C中的链表和读取多个文件的问题

Question

Here is a problem I am trying to solve. I have a task to create a function, which has to return newline from the file(accessing with fd). It has to use only functions read , malloc , free and the functions I wrote.

I used linked lists to add and save the data from the files. 1 node represents 1 specific file.

Please help me find out what is the problem in this case. It works well in all cases except when BUFFER_SIZE is 1 and we gave him more than 2 file descriptors.

In the firs call of get_next_line function it reads well for first 2 file descriptors and returns the line properly. For the 3rd fd it returns 2nd file descriptors data. At the second call it returns 2nd line of each fd(1st and 2nd) and returns 1st line of 3rd file.

Here is the way I have to compile my files for using this function.

gcc -Wall -Wextra -Werror -D BUFFER_SIZE=1 get_next_line_bonus.c get_next_line_utils_bonus.c get_next_line.h main.c 

./a.out

get_next_line.h

# define GET_NEXT_LINE_H
# include <unistd.h>
# include <stdlib.h>

typedef struct  s_info
{

    int             fd;
    char            *info;
    int             check;
    struct s_info   *next;
}               t_info;

int             get_next_line(int fd, char **line);

t_info          *ft_lstnew(int fd);

char            *get_line(char *str);

int             ncheck(char *str);

unsigned long   ft_strlen(const char *s);

char            *get_save(char *save);

void            *ft_memmove(void *dest, const void *src, size_t len);

char            *ft_strjoin(char const *s1, char const *s2);

t_info          *ft_find(int fd, t_info **start);

int             ft_lstdelone(t_info **start, int fd);

#endif

get_next_line.c

size_t  ft_strlen(const char *s)
{
    int i;

    i = 0;
    if (!s)
        return (0);
    while (s[i] != '\0')
        i++;
    return (i);
}

char    *ft_strjoin(char const *s1, char const *s2)
{
    size_t  s1_len;
    size_t  s2_len;
    size_t  stot_len;
    char    *rtn;

    if (!s1 && !s2)
        return (0);
    s1_len = ft_strlen((char *)s1);
    s2_len = ft_strlen((char *)s2);
    stot_len = s1_len + s2_len + 1;
    rtn = malloc(sizeof(char) * stot_len);
    if (!rtn)
        return (0);
    ft_memmove(rtn, s1, s1_len);
    ft_memmove(rtn + s1_len, s2, s2_len);
    rtn[stot_len - 1] = '\0';
    free((char *)s1);
    return (rtn);
}

t_info  *ft_lstnew(int fd)
{
    t_info  *i;

    if ((i = (t_info*)malloc(sizeof(t_info))) == 0)
        return (0);
    i->fd = fd;
    if ((i->info = malloc(sizeof(char*) * (1 + BUFFER_SIZE))) == 0)
        return (0);
    i->check = 1;
    i->next = NULL;
    return (i);
}

t_info  *ft_find(int fd, t_info **start)
{
    t_info *finder;
    t_info *new;

    finder = *start;
    while (finder)
    {
        if (finder->fd == fd)
            return (finder);
        finder = finder->next;
    }
    if ((new = ft_lstnew(fd)) == 0)
        return (0);
    if (!(*start))
    {
        *start = new;
        return (new);
    }
    new->next = *start;
    *start = new;
    return (new);
}

int     get_next_line(int fd, char **line)
{
    static t_info   *start = NULL;
    t_info          *tmp;
    char            *buff;

    if (fd < 0 || !line || BUFFER_SIZE <= 0 ||
    ((tmp = ft_find(fd, &start)) == 0) ||
    !(buff = malloc(sizeof(char) * (BUFFER_SIZE + 1))))
        return (-1);
    while (!ncheck(tmp->info) && tmp->check != 0)
    {
        if ((tmp->check = read(fd, buff, BUFFER_SIZE)) == -1)
        {
            free(buff);
            return (-1);
        }
        buff[tmp->check] = '\0';
        tmp->info = ft_strjoin(tmp->info, buff);
    }
    free(buff);
    *line = get_line(tmp->info);
    tmp->info = get_save(tmp->info);
    if (tmp->check == 0)
        return (ft_lstdelone(&start, fd));
    return (1);
}

