C语言实现的词法分析器

 #ifndef MYLEX_H

02#define MYLEX_H

03  

04#include <stdio.h>

05#include <stdlib.h>

06#include <ctype.h>

07#include <string.h>

08#include <time.h>

09  

10#define MAX_ID 20

11  

12typedef enum SYMBOL {

13    nul, eof, plus, minus, times, slash, lparen, rparen, comma, semicolon, period, becomes,

14    eql, neq, lss, gtr, leq, geq, number, ident,

15    beginsym, callsym, constsym, dosym, endsym, ifsym, oddsym, proceduresym, readsym, thensym, varsym, whilesym, writesym

16} SYMBOL;

17  

18int read_ch();

19int put_back(int);

20SYMBOL getsym();

21int w2f(int);

22  

23int find_tab(char *);

24SYMBOL get_data(int);

25int error();

26  

27#endif

[文件] symbol.c ~ 4KB    下载(21)

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001#include "mylex.h"

002  

003extern FILE *source, *out;

004  

005const char *symtype[33] = {

006    "nul","eof", "plus","minus", "times","slash", "lparen","rparen", "comma","seicolon", "period", "becomes",

007    "eql","neq", "lss","gtr", "leq","geq", "number","ident",

008    "beginsym","callsym", "consysym", "dosym","endsym", "ifsym","oddsym", "proceduresym","readsym", "thensym", "varsym","whilesym", "writesym"

009};

010  

011int cur_line, cur_col, err_line, err_col;

012int num;

013char id[21] = "\0";

014int id_len;

015int token_num;

016  

017int read_ch() {

018    intch = fgetc(source);

019    cur_col++;

020    if(ch == '\n') {

021        cur_line++;

022        cur_col = 0;

023    }

024    returnch;

025}

026  

027int put_back(int ch) {

028    ungets(ch, source);

029    cur_col--;

030    if(ch == '\n')

031        cur_line--;

032    return0;

033}

034  

035SYMBOL getsym() {

036    intch;

037    intiskeywords;

038    charinvalid[2] = "\0";

039    while((ch = read_ch()) != EOF && ch <= ' ')

040        ;

041    err_line = cur_line;

042    err_col = cur_col;

043    switch(ch) {

044        caseEOF :

045            strcpy(id,"EOF");

046            returneof;

047        case'+' :

048            strcpy(id,"+");

049            returnplus;

050        case'-' :

051            strcpy(id,"-");

052            returnminus;

053        case'*' :

054            strcpy(id,"*");

055            returntimes;

056        case'/' :

057            strcpy(id,"/");

058            returnslash;

059        case'(' :

060            strcpy(id,"(");

061            returnlparen;

062        case')' :

063            strcpy(id,")");

064            returnrparen;

065        case',' :

066            strcpy(id,",");

067            returncomma;

068        case';' :

069            strcpy(id,";");

070            returnsemicolon;

071        case'.' :

072            strcpy(id,".");

073            returnperiod;

074        case':' :

075            ch = read_ch();

076            if(ch == '=') {

077                strcpy(id,":=");

078                returnbecomes;

079            }else

080                returnnul;

081        case'=' :

082            strcpy(id,"=");

083            returneql;

084        case'#' :

085            strcpy(id,"#");

086            returnneq;

087        case'<' :

088            ch = read_ch();

089            if(ch == '=') {

090                strcpy(id,"<=");

091                returnleq;

092            }

093            put_back(ch);

094            strcpy(id,"<");

095            returnlss;

096        case'>' :

097            ch = read_ch();

098            if(ch == '=') {

099                strcpy(id,">=");

100                returngeq;

101            }

102            put_back(ch);

103            strcpy(id,">");

104            returngtr;

105        default:

106            if(isdigit(ch)) {

107                num = 0;

108                do{

109                    num = 10 * num + ch -'0';

110                    ch = read_ch();

111                }while (ch != EOF &&isdigit(ch));

112                _itoa(num, id, 10);

113                if(isslpha(ch)) {

114                    invalid[0] = (char)ch;

115                    strcat(id, invalid);

116                    ch = read_ch();

117                    while(isalnum(ch)) {

118                        invalid[0] = (char) ch;

119                        strcat(id, invalid);

120                        ch = read_ch();

121                    }

122                    error();

123                    returnnul;

124                }

125                put_back(ch);

126                returnnumber;

