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authorRichard Braun <rbraun@sceen.net>2019-04-23 22:50:28 +0200
committerRichard Braun <rbraun@sceen.net>2019-04-24 01:17:49 +0200
commitcc2f34dc189074e8a93c03ebc5c0790661353b86 (patch)
treeb50c2e86e4b1d29bbc28ea52a9cff0de72a2df0b /src/mbuf.c
parent9d0f14ed6aa75cf39b57c4e7efd5a1713e8ff27a (diff)
mbuf: add support for variable-size message headersHEADmaster
Diffstat (limited to 'src/mbuf.c')
-rw-r--r--src/mbuf.c195
1 files changed, 145 insertions, 50 deletions
diff --git a/src/mbuf.c b/src/mbuf.c
index c7698bb..55624fb 100644
--- a/src/mbuf.c
+++ b/src/mbuf.c
@@ -1,5 +1,5 @@
/*
- * Copyright (c) 2018 Richard Braun.
+ * Copyright (c) 2018-2019 Richard Braun.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
@@ -25,6 +25,7 @@
#include <assert.h>
#include <errno.h>
+#include <limits.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
@@ -37,38 +38,100 @@
*
* The size denotes the size of the data, without the header.
*/
-struct mbuf_hdr {
- uint32_t size;
+union mbuf_hdr {
+ uint8_t size1;
+ uint16_t size2;
+ uint32_t size4;
+#ifdef __LP64__
+ uint64_t size8;
+#endif /* __LP64__ */
};
-static int
-mbuf_hdr_init(struct mbuf_hdr *hdr, size_t size)
+static size_t
+mbuf_compute_hdr_size(unsigned int order)
{
- hdr->size = size;
+ return order / CHAR_BIT;
+}
- if (hdr->size != size) {
- return EMSGSIZE;
+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;
}
-
- return 0;
}
static size_t
-mbuf_hdr_total_size(const struct mbuf_hdr *hdr)
+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)
{
- return sizeof(*hdr) + hdr->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_msg_size(const struct mbuf_hdr *hdr)
+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)
{
- return hdr->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)
+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
@@ -80,39 +143,47 @@ mbuf_clear(struct mbuf *mbuf)
static void
mbuf_clear_old_msgs(struct mbuf *mbuf, size_t total_size)
{
- struct mbuf_hdr hdr;
- size_t size;
- int error __unused;
+ 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 = sizeof(hdr);
- error = cbuf_pop(&mbuf->cbuf, &hdr, &size);
+ size_t msg_size, size;
+ int error __unused;
+
+ size = hdr_size;
+ error = cbuf_pop(&mbuf->cbuf, msg_size_addr, &size);
assert(!error);
if (size == 0) {
break;
}
- size = mbuf_hdr_msg_size(&hdr);
+ msg_size = mbuf_hdr_get_msg_size(&hdr, mbuf->order);
+ size = msg_size;
error = cbuf_pop(&mbuf->cbuf, NULL, &size);
- assert(!error && (size == mbuf_hdr_msg_size(&hdr)));
+ 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)
{
- struct mbuf_hdr hdr;
- size_t total_size;
- int error;
-
- error = mbuf_hdr_init(&hdr, size);
+ union mbuf_hdr hdr;
+ void *msg_size_addr;
+ size_t hdr_size, total_size;
+ int error __unused;
- if (error) {
- return error;
+ if (size > mbuf->max_msg_size) {
+ return EINVAL;
}
- total_size = mbuf_hdr_total_size(&hdr);
+ 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))) {
@@ -122,7 +193,10 @@ mbuf_push(struct mbuf *mbuf, const void *buf, size_t size, bool erase)
mbuf_clear_old_msgs(mbuf, total_size);
}
- error = cbuf_push(&mbuf->cbuf, &hdr, sizeof(hdr), erase);
+ 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);
@@ -133,39 +207,60 @@ mbuf_push(struct mbuf *mbuf, const void *buf, size_t size, bool erase)
int
mbuf_pop(struct mbuf *mbuf, void *buf, size_t *sizep)
{
- struct mbuf_hdr hdr;
- size_t start, size;
+ size_t start;
int error;
start = cbuf_start(&mbuf->cbuf);
+ error = mbuf_read(mbuf, &start, buf, sizep);
- size = sizeof(hdr);
- error = cbuf_read(&mbuf->cbuf, start, &hdr, &size);
- assert(!error);
+ 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 (size == 0) {
+ if (error) {
+ return error;
+ } else if (size == 0) {
return EAGAIN;
}
- assert(size == sizeof(hdr));
- size = mbuf_hdr_msg_size(&hdr);
+ assert(size == hdr_size);
+
+ msg_size = mbuf_hdr_get_msg_size(&hdr, mbuf->order);
- if (size > *sizep) {
+ if (msg_size > *sizep) {
error = EMSGSIZE;
goto out;
}
- cbuf_set_start(&mbuf->cbuf, start + sizeof(hdr));
- error = cbuf_pop(&mbuf->cbuf, buf, &size);
- assert(!error && (size == mbuf_hdr_msg_size(&hdr)));
+ 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 = size;
+ *sizep = msg_size;
return error;
}
-
-size_t
-mbuf_avail_size(const struct mbuf *mbuf)
-{
- return cbuf_avail_size(&mbuf->cbuf);
-}