Reading and Saving Values from a CSV using C with Dynamic Allocation

Question

EDITS ON THE BOTTOM (I wrote this as an edit rather than its own question because it is so related):

I am writing a CSV reader that should save all the values as ch

Answer 1

try this

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

//https://tools.ietf.org/html/rfc4180
char *getCSVField(FILE *fp, char separator, int *state){
    int ch = fgetc(fp);

    if(ch == EOF)
        return NULL;

    size_t size = 1, index = 0;
    char *field = malloc(size);
    bool quoted_in = false;

    for(;ch != EOF; ch = fgetc(fp)){
        if(ch == '"'){
            if(quoted_in){
                int prefetch = fgetc(fp);
                if(prefetch == '"'){
                    ch = prefetch;
                } else {
                    quoted_in = false;
                    ungetc(prefetch, fp);
                    continue;
                }
            } else {
                quoted_in = true;
                continue;
            }
        } else if(!quoted_in && (ch == separator || ch == '\n')){
            break;
        }
        field[index++] = ch;
        char *temp = realloc(field, ++size);
        if(!temp){
            perror("realloc:");
            free(field);
            exit(EXIT_FAILURE);
        }
        field = temp;
    }
    field[index] = 0;
    *state = ch;
    if(quoted_in){
        fprintf(stderr, "The quotes is not closed.\n");
        free(field);
        return NULL;
    }
    return field;
}

char ***read_csv(const char *filename, size_t *rows, size_t *cols){
    *rows = *cols = 0;

    FILE *fp = fopen(filename, "r");
    if(!fp){
        fprintf(stderr, "%s can't open in %s\n", filename, __func__);
        perror("fopen");
        return NULL;
    }

    char *field;
    int state;
    size_t r = 0, c = 0;
    char ***mat = NULL;
    void *temp;

    while(field = getCSVField(fp, ',', &state)){
        if(c == 0){
            mat = realloc(mat, (r + 1)*sizeof(*mat));
            if(!mat){
                fprintf(stderr, "realloc failed in %s\n", __func__);
                exit(EXIT_FAILURE);
            }
            mat[r] = NULL;
        }
        mat[r] = realloc(mat[r], (c + 1)*sizeof(**mat));
        if(!mat[r]){
            fprintf(stderr, "realloc failed in %s\n", __func__);
            exit(EXIT_FAILURE);
        }
        mat[r][c++] = field;
        if(state == '\n' || state == EOF){
            if(*cols == 0){
                *cols = c;
            } else if(c != *cols){
                fprintf(stderr, "line %zu doesn't match number of columns in %s\n", r, filename);
                exit(EXIT_FAILURE);
            }
            c  = 0;
            *rows = ++r;
        }
    }
    fclose(fp);

    return mat;
}

#include <ctype.h>

char *trim(char *s){
    if(!s || !*s)
        return s;

    char *from, *to;

    for(from = s; *from && isspace((unsigned char)*from); ++from);
    for(to = s; *from;){
        *to++ = *from++;
    }
    *to = 0;
    while(s != to && isspace((unsigned char)to[-1])){
        *--to = 0;
    }
    return s;
}

int main(void){
    size_t rows, cols;
    char ***mat = read_csv("simp.csv", &rows, &cols);
    for(size_t r = 0; r < rows; ++r){
        for(size_t c = 0; c < cols; ++c){
            if(c)
                putchar(',');
            printf("%s", trim(mat[r][c]));
            free(mat[r][c]);
        }
        puts("");
        free(mat[r]);
    }
    free(mat);
    return 0;
}