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authorRichard Braun <rbraun@sceen.net>2019-01-07 23:00:40 +0100
committerRichard Braun <rbraun@sceen.net>2019-04-24 01:09:03 +0200
commitb99a7a8477947305489d3fbc8db57e7e1511272e (patch)
tree088e34b97314b4d3b98cffeca7c7163b8eb77f22
parent558e96c137bdd7cf7b8f2fac0cadddeb32c830bc (diff)
kern/mbuf: new module
-rw-r--r--kern/Makefile1
-rw-r--r--kern/mbuf.c261
-rw-r--r--kern/mbuf.h125
3 files changed, 387 insertions, 0 deletions
diff --git a/kern/Makefile b/kern/Makefile
index 1d9559f3..19a15e5c 100644
--- a/kern/Makefile
+++ b/kern/Makefile
@@ -15,6 +15,7 @@ x15_SOURCES-y += \
kern/kmem.c \
kern/latomic.c \
kern/log.c \
+ kern/mbuf.c \
kern/mutex.c \
kern/panic.c \
kern/percpu.c \
diff --git a/kern/mbuf.c b/kern/mbuf.c
new file mode 100644
index 00000000..5ac06955
--- /dev/null
+++ b/kern/mbuf.c
@@ -0,0 +1,261 @@
+/*
+ * Copyright (c) 2018-2019 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Upstream site with license notes :
+ * http://git.sceen.net/rbraun/librbraun.git/
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <kern/macros.h>
+#include <kern/mbuf.h>
+
+/*
+ * Message header.
+ *
+ * The size denotes the size of the data, without the header.
+ */
+union mbuf_hdr {
+ uint8_t size1;
+ uint16_t size2;
+ uint32_t size4;
+#ifdef __LP64__
+ uint64_t size8;
+#endif /* __LP64__ */
+};
+
+static size_t
+mbuf_compute_hdr_size(unsigned int order)
+{
+ return order / CHAR_BIT;
+}
+
+static void *
+mbuf_hdr_get_msg_size_addr(union mbuf_hdr *hdr, unsigned int order)
+{
+ switch (order) {
+ case 8:
+ return &hdr->size1;
+ case 16:
+ return &hdr->size2;
+ default:
+#ifdef __LP64__
+ return &hdr->size8;
+ case 32:
+#endif /* __LP64__ */
+ return &hdr->size4;
+ }
+}
+
+static size_t
+mbuf_hdr_get_msg_size(const union mbuf_hdr *hdr, unsigned int order)
+{
+ switch (order) {
+ case 8:
+ return hdr->size1;
+ case 16:
+ return hdr->size2;
+ default:
+#ifdef __LP64__
+ return hdr->size8;
+ case 32:
+#endif /* __LP64__ */
+ return hdr->size4;
+ }
+}
+
+static void
+mbuf_hdr_init(union mbuf_hdr *hdr, unsigned int order, size_t size)
+{
+ switch (order) {
+ case 8:
+ assert(size <= UINT8_MAX);
+ hdr->size1 = size;
+ break;
+ case 16:
+ assert(size <= UINT16_MAX);
+ hdr->size2 = size;
+ break;
+ default:
+#ifdef __LP64__
+ hdr->size8 = size;
+ break;
+ case 32:
+ assert(size <= UINT32_MAX);
+#endif /* __LP64__ */
+ hdr->size4 = size;
+ }
+}
+
+static size_t
+mbuf_hdr_get_total_msg_size(const union mbuf_hdr *hdr, unsigned int order)
+{
+ return mbuf_compute_hdr_size(order) + mbuf_hdr_get_msg_size(hdr, order);
+}
+
+static unsigned int
+mbuf_compute_order(size_t max_msg_size)
+{
+ unsigned int order;
+
+ assert(max_msg_size != 0);
+ order = (sizeof(max_msg_size) * CHAR_BIT) - __builtin_clzl(max_msg_size);
+ return P2ROUND(order, CHAR_BIT);
+}
+
+void
+mbuf_init(struct mbuf *mbuf, void *buf, size_t capacity, size_t max_msg_size)
+{
+ cbuf_init(&mbuf->cbuf, buf, capacity);
+ mbuf->max_msg_size = max_msg_size;
