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//go:generate re2go $INPUT -o $OUTPUT package main import ( "os" "strings" ) /*!max:re2c*/ const BUFSIZE int = 4096 type Input struct { file *os.File buf []byte cur int tok int lim int eof bool } func fill(in *Input, need int) int { if in.eof { return -1 } // unexpected EOF // Error: lexeme too long. In real life can reallocate a larger buffer. if in.tok < need { return -2 } // Shift buffer contents (discard everything up to the current token). copy(in.buf[0:], in.buf[in.tok:in.lim]) in.cur -= in.tok in.lim -= in.tok in.tok = 0 // Fill free space at the end of buffer with new data from file. n, _ := in.file.Read(in.buf[in.lim:BUFSIZE]) in.lim += n // If read less than expected, this is end of input => add zero padding // so that the lexer can access characters at the end of buffer. if in.lim < BUFSIZE { in.eof = true for i := 0; i < YYMAXFILL; i += 1 { in.buf[in.lim+i] = 0 } in.lim += YYMAXFILL } return 0 } func lex(in *Input) int { count := 0 for { in.tok = in.cur /*!re2c re2c:define:YYCTYPE = byte; re2c:define:YYPEEK = "in.buf[in.cur]"; re2c:define:YYSKIP = "in.cur += 1"; re2c:define:YYLESSTHAN = "in.lim-in.cur < @@"; re2c:define:YYFILL = "if r := fill(in, @@); r != 0 { return r }"; str = ['] ([^'\\] | [\\][^])* [']; [\x00] { // Check that it is the sentinel, not some unexpected null. if in.tok == in.lim - YYMAXFILL { return count } else { return -1 } } str { count += 1; continue } [ ]+ { continue } * { return -1 } */ } } func main() () { fname := "input" content := "'qu\000tes' 'are' 'fine: \\'' "; // Prepare input file: a few times the size of the buffer, containing // strings with zeroes and escaped quotes. f, _ := os.Create(fname) f.WriteString(strings.Repeat(content, BUFSIZE)) f.Seek(0, 0) count := 3 * BUFSIZE // number of quoted strings written to file // Prepare lexer state: all offsets are at the end of buffer. // This immediately triggers YYFILL, as the YYLESSTHAN condition is true. in := &Input{ file: f, buf: make([]byte, BUFSIZE+YYMAXFILL), cur: BUFSIZE, tok: BUFSIZE, lim: BUFSIZE, eof: false, } // Run the lexer. if lex(in) != count { panic("error"); } // Cleanup: remove input file. f.Close(); os.Remove(fname); }