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refactor(cron): expression parser now uses bitfields (closes #148)

Jef Roosens 2022-10-04 16:45:28 +02:00
parent 54f40b7638
commit 71c77e90bc
Signed by untrusted user: Jef Roosens
GPG Key ID: B75D4F293C7052DB
4 changed files with 162 additions and 163 deletions
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1
CHANGELOG.md
View File

@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
### Changed
* Migrated codebase to V 0.3.2
* Cron expression parser now uses bitfields instead of bool arrays
### Fixed

139
src/cron/expression/expression.v
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@ -134,142 +134,3 @@ pub fn (ce &CronExpression) next_n(ref time.Time, n int) ![]time.Time {
return times
}
// parse_range parses a given string into a range of sorted integers, if
// possible.
fn parse_range(s string, min int, max int, mut bitv []bool) ! {
mut start := min
mut end := max
mut interval := 1
exps := s.split('/')
if exps.len > 2 {
return error('Invalid expression.')
}
if exps[0] != '*' {
dash_parts := exps[0].split('-')
if dash_parts.len > 2 {
return error('Invalid expression.')
}
start = dash_parts[0].int()
// The builtin parsing functions return zero if the string can't be
// parsed into a number, so we have to explicitely check whether they
// actually entered zero or if it's an invalid number.
if start == 0 && dash_parts[0] != '0' {
return error('Invalid number.')
}
// Check whether the start value is out of range
if start < min || start > max {
return error('Out of range.')
}
if dash_parts.len == 2 {
end = dash_parts[1].int()
if end == 0 && dash_parts[1] != '0' {
return error('Invalid number.')
}
if end < start || end > max {
return error('Out of range.')
}
}
}
if exps.len > 1 {
interval = exps[1].int()
// interval being zero is always invalid, but we want to check why
// it's invalid for better error messages.
if interval == 0 {
if exps[1] != '0' {
return error('Invalid number.')
} else {
return error('Step size zero not allowed.')
}
}
if interval > max - min {
return error('Step size too large.')
}
}
// Here, s solely consists of a number, so that's the only value we
// should return.
else if exps[0] != '*' && !exps[0].contains('-') {
bitv[start - min] = true
return
}
for start <= end {
bitv[start - min] = true
start += interval
}
}
// bitv_to_ints converts a bit vector into an array containing the
// corresponding values.
fn bitv_to_ints(bitv []bool, min int) []int {
mut out := []int{}
for i in 0 .. bitv.len {
if bitv[i] {
out << min + i
}
}
return out
}
// parse_part parses a given part of a cron expression & returns the
// corresponding array of ints.
fn parse_part(s string, min int, max int) ![]int {
mut bitv := []bool{len: max - min + 1, init: false}
for range in s.split(',') {
parse_range(range, min, max, mut bitv)!
}
return bitv_to_ints(bitv, min)
}
// parse_expression parses an entire cron expression string into a
// CronExpression object, if possible.
pub fn parse_expression(exp string) !CronExpression {
// The filter allows for multiple spaces between parts
mut parts := exp.split(' ').filter(it != '')
if parts.len < 2 || parts.len > 4 {
return error('Expression must contain between 2 and 4 space-separated parts.')
}
// For ease of use, we allow the user to only specify as many parts as they
// need.
for parts.len < 4 {
parts << '*'
}
mut part_results := [][]int{}
mins := [0, 0, 1, 1]
maxs := [59, 23, 31, 12]
// This for loop allows us to more clearly propagate the error to the user.
for i, min in mins {
part_results << parse_part(parts[i], min, maxs[i]) or {
return error('An error occurred with part $i: $err.msg()')
}
}
return CronExpression{
minutes: part_results[0]
hours: part_results[1]
days: part_results[2]
months: part_results[3]
}
}

