diff --git a/Knot.files b/Knot.files
index 2d42bf6a0ca9014a402777da2bc50370adf3a31a..50c9fd64b7f16a71b19bfe943891e1fb37a045d1 100644
--- a/Knot.files
+++ b/Knot.files
@@ -107,6 +107,10 @@ src/common/general-tree.h
src/common/general-tree.c
src/common/WELL1024a.c
src/common/WELL1024a.h
+src/common/os_fdset.h
+src/common/os_fdset.c
+src/common/os_fdset_poll.c
+src/common/os_fdset_epoll.c
src/zcompile/parser-descriptor.h
src/zcompile/parser-descriptor.c
src/zcompile/parser-util.h
diff --git a/src/Makefile.am b/src/Makefile.am
index 82778ec524a1128498e7fb10fabb737149eefaf0..34065ef0f27a3963a79d230fbe91f03cd0260f6a 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -175,8 +175,10 @@ libknots_la_SOURCES = \
common/ref.c \
common/errors.h \
common/errors.c \
- common/WELL1024a.h \
- common/WELL1024a.c
+ common/WELL1024a.h \
+ common/WELL1024a.c \
+ common/os_fdset.h \
+ common/os_fdset.c
libknotd_la_SOURCES = \
knot/stat/gatherer.c \
diff --git a/src/common/os_fdset.c b/src/common/os_fdset.c
new file mode 100644
index 0000000000000000000000000000000000000000..1bbe1222fc062e55fd83b2c0779f483a58fef7cc
--- /dev/null
+++ b/src/common/os_fdset.c
@@ -0,0 +1,7 @@
+#include "os_fdset.h"
+
+#ifdef HAVE_EPOLL
+#include "os_fdset_epoll.c"
+#else
+#include "os_fdset_poll.c"
+#endif
diff --git a/src/common/os_fdset.h b/src/common/os_fdset.h
new file mode 100644
index 0000000000000000000000000000000000000000..3dcbbbc76b2337681ed1b7fbe3851aa022064b88
--- /dev/null
+++ b/src/common/os_fdset.h
@@ -0,0 +1,139 @@
+/*!
+ * \file os_fdset.h
+ *
+ * \author Marek Vavrusa <marek.vavrusa@nic.cz>
+ *
+ * \brief Wrapper for native I/O multiplexing.
+ *
+ * Selects best implementation according to config.
+ * - select()
+ * - poll() \todo
+ * - epoll()
+ * - kqueue()
+ *
+ * \addtogroup common_lib
+ * @{
+ */
+
+#ifndef _KNOTD_OS_FDSET_H_
+#define _KNOTD_OS_FDSET_H_
+
+#include <stddef.h>
+
+/*! \brief Opaque pointer to implementation-specific fdset data. */
+struct os_fdset_t;
+
+/*! \brief Single event descriptor. */
+typedef struct os_fd_t {
+ int fd;
+ int events;
+ size_t pos;
+} os_fd_t;
+
+/*! \brief Unified event types. */
+enum os_ev_t {
+ OS_EV_READ = 1 << 0,
+ OS_EV_WRITE = 1 << 1,
+ OS_EV_ERROR = 1 << 2
+};
+
+/*!
+ * \brief Create new fdset.
+ *
+ * FDSET implementation depends on system.
+ *
+ * \retval Pointer to initialized FDSET structure if successful.
+ * \retval NULL on error.
+ */
+struct os_fdset_t *os_fdset_new();
+
+/*!
+ * \brief Destroy FDSET.
+ *
+ * \retval 0 if successful.
+ * \retval -1 on error.
+ */
+int os_fdset_destroy(struct os_fdset_t * fdset);
+
+/*!
+ * \brief Add file descriptor to watched set.
+ *
+ * \param fdset Target set.
+ * \param fd Added file descriptor.
+ * \param events Mask of watched events.
+ *
+ * \retval 0 if successful.
+ * \retval -1 on errors.
+ */
+int os_fdset_add(struct os_fdset_t *fdset, int fd, int events);
+
+/*!
