refactor(cron): expression parser now uses bitfields (closes #148)
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8ebc2c8464
commit
faedfe1055
GPG Key ID:
B75D4F293C7052DB
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@ -134,142 +134,3 @@ pub fn (ce &CronExpression) next_n(ref time.Time, n int) ?[]time.Time {
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return times
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}
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// parse_range parses a given string into a range of sorted integers, if
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// possible.
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fn parse_range(s string, min int, max int, mut bitv []bool) ? {
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mut start := min
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mut end := max
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mut interval := 1
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exps := s.split('/')
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if exps.len > 2 {
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return error('Invalid expression.')
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}
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if exps[0] != '*' {
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dash_parts := exps[0].split('-')
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if dash_parts.len > 2 {
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return error('Invalid expression.')
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}
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start = dash_parts[0].int()
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// The builtin parsing functions return zero if the string can't be
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// parsed into a number, so we have to explicitely check whether they
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// actually entered zero or if it's an invalid number.
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if start == 0 && dash_parts[0] != '0' {
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return error('Invalid number.')
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}
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// Check whether the start value is out of range
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if start < min || start > max {
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return error('Out of range.')
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}
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if dash_parts.len == 2 {
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end = dash_parts[1].int()
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if end == 0 && dash_parts[1] != '0' {
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return error('Invalid number.')
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}
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if end < start || end > max {
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return error('Out of range.')
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}
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}
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}
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if exps.len > 1 {
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interval = exps[1].int()
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// interval being zero is always invalid, but we want to check why
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// it's invalid for better error messages.
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if interval == 0 {
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if exps[1] != '0' {
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return error('Invalid number.')
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} else {
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return error('Step size zero not allowed.')
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}
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}
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if interval > max - min {
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return error('Step size too large.')
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}
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}
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// Here, s solely consists of a number, so that's the only value we
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// should return.
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else if exps[0] != '*' && !exps[0].contains('-') {
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bitv[start - min] = true
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return
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}
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for start <= end {
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bitv[start - min] = true
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start += interval
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}
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}
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// bitv_to_ints converts a bit vector into an array containing the
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// corresponding values.
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fn bitv_to_ints(bitv []bool, min int) []int {
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mut out := []int{}
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for i in 0 .. bitv.len {
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if bitv[i] {
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out << min + i
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}
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}
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return out
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}
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// parse_part parses a given part of a cron expression & returns the
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// corresponding array of ints.
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fn parse_part(s string, min int, max int) ?[]int {
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mut bitv := []bool{len: max - min + 1, init: false}
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for range in s.split(',') {
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parse_range(range, min, max, mut bitv)?
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}
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return bitv_to_ints(bitv, min)
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}
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// parse_expression parses an entire cron expression string into a
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// CronExpression object, if possible.
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pub fn parse_expression(exp string) ?CronExpression {
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// The filter allows for multiple spaces between parts
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mut parts := exp.split(' ').filter(it != '')
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if parts.len < 2 || parts.len > 4 {
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return error('Expression must contain between 2 and 4 space-separated parts.')
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}
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// For ease of use, we allow the user to only specify as many parts as they
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// need.
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for parts.len < 4 {
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parts << '*'
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}
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mut part_results := [][]int{}
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mins := [0, 0, 1, 1]
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maxs := [59, 23, 31, 12]
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// This for loop allows us to more clearly propagate the error to the user.
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for i, min in mins {
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part_results << parse_part(parts[i], min, maxs[i]) or {
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return error('An error occurred with part $i: $err.msg()')
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}
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}
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return CronExpression{
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minutes: part_results[0]
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hours: part_results[1]
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days: part_results[2]
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months: part_results[3]
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}
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}
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@ -0,0 +1,146 @@
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module expression
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import bitfield
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// parse_range parses a given string into a range of sorted integers. Its
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// result is a BitField with set bits for all numbers in the result.
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fn parse_range(s string, min int, max int) ?bitfield.BitField {
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mut start := min
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mut end := max
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mut interval := 1
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mut bf := bitfield.new(max - min + 1)
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exps := s.split('/')
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if exps.len > 2 {
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return error('Invalid expression.')
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}
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if exps[0] != '*' {
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dash_parts := exps[0].split('-')
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if dash_parts.len > 2 {
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return error('Invalid expression.')
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}
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start = dash_parts[0].int()
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// The builtin parsing functions return zero if the string can't be
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// parsed into a number, so we have to explicitely check whether they
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// actually entered zero or if it's an invalid number.
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if start == 0 && dash_parts[0] != '0' {
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return error('Invalid number.')
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}
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// Check whether the start value is out of range
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if start < min || start > max {
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return error('Out of range.')
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}
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if dash_parts.len == 2 {
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end = dash_parts[1].int()
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if end == 0 && dash_parts[1] != '0' {
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return error('Invalid number.')
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}
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if end < start || end > max {
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return error('Out of range.')
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}
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}
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}
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if exps.len > 1 {
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interval = exps[1].int()
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// interval being zero is always invalid, but we want to check why
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// it's invalid for better error messages.
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if interval == 0 {
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if exps[1] != '0' {
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return error('Invalid number.')
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} else {
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return error('Step size zero not allowed.')
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}
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}
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if interval > max - min {
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return error('Step size too large.')
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}
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}
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// Here, s solely consists of a number, so that's the only value we
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// should return.
