Processo de varredura de um arquivo de C++ onde ele separa por palavras reservadas, identificadores, números, operadores e comentários.
#include#include #include #include #define SOURCE_FILENAME src.txt #define OUTPUT_FILENAME out.txt #define LINE_MAX_LEN 500 #define TOKEN_MAX_LEN 50 enum toktype { UNKNOW, OPERATOR, NUMBER, IDENTIFIER, RESWORD, COMMOPEN, COMMCLOSE }; struct token { char lex[TOKEN_MAX_LEN + 1]; enum toktype type; }; #define STR(s) _STR(s) #define _STR(s) #s struct token *get_tok(const char *cs, const char **lastc); int main(int argc, char *argv[]) { FILE *src_fd; FILE *outp_fd; if ((src_fd = fopen(STR(SOURCE_FILENAME), "r")) == NULL || (outp_fd = fopen(STR(OUTPUT_FILENAME), "w")) == NULL) { perror(argv[0]); return -1; } int line_num; char line[LINE_MAX_LEN]; line_num = 0; while (fgets(line, sizeof line, src_fd) != NULL) { fprintf(outp_fd, "%dn", ++line_num); struct token *tok; const char *tok_firstc_ptr, *tok_lastc_ptr; for (tok_firstc_ptr = line; (tok = get_tok(tok_firstc_ptr, &tok_lastc_ptr)) != NULL; tok_firstc_ptr = tok_lastc_ptr + 1) { if (tok->type == COMMOPEN) { const char *comm_open = tok_lastc_ptr; for (tok_firstc_ptr = tok_lastc_ptr + 1; (tok = get_tok(tok_firstc_ptr, &tok_lastc_ptr)) != NULL && tok->type != COMMCLOSE; tok_firstc_ptr = tok_lastc_ptr + 1) ; const char *comm_close = tok_lastc_ptr; fprintf(outp_fd, "%17s: ", "comentario"); while (comm_open <= comm_close) fputc(*comm_open++, outp_fd); fputc('n', outp_fd); continue; } const char *type_name; switch (tok->type) { case NUMBER: type_name = "numeral"; break; case OPERATOR: type_name = "operador"; break; case IDENTIFIER: type_name = "identificador"; break; case RESWORD: type_name = "palavra reservada"; break; case UNKNOW: default: type_name = "desconhecido"; break; } fprintf(outp_fd, "%17s: %sn", type_name, tok->lex); } } exit(EXIT_SUCCESS); } int get_lex(char *lex, size_t lex_maxlen, const char *cs); enum toktype get_toktype(const char *lex); struct token *get_tok(const char *cs, const char **lastc) { if (cs == NULL || lastc == NULL) return NULL; char tmp_lex[TOKEN_MAX_LEN + 1]; int ccnt; /* Contador de caracteres lidos pelo scanner. */ if ((ccnt = get_lex(tmp_lex, sizeof tmp_lex, cs)) == 0) { *lastc = cs; return NULL; } else if (tmp_lex[0] == '') { *lastc = &cs[ccnt - 1]; return NULL; } *lastc = &cs[ccnt - 1]; struct token *tok; if ((tok = malloc(sizeof(struct token))) == NULL) { perror("gettok()"); exit(EXIT_FAILURE); } strncpy(tok->lex, tmp_lex, sizeof tmp_lex); tok->type = get_toktype(tok->lex); return tok; } int get_lex(char *lex, size_t lex_maxlen, const char *cs) { if (lex == NULL || lex_maxlen < 1 || cs == NULL || cs[0] == '') return 0; const char *strp = cs; /* Aponta para o proximo caracter da string fonte. */ while (isspace(lex[0] = *strp++)) /* Espaco em branco nao eh relevante. */ ; /* Se a string nao possui lexemas, devemos retornar uma string nula, pois o contador de caracteres nao pode ser usado para determinar tal informacao. */ if (lex[0] == '') return strp - cs; /* A partir desse ponto a string possui um lexema. Iniciarei a busca do lexema supondo que ele eh um numeral. */ char *lexp = &lex[1]; /* aponta para o proximo caracter do lexema. */ if (isdigit(lex[0]) || lex[0] == '.' && isdigit(*strp)) while (lexp - lex < lex_maxlen && (isdigit(*strp) || *strp == '.')) *lexp++ = *strp++; /* Ate aqui nenhum caracter serviu na busca por um numeral entao procuraremos por caracteres compativeis com palavras reservadas ou identificadores. */ else if (isalpha(lex[0]) || lex[0] == '_') while (lexp - lex < lex_maxlen && (isalnum(*strp) || *strp == '_')) *lexp++ = *strp++; /* Ainda nao sendo adequado so me resta supor que seja um operador. ispunct() procura por caracteres imprimiveis que nao sao nem espaco nem alfanumericos, justamente os adequados para tal. */ else if (ispunct(lex[0])) while (lexp - lex < lex_maxlen && ispunct(*strp)) *lexp++ = *strp++; *lexp = ''; return strp - cs; } int is_numeral(const char *lex); int is_operator(const char *lex); int is_resword(const char *lex); int is_identifier(const char *lex); int is_commet_open(const char *lex); int is_commet_close(const char *lex); enum toktype get_toktype(const char *lex) { if (is_numeral(lex)) return NUMBER; if (is_operator(lex)) return OPERATOR; if (is_resword(lex)) return RESWORD; if (is_identifier(lex)) return IDENTIFIER; if (is_commopen(lex)) return COMMOPEN; if (is_commclose(lex)) return COMMCLOSE; return UNKNOW; } int is_commopen(const char *lex) { if (lex == NULL) return 0; if (strcmp(lex, "{") == 0) return 1; return 0; } int is_commclose(const char *lex) { if (lex == NULL) return 0; if (strcmp(lex, "}") == 0) return 1; return 0; } int is_numeral(const char *lex) { if (lex == NULL) return 0; if (isdigit(*lex)) while (isdigit(*++lex)) ; if (*lex == '.') while (isdigit(*++lex)) ; if (*lex == '') return 1; return 0; } int is_operator(const char *lex) { const char *l_opers[] = { "+", "-", "*", "/", "<>", "=", ">", "<", ">=", "<=", ":=", ";" }; if (lex != NULL) { int i; for (i = 0; i < sizeof l_opers / sizeof(const char *); i++) if (strcmp(lex, l_opers[i]) == 0) return 1; } return 0; } int is_resword(const char *lex) { const char *l_reswords[] = { "read", "write", "begin", "end", "if", "else", "then", "for", "while", "do", "until", "repeat" }; if (lex != NULL && isalpha(*lex)) { int i; for (i = 0; i < sizeof l_reswords / sizeof(const char *); i++) if (strcmp(lex, l_reswords[i]) == 0) return 1; } return 0; } int is_identifier(const char *lex) { if (lex != NULL && (isalpha(lex[0]) || lex[0] == '_' && isalpha(lex[1]))) if (!is_resword(lex)) { while (isalnum(*++lex)) ; if (*lex == '') return 1; } return 0; }
