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.
| paddy@0 | 1 package pqarrays |
| paddy@0 | 2 |
| paddy@0 | 3 import ( |
| paddy@0 | 4 "errors" |
| paddy@0 | 5 ) |
| paddy@0 | 6 |
| paddy@0 | 7 func parse(l *lexer) ([]*string, error) { |
| paddy@0 | 8 var parsed []*string |
| paddy@0 | 9 pchan := make(chan *string) |
| paddy@0 | 10 errchan := make(chan error) |
| paddy@0 | 11 done := make(chan struct{}) |
| paddy@0 | 12 go runParse(l, pchan, errchan, done) |
| paddy@0 | 13 for { |
| paddy@0 | 14 select { |
| paddy@0 | 15 case err := <-errchan: |
| paddy@0 | 16 return parsed, err |
| paddy@0 | 17 case item := <-pchan: |
| paddy@0 | 18 parsed = append(parsed, item) |
| paddy@0 | 19 case <-done: |
| paddy@0 | 20 return parsed, nil |
| paddy@0 | 21 } |
| paddy@0 | 22 } |
| paddy@0 | 23 } |
| paddy@0 | 24 |
| paddy@0 | 25 func runParse(l *lexer, parsed chan *string, err chan error, done chan struct{}) { |
| paddy@0 | 26 var state parseFunc = parseStart |
| paddy@0 | 27 for { |
| paddy@0 | 28 var e error |
| paddy@0 | 29 state, e = state(l, parsed) |
| paddy@0 | 30 if e != nil { |
| paddy@0 | 31 err <- e |
| paddy@0 | 32 break |
| paddy@0 | 33 } |
| paddy@0 | 34 if state == nil { |
| paddy@0 | 35 break |
| paddy@0 | 36 } |
| paddy@0 | 37 } |
| paddy@0 | 38 close(done) |
| paddy@0 | 39 } |
| paddy@0 | 40 |
| paddy@0 | 41 type parseFunc func(*lexer, chan *string) (parseFunc, error) |
| paddy@0 | 42 |
| paddy@0 | 43 func parseEOF(l *lexer, parsed chan *string) (parseFunc, error) { |
| paddy@0 | 44 tok := l.nextToken() |
| paddy@0 | 45 if tok.typ == tokenWhitespace { |
| paddy@0 | 46 tok = l.nextToken() |
| paddy@0 | 47 } |
| paddy@0 | 48 if tok.typ != tokenEOF { |
| paddy@0 | 49 return nil, errors.New("expected EOF, got " + tok.typ.String()) |
| paddy@0 | 50 } |
| paddy@0 | 51 return nil, nil |
| paddy@0 | 52 } |
| paddy@0 | 53 |
| paddy@0 | 54 func parseStringOrNull(l *lexer, parsed chan *string) (parseFunc, error) { |
| paddy@0 | 55 tok := l.nextToken() |
| paddy@0 | 56 if tok.typ == tokenWhitespace { |
| paddy@0 | 57 tok = l.nextToken() |
| paddy@0 | 58 } else if tok.typ == tokenString { |
| paddy@0 | 59 parsed <- &tok.val |
| paddy@0 | 60 return parseSeparatorOrDelim, nil |
| paddy@0 | 61 } else if tok.typ == tokenNull { |
| paddy@0 | 62 parsed <- nil |
| paddy@0 | 63 return parseSeparatorOrDelim, nil |
| paddy@0 | 64 } |
| paddy@0 | 65 return nil, errors.New("expected string, got " + tok.typ.String()) |
| paddy@0 | 66 } |
| paddy@0 | 67 |
| paddy@0 | 68 func parseSeparatorOrDelim(l *lexer, parsed chan *string) (parseFunc, error) { |
| paddy@0 | 69 tok := l.nextToken() |
| paddy@0 | 70 if tok.typ == tokenWhitespace { |
| paddy@0 | 71 return parseSeparatorOrDelim, nil |
| paddy@0 | 72 } else if tok.typ == tokenSeparator { |
| paddy@0 | 73 return parseStringOrNull, nil |
| paddy@0 | 74 } else if tok.typ == tokenArrayEnd { |
| paddy@0 | 75 return parseEOF, nil |
| paddy@0 | 76 } |
| paddy@0 | 77 return nil, errors.New("expected separator or delim, got " + tok.typ.String()) |
| paddy@0 | 78 } |
| paddy@0 | 79 |
| paddy@0 | 80 func parseStart(l *lexer, parsed chan *string) (parseFunc, error) { |
| paddy@0 | 81 tok := l.nextToken() |
| paddy@0 | 82 if tok.typ == tokenWhitespace { |
| paddy@0 | 83 return parseStart, nil |
| paddy@0 | 84 } else if tok.typ == tokenArrayStart { |
| paddy@0 | 85 return parseStringOrNull, nil |
| paddy@0 | 86 } |
| paddy@0 | 87 return nil, errors.New("expected separator or delim, got " + tok.typ.String()) |
| paddy@0 | 88 } |