From 0f1704a0f8c5fd2a4da6f530694bdd93a7ca3226 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Ond=C5=99ej=20Poho=C5=99elsk=C3=BD?=

 <35430604+opohorel@users.noreply.github.com>

Date: Mon, 8 Nov 2021 16:20:09 +0100

Subject: [PATCH] Add random within range '~' operator

With the operator one can specify for a job a random time or date within

a specified range for a field.

The random value is generated when the crontab where the job is

specified, is loaded.

---

 man/crontab.5 |   9 ++

 src/entry.c   | 262 ++++++++++++++++++++++++++++++++------------------

 2 files changed, 176 insertions(+), 95 deletions(-)

diff --git a/man/crontab.5 b/man/crontab.5

index a011c89..ba8f0c3 100644

--- a/man/crontab.5

+++ b/man/crontab.5

@@ -199,6 +199,15 @@ hyphen.  The specified range is inclusive.  For example, 8-11 for

 an 'hours' entry specifies execution at hours 8, 9, 10, and 11. The first

 number must be less than or equal to the second one.

 .PP

+Randomization of the execution time within a range can be used.

+A random number within a range specified as two numbers separated with

+a tilde is picked.  The specified range is inclusive.

+For example, 6~15 for a 'minutes' entry picks a random minute

+within 6 to 15 range.  The random number is picked when crontab file is parsed.

+The first number must be less than or equal to the second one. You might omit

+one or both of the numbers specifying the range.  For example, ~ for a 'minutes'

+entry picks a random minute within 0 to 59 range.

+.PP

 Lists are allowed.  A list is a set of numbers (or ranges) separated by

 commas.  Examples: "1,2,5,9", "0-4,8-12".

 .PP

diff --git a/src/entry.c b/src/entry.c

index 92b55f5..9276f47 100644

--- a/src/entry.c

+++ b/src/entry.c

@@ -62,9 +62,22 @@ static const char *ecodes[] = {

 	"out of memory"

 };

+typedef enum {

+	R_START,

+	R_AST,

+	R_STEP,

+	R_TERMS,

+	R_NUM1,

+	R_RANGE,

+	R_RANGE_NUM2,

+	R_RANDOM,

+	R_RANDOM_NUM2,

+	R_FINISH,

+} range_state_t;

+

 static int get_list(bitstr_t *, int, int, const char *[], int, FILE *),

-get_range(bitstr_t *, int, int, const char *[], int, FILE *),

-get_number(int *, int, const char *[], int, FILE *, const char *),

+get_range(bitstr_t *, int, int, const char *[], FILE *),

+get_number(int *, int, const char *[], FILE *),

 set_element(bitstr_t *, int, int, int);

 void free_entry(entry * e) {

@@ -449,11 +462,14 @@ get_list(bitstr_t * bits, int low, int high, const char *names[],

 	/* process all ranges

 	 */

 	done = FALSE;

+	/* unget ch to allow get_range() to process it properly 

+	 */

+	unget_char(ch, file);

 	while (!done) {

-		if (EOF == (ch = get_range(bits, low, high, names, ch, file)))

+		if (EOF == (ch = get_range(bits, low, high, names, file)))

 			return (EOF);

 		if (ch == ',')

-			ch = get_char(file);

+			continue;

 		else

 			done = TRUE;

 	}

@@ -468,137 +484,193 @@ get_list(bitstr_t * bits, int low, int high, const char *names[],

 	return (ch);

 }

+inline static int is_separator(int ch) {

+	switch (ch) {

+		case '\t':

+		case '\n':

+		case ' ':

+		case ',':

+			return 1;

+		default:

+			return 0;

+	}

+}

+

+

 static int

 get_range(bitstr_t * bits, int low, int high, const char *names[],

-	int ch, FILE * file) {

+		FILE * file) {

 	/* range = number | number "-" number [ "/" number ]

+	 *         | [number] "~" [number]

 	 */

+	

+	int ch, i, num1, num2, num3;

-	int i, num1, num2, num3;

+	/* default value for step

+	 */

+	num3 = 1;

+	range_state_t state = R_START;

+

+	while (state != R_FINISH && ((ch = get_char(file)) != EOF)) {

+		switch (state) {

+			case R_START:

+				if (ch == '*') {

+					num1 = low;

+					num2 = high;

+					state = R_AST;

+					break;

+				}

+				if (ch == '~') {

+					num1 = low;

+					state = R_RANDOM;

+					break;

+				}

+				unget_char(ch, file);

+				if (get_number(&num1, low, names, file) != EOF) {

+					state = R_NUM1;

+					break;

+				}

+				return (EOF);

-	Debug(DPARS | DEXT, ("get_range()...entering, exit won't show\n"));

+			case R_AST:

+				if (ch == '/') {

+					state = R_STEP;

+					break;

+				}

+				if (is_separator(ch)) {

+					state = R_FINISH;

+					break;

+				}

+				return (EOF);

-		if (ch == '*') {

-		/* '*' means "first-last" but can still be modified by /step

-		 */

-		num1 = low;

-		num2 = high;

-		ch = get_char(file);

-		if (ch == EOF)

-			return (EOF);

-	}

-	else {

-		ch = get_number(&num1, low, names, ch, file, ",- \t\n");

-		if (ch == EOF)

-			return (EOF);

+			case R_STEP:

+				if (get_number(&num3, 0, PPC_NULL, file) != EOF) {

+					state = R_TERMS;

+					break;

+				}

+				return (EOF);

-		if (ch != '-') {

-			/* not a range, it's a single number.

