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Buffer references #24

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119 buffer.c
@@ -149,6 +149,7 @@ static struct evbuffer_chain *evbuffer_expand_singlechain(struct evbuffer *buf,
size_t datlen);
static int evbuffer_ptr_subtract(struct evbuffer *buf, struct evbuffer_ptr *pos,
size_t howfar);
+static inline void evbuffer_chain_incref(struct evbuffer_chain *chain);
static struct evbuffer_chain *
evbuffer_chain_new(size_t size)
@@ -176,17 +177,29 @@ evbuffer_chain_new(size_t size)
*/
chain->buffer = EVBUFFER_CHAIN_EXTRA(u_char, chain);
+ chain->refcnt = 1;
+
return (chain);
}
static inline void
evbuffer_chain_free(struct evbuffer_chain *chain)
{
+ EVUTIL_ASSERT(chain->refcnt > 0);
+ if (--chain->refcnt > 0) {
+ // chain is still referenced by other chains
+ return;
+ }
+
if (CHAIN_PINNED(chain)) {
+ // will get freed once no longer dangling
+ chain->refcnt++;
chain->flags |= EVBUFFER_DANGLING;
return;
}
-
+
+ // safe to release chain, it's either a referencing
+ // chain or all references to it have been freed
if (chain->flags & EVBUFFER_REFERENCE) {
struct evbuffer_chain_reference *info =
EVBUFFER_CHAIN_EXTRA(
@@ -210,6 +223,21 @@ evbuffer_chain_free(struct evbuffer_chain *chain)
evbuffer_file_segment_free(info->segment);
}
}
+ if (chain->flags & EVBUFFER_MULTICAST) {
+ struct evbuffer_multicast_parent *info =
+ EVBUFFER_CHAIN_EXTRA(
+ struct evbuffer_multicast_parent,
+ chain);
+ // referencing chain is being freed, decrease
+ // refcounts of source chain and associated
+ // evbuffer (which get freed once both reach
+ // zero)
+ EVUTIL_ASSERT(info->source != NULL);
+ EVUTIL_ASSERT(info->parent != NULL);
+ EVBUFFER_LOCK(info->source);
+ evbuffer_chain_free(info->parent);
+ _evbuffer_decref_and_unlock(info->source);
+ }
mm_free(chain);
}
@@ -299,6 +327,12 @@ _evbuffer_chain_unpin(struct evbuffer_chain *chain, unsigned flag)
evbuffer_chain_free(chain);
}
+static inline void
+evbuffer_chain_incref(struct evbuffer_chain *chain)
+{
+ ++chain->refcnt;
+}
+
struct evbuffer *
evbuffer_new(void)
{
@@ -782,6 +816,46 @@ APPEND_CHAIN(struct evbuffer *dst, struct evbuffer *src)
dst->total_len += src->total_len;
}
+static inline void
+APPEND_CHAIN_MULTICAST(struct evbuffer *dst, struct evbuffer *src)
+{
+ struct evbuffer_chain *tmp;
+ struct evbuffer_chain *chain = src->first;
+ struct evbuffer_multicast_parent *extra;
+
+ ASSERT_EVBUFFER_LOCKED(dst);
+ ASSERT_EVBUFFER_LOCKED(src);
+
+ for (; chain; chain = chain->next) {
+ if (!chain->off || chain->flags & EVBUFFER_DANGLING) {
+ // skip empty chains
+ continue;
+ }
+
+ tmp = evbuffer_chain_new(sizeof(struct evbuffer_multicast_parent));
+ if (!tmp) {
+ event_warn("%s: out of memory", __func__);
+ return;
+ }
+ extra = EVBUFFER_CHAIN_EXTRA(struct evbuffer_multicast_parent, tmp);
+ // reference evbuffer containing source chain so it
+ // doesn't get released while the chain is still
+ // being referenced to
+ _evbuffer_incref(src);
+ extra->source = src;
+ // reference source chain which now becomes immutable
+ evbuffer_chain_incref(chain);
+ extra->parent = chain;
+ chain->flags |= EVBUFFER_IMMUTABLE;
+ tmp->buffer_len = chain->buffer_len;
+ tmp->misalign = chain->misalign;
