Creating an array of array of structures - c

Question

Objective
To create an array of an array of structs, the dimensions based on a file. Then store that into a Linked List.
I am reading from a file formatted like this:
Read a file that is in the form:
name (string) country (string) age (int)
john USA 54
Sam Aus 18
ect
I dont know how many rows and columns the file will have , nor do I know what varible type each column will be
So in theory the first array of struct will contain [NUMBER OF COLUMNS] strucs that will store each variable (using a void pointer and typecasting) along the line( so strucArrayCol[0] = john , structArrayCol[1] = USA ect).
Each of these array of strucs will be stored into another array of strucs which will have [NUMBER OF ROWS] elements so strucArray2Row[0] = strucArrayCol (which contains john , USA and 54) and strucArrayRow[1] will contain another strucArrayCol which contains (sam Aus 18).
So right now I can read the file, and find the number or rows, columns and the variable type of each column.
This is where i start having trouble as im not sure how to go about
1. How to create this array within array ( I know i need to use Malloc)
2.How I would store the variables in the first array of struc, if I
wanted to store age could I just do
void *data = malloc(sizeof(int));
*((int*)data) = TEMP_AGE;
void data being a struc in StrucArrayCol ( in the case of the example if I wanted to store the age of John void* data would be in StrucArrayCol[3] which is inside StucArrayRow[0], as its the 3rd col in the first line)
Sorry if this dosent make sense
Thanks

Answer 1

You can create a linked-list within a linked-list, assuming there is aversion to anything which is not a linked-list! Declare two linked-list node structures, one for rows in the file, and one for columns within each row:
struct column
{
char *buf;
struct column *next;
};
struct row
{
struct column *head;
struct row *next;
};
Read the file one line at a time, add one row node for each line. Each row will have its own link-lists, it will parse the line in to columns.
struct column* column_create(struct column* cursor, char *line)
{
struct column *node = malloc(sizeof(struct column));
node->next = 0;
node->buf = malloc(strlen(line) + 1);
strcpy(node->buf, line);
if (cursor)
cursor->next = node;
return node;
}
struct row* row_create(struct row* cursor, char *line)
{
struct row *node = malloc(sizeof(struct row));
node->next = 0;
node->head = 0;
//parse the line in to columns
struct column *col = 0;
char *token = strtok(line, " \n");
while (token)
{
col = column_create(col, token);
if (!node->head)
node->head = col;
token = strtok(NULL, " \n");
}
if (cursor)
cursor->next = node;
return node;
}
Or you can do this with a 2-dimensional array of text (which would be 3-dimensional array of characters). Or use an array of strings to hold all the lines in the file, then parse each line in to column. From there, you can test each column to see if it is integer or not.
If you don't know the number of lines in the file, use realloc to allocate as much memory is needed during run time. This example reads all the lines in file, and copies it to an array of lines:
int main()
{
FILE *f = fopen("test.txt", "r");
char **lines = 0;
int lines_size = 0;
int lines_capacity = 0;
char buf[1024];
while (fgets(buf, sizeof(buf), f))
{
int len = strlen(buf);
if (!len) continue;
if (lines_size == lines_capacity)
{
lines_capacity += 16;
lines = realloc(lines, lines_capacity * sizeof(char*));
}
lines[lines_size] = malloc(len + 1);
strcpy(lines[lines_size], buf);
lines_size++;
}
int i;
for (i = 0; i < lines_size; i++)
printf("%s", lines[i]);
printf("\n");
for (i = 0; i < lines_size; i++)
free(lines[i]);
free(lines);
return 0;
}
This will work as long as line length in the file never exceeds 1024. Separately, you can parse each line using strtok
void parseline(char *line)
{
char copy[1024];
strcpy(copy, line);
char *token = strtok(copy, " \n");
while (token)
{
printf("[%s], ", token);
token = strtok(NULL, " \n");
}
printf("\n");
}

Answer 2

You need a linked list in a linked list.
Barmak wrote how to get the data. So here is how to get the linked list.
struct sString{
char* str;
void* next_hor;
void* next_ver;
};
struct sInt{
char* Int;
void* next_hor;
void* next_ver;
};
in first column
if ( check type of column)
{for each row
{
generate corresponding struct and link it to previous element (add-function)
}
}
for other columns
{
( check type of column)
{for each row
{
generate corresponding struct and link it to previous element (add-function)
also iterate though linked list and insert the horizontal link
}
}
}
Its very clustered, has tons of overhead and is hard to manage but it should work.
The vertical pointer could also be of the right type as the types don't change in a column.