+ * \brief Remove file descriptor from watched set.
+ *
+ * \param fdset Target set.
+ * \param fd File descriptor to be removed.
+ *
+ * \retval 0 if successful.
+ * \retval -1 on errors.
+ */
+int os_fdset_remove(struct os_fdset_t *fdset, int fd);
+
+/*!
+ * \brief Poll set for new events.
+ *
+ * \param fdset Target set.
+ *
+ * \retval Number of events if successful.
+ * \retval -1 on errors.
+ *
+ * \todo Timeout.
+ */
+int os_fdset_poll(struct os_fdset_t *fdset);
+
+/*!
+ * \brief Set event iterator to the beginning of last polled events.
+ *
+ * \param fdset Target set.
+ * \param it Event iterator.
+ *
+ * \retval 0 if successful.
+ * \retval -1 on errors.
+ */
+int os_fdset_begin(struct os_fdset_t *fdset, os_fd_t *it);
+
+/*!
+ * \brief Set event iterator to the end of last polled events.
+ *
+ * \param fdset Target set.
+ * \param it Event iterator.
+ *
+ * \retval 0 if successful.
+ * \retval -1 on errors.
+ */
+int os_fdset_end(struct os_fdset_t *fdset, os_fd_t *it);
+
+/*!
+ * \brief Set event iterator to the next event.
+ *
+ * Event iterator fd will be set to -1 if next event doesn't exist.
+ *
+ * \param fdset Target set.
+ * \param it Event iterator.
+ *
+ * \retval 0 if successful.
+ * \retval -1 on errors.
+ */
+int os_fdset_next(struct os_fdset_t *fdset, os_fd_t *it);
+
+
+/*!
+ * \brief Returned name of underlying poll method.
+ *
+ * \retval Name if successful.
+ * \retval NULL if no method was loaded (shouldn't happen).
+ */
+const char* os_fdset_method();
+
+#endif /* _KNOTD_OS_FDSET_H_ */
+
+/*! @} */
diff --git a/src/common/os_fdset_epoll.c b/src/common/os_fdset_epoll.c
new file mode 100644
index 0000000000000000000000000000000000000000..5e8b20b5e3cf3a235491ff89b27764987af650c1
--- /dev/null
+++ b/src/common/os_fdset_epoll.c
@@ -0,0 +1,3 @@
+#include "os_fdset.h"
+
+
diff --git a/src/common/os_fdset_poll.c b/src/common/os_fdset_poll.c
new file mode 100644
index 0000000000000000000000000000000000000000..7340ef8474eb2c862edb567406e0ab8f6402b7fd
--- /dev/null
+++ b/src/common/os_fdset_poll.c
@@ -0,0 +1,191 @@
+#include <stdlib.h>
+#include <string.h>
+#include <sys/poll.h>
+#include <stddef.h>
+
+#include "os_fdset.h"
+
+struct os_fdset_t {
+ struct pollfd *fds;
+ nfds_t nfds;
+ size_t reserved;
+ size_t polled;
+ size_t begin;
+};
+
+struct os_fdset_t *os_fdset_new()
+{
+ struct os_fdset_t *set = malloc(sizeof(struct os_fdset_t));
+ if (!set) {
+ return 0;
+ }
+
+ /* Blank memory. */
+ memset(set, 0, sizeof(struct os_fdset_t));
+ return set;
+}
+
+int os_fdset_destroy(struct os_fdset_t * fdset)
+{
+ if(!fdset) {
+ return -1;
+ }
+
+ /*! \todo No teardown required I guess. */
+
+ /* OK if NULL. */
+ free(fdset->fds);
+ free(fdset);
+ return 0;
+}
+
+int os_fdset_add(struct os_fdset_t *fdset, int fd, int events)
+{
+ if (!fdset || fd < 0 || events <= 0) {
+ return -1;
+ }
+
+ /* Realloc needed. */
+ if (fdset->nfds == fdset->reserved) {
