buffer_write
ret = buffer_write(&out_buffer, buf, len);
buffer_write(&out_buffer, &ch, 1);
ret = buffer_write(&out_buffer, buf, len);
buffer_write(&out_buffer, &ch, 1);
static int buffer_write(BIO *h, const char *buf, int num);
buffer_write,
return buffer_write(b, str, strlen(str));