-			 */

-			if (EOF == set_element(bits, low, high, num1)) {

-				unget_char(ch, file);

+			case R_TERMS:

+				if (is_separator(ch)) {

+					state = R_FINISH;

+					break;

+				}

 				return (EOF);

-			}

-			return (ch);

-		}

-		else {

-			/* eat the dash

-			 */

-			ch = get_char(file);

-			if (ch == EOF)

+

+			case R_NUM1:

+				if (ch == '-') {

+					state = R_RANGE;

+					break;

+				}

+				if (ch == '~') {

+					state = R_RANDOM;

+					break;

+				}

+				if (is_separator(ch)) {

+					num2 = num1;

+					state = R_FINISH;

+					break;

+				}

 				return (EOF);

-			/* get the number following the dash

-			 */

-			ch = get_number(&num2, low, names, ch, file, "/, \t\n");

-			if (ch == EOF || num1 > num2)

+			case R_RANGE:

+				if (get_number(&num2, low, names, file) != EOF) {

+					state = R_RANGE_NUM2;

+					break;

+				}

 				return (EOF);

-		}

-	}

-	/* check for step size

-	 */

-	if (ch == '/') {

-		/* eat the slash

-		 */

-		ch = get_char(file);

-		if (ch == EOF)

-			return (EOF);

+			case R_RANGE_NUM2:

+				if (ch == '/') {

+					state = R_STEP;

+					break;

+				}

+				if (is_separator(ch)) {

+					state = R_FINISH;

+					break;

+				}

+				return (EOF);

-		/* get the step size -- note: we don't pass the

-		 * names here, because the number is not an

-		 * element id, it's a step size.  'low' is

-		 * sent as a 0 since there is no offset either.

-		 */

-		ch = get_number(&num3, 0, PPC_NULL, ch, file, ", \t\n");

-		if (ch == EOF || num3 == 0)

-			return (EOF);

-	}

-	else {

-		/* no step.  default==1.

-		 */

-		num3 = 1;

+			case R_RANDOM:

+				if (is_separator(ch)) {

+					num2 = high;

+					state = R_FINISH;

+				}

+				else if (unget_char(ch, file),

+						get_number(&num2, low, names, file) != EOF) {

+					state = R_TERMS;

+				}

+				/* fail if couldn't find match on previous term

+				 */

+				else

+					return (EOF);

+

+				/* if invalid random range was selected */

+				if (num1 > num2)

+					return (EOF);

+

+				/* select random number in range <num1, num2>

+				 */

+				num1 = num2 = random() % (num2 - num1 + 1) + num1;

+				break;

+

+

+			default:

+				/* We should never get here

+				 */

+				return (EOF);

+		}

 	}

+	if (state != R_FINISH || ch == EOF)

+		return (EOF);

-	/* range. set all elements from num1 to num2, stepping

-	 * by num3.  (the step is a downward-compatible extension

-	 * proposed conceptually by bob@acornrc, syntactically

-	 * designed then implemented by paul vixie).

-	 */

 	for (i = num1; i <= num2; i += num3)

 		if (EOF == set_element(bits, low, high, i)) {

 			unget_char(ch, file);

 			return (EOF);

 		}

-

-	return (ch);

+	return ch;

 }

 static int

-get_number(int *numptr, int low, const char *names[], int ch, FILE * file,

-	const char *terms) {

+get_number(int *numptr, int low, const char *names[], FILE * file) {

 	char temp[MAX_TEMPSTR], *pc;

-	int len, i;

+	int len, i, ch;

+	char *endptr;

 	pc = temp;

 	len = 0;

-	/* first look for a number */

-	while (isdigit((unsigned char) ch)) {

+	/* get all alnum characters available */

+	while (isalnum((ch = get_char(file)))) {

 		if (++len >= MAX_TEMPSTR)

 			goto bad;

 		*pc++ = (char)ch;

-		ch = get_char(file);

 	}

-	*pc = '\0';

-	if (len != 0) {

-		/* got a number, check for valid terminator */

-		if (!strchr(terms, ch))

-			goto bad;

-		*numptr = atoi(temp);

-		return (ch);

+	if (len == 0)

+		goto bad;

+

+	unget_char(ch, file);

+

+	/* try to get number */

+	*numptr = (int) strtol(temp, &endptr, 10);

+	if (*endptr == '\0' && temp != endptr) {

+		/* We have a number */

+		return 0;

 	}

 	/* no numbers, look for a string if we have any */

 	if (names) {

-		while (isalpha((unsigned char) ch)) {

-			if (++len >= MAX_TEMPSTR)

-				goto bad;

-			*pc++ = (char)ch;

-			ch = get_char(file);

-		}

-		*pc = '\0';

-		if (len != 0 && strchr(terms, ch)) {

-			for (i = 0; names[i] != NULL; i++) {

-				Debug(DPARS | DEXT,

-					("get_num, compare(%s,%s)\n", names[i], temp));

-					if (!strcasecmp(names[i], temp)) {

-					*numptr = i + low;

-					return (ch);

-				}

+		for (i = 0; names[i] != NULL; i++) {

+			Debug(DPARS | DEXT, ("get_num, compare(%s,%s)\n", names[i], temp));

+			if (strcasecmp(names[i], temp) == 0) {

+				*numptr = i + low;

+				return 0;

 			}

 		}

+	} else {

+		goto bad;

 	}

   bad:

-- 

2.35.1