shared: add ring buffer
New "struct ring" object that implements a basic ring buffer for arbitrary byte-streams. A new basic runtime test is also added. This will be needed for our pty helpers for systemd-console and friends.
This commit is contained in:
David Herrmann
parent
625e870b4f
commit
e0dd92729e
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@ -180,6 +180,7 @@
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/test-path-util
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/test-prioq
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/test-replace-var
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/test-ring
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/test-rtnl
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/test-sched-prio
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/test-sleep
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@ -801,6 +801,8 @@ libsystemd_shared_la_SOURCES = \
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src/shared/clean-ipc.c \
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src/shared/login-shared.c \
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src/shared/login-shared.h \
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src/shared/ring.c \
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src/shared/ring.h \
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src/shared/async.c \
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src/shared/async.h
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@ -1198,6 +1200,7 @@ tests += \
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test-utf8 \
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test-ellipsize \
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test-util \
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test-ring \
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test-tmpfiles \
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test-namespace \
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test-date \
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@ -1325,6 +1328,12 @@ test_util_SOURCES = \
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test_util_LDADD = \
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libsystemd-core.la
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test_ring_SOURCES = \
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src/test/test-ring.c
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test_ring_LDADD = \
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libsystemd-core.la
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test_tmpfiles_SOURCES = \
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src/test/test-tmpfiles.c
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@ -0,0 +1,208 @@
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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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/***
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This file is part of systemd.
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Copyright 2014 David Herrmann <dh.herrmann@gmail.com>
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <inttypes.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/uio.h>
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#include "macro.h"
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#include "ring.h"
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#define RING_MASK(_r, _v) ((_v) & ((_r)->size - 1))
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void ring_flush(struct ring *r) {
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assert(r);
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r->start = 0;
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r->used = 0;
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}
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void ring_clear(struct ring *r) {
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free(r->buf);
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zero(*r);
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}
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/*
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* Get data pointers for current ring-buffer data. @vec must be an array of 2
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* iovec objects. They are filled according to the data available in the
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* ring-buffer. 0, 1 or 2 is returned according to the number of iovec objects
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* that were filled (0 meaning buffer is empty).
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*
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* Hint: "struct iovec" is defined in <sys/uio.h> and looks like this:
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* struct iovec {
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* void *iov_base;
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* size_t iov_len;
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* };
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*/
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size_t ring_peek(struct ring *r, struct iovec *vec) {
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assert(r);
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if (r->used == 0) {
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return 0;
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} else if (r->start + r->used <= r->size) {
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if (vec) {
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vec[0].iov_base = &r->buf[r->start];
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vec[0].iov_len = r->used;
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}
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return 1;
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} else {
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if (vec) {
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vec[0].iov_base = &r->buf[r->start];
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vec[0].iov_len = r->size - r->start;
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vec[1].iov_base = r->buf;
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vec[1].iov_len = r->used - (r->size - r->start);
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}
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return 2;
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}
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}
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/*
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* Copy data from the ring buffer into the linear external buffer @buf. Copy
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* at most @size bytes. If the ring buffer size is smaller, copy less bytes and
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* return the number of bytes copied.
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*/
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size_t ring_copy(struct ring *r, void *buf, size_t size) {
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size_t l;
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assert(r);
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assert(buf);
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if (size > r->used)
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size = r->used;
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if (size > 0) {
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l = r->size - r->start;
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if (size <= l) {
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memcpy(buf, &r->buf[r->start], size);
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} else {
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memcpy(buf, &r->buf[r->start], l);
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memcpy((uint8_t*)buf + l, r->buf, size - l);
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}
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}
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return size;
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}
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/*
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* Resize ring-buffer to size @nsize. @nsize must be a power-of-2, otherwise
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* ring operations will behave incorrectly.
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*/
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static int ring_resize(struct ring *r, size_t nsize) {
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uint8_t *buf;
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size_t l;
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assert(r);
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assert(nsize > 0);
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buf = malloc(nsize);
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if (!buf)
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return -ENOMEM;
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if (r->used > 0) {
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l = r->size - r->start;
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if (r->used <= l) {
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memcpy(buf, &r->buf[r->start], r->used);
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} else {
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memcpy(buf, &r->buf[r->start], l);
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memcpy(&buf[l], r->buf, r->used - l);
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}
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}
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free(r->buf);
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r->buf = buf;
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r->size = nsize;
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r->start = 0;
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return 0;
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}
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/*
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* Resize ring-buffer to provide enough room for @add bytes of new data. This
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* resizes the buffer if it is too small. It returns -ENOMEM on OOM and 0 on
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* success.
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*/
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static int ring_grow(struct ring *r, size_t add) {
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size_t need;
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assert(r);
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if (r->size - r->used >= add)
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return 0;
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need = r->used + add;
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if (need <= r->used)
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return -ENOMEM;
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else if (need < 4096)
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need = 4096;
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need = ALIGN_POWER2(need);
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if (need == 0)
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return -ENOMEM;
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return ring_resize(r, need);
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}
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/*
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* Push @len bytes from @u8 into the ring buffer. The buffer is resized if it
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* is too small. -ENOMEM is returned on OOM, 0 on success.