+ const size_t chunk = 8;
+ const size_t nsize = sizeof(struct pollfd) * (fdset->reserved + chunk);
+ struct pollfd *fds_n = malloc(nsize);
+ if (!fds_n) {
+ return -1;
+ }
+
+ /* Clear and copy old fdset data. */
+ memset(fds_n, 0, nsize);
+ memcpy(fds_n, fdset->fds, fdset->nfds * sizeof(struct pollfd));
+ free(fdset->fds);
+ fdset->fds = fds_n;
+ fdset->reserved += chunk;
+ }
+
+ /* Append. */
+ int nid = fdset->nfds++;
+ fdset->fds[nid].fd = fd;
+ fdset->fds[nid].events = POLLIN; /*! \todo Map events to POLL events. */
+ return 0;
+}
+
+int os_fdset_remove(struct os_fdset_t *fdset, int fd)
+{
+ if (!fdset || fd < 0) {
+ return -1;
+ }
+
+ /* Find file descriptor. */
+ unsigned found = 0;
+ size_t pos = 0;
+ for (size_t i = 0; i < fdset->nfds; ++i) {
+ if (fdset->fds[i].fd == fd) {
+ found = 1;
+ pos = i;
+ break;
+ }
+ }
+
+ /* Check. */
+ if (!found) {
+ return -1;
+ }
+
+ /* Overwrite current item. */
+ size_t remaining = ((fdset->nfds - pos) - 1) * sizeof(struct pollfd);
+ memmove(fdset->fds + pos, fdset->fds + (pos + 1), remaining);
+ --fdset->nfds;
+
+ /*! \todo Return memory if overallocated (nfds is far lower than reserved). */
+ return 0;
+}
+
+int os_fdset_poll(struct os_fdset_t *fdset)
+{
+ if (!fdset || fdset->nfds < 1 || !fdset->fds) {
+ return -1;
+ }
+
+ /* Initialize pointers. */
+ fdset->polled = 0;
+ fdset->begin = 0;
+
+ /* Poll for events. */
+ int ret = poll(fdset->fds, fdset->nfds, -1);
+ if (ret < 0) {
+ return -1;
+ }
+
+ /* Set pointers for iterating. */
+ fdset->polled = ret;
+ fdset->begin = 0;
+ return ret;
+}
+
+int os_fdset_begin(struct os_fdset_t *fdset, os_fd_t *it)
+{
+ if (!fdset || !it) {
+ return -1;
+ }
+
+ /* Find first. */
+ it->pos = 0;
+ return os_fdset_next(fdset, it);
+}
+
+int os_fdset_end(struct os_fdset_t *fdset, os_fd_t *it)
+{
+ if (!fdset || !it || fdset->nfds < 1) {
+ return -1;
+ }
+
+ /* Check for polled events. */
+ if (fdset->polled < 1) {
+ it->fd = -1;
+ it->pos = 0;
+ return -1;
+ }
+
+ /* Trace last matching item from the end. */
+ struct pollfd* pfd = fdset->fds + fdset->nfds - 1;
+ while (pfd != fdset->fds) {
+ if (pfd->events & pfd->revents) {
+ it->fd = pfd->fd;
+ it->pos = pfd - fdset->fds;
+ return 0;
+ }
+ }
+
+ /* No end found, ends on the beginning. */
+ it->fd = -1;
+ it->pos = 0;
+ return -1;
+}
+
+int os_fdset_next(struct os_fdset_t *fdset, os_fd_t *it)
+{
+ if (!fdset || !it || fdset->nfds < 1) {
+ return -1;
+ }
+
+ /* Find next with matching flags. */
+ for (; it->pos < fdset->nfds; ++it->pos) {
+ struct pollfd* pfd = fdset->fds + it->pos;
+ if (pfd->events & pfd->revents) {
+ it->fd = pfd->fd;
+ it->events = pfd->revents; /*! \todo MAP events. */
+ ++it->pos; /* Next will start after current. */
+ return 0;
+ }
+ }
+
+ /* No matching event found. */
+ it->fd = -1;
+ it->pos = 0;
+ return -1;
+}
+
+const char* os_fdset_method()
+{
+ return "poll";
+}