-01-01 04:00:00', '2002-01-01 07:00:00')! */
+	util_test_time('0 3/4', '2002-01-01 04:00:00', '2002-01-01 07:00:00')!
 
 	/* // Overlap to next month */
-	/* util_test_time('0 3', '2002-11-31 04:00:00', '2002-12-01 03:00:00')! */
+	util_test_time('0 3', '2002-11-31 04:00:00', '2002-12-01 03:00:00')!
 
 	/* // Overlap to next year */
-	/* util_test_time('0 3', '2002-12-31 04:00:00', '2003-01-01 03:00:00')! */
+	util_test_time('0 3', '2002-12-31 04:00:00', '2003-01-01 03:00:00')!
 }