[dpdk-dev] [PATCH 3/5] mbuf: new helper to write data in a mbuf chain

[Olivier Matz <olivier.matz@6wind.com>]

Introduce a new helper to write data in a chain of mbufs,
spreading it in the segments.

Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
---
 app/test/test_mbuf.c                 | 21 +++++++++++++++
 lib/librte_mbuf/rte_mbuf.c           | 44 +++++++++++++++++++++++++++++++
 lib/librte_mbuf/rte_mbuf.h           | 50 ++++++++++++++++++++++++++++++++++++
 lib/librte_mbuf/rte_mbuf_version.map |  6 +++++
 4 files changed, 121 insertions(+)

diff --git a/app/test/test_mbuf.c b/app/test/test_mbuf.c
index 7656a4d..5f1bc5d 100644
--- a/app/test/test_mbuf.c
+++ b/app/test/test_mbuf.c
@@ -335,6 +335,10 @@ testclone_testupdate_testdetach(void)
 	struct rte_mbuf *clone2 = NULL;
 	struct rte_mbuf *m2 = NULL;
 	unaligned_uint32_t *data;
+	uint32_t magic = MAGIC_DATA;
+	uint32_t check_data[2];
+
+	memset(check_data, 0, sizeof(check_data));
 
 	/* alloc a mbuf */
 	m = rte_pktmbuf_alloc(pktmbuf_pool);
@@ -421,6 +425,8 @@ testclone_testupdate_testdetach(void)
 	if (m2 == NULL)
 		GOTO_FAIL("cannot allocate m2");
 	rte_pktmbuf_append(m2, sizeof(uint32_t));
+	if (rte_pktmbuf_write(m2, 0, sizeof(uint32_t), &magic) < 0)
+		GOTO_FAIL("cannot write data in m2");
 	rte_pktmbuf_chain(m2, clone);
 	clone = NULL;
 
@@ -430,6 +436,21 @@ testclone_testupdate_testdetach(void)
 			rte_pktmbuf_pkt_len(m2) - sizeof(uint32_t)) == 0)
 		GOTO_FAIL("m2 data should be marked as shared");
 
+	/* check data content */
+	data = rte_pktmbuf_read(m2, 0, sizeof(uint32_t), check_data);
+	if (data == NULL)
+		GOTO_FAIL("cannot read data");
+	if (*data != MAGIC_DATA)
+		GOTO_FAIL("invalid data");
+	if (data == check_data)
+		GOTO_FAIL("data should not have been copied");
+	data = rte_pktmbuf_read(m2, 0, sizeof(uint32_t) * 2, check_data);
+	if (data == NULL)
+		GOTO_FAIL("cannot read data");
+	if (data[0] != MAGIC_DATA || data[1] != MAGIC_DATA)
+		GOTO_FAIL("invalid data");
+	if (data != check_data)
+		GOTO_FAIL("data should have been copied");
 	/* free mbuf */
 	rte_pktmbuf_free(m);
 	m = NULL;
diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
index b31958e..ed56193 100644
--- a/lib/librte_mbuf/rte_mbuf.c
+++ b/lib/librte_mbuf/rte_mbuf.c
@@ -298,6 +298,50 @@ void *__rte_pktmbuf_read(const struct rte_mbuf *m, uint32_t off,
 	return buf;
 }
 