+ mbuf->order = mbuf_compute_order(max_msg_size);
+}
+
+void
+mbuf_clear(struct mbuf *mbuf)
+{
+ return cbuf_clear(&mbuf->cbuf);
+}
+
+static void
+mbuf_clear_old_msgs(struct mbuf *mbuf, size_t total_size)
+{
+ union mbuf_hdr hdr;
+ void *msg_size_addr;
+ size_t hdr_size;
+
+ hdr_size = mbuf_compute_hdr_size(mbuf->order);
+ msg_size_addr = mbuf_hdr_get_msg_size_addr(&hdr, mbuf->order);
+
+ do {
+ size_t msg_size, size;
+ int error;
+
+ size = hdr_size;
+ error = cbuf_pop(&mbuf->cbuf, msg_size_addr, &size);
+ assert(!error);
+
+ if (size == 0) {
+ break;
+ }
+
+ msg_size = mbuf_hdr_get_msg_size(&hdr, mbuf->order);
+ size = msg_size;
+ error = cbuf_pop(&mbuf->cbuf, NULL, &size);
+ assert(!error && (size == msg_size));
+ } while (cbuf_avail_size(&mbuf->cbuf) < total_size);
+}
+
+int
+mbuf_push(struct mbuf *mbuf, const void *buf, size_t size, bool erase)
+{
+ union mbuf_hdr hdr;
+ void *msg_size_addr;
+ size_t hdr_size, total_size;
+ int error;
+
+ if (size > mbuf->max_msg_size) {
+ return EINVAL;
+ }
+
+ mbuf_hdr_init(&hdr, mbuf->order, size);
+
+ total_size = mbuf_hdr_get_total_msg_size(&hdr, mbuf->order);
+
+ if (total_size > cbuf_avail_size(&mbuf->cbuf)) {
+ if (!erase || (total_size > cbuf_capacity(&mbuf->cbuf))) {
+ return EMSGSIZE;
+ }
+
+ mbuf_clear_old_msgs(mbuf, total_size);
+ }
+
+ hdr_size = mbuf_compute_hdr_size(mbuf->order);
+ msg_size_addr = mbuf_hdr_get_msg_size_addr(&hdr, mbuf->order);
+
+ error = cbuf_push(&mbuf->cbuf, msg_size_addr, hdr_size, erase);
+ assert(!error);
+ error = cbuf_push(&mbuf->cbuf, buf, size, erase);
+ assert(!error);
+
+ return 0;
+}
+
+int
+mbuf_pop(struct mbuf *mbuf, void *buf, size_t *sizep)
+{
+ size_t start;
+ int error;
+
+ start = cbuf_start(&mbuf->cbuf);
+ error = mbuf_read(mbuf, &start, buf, sizep);
+
+ if (!error) {
+ cbuf_set_start(&mbuf->cbuf, start);
+ }
+
+ return error;
+}
+
+int
+mbuf_read(const struct mbuf *mbuf, size_t *indexp, void *buf, size_t *sizep)
+{
+ union mbuf_hdr hdr;
+ void *msg_size_addr;
+ size_t hdr_size, msg_size, size;
+ int error;
+
+ hdr_size = mbuf_compute_hdr_size(mbuf->order);
+ msg_size_addr = mbuf_hdr_get_msg_size_addr(&hdr, mbuf->order);
+
+ size = hdr_size;
+ error = cbuf_read(&mbuf->cbuf, *indexp, msg_size_addr, &size);
+
+ if (error) {
+ return error;
+ } else if (size == 0) {
+ return EAGAIN;
+ }
+
+ assert(size == hdr_size);
+
+ msg_size = mbuf_hdr_get_msg_size(&hdr, mbuf->order);
+
+ if (msg_size > *sizep) {
+ error = EMSGSIZE;
+ goto out;
+ }
+
+ size = msg_size;
+ error = cbuf_read(&mbuf->cbuf, *indexp + hdr_size, buf, &size);
+
+ if (error) {
+ goto out;
+ }
+
+ assert(size == msg_size);
+
+ *indexp += hdr_size + size;
+
+out:
+ *sizep = msg_size;
+ return error;
+}
diff --git a/kern/mbuf.h b/kern/mbuf.h
new file mode 100644
index 00000000..1c36afb5
--- /dev/null
+++ b/kern/mbuf.h
@@ -0,0 +1,125 @@
+/*
+ * Copyright (c) 2018-2019 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Upstream site with license notes :
+ * http://git.sceen.net/rbraun/librbraun.git/
+ *
+ *
+ * FIFO message buffer.