+ tmp->off = chain->off;
+ tmp->flags |= EVBUFFER_MULTICAST|EVBUFFER_IMMUTABLE;
+ tmp->buffer = chain->buffer;
+ evbuffer_chain_insert(dst, tmp);
+ }
+}
+
static void
PREPEND_CHAIN(struct evbuffer *dst, struct evbuffer *src)
{
@@ -847,6 +921,49 @@ evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
}
int
+evbuffer_add_buffer_reference(struct evbuffer *outbuf, struct evbuffer *inbuf)
+{
+ size_t in_total_len, out_total_len;
+ struct evbuffer_chain *chain;
+ int result = 0;
+
+ EVBUFFER_LOCK2(inbuf, outbuf);
+ in_total_len = inbuf->total_len;
+ out_total_len = outbuf->total_len;
+ chain = inbuf->first;
+
+ if (in_total_len == 0)
+ goto done;
+
+ if (outbuf->freeze_end || outbuf == inbuf) {
+ result = -1;
+ goto done;
+ }
+
+ for (; chain; chain = chain->next) {
+ if ((chain->flags & (EVBUFFER_FILESEGMENT|EVBUFFER_SENDFILE|EVBUFFER_MULTICAST)) != 0) {
+ // chain type can not be referenced
+ result = -1;
+ goto done;
+ }
+ }
+
+ if (out_total_len == 0) {
+ /* There might be an empty chain at the start of outbuf; free
+ * it. */
+ evbuffer_free_all_chains(outbuf->first);
+ }
+ APPEND_CHAIN_MULTICAST(outbuf, inbuf);
+
+ outbuf->n_add_for_cb += in_total_len;
+ evbuffer_invoke_callbacks(outbuf);
+
+done:
+ EVBUFFER_UNLOCK2(inbuf, outbuf);
+ return result;
+}
+
+int
evbuffer_prepend_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
{
struct evbuffer_chain *pinned, *last;
View
@@ -183,6 +183,11 @@ struct evbuffer_chain {
/** a chain that should be freed, but can't be freed until it is
* un-pinned. */
#define EVBUFFER_DANGLING 0x0040
+ /** a chain that is a referenced copy of another chain */
+#define EVBUFFER_MULTICAST 0x0080
+
+ /** number of references to this chain */
+ int refcnt;
/** Usually points to the read-write memory belonging to this
* buffer allocated as part of the evbuffer_chain allocation.
@@ -240,6 +245,15 @@ struct evbuffer_file_segment {
ev_off_t length;
};
+/** Information about the multicast parent of a chain. Lives at the
+ * end of an evbuffer_chain with the EVBUFFER_MULTICAST flag set. */
+struct evbuffer_multicast_parent {
+ /** source buffer the multicast parent belongs to */
+ struct evbuffer *source;
+ /** multicast parent for this chain */
+ struct evbuffer_chain *parent;
+};
+
#define EVBUFFER_CHAIN_SIZE sizeof(struct evbuffer_chain)
/** Return a pointer to extra data allocated along with an evbuffer. */
#define EVBUFFER_CHAIN_EXTRA(t, c) (t *)((struct evbuffer_chain *)(c) + 1)
View
@@ -388,6 +388,22 @@ char *evbuffer_readln(struct evbuffer *buffer, size_t *n_read_out,
int evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf);
/**
+ Copy data from one evbuffer into another evbuffer.
+
+ This is a non-destructive add. The data from one buffer is copied
+ into the other buffer. However, no unnecessary memory copies occur.
+
+ Note that buffers already containing buffer references can't be added
+ to other buffers.
+
+ @param outbuf the output buffer
+ @param inbuf the input buffer
+ @return 0 if successful, or -1 if an error occurred
+ */
+int evbuffer_add_buffer_reference(struct evbuffer *outbuf,
+ struct evbuffer *inbuf);
+
+/**
A cleanup function for a piece of memory added to an evbuffer by
reference.
