Simple Quick Recursive Descent Parser

main.c

/*
    Recursive Descent Parser
    by DreamVB
*/

#include <stdio.h>
#include <stdlib.h>

#define MAX_TOKEN 255

char *src;
char ch = '\0';
char token[MAX_TOKEN];

int pi = 0;
int ti = 0;

enum T_TOKEN{
    DIGIT = 1,
    ALPHA,
    QSTRING,
    SYMBOL,
    EOP
}token_type;

int buffer_size = 0;

int get_filesize(char *Filename){
    FILE *fp = NULL;
    int f_size = 0;
    fp = fopen(Filename,"rb");
    //Move to end of file
    fseek(fp,0,SEEK_END);
    //Get the size of the file
    f_size = ftell(fp);
    //Close file
    fclose(fp);
    //Return file length
    return f_size;
}

void _GetProgramData(char * Filename){
    FILE *fp = NULL;
    int ti = 0;
    char ch = '\0';
    //Open source file
    fp = fopen(Filename,"rb");
        //While not end of file read data.
        while(!feof(fp)){
            if(!feof(fp)){
                //Read char
                ch = fgetc(fp);
                src[ti] = ch;
                //INC ti
                ti++;
            }
        }
    fclose(fp);
    src[ti - 1] = '\0';
}

int IsSym(char c){

    if(c == '+' || c == '-' || c == '*'
       || c == '/' || c == '='
       || c == '<' || c == '>' || c == '%'
       || c == '^' || c == '$' || c == '&'
       || c == '(' || c == ')'){
        return 1;
    }else{
        return 0;
    }
}

void CheckEOP(){
    if(pi >= buffer_size){
        token_type = EOP;
    }
}

void get_token(){
    ti = 0;

    CheckEOP();

    //Skip spaces
    while(isspace(src[pi]) && (pi < buffer_size)){
        pi++;
    }

    //Check for alpha
    if(isalpha(src[pi])){
        while(isalpha(src[pi])){
            token[ti] = src[pi];
            ti++;
            pi++;
        }
        token[ti] = '\0';
        token_type = ALPHA;
    //Check for quotes strings eg "hello world"
    }else if(src[pi] == '\"'){
        pi++;
        while(src[pi] != '\"'){
            token[ti] = src[pi];
            ti++;
            pi++;
        }
        token[ti] = '\0';
        token_type = QSTRING;
        pi++;
    //Check for digits
    }else if(isdigit(src[pi])){
        while(isdigit(src[pi])){
            token[ti] = src[pi];
            ti++;
            pi++;
        }
        token[ti] = '\0';
        token_type = DIGIT;
    }
    //Check for symbols
    else if(IsSym(src[pi])){
        while(IsSym(src[pi])){
            token[ti] = src[pi];
            pi++;
            ti++;
        }
        token[ti] = '\0';
        token_type = SYMBOL;
    }else{
        //Check if we have not hit the end of the code.
        CheckEOP();
    }
}

int main(int argc, char**argv)
{
    if(argc == 1){
        printf("TokenScan.exe program_name.bat\n");
        return 0;
    }

    //Get size of file.
    buffer_size = get_filesize(argv[1]);

    //Check we have a vaild length
    if(buffer_size == 0){
        printf("Program Data Not Found.\n");
        return 0;
    }

    //Resize program data array
    src = malloc(buffer_size);
    //Get program file data.
    _GetProgramData(argv[1]);

    //Get first token
    get_token();
    //While we are not at the end of the program code
    while(token_type != EOP){
        //Print token and token type
        printf("Token : %s\nType  : %d\n\n",token,token_type);
        //Get next token.
        get_token();
    }

    //Cleat up.
    free(src);
    free(token);

    return 0;
}