read all file contents

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

void * fread_all(const char * filename) {
        FILE            * f = NULL;
        char            * buf = NULL, * buf_t = NULL;
        const size_t    m_shift = 14, m_thres = 1 << m_shift;
        size_t          buf_len = 0, read = 0, i = 0;

        f = fopen(filename, "r");
        if (!f) { return NULL; }

        buf = malloc(m_thres);
        if (!buf) { goto file_cleanup; }

        memset(buf, 0, m_thres);

        while (1) {
                buf_t = buf + buf_len;
                read = fread(buf_t, 1, m_thres, f);
                if (!read) { break; }

                buf_len += read;
                if (read != m_thres) { break; }

                buf_t = realloc(buf, ((buf_len >> m_shift) + 1) << m_shift);
                if (!buf_t) { goto buf_cleanup; }

                buf = buf_t;
                memset(buf + buf_len, 0, m_thres);
        }

        if (!buf_len) { goto buf_cleanup; }
        if (!buf) { goto file_cleanup; }

        // trim trailing \n's
        for (i = buf_len - 1; i; i--) {
                if (buf[i] == '\0') { continue; }
                if (buf[i] == '\n') {
                        buf[i] = '\0';
                        continue;
                }
                break;
        }

        goto ok;

buf_cleanup:
        if (buf) { free(buf); buf = NULL; }

ok:
file_cleanup:
        if (f) { fclose(f); f = NULL; }

        return buf;
}