View
@@ -1521,6 +1521,111 @@ test_evbuffer_add_reference(void *ptr)
evbuffer_free(buf2);
}
+static void
+test_evbuffer_multicast(void *ptr)
+{
+ const char chunk1[] = "If you have found the answer to such a problem";
+ const char chunk2[] = "you ought to write it up for publication";
+ /* -- Knuth's "Notes on the Exercises" from TAOCP */
+ char tmp[16];
+ size_t len1 = strlen(chunk1), len2=strlen(chunk2);
+
+ struct evbuffer *buf1 = NULL, *buf2 = NULL;
+
+ buf1 = evbuffer_new();
+ tt_assert(buf1);
+
+ evbuffer_add(buf1, chunk1, len1);
+ evbuffer_add(buf1, ", ", 2);
+ evbuffer_add(buf1, chunk2, len2);
+ tt_int_op(evbuffer_get_length(buf1), ==, len1+len2+2);
+
+ buf2 = evbuffer_new();
+ tt_assert(buf2);
+
+ tt_int_op(evbuffer_add_buffer_reference(buf2, buf1), ==, 0);
+ // nested references are not allowed
+ tt_int_op(evbuffer_add_buffer_reference(buf2, buf2), ==, -1);
+ tt_int_op(evbuffer_add_buffer_reference(buf1, buf2), ==, -1);
+
+ // both buffers contain the same amount of data
+ tt_int_op(evbuffer_get_length(buf1), ==, evbuffer_get_length(buf1));
+
+ /* Make sure we can drain a little from the first buffer. */
+ tt_int_op(evbuffer_remove(buf1, tmp, 6), ==, 6);
+ tt_int_op(memcmp(tmp, "If you", 6), ==, 0);
+ tt_int_op(evbuffer_remove(buf1, tmp, 5), ==, 5);
+ tt_int_op(memcmp(tmp, " have", 5), ==, 0);
+
+ /* Make sure that prepending does not meddle with immutable data */
+ tt_int_op(evbuffer_prepend(buf1, "I have ", 7), ==, 0);
+ tt_int_op(memcmp(chunk1, "If you", 6), ==, 0);
+ evbuffer_validate(buf1);
+
+ /* Make sure we can drain a little from the second buffer. */
+ tt_int_op(evbuffer_remove(buf2, tmp, 6), ==, 6);
+ tt_int_op(memcmp(tmp, "If you", 6), ==, 0);
+ tt_int_op(evbuffer_remove(buf2, tmp, 5), ==, 5);
+ tt_int_op(memcmp(tmp, " have", 5), ==, 0);
+
+ /* Make sure that prepending does not meddle with immutable data */
+ tt_int_op(evbuffer_prepend(buf2, "I have ", 7), ==, 0);
+ tt_int_op(memcmp(chunk1, "If you", 6), ==, 0);
+ evbuffer_validate(buf2);
+
+ /* Make sure the data can be read from the second buffer when the first is freed */
+ evbuffer_free(buf1);
+ buf1 = NULL;
+
+ tt_int_op(evbuffer_remove(buf2, tmp, 6), ==, 6);
+ tt_int_op(memcmp(tmp, "I have", 6), ==, 0);
+
+ tt_int_op(evbuffer_remove(buf2, tmp, 6), ==, 6);
+ tt_int_op(memcmp(tmp, " foun", 6), ==, 0);
+
+end:
+ if (buf1)
+ evbuffer_free(buf1);
+ if (buf2)
+ evbuffer_free(buf2);
+}
+
+static void
+test_evbuffer_multicast_drain(void *ptr)
+{
+ const char chunk1[] = "If you have found the answer to such a problem";
+ const char chunk2[] = "you ought to write it up for publication";
+ /* -- Knuth's "Notes on the Exercises" from TAOCP */
+ size_t len1 = strlen(chunk1), len2=strlen(chunk2);
+
+ struct evbuffer *buf1 = NULL, *buf2 = NULL;
+
+ buf1 = evbuffer_new();
+ tt_assert(buf1);
+
+ evbuffer_add(buf1, chunk1, len1);
+ evbuffer_add(buf1, ", ", 2);
+ evbuffer_add(buf1, chunk2, len2);
+ tt_int_op(evbuffer_get_length(buf1), ==, len1+len2+2);
+
+ buf2 = evbuffer_new();
+ tt_assert(buf2);
+
+ tt_int_op(evbuffer_add_buffer_reference(buf2, buf1), ==, 0);
+ tt_int_op(evbuffer_get_length(buf2), ==, len1+len2+2);
+ tt_int_op(evbuffer_drain(buf1, evbuffer_get_length(buf1)), ==, 0);
+ tt_int_op(evbuffer_get_length(buf2), ==, len1+len2+2);
+ tt_int_op(evbuffer_drain(buf2, evbuffer_get_length(buf2)), ==, 0);
+ evbuffer_validate(buf1);
+ evbuffer_validate(buf2);
+
+end:
+ if (buf1)
+ evbuffer_free(buf1);
+ if (buf2)
+ evbuffer_free(buf2);
+}
+
/* Some cases that we didn't get in test_evbuffer() above, for more coverage. */
static void
test_evbuffer_prepend(void *ptr)
@@ -1811,6 +1916,8 @@ struct testcase_t evbuffer_testcases[] = {
{ "search", test_evbuffer_search, 0, NULL, NULL },
{ "callbacks", test_evbuffer_callbacks, 0, NULL, NULL },
{ "add_reference", test_evbuffer_add_reference, 0, NULL, NULL },
+ { "multicast", test_evbuffer_multicast, 0, NULL, NULL },
+ { "multicast_drain", test_evbuffer_multicast_drain, 0, NULL, NULL },
{ "prepend", test_evbuffer_prepend, TT_FORK, NULL, NULL },
{ "peek", test_evbuffer_peek, 0, NULL, NULL },
{ "freeze_start", test_evbuffer_freeze, 0, &nil_setup, (void*)"start" },