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else if exps[0] != '*' && !exps[0].contains('-') {
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bf.set_bit(start - min)
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return bf
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}
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for start <= end {
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bf.set_bit(start - min)
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start += interval
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}
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return bf
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}
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// bf_to_ints takes a BitField and converts it into the expected list of actual
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// integers.
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fn bf_to_ints(bf bitfield.BitField, min int) []int {
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mut out := []int{}
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for i in 0 .. bf.get_size() {
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if bf.get_bit(i) == 1 {
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out << min + i
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}
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}
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return out
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}
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// parse_part parses a given part of a cron expression & returns the
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// corresponding array of ints.
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fn parse_part(s string, min int, max int) ?[]int {
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mut bf := bitfield.new(max - min + 1)
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for range in s.split(',') {
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bf2 := parse_range(range, min, max)?
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bf = bitfield.bf_or(bf, bf2)
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}
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return bf_to_ints(bf, min)
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}
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// parse_expression parses an entire cron expression string into a
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// CronExpression object, if possible.
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pub fn parse_expression(exp string) ?CronExpression {
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// The filter allows for multiple spaces between parts
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mut parts := exp.split(' ').filter(it != '')
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if parts.len < 2 || parts.len > 4 {
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return error('Expression must contain between 2 and 4 space-separated parts.')
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}
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// For ease of use, we allow the user to only specify as many parts as they
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// need.
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for parts.len < 4 {
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parts << '*'
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}
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mut part_results := [][]int{}
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mins := [0, 0, 1, 1]
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maxs := [59, 23, 31, 12]
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// This for loop allows us to more clearly propagate the error to the user.
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for i, min in mins {
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part_results << parse_part(parts[i], min, maxs[i]) or {
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return error('An error occurred with part $i: $err.msg()')
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}
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}
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return CronExpression{
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minutes: part_results[0]
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hours: part_results[1]
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days: part_results[2]
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months: part_results[3]
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}
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}
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@ -3,26 +3,22 @@ module expression
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// parse_range_error returns the returned error message. If the result is '',
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// that means the function didn't error.
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fn parse_range_error(s string, min int, max int) string {
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mut bitv := []bool{len: max - min + 1, init: false}
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parse_range(s, min, max, mut bitv) or { return err.msg }
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parse_range(s, min, max) or { return err.msg }
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return ''
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}
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// =====parse_range=====
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fn test_range_star_range() ? {
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mut bitv := []bool{len: 6, init: false}
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parse_range('*', 0, 5, mut bitv)?
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bf := parse_range('*', 0, 5)?
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assert bitv == [true, true, true, true, true, true]
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assert bf_to_ints(bf, 0) == [0, 1, 2, 3, 4, 5]
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}
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fn test_range_number() ? {
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mut bitv := []bool{len: 6, init: false}
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parse_range('4', 0, 5, mut bitv)?
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bf := parse_range('4', 0, 5)?
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assert bitv_to_ints(bitv, 0) == [4]
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assert bf_to_ints(bf, 0) == [4]
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}
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fn test_range_number_too_large() ? {
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@ -38,17 +34,15 @@ fn test_range_number_invalid() ? {
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}
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fn test_range_step_star_1() ? {
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mut bitv := []bool{len: 21, init: false}
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parse_range('*/4', 0, 20, mut bitv)?
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bf := parse_range('*/4', 0, 20)?
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assert bitv_to_ints(bitv, 0) == [0, 4, 8, 12, 16, 20]
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assert bf_to_ints(bf, 0) == [0, 4, 8, 12, 16, 20]
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}
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fn test_range_step_star_2() ? {
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mut bitv := []bool{len: 8, init: false}
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parse_range('*/3', 1, 8, mut bitv)?
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bf := parse_range('*/3', 1, 8)?
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assert bitv_to_ints(bitv, 1) == [1, 4, 7]
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assert bf_to_ints(bf, 1) == [1, 4, 7]
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}
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fn test_range_step_star_too_large() ? {
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@ -60,10 +54,9 @@ fn test_range_step_zero() ? {
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}
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fn test_range_step_number() ? {
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mut bitv := []bool{len: 21, init: false}
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parse_range('5/4', 2, 22, mut bitv)?
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bf := parse_range('5/4', 2, 22)?
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assert bitv_to_ints(bitv, 2) == [5, 9, 13, 17, 21]
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assert bf_to_ints(bf, 2) == [5, 9, 13, 17, 21]
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}
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fn test_range_step_number_too_large() ? {
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@ -75,17 +68,15 @@ fn test_range_step_number_too_small() ? {
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}
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fn test_range_dash() ? {
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mut bitv := []bool{len: 10, init: false}
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parse_range('4-8', 0, 9, mut bitv)?
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bf := parse_range('4-8', 0, 9)?
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assert bitv_to_ints(bitv, 0) == [4, 5, 6, 7, 8]
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assert bf_to_ints(bf, 0) == [4, 5, 6, 7, 8]
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}
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fn test_range_dash_step() ? {
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mut bitv := []bool{len: 10, init: false}
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parse_range('4-8/2', 0, 9, mut bitv)?
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bf := parse_range('4-8/2', 0, 9)?
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assert bitv_to_ints(bitv, 0) == [4, 6, 8]
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assert bf_to_ints(bf, 0) == [4, 6, 8]
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}
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// =====parse_part=====
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