简易词法分析器

最近开始学习编译器，希望能坚持下去，通过做编译器也把c++练好点，今天花了一天做了一个简单的词法分析器，过几天编译原理书到了后，希望能通过看书得到更好的方法。

//learn.cpp

#include <iostream>
#include "learn.h"
#include <fstream>
using namespace std;
static char *st_line;
static int st_line_pos;
int length;

typedef enum {
    INITIAL_STATUS,
    IN_INT_PART_STATUS,
    IN_FRAC_PART_STATUS,
    DOT_STATUS,
} ParseStatus;

void
get_token(Token *token) {
    int out_pos = 0;
    ParseStatus status = INITIAL_STATUS;
    char current_char;
    string temp;

    token->kind = BAD_TOKEN;
    while (st_line[st_line_pos] != ‘\0‘) {
        current_char = st_line[st_line_pos];
        if ((status == IN_INT_PART_STATUS ||
             status == IN_FRAC_PART_STATUS) && !isdigit(current_char) && current_char != ‘.‘) {
            token->kind = NUMBER_TOKEN;
            sscanf(token->str, "%lf", &token->value);
            return;
        }
        if (isalpha(current_char)) {
            while (current_char != ‘=‘ && current_char != ‘;‘ && current_char != ‘<‘ && current_char != ‘>‘ &&
                   current_char != ‘+‘ && current_char != ‘-‘ && current_char != ‘*‘ && current_char != ‘/‘ &&
                   current_char != ‘(‘ && current_char != ‘)‘) {
                temp += current_char;
                token->str[out_pos] = st_line[st_line_pos];
                ++st_line_pos;
                ++out_pos;
                current_char = st_line[st_line_pos];
                token->str[out_pos + 1] = ‘\0‘;
                if (temp == "if") {
                    token->kind = IF_OPERATOR_TOKEN;
                    return;
                } else if (temp == "while") {
                    token->kind = WHILE_OPERATOR_TOKEN;
                    return;
                } else if (temp == "for") {
                    token->kind = FOR_PAREN_TOKEN;
                    return;
                } else if (temp == "int") {
                    token->kind = INT_TOKEN;
                    return;
                } else if (temp == "double") {
                    token->kind = DOUBLE_TOKEN;
                    return;
                } else if (temp == "string") {
                    token->kind = STRING_TOKEN;
                    return;
                } else if (temp == "cout") {
                    token->kind = COUT_TOKEN;
                    return;
                } else if (temp == "return") {
                    token->kind = RETURN_TOKEN;
                    return;
                } else if (temp == "main") {
                    token->kind = MAIN_TOKEN;
                    return;
                }
            }
            token->kind = VARIABLE_NAME_TOKEN;
            token->string_value = temp;
            token->str[out_pos] = ‘\0‘;
            return;
        }
        if ((current_char == ‘"‘ || current_char == ‘\‘‘) && status == INITIAL_STATUS) {
            current_char = st_line[++st_line_pos];
            while (current_char != ‘"‘ && current_char != ‘\‘‘) {
                token->str[out_pos] = st_line[st_line_pos];
                out_pos++;
                temp += current_char;
                current_char = st_line[++st_line_pos];
            }
            token->string_value = temp;
            token->kind = STRING_VARIABLE_TOKEN;
            st_line_pos++;
            token->str[++out_pos] = ‘\0‘;
            return;
        }
        if (isspace(current_char)) {
            if (status == INITIAL_STATUS) {
                st_line_pos++;
                continue;
            }
        }

        token->str[out_pos] = st_line[st_line_pos];
        st_line_pos++;
        out_pos++;
        token->str[out_pos] = ‘\0‘;

