103 lines
1.6 KiB
Go
103 lines
1.6 KiB
Go
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package parser
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import (
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"fmt"
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)
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// buildScheme builds a 'basic' scheme
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// from a pattern string
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func buildScheme(ss []string) (Scheme, error) {
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/* (1) Build scheme */
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sch := make(Scheme, 0, maxMatch)
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for _, s := range ss {
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/* (2) ignore empty */
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if len(s) == 0 { continue }
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m := new(matcher)
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switch s {
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/* (3) Card: 0, N */
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case "**":
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m.req = false
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m.mul = true
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sch = append(sch, m)
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/* (4) Card: 1, N */
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case "..":
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m.req = true
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m.mul = true
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sch = append(sch, m)
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/* (5) Card: 0, 1 */
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case "*":
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m.req = false
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m.mul = false
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sch = append(sch, m)
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/* (6) Card: 1 */
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case ".":
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m.req = true
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m.mul = false
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sch = append(sch, m)
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/* (7) Card: 1, literal string */
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default:
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m.req = true
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m.mul = false
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m.pat = fmt.Sprintf("/%s", s)
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sch = append(sch, m)
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}
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}
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return sch, nil
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}
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// optimise optimised the scheme for further parsing
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func (s Scheme) optimise() (Scheme, error) {
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/* (1) Nothing to do if only 1 element */
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if len(s) <= 1 {
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return s, nil
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}
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/* (2) Init reshifted scheme */
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rshift := make(Scheme, 0, maxMatch)
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rshift = append(rshift, s[0])
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/* (2) Iterate over matchers */
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for p, i, l := 0, 1, len(s) ; i < l ; i++ {
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pre, cur := s[p], s[i]
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/* Merge: 2 following literals */
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if len(pre.pat) > 0 && len(cur.pat) > 0 {
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// merge strings into previous
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pre.pat = fmt.Sprintf("%s%s", pre.pat, cur.pat)
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// delete current
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s[i] = nil
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}
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// increment previous (only if current is not nul)
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if s[i] != nil {
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rshift = append(rshift, s[i])
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p = i
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}
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}
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return rshift, nil
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}
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