+ */
+
+#ifndef KERN_MBUF_H
+#define KERN_MBUF_H
+
+#include <stdbool.h>
+#include <stddef.h>
+
+#include <kern/cbuf.h>
+
+/*
+ * Message buffer.
+ *
+ * Message buffers are built on top of circular byte buffers. They provide
+ * discrete message transfer from a producer to a consumer.
+ *
+ * The order is computed from the maximum message size, and is used to
+ * determine a header size that can represent up to 2^order - 1 bytes.
+ */
+struct mbuf {
+ struct cbuf cbuf;
+ size_t max_msg_size;
+ unsigned int order;
+};
+
+static inline size_t
+mbuf_start(const struct mbuf *mbuf)
+{
+ return cbuf_start(&mbuf->cbuf);
+}
+
+static inline size_t
+mbuf_end(const struct mbuf *mbuf)
+{
+ return cbuf_end(&mbuf->cbuf);
+}
+
+/*
+ * Initialize a message buffer.
+ *
+ * The descriptor is set to use the given buffer for storage. Capacity
+ * must be a power-of-two.
+ */
+void mbuf_init(struct mbuf *mbuf, void *buf, size_t capacity,
+ size_t max_msg_size);
+
+/*
+ * Clear a message buffer.
+ */
+void mbuf_clear(struct mbuf *mbuf);
+
+/*
+ * Push a message to a message buffer.
+ *
+ * If the message doesn't fit in the message buffer, either because it is
+ * larger than the capacity, or because the function isn't allowed to erase
+ * old messages and the message buffer doesn't have enough available memory
+ * for the new message, EMSGSIZE is returned. If the message is larger than
+ * the maximum message size, EINVAL is returned.
+ */
+int mbuf_push(struct mbuf *mbuf, const void *buf, size_t size, bool erase);
+
+/*
+ * Pop a message from a message buffer.
+ *
+ * On entry, the sizep argument points to the size of the output buffer.
+ * On return, it is updated to the size of the message. If the message
+ * doesn't fit in the output buffer, it is not popped, EMSGSIZE is
+ * returned, but the sizep argument is updated nonetheless to let the
+ * user know the message size, to potentially retry with a larger buffer.
+ *
+ * If the buffer is empty, EAGAIN is returned, and the size of the output
+ * buffer is unmodified.
+ *
+ * The output buffer may be NULL, in which case this function acts as if
+ * it wasn't, but without writing output data.
+ */
+int mbuf_pop(struct mbuf *mbuf, void *buf, size_t *sizep);
+
+/*
+ * Read a message from a message buffer.
+ *
+ * On entry, the indexp argument points to the index of the message to
+ * read in the message buffer, and the sizep argument points to the size
+ * of the output buffer. On return, if successful, indexp is updated
+ * to the index of the next message, and sizep to the size of the
+ * message read.
+ *
+ * If the message doesn't fit in the output buffer, it is not read,
+ * EMSGSIZE is returned, and the sizep argument is updated nonetheless
+ * to let the user know the message size, to potentially retry with a
+ * larger buffer.
+ *
+ * If the given index refers to the end of the buffer, then EAGAIN is
+ * returned. If it's outside buffer boundaries, EINVAL is returned.
+ * Otherwise, if it doesn't point to the beginning of a message, the
+ * behavior is undefined.
+ *
+ * The message buffer isn't changed by this operation.
+ */
+int mbuf_read(const struct mbuf *mbuf, size_t *indexp,
+ void *buf, size_t *sizep);
+
+#endif /* KERN_MBUF_H */