pqarrays
2015-04-19
Child:ce9c92fc81ab
pqarrays/parser.go
First pass implementation. Use a lexer to generate tokens out of the Array type responses that PostgreSQL will send. Write a parser for string[] array types. Create a StringArray type that fulfills the driver.Valuer and sql.Scanner interfaces using the parser and lexer.
1 package pqarrays
3 import (
4 "errors"
5 )
7 func parse(l *lexer) ([]*string, error) {
8 var parsed []*string
9 pchan := make(chan *string)
10 errchan := make(chan error)
11 done := make(chan struct{})
12 go runParse(l, pchan, errchan, done)
13 for {
14 select {
15 case err := <-errchan:
16 return parsed, err
17 case item := <-pchan:
18 parsed = append(parsed, item)
19 case <-done:
20 return parsed, nil
21 }
22 }
23 }
25 func runParse(l *lexer, parsed chan *string, err chan error, done chan struct{}) {
26 var state parseFunc = parseStart
27 for {
28 var e error
29 state, e = state(l, parsed)
30 if e != nil {
31 err <- e
32 break
33 }
34 if state == nil {
35 break
36 }
37 }
38 close(done)
39 }
41 type parseFunc func(*lexer, chan *string) (parseFunc, error)
43 func parseEOF(l *lexer, parsed chan *string) (parseFunc, error) {
44 tok := l.nextToken()
45 if tok.typ == tokenWhitespace {
46 tok = l.nextToken()
47 }
48 if tok.typ != tokenEOF {
49 return nil, errors.New("expected EOF, got " + tok.typ.String())
50 }
51 return nil, nil
52 }
54 func parseStringOrNull(l *lexer, parsed chan *string) (parseFunc, error) {
55 tok := l.nextToken()
56 if tok.typ == tokenWhitespace {
57 tok = l.nextToken()
58 } else if tok.typ == tokenString {
59 parsed <- &tok.val
60 return parseSeparatorOrDelim, nil
61 } else if tok.typ == tokenNull {
62 parsed <- nil
63 return parseSeparatorOrDelim, nil
64 }
65 return nil, errors.New("expected string, got " + tok.typ.String())
66 }
68 func parseSeparatorOrDelim(l *lexer, parsed chan *string) (parseFunc, error) {
69 tok := l.nextToken()
70 if tok.typ == tokenWhitespace {
71 return parseSeparatorOrDelim, nil
72 } else if tok.typ == tokenSeparator {
73 return parseStringOrNull, nil
74 } else if tok.typ == tokenArrayEnd {
75 return parseEOF, nil
76 }
77 return nil, errors.New("expected separator or delim, got " + tok.typ.String())
78 }
80 func parseStart(l *lexer, parsed chan *string) (parseFunc, error) {
81 tok := l.nextToken()
82 if tok.typ == tokenWhitespace {
83 return parseStart, nil
84 } else if tok.typ == tokenArrayStart {
85 return parseStringOrNull, nil
86 }
87 return nil, errors.New("expected separator or delim, got " + tok.typ.String())
88 }