shared/ring: ring_contig

3 files changed, 43 insertions, 7 deletions

diff --git a/src/kernel/tests/util.c b/src/kernel/tests/util.c
index cf16b75..b7123b4 100644
--- a/src/kernel/tests/util.c
+++ b/src/kernel/tests/util.c
@@ -32,12 +32,23 @@ TEST(strcmp) {
 }
 
 TEST(ring) {
-	char backbuf[16];
+	char backbuf[16], cmpbuf[16];
 	size_t num_read = 0, num_written = 0;
 	uint8_t c;
 
 	ring_t r = {backbuf, 16, 0, 0};
 
+	// test aliasing
+	for (size_t i = 0; i < 16; i++) {
+		TEST_COND(ring_size(&r) == 0);
+		ring_put(&r, "11 bytes...", 11);
+		TEST_COND(ring_size(&r) == 11);
+
+		memset(cmpbuf, 0, sizeof cmpbuf);
+		TEST_COND(ring_get(&r, cmpbuf, 16) == 11);
+		TEST_COND(memcmp(cmpbuf, "11 bytes...", 11) == 0);
+	}
+
 	TEST_COND(ring_size(&r) == 0);
 	for (size_t i = 0; i < 7; i++)
 		ring_put1b(&r, num_written++);
diff --git a/src/shared/container/ring.c b/src/shared/container/ring.c
index 5073b4a..67944b0 100644
--- a/src/shared/container/ring.c
+++ b/src/shared/container/ring.c
@@ -1,6 +1,6 @@
 #include <shared/container/ring.h>
+#include <shared/mem.h>
 #include <stdbool.h>
-// TODO use memcpy
 
 static bool at_end(ring_t *r) {
 	return  r->_head + 1 == r->_tail
@@ -15,6 +15,7 @@ size_t ring_size(ring_t *r) {
 }
 
 void ring_put(ring_t *r, void *buf, size_t len) {
+	// TODO do something similar to ring_get
 	for (size_t i = 0; i < len; i++)
 		ring_put1b(r, ((uint8_t*)buf)[i]);
 }
@@ -26,10 +27,30 @@ void ring_put1b(ring_t *r, uint8_t byte) {
 }
 
 size_t ring_get(ring_t *r, void *buf, size_t len) {
-	for (size_t i = 0; i < len; i++) {
-		if (r->_head == r->_tail || at_end(r)) return i;
-		((uint8_t*)buf)[i] = r->buf[r->_tail++];
-		if (r->_tail >= r->capacity) r->_tail = 0;
+	size_t read = 0;
+	size_t plen;
+	void *pbuf;
+	for (size_t i = 0; i < 2; i++) {
+		plen = len - read;
+		pbuf = ring_contig(r, &plen);
+		if (buf) memcpy(buf + read, pbuf, plen);
+		read += plen;
 	}
-	return len;
+	return read;
+}
+
+void *ring_contig(ring_t *r, size_t *len) {
+	void *ret = &r->buf[r->_tail];
+	size_t avail;
+	if (r->_head >= r->_tail)
+		avail = r->_head - r->_tail;
+	else
+		avail = r->capacity - r->_tail;
+
+	if (*len > avail)
+		*len = avail;
+
+	r->_tail += *len;
+	if (r->_tail >= r->capacity) r->_tail = 0;
+	return ret;
 }
diff --git a/src/shared/container/ring.h b/src/shared/container/ring.h
index 219f4fb..bc978ce 100644
--- a/src/shared/container/ring.h
+++ b/src/shared/container/ring.h
@@ -14,3 +14,7 @@ void	ring_put(ring_t*, void*, size_t);
 void	ring_put1b(ring_t*, uint8_t);
 
 size_t	ring_get(ring_t*, void*, size_t);
+
+/** Consumes up to `len` bytes, and returns a pointer to the buffer where it's stored.
+ * Not thread-safe. */
+void*	ring_contig(ring_t*, size_t *len);