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-rw-r--r--src/shared/ring.c208
-rw-r--r--src/shared/ring.h59
2 files changed, 267 insertions, 0 deletions
diff --git a/src/shared/ring.c b/src/shared/ring.c
new file mode 100644
index 0000000000..8ae61234c7
--- /dev/null
+++ b/src/shared/ring.c
@@ -0,0 +1,208 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+ This file is part of systemd.
+
+ Copyright 2014 David Herrmann <dh.herrmann@gmail.com>
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/uio.h>
+#include "macro.h"
+#include "ring.h"
+
+#define RING_MASK(_r, _v) ((_v) & ((_r)->size - 1))
+
+void ring_flush(struct ring *r) {
+ assert(r);
+
+ r->start = 0;
+ r->used = 0;
+}
+
+void ring_clear(struct ring *r) {
+ free(r->buf);
+ zero(*r);
+}
+
+/*
+ * Get data pointers for current ring-buffer data. @vec must be an array of 2
+ * iovec objects. They are filled according to the data available in the
+ * ring-buffer. 0, 1 or 2 is returned according to the number of iovec objects
+ * that were filled (0 meaning buffer is empty).
+ *
+ * Hint: "struct iovec" is defined in <sys/uio.h> and looks like this:
+ * struct iovec {
+ * void *iov_base;
+ * size_t iov_len;
+ * };
+ */
+size_t ring_peek(struct ring *r, struct iovec *vec) {
+ assert(r);
+
+ if (r->used == 0) {
+ return 0;
+ } else if (r->start + r->used <= r->size) {
+ if (vec) {
+ vec[0].iov_base = &r->buf[r->start];
+ vec[0].iov_len = r->used;
+ }
+ return 1;
+ } else {
+ if (vec) {
+ vec[0].iov_base = &r->buf[r->start];
+ vec[0].iov_len = r->size - r->start;
+ vec[1].iov_base = r->buf;
+ vec[1].iov_len = r->used - (r->size - r->start);
+ }
+ return 2;
+ }
+}
+
+/*
+ * Copy data from the ring buffer into the linear external buffer @buf. Copy
+ * at most @size bytes. If the ring buffer size is smaller, copy less bytes and
+ * return the number of bytes copied.
+ */
+size_t ring_copy(struct ring *r, void *buf, size_t size) {
+ size_t l;
+
+ assert(r);
+ assert(buf);
+
+ if (size > r->used)
+ size = r->used;
+
+ if (size > 0) {
+ l = r->size - r->start;
+ if (size <= l) {
+ memcpy(buf, &r->buf[r->start], size);
+ } else {
+ memcpy(buf, &r->buf[r->start], l);
+ memcpy((uint8_t*)buf + l, r->buf, size - l);
+ }
+ }
+
+ return size;
+}
+
+/*
+ * Resize ring-buffer to size @nsize. @nsize must be a power-of-2, otherwise
+ * ring operations will behave incorrectly.
+ */
+static int ring_resize(struct ring *r, size_t nsize) {
+ uint8_t *buf;
+ size_t l;
+
+ assert(r);
+ assert(nsize > 0);
+
+ buf = malloc(nsize);
+ if (!buf)
+ return -ENOMEM;
+
+ if (r->used > 0) {
+ l = r->size - r->start;
+ if (r->used <= l) {
+ memcpy(buf, &r->buf[r->start], r->used);
+ } else {
+ memcpy(buf, &r->buf[r->start], l);
+ memcpy(&buf[l], r->buf, r->used - l);
+ }
+ }
+
+ free(r->buf);
+ r->buf = buf;
+ r->size = nsize;
+ r->start = 0;
+
+ return 0;
+}
+
+/*
+ * Resize ring-buffer to provide enough room for @add bytes of new data. This
+ * resizes the buffer if it is too small. It returns -ENOMEM on OOM and 0 on
+ * success.
+ */
+static int ring_grow(struct ring *r, size_t add) {
+ size_t need;
+
+ assert(r);
+
+ if (r->size - r->used >= add)
+ return 0;
+
+ need = r->used + add;
+ if (need <= r->used)
+ return -ENOMEM;
+ else if (need < 4096)
+ need = 4096;
+
+ need = ALIGN_POWER2(need);
+ if (need == 0)
+ return -ENOMEM;
+
+ return ring_resize(r, need);
+}
+
+/*
+ * Push @len bytes from @u8 into the ring buffer. The buffer is resized if it
+ * is too small. -ENOMEM is returned on OOM, 0 on success.
+ */
+int ring_push(struct ring *r, const void *u8, size_t size) {
+ int err;
+ size_t pos, l;
+
+ assert(r);
+ assert(u8);
+
+ if (size == 0)
+ return 0;
+
+ err = ring_grow(r, size);
+ if (err < 0)
+ return err;
+
+ pos = RING_MASK(r, r->start + r->used);
+ l = r->size - pos;
+ if (l >= size) {
+ memcpy(&r->buf[pos], u8, size);
+ } else {
+ memcpy(&r->buf[pos], u8, l);
+ memcpy(r->buf, (const uint8_t*)u8 + l, size - l);
+ }
+
+ r->used += size;
+
+ return 0;
+}
+
+/*
+ * Remove @len bytes from the start of the ring-buffer. Note that we protect
+ * against overflows so removing more bytes than available is safe.
+ */
+void ring_pull(struct ring *r, size_t size) {
+ assert(r);
+
+ if (size > r->used)
+ size = r->used;
+
+ r->start = RING_MASK(r, r->start + size);
+ r->used -= size;
+}
diff --git a/src/shared/ring.h b/src/shared/ring.h
new file mode 100644
index 0000000000..6b12530e31
--- /dev/null
+++ b/src/shared/ring.h
@@ -0,0 +1,59 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+#pragma once
+
+/***
+ This file is part of systemd.
+
+ Copyright 2014 David Herrmann <dh.herrmann@gmail.com>
+
+ systemd is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as published by
+ the Free Software Foundation; either version 2.1 of the License, or
+ (at your option) any later version.
+
+ systemd is distributed in the hope that it will be useful, but
+ WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public License
+ along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/uio.h>
+
+struct ring {
+ uint8_t *buf; /* buffer or NULL */
+ size_t size; /* actual size of @buf */
+ size_t start; /* start position of ring */
+ size_t used; /* number of actually used bytes */
+};
+
+/* flush buffer so it is empty again */
+void ring_flush(struct ring *r);
+
+/* flush buffer, free allocated data and reset to initial state */
+void ring_clear(struct ring *r);
+
+/* get pointers to buffer data and their length */
+size_t ring_peek(struct ring *r, struct iovec *vec);
+
+/* copy data into external linear buffer */
+size_t ring_copy(struct ring *r, void *buf, size_t size);
+
+/* push data to the end of the buffer */
+int ring_push(struct ring *r, const void *u8, size_t size);
+
+/* pull data from the front of the buffer */
+void ring_pull(struct ring *r, size_t size);
+
+/* return size of occupied buffer in bytes */
+static inline size_t ring_get_size(struct ring *r)
+{
+ return r->used;
+}
generated by cgit v1.2.3-54-g00ecf (git 2.45.2) at 2024-11-18 04:25:43 +0000