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void tmpfs_write(ipc_callid_t rid, ipc_call_t *request)

{

    int dev_handle = IPC_GET_ARG1(*request);

    unsigned long index = IPC_GET_ARG2(*request);

    off_t pos = IPC_GET_ARG3(*request);

    /*

     * Lookup the respective dentry.

     */

    link_t *hlp;

    hlp = hash_table_find(&dentries, &index);

    if (!hlp) {

        ipc_answer_0(rid, ENOENT);

        return;

    }

    tmpfs_dentry_t *dentry = hash_table_get_instance(hlp, tmpfs_dentry_t,

        dh_link);

    /*

     * Receive the write request.

     */

    ipc_callid_t callid;

    size_t size;

    if (!ipc_data_write_receive(&callid, NULL, &size)) {

        ipc_answer_0(callid, EINVAL);  

        ipc_answer_0(rid, EINVAL);

        return;

    }

    /*

     * At this point, we are deliberately extremely straightforward and

     * simply realloc the contents of the file on every write. In the end,

     * the situation might not be as bad as it may look: our heap allocator

     * can save us and just grow the block whenever possible.

     */

    void *newdata = realloc(dentry->data, size);

    if (!newdata) {

        ipc_answer_0(callid, ENOMEM);

        ipc_answer_1(rid, EOK, 0);

        return;

    }

    dentry->size = size;

    dentry->data = newdata;

    (void) ipc_data_write_deliver(callid, dentry->data + pos, size);

    /*

     * Answer the VFS_WRITE call.

     */

    ipc_answer_1(rid, EOK, size);

}