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*/
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int ring_push(struct ring *r, const void *u8, size_t size) {
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int err;
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size_t pos, l;
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assert(r);
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assert(u8);
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if (size == 0)
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return 0;
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err = ring_grow(r, size);
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if (err < 0)
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return err;
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pos = RING_MASK(r, r->start + r->used);
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l = r->size - pos;
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if (l >= size) {
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memcpy(&r->buf[pos], u8, size);
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} else {
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memcpy(&r->buf[pos], u8, l);
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memcpy(r->buf, (const uint8_t*)u8 + l, size - l);
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}
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r->used += size;
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return 0;
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}
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/*
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* Remove @len bytes from the start of the ring-buffer. Note that we protect
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* against overflows so removing more bytes than available is safe.
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*/
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void ring_pull(struct ring *r, size_t size) {
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assert(r);
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if (size > r->used)
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size = r->used;
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r->start = RING_MASK(r, r->start + size);
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r->used -= size;
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}
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@ -0,0 +1,59 @@
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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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#pragma once
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/***
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This file is part of systemd.
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Copyright 2014 David Herrmann <dh.herrmann@gmail.com>
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <inttypes.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/uio.h>
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struct ring {
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uint8_t *buf; /* buffer or NULL */
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size_t size; /* actual size of @buf */
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size_t start; /* start position of ring */
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size_t used; /* number of actually used bytes */
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};
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/* flush buffer so it is empty again */
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void ring_flush(struct ring *r);
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/* flush buffer, free allocated data and reset to initial state */
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void ring_clear(struct ring *r);
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/* get pointers to buffer data and their length */
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size_t ring_peek(struct ring *r, struct iovec *vec);
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/* copy data into external linear buffer */
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size_t ring_copy(struct ring *r, void *buf, size_t size);
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/* push data to the end of the buffer */
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int ring_push(struct ring *r, const void *u8, size_t size);
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/* pull data from the front of the buffer */
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void ring_pull(struct ring *r, size_t size);
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/* return size of occupied buffer in bytes */
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static inline size_t ring_get_size(struct ring *r)
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{
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return r->used;
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}
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@ -0,0 +1,135 @@
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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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/***
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This file is part of systemd.
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Copyright 2014 David Herrmann <dh.herrmann@gmail.com>
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <string.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <locale.h>
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#include <errno.h>
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#include "def.h"
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#include "ring.h"
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#include "util.h"
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static void test_ring(void) {
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static const char buf[8192];
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struct ring r;
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size_t l;
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struct iovec vec[2];
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int s;
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memset(&r, 0, sizeof(r));
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l = ring_peek(&r, vec);
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assert_se(l == 0);
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s = ring_push(&r, buf, 2048);
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assert_se(!s);
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assert_se(ring_get_size(&r) == 2048);
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l = ring_peek(&r, vec);
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assert_se(l == 1);
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assert_se(vec[0].iov_len == 2048);
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assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
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assert_se(ring_get_size(&r) == 2048);
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ring_pull(&r, 2048);
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assert_se(ring_get_size(&r) == 0);
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l = ring_peek(&r, vec);
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assert_se(l == 0);
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assert_se(ring_get_size(&r) == 0);
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s = ring_push(&r, buf, 2048);
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assert_se(!s);
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assert_se(ring_get_size(&r) == 2048);
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l = ring_peek(&r, vec);
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assert_se(l == 1);
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assert_se(vec[0].iov_len == 2048);
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assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
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assert_se(ring_get_size(&r) == 2048);
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s = ring_push(&r, buf, 1);
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assert_se(!s);
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assert_se(ring_get_size(&r) == 2049);
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l = ring_peek(&r, vec);
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assert_se(l == 2);
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assert_se(vec[0].iov_len == 2048);
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assert_se(vec[1].iov_len == 1);
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assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
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assert_se(!memcmp(vec[1].iov_base, buf, vec[1].iov_len));
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assert_se(ring_get_size(&r) == 2049);
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ring_pull(&r, 2048);
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assert_se(ring_get_size(&r) == 1);
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l = ring_peek(&r, vec);
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assert_se(l == 1);
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assert_se(vec[0].iov_len == 1);
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assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
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assert_se(ring_get_size(&r) == 1);
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ring_pull(&r, 1);
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assert_se(ring_get_size(&r) == 0);
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s = ring_push(&r, buf, 2048);
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assert_se(!s);
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assert_se(ring_get_size(&r) == 2048);
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s = ring_push(&r, buf, 2049);
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assert_se(!s);
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assert_se(ring_get_size(&r) == 4097);
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l = ring_peek(&r, vec);
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assert_se(l == 1);
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assert_se(vec[0].iov_len == 4097);
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assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
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assert_se(ring_get_size(&r) == 4097);
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ring_pull(&r, 1);
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assert_se(ring_get_size(&r) == 4096);
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s = ring_push(&r, buf, 4096);
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assert_se(!s);
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assert_se(ring_get_size(&r) == 8192);
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l = ring_peek(&r, vec);
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assert_se(l == 2);
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assert_se(vec[0].iov_len == 8191);
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assert_se(vec[1].iov_len == 1);
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assert_se(!memcmp(vec[0].iov_base, buf, vec[0].iov_len));
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assert_se(!memcmp(vec[1].iov_base, buf, vec[1].iov_len));
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assert_se(ring_get_size(&r) == 8192);
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ring_clear(&r);
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assert_se(ring_get_size(&r) == 0);
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}
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int main(int argc, char *argv[]) {
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log_parse_environment();
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log_open();
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test_ring();
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return 0;
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}
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