+/* write len data bytes in a mbuf at specified offset (internal) */
+int
+__rte_pktmbuf_write(const struct rte_mbuf *m, uint32_t off,
+	uint32_t len, const void *buf)
+{
+	const struct rte_mbuf *seg = m;
+	uint32_t buf_off = 0, copy_len;
+	char *dst;
+
+	if (off + len > rte_pktmbuf_pkt_len(m))
+		return -1;
+
+	while (off >= rte_pktmbuf_data_len(seg)) {
+		off -= rte_pktmbuf_data_len(seg);
+		seg = seg->next;
+	}
+
+	dst = rte_pktmbuf_mtod_offset(seg, char *, off);
+	if (buf == dst)
+		return 0;
+
+	if (off + len <= rte_pktmbuf_data_len(seg)) {
+		RTE_ASSERT(!rte_pktmbuf_is_shared(seg));
+		rte_memcpy(dst, buf, len);
+		return 0;
+	}
+
+	/* copy data in several segments */
+	while (len > 0) {
+		RTE_ASSERT(!rte_pktmbuf_is_shared(seg));
+		copy_len = rte_pktmbuf_data_len(seg) - off;
+		if (copy_len > len)
+			copy_len = len;
+		dst = rte_pktmbuf_mtod_offset(seg, char *, off);
+		rte_memcpy(dst, (const char *)buf + buf_off, copy_len);
+		off = 0;
+		buf_off += copy_len;
+		len -= copy_len;
+		seg = seg->next;
+	}
+
+	return 0;
+}
+
 /*
  * Get the name of a RX offload flag. Must be kept synchronized with flag
  * definitions in rte_mbuf.h.
diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
index cd77a56..e898d25 100644
--- a/lib/librte_mbuf/rte_mbuf.h
+++ b/lib/librte_mbuf/rte_mbuf.h
@@ -1678,6 +1678,56 @@ static inline void *rte_pktmbuf_read(const struct rte_mbuf *m,
 }
 
 /**
+ * @internal used by rte_pktmbuf_write().
+ */
+int __rte_pktmbuf_write(const struct rte_mbuf *m, uint32_t off,
+	uint32_t len, const void *buf);
+
+/**
+ * Write len data bytes in a mbuf at specified offset.
+ *
+ * If the mbuf is contiguous between off and off+len, rte_memcpy() is
+ * called. Else, it will split the data in the segments.
+ *
+ * The caller must ensure that all destination segments are writable
+ * (not shared).
+ *
+ * If the destination pointer in the mbuf is the same than the source
+ * buffer, the function do nothing and is successful.
+ *
+ * If the mbuf is too small, the function fails.
+ *
+ * @param m
+ *   The pointer to the mbuf.
+ * @param off
+ *   The offset of the data in the mbuf.
+ * @param len
+ *   The amount of bytes to read.
+ * @param buf
+ *   The buffer where data is copied if it is not contiguous in mbuf
+ *   data. Its length should be at least equal to the len parameter.
+ * @return
+ *   - (0) on success (data is updated in the mbuf)
+ *   - (-1) on error: mbuf is too small or not writable
+ */
+static inline int rte_pktmbuf_write(const struct rte_mbuf *m,
+	uint32_t off, uint32_t len, const void *buf)
+{
+	char *dst = rte_pktmbuf_mtod_offset(m, char *, off);
+
+	if (buf == dst)
+		return 0;
+
+	if (off + len <= rte_pktmbuf_data_len(m)) {
+		RTE_ASSERT(!rte_pktmbuf_is_shared(m));
+		rte_memcpy(dst, buf, len);
+		return 0;
+	}
+
+	return __rte_pktmbuf_write(m, off, len, buf);
+}
+
+/**
  * Chain an mbuf to another, thereby creating a segmented packet.
  *
  * Note: The implementation will do a linear walk over the segments to find
diff --git a/lib/librte_mbuf/rte_mbuf_version.map b/lib/librte_mbuf/rte_mbuf_version.map
index 6e2ea84..b2c057e 100644
--- a/lib/librte_mbuf/rte_mbuf_version.map
+++ b/lib/librte_mbuf/rte_mbuf_version.map
@@ -35,3 +35,9 @@ DPDK_16.11 {
 	rte_get_tx_ol_flag_list;
 
 } DPDK_2.1;
+
+DPDK_17.02 {
+	global:
+
+	__rte_pktmbuf_write;
+} DPDK_16.11;
-- 
2.8.1