Custom BIOs

custom_bio.c

#include <string.h>
#include <stdlib.h>

#include "custom_bio.h"

BIO_METHOD dotter_method = {
    BIO_TYPE_FILTER,
    "dotter filter",
    dotter_write,
    dotter_read,
    NULL,
    NULL,
    NULL,
    dotter_new,
    NULL,
    NULL
};
BIO_METHOD* BIO_f_dotter() {
    return &dotter_method;
}
BIO_METHOD dasher_method = {
    BIO_TYPE_FILTER,
    "dasher filter",
    dasher_write,
    dasher_read,
    NULL,
    NULL,
    NULL,
    dasher_new,
    NULL,
    NULL
};
BIO_METHOD* BIO_f_dasher() {
    return &dasher_method;
}

int dotter_write(BIO* b, const char* text, int len) {
    if (text == NULL || len <= 0 || b->next_bio == NULL) return 0;

    int new_len = len * 2, i = 0;

    char new_text[new_len];

    for(; i < new_len; i++) {
        new_text[i] = i % 2 == 0 ? '.' : text[i / 2];
    }

    return BIO_write(b->next_bio, new_text, new_len);
}

int dotter_read(BIO* b, char* text, int len) {
    if (text == NULL || len <= 0 || b->next_bio == NULL) return 0;

    return BIO_read(b->next_bio, text, len);
}

int dotter_new(BIO* b) {
    b->init = 1; // BIOs need to be initialized.

    return 1;
}

int dasher_write(BIO* b, const char* text, int len) {
    if (text == NULL || len <= 0 || b->next_bio == NULL) return 0;

    int new_len = len * 2, i = 0;

    char new_text[new_len];

    for(; i < new_len; i++) {
        new_text[i] = i % 2 != 0 ? '-' : text[i / 2];
    }

    return BIO_write(b->next_bio, new_text, new_len);
}

int dasher_read(BIO* b, char* text, int len) {
    if (text == NULL || len <= 0 || b->next_bio == NULL) return 0;

    return BIO_read(b->next_bio, text, len);
}

int dasher_new(BIO* b) {
    b->init = 1; // BIOs need to be initialized.

    return 1;
}

custom_bio.h

#ifndef __CUSTOM_BIO__
#define __CUSTOM_BIO__

#include <openssl/bio.h>

BIO_METHOD* BIO_f_dotter();
BIO_METHOD* BIO_f_dasher();

int dotter_write(BIO*, const char*, int);
int dotter_read(BIO*, char*, int);
int dotter_new(BIO*);

int dasher_write(BIO*, const char*, int);
int dasher_read(BIO*, char*, int);
int dasher_new(BIO*);

#endif

main.c

#include <string.h>
#include <stdlib.h>

#include "custom_bio.h"

int main(int argc, char const *argv[]) {
    BIO *dotter, *dasher, *stdout_bio;

    dotter = BIO_new(BIO_f_dotter());
    dasher = BIO_new(BIO_f_dasher());

    stdout_bio = BIO_new_fp(stdout, BIO_NOCLOSE);

    // input -> dotter -> dasher -> output.
    BIO_push(dotter, dasher);
    BIO_push(dasher, stdout_bio);

    const char text[] = "foobar";
    BIO_write(dotter, text, strlen(text));
    BIO_flush(dotter);

    BIO_free_all(dotter);

    return EXIT_SUCCESS;
}