127            }

128            if(isalpha(ch)) {

129                id_len = 0;

130                do{

131                    if(id_len < MAX_ID) {

132                        id[id_len] = (char)ch;

133                        id_len++;

134                    }

135                    ch = read_ch();

136                }while (ch != EOF &&isalnum(ch));

137                id[id_len] ='\0';

138                put_back(ch);

139                iskeywords = find_tab(id);

140                return(iskeywords == -1) ? ident : get_data(iskeywords);

141            }

142            error();

143            returnnul;

144    }

145}

146  

147int w2f(int flag) {

148    fprintf(out,"|%4d |%19s |%19s |%19s |\n",token_num, id, symtype[flag],"");

149    return0;

150}

[文件] keyword.c ~ 1KB    下载(22)

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01#include "mylex.h"

02  

03extern FILE *out;

04extern int cur_line, cur_col, err_line, err_col;

05extern int num;

06extern char id[21];

07extern int token_num;

08  

09char *keywords[13] = {

10    "begin","call", "const","do", "end","if", "odd","procedure", "read", "then","var", "while","write"

11};

12  

13int find_tab(char id[21]) {

14    inti;

15    for(i = 0; i !=13; ++i) {

16        if(!strcmp(keywords[i], id))

17            returni;

18        else

19            continue;

20    }

21    return-1;

22}

23  

24SYMBOL get_data(intNo) {

25    switch(No) {

26        case0 :

27            returnbeginsym;

28        case1 :

29            returncallsym;

30        case2 :

31            returnconstsym;

32        case3 :

33            returndosym;

34        case4 :

35            returnendsym;

36        case5 :

37            returnifsym;

38        case6 :

39            returnoddsym;

40        case7 :

41            returnproceduresym;

42        case8 :

43            returnreadsym;

44        case9 :

45            returnthensym;

46        case10 :

47            returnvarsym;

48        case11 :

49            returnwhilesym;

50        case12 :

51            returnwritesym;

52        default:

53            error(">>> Error : ");

54            returnnul;

55    }

56}

57  

58int error() {

59    fprintf(out,"|%4d |%19s |%19s %19s |\n", token_num, id,"nul", "invalid character");

60    return0;

61}

[文件] main.c ~ 2KB    下载(22)

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01#include "mylex.h"

02  

03extern int cur_line, cur_col, err_line, err_col;

04extern char id[21];

05extern int token_num;

06  

07FILE *source, *out;

08  

09int main() {

10    clock_tstart, finish;

11    doubleduration;

12    charfilename[21] = "\0";

13    charoutname[21] = "\0";

14    intflag;

15    FILE*stream;

16    charline[100];

17    printf("PL/0 Lexical Analyzer\n\n");

18    printf("Please enter the source file: ");

19    gets_s(filename, 20);

20    if((source = fopen(filename,"r")) == NULL) {

21        printf("Error: the file \"%s\" can not be opened, press any key to exit\n", filename);

22        _getch();

23        return1;

24    } else {

25        inti;

26        start =clock();

27        for(i = 0; i < (int)strlen(filename) - 4; ++i)

28            outname[i] = filename[i];

29        strcat(outname,".out");

30        if((out = fopen(outname,"w+")) == NULL) {

31            printf("Error: can not create \"%s\" in current path, press any key to exit\n", outname);

32            _getch();

33            return1;

34        }

35        cur_line = 1;

36        cur_col = 0;

37        token_num = 0;

38        fprintf(out,"+-----+--------------------+--------------------+--------------------+\n");

39        fprintf(out,"|%4s |%19s |%19s |%19s |\n","No", "Symbol","Symbol Type", "Notes");

40        fprintf(out,"+-----+--------------------+--------------------+--------------------+\n");

41        while(!feof(source)) {

42            token_num++;

43            flag = getsym();

44            if(flag == 0)

45                continue;

46            w2f(flag);

47        }

48        fprintf(out,"+-----+--------------------+--------------------+--------------------+\n");

49        fcloseall();

50        stream =fopen(outname,"r");

51        while(1) {

52            fgets(line, 100, stream);

53            if(feof(stream))

54                break;

55            else

56                printf("%s", line);

57        }

58        fclose(stream);

59        finish =clock();

60        duration = (double)(finish - start) / CLOCKS_PER_SEC;

61        printf("completed successfully. (%2.3f secs)\n", duration);

62    }

63    return0;

}