146
src/cron/expression/expression_parse.v 100644
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@ -0,0 +1,146 @@
module expression
import bitfield
// parse_range parses a given string into a range of sorted integers. Its
// result is a BitField with set bits for all numbers in the result.
fn parse_range(s string, min int, max int) !bitfield.BitField {
mut start := min
mut end := max
mut interval := 1
mut bf := bitfield.new(max - min + 1)
exps := s.split('/')
if exps.len > 2 {
return error('Invalid expression.')
}
if exps[0] != '*' {
dash_parts := exps[0].split('-')
if dash_parts.len > 2 {
return error('Invalid expression.')
}
start = dash_parts[0].int()
// The builtin parsing functions return zero if the string can't be
// parsed into a number, so we have to explicitely check whether they
// actually entered zero or if it's an invalid number.
if start == 0 && dash_parts[0] != '0' {
return error('Invalid number.')
}
// Check whether the start value is out of range
if start < min || start > max {
return error('Out of range.')
}
if dash_parts.len == 2 {
end = dash_parts[1].int()
if end == 0 && dash_parts[1] != '0' {
return error('Invalid number.')
}
if end < start || end > max {
return error('Out of range.')
}
}
}
if exps.len > 1 {
interval = exps[1].int()
// interval being zero is always invalid, but we want to check why
// it's invalid for better error messages.
if interval == 0 {
if exps[1] != '0' {
return error('Invalid number.')
} else {
return error('Step size zero not allowed.')
}
}
if interval > max - min {
return error('Step size too large.')
}
}
// Here, s solely consists of a number, so that's the only value we
// should return.
else if exps[0] != '*' && !exps[0].contains('-') {
bf.set_bit(start - min)
return bf
}
for start <= end {
bf.set_bit(start - min)
start += interval
}
return bf
}
// bf_to_ints takes a BitField and converts it into the expected list of actual
// integers.
fn bf_to_ints(bf bitfield.BitField, min int) []int {
mut out := []int{}
for i in 0 .. bf.get_size() {
if bf.get_bit(i) == 1 {
out << min + i
}
}
return out
}
// parse_part parses a given part of a cron expression & returns the
// corresponding array of ints.
fn parse_part(s string, min int, max int) ![]int {
mut bf := bitfield.new(max - min + 1)
for range in s.split(',') {
bf2 := parse_range(range, min, max)!
bf = bitfield.bf_or(bf, bf2)
}
return bf_to_ints(bf, min)
}
// parse_expression parses an entire cron expression string into a
// CronExpression object, if possible.
pub fn parse_expression(exp string) !CronExpression {
// The filter allows for multiple spaces between parts
mut parts := exp.split(' ').filter(it != '')
if parts.len < 2 || parts.len > 4 {
return error('Expression must contain between 2 and 4 space-separated parts.')
}
// For ease of use, we allow the user to only specify as many parts as they
// need.
for parts.len < 4 {
parts << '*'
}
mut part_results := [][]int{}
mins := [0, 0, 1, 1]
maxs := [59, 23, 31, 12]
// This for loop allows us to more clearly propagate the error to the user.
for i, min in mins {
part_results << parse_part(parts[i], min, maxs[i]) or {
return error('An error occurred with part $i: $err.msg()')
}
}
return CronExpression{
minutes: part_results[0]
hours: part_results[1]
days: part_results[2]
months: part_results[3]
}
}

39
src/cron/expression/expression_parse_test.v
View File

@ -3,26 +3,22 @@ module expression
// parse_range_error returns the returned error message. If the result is '',
// that means the function didn't error.
fn parse_range_error(s string, min int, max int) string {
mut bitv := []bool{len: max - min + 1, init: false}
parse_range(s, min, max, mut bitv) or { return err.msg }
parse_range(s, min, max) or { return err.msg }
return ''
}
// =====parse_range=====
fn test_range_star_range() ! {
mut bitv := []bool{len: 6, init: false}
parse_range('*', 0, 5, mut bitv)!
bf := parse_range('*', 0, 5)!
assert bitv == [true, true, true, true, true, true]
assert bf_to_ints(bf, 0) == [0, 1, 2, 3, 4, 5]
}
fn test_range_number() ! {
mut bitv := []bool{len: 6, init: false}
parse_range('4', 0, 5, mut bitv)!
bf := parse_range('4', 0, 5)!
assert bitv_to_ints(bitv, 0) == [4]
assert bf_to_ints(bf, 0) == [4]
}
fn test_range_number_too_large() ! {
@ -38,17 +34,15 @@ fn test_range_number_invalid() ! {
}
fn test_range_step_star_1() ! {
mut bitv := []bool{len: 21, init: false}
parse_range('*/4', 0, 20, mut bitv)!
bf := parse_range('*/4', 0, 20)!
assert bitv_to_ints(bitv, 0) == [0, 4, 8, 12, 16, 20]
assert bf_to_ints(bf, 0) == [0, 4, 8, 12, 16, 20]
}
fn test_range_step_star_2() ! {
mut bitv := []bool{len: 8, init: false}
parse_range('*/3', 1, 8, mut bitv)!
bf := parse_range('*/3', 1, 8)!
assert bitv_to_ints(bitv, 1) == [1, 4, 7]
assert bf_to_ints(bf, 1) == [1, 4, 7]
}
fn test_range_step_star_too_large() ! {
@ -60,10 +54,9 @@ fn test_range_step_zero() ! {
}
fn test_range_step_number() ! {
mut bitv := []bool{len: 21, init: false}
parse_range('5/4', 2, 22, mut bitv)!
bf := parse_range('5/4', 2, 22)!
assert bitv_to_ints(bitv, 2) == [5, 9, 13, 17, 21]
assert bf_to_ints(bf, 2) == [5, 9, 13, 17, 21]
}
fn test_range_step_number_too_large() ! {
@ -75,17 +68,15 @@ fn test_range_step_number_too_small() ! {
}
fn test_range_dash() ! {
mut bitv := []bool{len: 10, init: false}
parse_range('4-8', 0, 9, mut bitv)!
bf := parse_range('4-8', 0, 9)!
assert bitv_to_ints(bitv, 0) == [4, 5, 6, 7, 8]
assert bf_to_ints(bf, 0) == [4, 5, 6, 7, 8]
}
fn test_range_dash_step() ! {
mut bitv := []bool{len: 10, init: false}
parse_range('4-8/2', 0, 9, mut bitv)!
bf := parse_range('4-8/2', 0, 9)!
assert bitv_to_ints(bitv, 0) == [4, 6, 8]
assert bf_to_ints(bf, 0) == [4, 6, 8]
}
// =====parse_part=====