split_stream.cpp

split_stream.cpp

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

struct split_stream_pair {
    FILE* original_stream;
    FILE* auxiliary_stream;

    split_stream_pair(FILE* original_stream, FILE* auxiliary_stream) :
        original_stream(original_stream),
        auxiliary_stream(auxiliary_stream) { }
};
std::vector<split_stream_pair*> split_stream_pairs;


int split_stream_callback(void *cookie, const char *string, int bytes) {
    split_stream_pair* pair = (split_stream_pair*)cookie;
    if (!pair)
        return 0;

    fprintf(pair->original_stream, "%s", string);
    fprintf(pair->auxiliary_stream, "%s", string);
    syslog(LOG_WARNING, "%s", string);

    return bytes;
}

FILE* split_stream(FILE* in, FILE* out) {
    split_stream_pair* pair = new split_stream_pair(in, out);
    split_stream_pairs.push_back(pair);
    return fwopen((void*)pair, split_stream_callback);
}

void cleanup_split_streams() {
    std::vector<split_stream_pair*>::iterator it = split_stream_pairs.begin();
    for(; it != split_stream_pairs.end(); it++) {
        split_stream_pair* pair = *it;
        delete pair;
    }
    split_stream_pairs.clear();
}

int main(int argc, char** argv) {
    FILE* out = fopen("out.txt", "w+");
    FILE* split_stderr = split_stream(stderr, out);

    fprintf(split_stderr, "%d + %d = %d\n", 2, 3, 5);

    cleanup_split_streams();

    fclose(split_stderr);
    fclose(out);

    return EXIT_SUCCESS;
}