get_next_line_utils.c

char        *get_save(char *save)
{
    char    *rtn;
    int     i;
    int     j;

    i = 0;
    j = 0;
    if (!save)
        return (0);
    while (save[i] && save[i] != '\n')
        i++;
    if (!save[i])
    {
        free(save);
        return (0);
    }
    if (!(rtn = malloc(sizeof(char) * ((ft_strlen(save) - i) + 1))))
        return (0);
    i++;
    while (save[i])
        rtn[j++] = save[i++];
    rtn[j] = '\0';
    free(save);
    return (rtn);
}

char        *get_line(char *str)
{
    int     i;
    char    *rtn;

    i = 0;
    if (!str)
        return (0);
    while (str[i] && str[i] != '\n')
        i++;
    if (!(rtn = malloc(sizeof(char) * (i + 1))))
        return (0);
    i = 0;
    while (str[i] && str[i] != '\n')
    {
        rtn[i] = str[i];
        i++;
    }
    rtn[i] = '\0';
    return (rtn);
}

void        *ft_memmove(void *dst, const void *src, size_t len)
{
    char *d;
    char *s;

    d = (char *)dst;
    s = (char *)src;
    if (dst == src)
        return (dst);
    if (s < d)
    {
        while (len--)
            *(d + len) = *(s + len);
        return (dst);
    }
    while (len--)
        *d++ = *s++;
    return (dst);
}

int         ncheck(char *str)
{
    int i;

    i = 0;
    if (!str)
        return (0);
    while (str[i])
    {
        if (str[i] == '\n')
            return (1);
        i++;
    }
    return (0);
}

int         ft_lstdelone(t_info **start, int fd)
{
    t_info *finder;
    t_info *tmp;

    finder = *start;
    if (finder->fd == fd)
    {
        free(finder->info);
        *start = (*start)->next;
        free(finder);
    }
    else
    {
        while (finder->next->fd != fd && finder->next)
            finder = finder->next;
        free(finder->next->info);
        tmp = finder->next;
        finder->next = tmp->next;
        free(tmp);
    }
    return (0);
}

Here is the behaviour of my test main I used.

c1r6s3% gcc -Wall -Wextra -Werror -D BUFFER_SIZE=1 get_next_line_bonus.c get_next_line_utils_bonus.c get_next_line.h main.c &&./a.out

1st call

buffer1=t morning; should have arrived at 6:46, but train w

buffer2=1.Aasdasndmbc this is 1st line of 2nd file

buffer3=1.Aasdasndmbc this is not what supposed to be in 3rd file

2nd call

buffer1=as anhour late. Buda-Pesth seems a wonderful place, from the glimpse which Igot of it from the train

buffer2=2.Dcccsadkajskldjaskld

buffer3=1.Abc 1st line of 3rd file

buffer1=and the little I could walk through thestreets. I feared to go very far from the station, as we had arr

buffer2=3.Saksadklasjdlkasjd

buffer3=2.Dccc

buffer1=ivedlate and would start as near the correct time as possible. Theimpression I had was that we were leaving the West and entering theEast; the most western of splendid bridges over the Danube, which ish

buffer2=4.Sakdljlkasjdlkasjsadlkasjdklasjd

buffer3=3.Sak

Answer 1

During debug process I found out my nodes took the previous node's info. I wrote a small check in my get_next_line function. if(fd > 3 && BUFFER_SIZE == 1) // means this is not the first file to read && the specific case for BUFFER_SIZE tmp->info = NULL; It will not look at the same value as the previous so we can give him another value in our calls.