        if (current_char == ‘+‘) {
            if (st_line[st_line_pos] == ‘+‘) {
                token->str[out_pos] = st_line[st_line_pos];
                token->str[out_pos + 1] = ‘\0‘;
                ++st_line_pos;
                token->kind = SELF_PLUS_ONE_OPERATOR_TOKEN;
                return;
            } else {
                token->kind = ADD_OPERATOR_TOKEN;
                return;
            }
        } else if (current_char == ‘-‘) {
            if (st_line[st_line_pos] == ‘-‘) {
                token->str[out_pos] = st_line[st_line_pos];
                token->str[out_pos + 1] = ‘\0‘;
                ++st_line_pos;
                token->kind = SELF_SUB_ONE_OPERATOR_TOKEN;
                return;
            } else {
                token->kind = SUB_OPERATOR_TOKEN;
                return;
            }
        } else if (current_char == ‘<‘) {
            if (st_line[st_line_pos] == ‘<‘) {
                token->str[out_pos] = st_line[st_line_pos];
                token->str[out_pos + 1] = ‘\0‘;
                ++st_line_pos;
                token->kind = OUT_OPERATER_TOKEN;
                return;
            } else {
                token->kind = LESS_OPERATER_TOKEN;
                return;
            }
        } else if (current_char == ‘>‘) {
            if (st_line[st_line_pos] == ‘>‘) {
                token->str[out_pos] = st_line[st_line_pos];
                token->str[out_pos + 1] = ‘\0‘;
                ++st_line_pos;
                token->kind = GET_OPERATER_TOKEN;
                return;
            } else {
                token->kind = GREATE_OPERATER_TOKEN;
                return;
            }
        } else if (current_char == ‘*‘) {
            token->kind = MUL_OPERATOR_TOKEN;
            return;
        } else if (current_char == ‘/‘) {
            token->kind = DIV_OPERATOR_TOKEN;
            return;
        } else if (current_char == ‘;‘) {
            token->kind = END_OF_LINE_TOKEN;
            return;
        } else if (current_char == ‘{‘) {
            token->kind = LEFT_BRACE_TOKEN;
            return;
        } else if (current_char == ‘}‘) {
            token->kind = RIGHT_BRACE_TOKEN;
            return;
        } else if (current_char == ‘(‘) {
            token->kind = LEFT_PARENTHESS_TOKEN;
            return;
        } else if (current_char == ‘)‘) {
            token->kind = RIGHT_PARENTHESE_TOKEN;
            return;
        } else if (current_char == ‘=‘) {
            if (st_line[st_line_pos] == ‘=‘) {
                token->kind = EQUAL_PAREN_TOKEN;
                return;
            } else {
                token->kind = ASSIGMENT_PAREN_TOKEN;
                return;
            }
        } else if (isdigit(current_char)) {
            if (status == INITIAL_STATUS) {
                status = IN_INT_PART_STATUS;
            } else if (status == DOT_STATUS) {
                status = IN_FRAC_PART_STATUS;
            }
        } else if (current_char == ‘.‘) {
            if (status == IN_INT_PART_STATUS) {
                status = DOT_STATUS;
            } else {
                fprintf(stderr, "syntax error.\n");
                exit(1);
            }
        }
    }
}

//void
//set_line(char *line) {
//    st_line = line;
//    st_line_pos = 0;
//}

void
parse_line(string filename) {
    Token token;
    st_line_pos = 0;
    char temp, test[1024];
    ifstream get;
    get.open(filename);
    int i = 0;
    while (!get.eof()) {
        get.read(&temp, 1);
        test[i++] = temp;
    }
    length = i;
    st_line = test;
    for (;;) {
        get_token(&token);
        if (st_line_pos == length) {
            return;
        }
        printf("kind..%d, str..%s\n", token.kind, token.str);
    }
}

int main() {
    string filename = "/home/liuyu/文档/test";
    parse_line(filename);
    return 0;
}

//learn.h

#ifndef LEARN_LEARN_H
#define LEARN_LEARN_H

#include <iostream>
using namespace std;

typedef enum {
    BAD_TOKEN,
    NUMBER_TOKEN,
    STRING_TOKEN,
    INT_TOKEN,
    DOUBLE_TOKEN,
    COUT_TOKEN,
    RETURN_TOKEN,
    MAIN_TOKEN,
    IF_OPERATOR_TOKEN,
    OUT_OPERATER_TOKEN,
    GET_OPERATER_TOKEN,
    LESS_OPERATER_TOKEN,
    GREATE_OPERATER_TOKEN,
    LEFT_BRACE_TOKEN,
    RIGHT_BRACE_TOKEN,
    LEFT_PARENTHESS_TOKEN,
    RIGHT_PARENTHESE_TOKEN,
    WHILE_OPERATOR_TOKEN,
    EQUAL_PAREN_TOKEN,
    FOR_PAREN_TOKEN,
    ASSIGMENT_PAREN_TOKEN,
    END_OF_LINE_TOKEN,
    VARIABLE_NAME_TOKEN,
    STRING_VARIABLE_TOKEN,
    ADD_OPERATOR_TOKEN,
    SUB_OPERATOR_TOKEN,
    MUL_OPERATOR_TOKEN,
    DIV_OPERATOR_TOKEN,
    SELF_PLUS_ONE_OPERATOR_TOKEN,
    SELF_SUB_ONE_OPERATOR_TOKEN,
    END_TOKEN
} TokenKind;

#define MAX_TOKEN_SIZE (100)

typedef struct {
    TokenKind kind;
    double      value;
    string      string_value;
    char        str[MAX_TOKEN_SIZE];
} Token;

void set_line(char *line);
void get_token(Token *token);

#endif

测试：