[dpdk-dev] [PATCH v3] eal: support strlcat function

[Bruce Richardson <bruce.richardson@intel.com>]

Add the strlcat function to DPDK to exist alongside the strlcpy one.
While strncat is generally safe for use for concatenation, the API for the
strlcat function is perhaps a little nicer to use, and supports truncation
detection.

See commit 5364de644a4b ("eal: support strlcpy function") for more
details on the function selection logic, since we only should be using the
DPDK-provided version when no system-provided version is present.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>

---
V3: fix compiler error by making the test function static
CC: Reshma Pattan <reshma.pattan@intel.com>

V2: place ternary operator with regular if statement for readability
CC: Ferruh Yigit <ferruh.yigit@intel.com>
---
 .../common/include/rte_string_fns.h           | 16 +++++++
 test/test/test_string_fns.c                   | 45 +++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/lib/librte_eal/common/include/rte_string_fns.h b/lib/librte_eal/common/include/rte_string_fns.h
index 9a2a1ff90..35c6b003c 100644
--- a/lib/librte_eal/common/include/rte_string_fns.h
+++ b/lib/librte_eal/common/include/rte_string_fns.h
@@ -59,10 +59,25 @@ rte_strlcpy(char *dst, const char *src, size_t size)
 	return (size_t)snprintf(dst, size, "%s", src);
 }
 
+/**
+ * @internal
+ * DPDK-specific version of strlcat for systems without
+ * libc or libbsd copies of the function
+ */
+static inline size_t
+rte_strlcat(char *dst, const char *src, size_t size)
+{
+	size_t l = strnlen(dst, size);
+	if (l < size)
+		return l + rte_strlcpy(&dst[l], src, size - l);
+	return l + strlen(src);
+}
+
 /* pull in a strlcpy function */
 #ifdef RTE_EXEC_ENV_BSDAPP
 #ifndef __BSD_VISIBLE /* non-standard functions are hidden */
 #define strlcpy(dst, src, size) rte_strlcpy(dst, src, size)
+#define strlcat(dst, src, size) rte_strlcat(dst, src, size)
 #endif
 
 #else /* non-BSD platforms */
@@ -71,6 +86,7 @@ rte_strlcpy(char *dst, const char *src, size_t size)
 
 #else /* no BSD header files, create own */
 #define strlcpy(dst, src, size) rte_strlcpy(dst, src, size)
+#define strlcat(dst, src, size) rte_strlcat(dst, src, size)
 
 #endif /* RTE_USE_LIBBSD */
 #endif /* BSDAPP */
diff --git a/test/test/test_string_fns.c b/test/test/test_string_fns.c
index 3f091ab92..5e105d2bb 100644
--- a/test/test/test_string_fns.c
+++ b/test/test/test_string_fns.c
@@ -129,11 +129,56 @@ test_rte_strsplit(void)
 	return 0;
 }
 
+static int
+test_rte_strlcat(void)
+{
+	/* only run actual unit tests if we have system-provided strlcat */
+#if defined(__BSD_VISIBLE) || defined(RTE_USE_LIBBSD)
+#define BUF_LEN 32
+	const char dst[BUF_LEN] = "Test string";
+	const char src[] = " appended";
+	char bsd_dst[BUF_LEN];
+	char rte_dst[BUF_LEN];
+	size_t i, bsd_ret, rte_ret;
+
+	LOG("dst = '%s', strlen(dst) = %zu\n", dst, strlen(dst));
+	LOG("src = '%s', strlen(src) = %zu\n", src, strlen(src));
+	LOG("---\n");
+
+	for (i = 0; i < BUF_LEN; i++) {
+		/* initialize destination buffers */
+		memcpy(bsd_dst, dst, BUF_LEN);
+		memcpy(rte_dst, dst, BUF_LEN);
+		/* compare implementations */
+		bsd_ret = strlcat(bsd_dst, src, i);
+		rte_ret = rte_strlcat(rte_dst, src, i);
+		if (bsd_ret != rte_ret) {
+			LOG("Incorrect retval for buf length = %zu\n", i);
+			LOG("BSD: '%zu', rte: '%zu'\n", bsd_ret, rte_ret);
+			return -1;
+		}
+		if (memcmp(bsd_dst, rte_dst, BUF_LEN) != 0) {
+			LOG("Resulting buffers don't match\n");
+			LOG("BSD: '%s', rte: '%s'\n", bsd_dst, rte_dst);
+			return -1;
+		}
+		LOG("buffer size = %zu: dst = '%s', ret = %zu\n",
+			i, rte_dst, rte_ret);
+	}
+	LOG("Checked %zu combinations\n", i);
+#undef BUF_LEN
+#endif /* defined(__BSD_VISIBLE) || defined(RTE_USE_LIBBSD) */
+
+	return 0;
+}
+
 static int
 test_string_fns(void)
 {
 	if (test_rte_strsplit() < 0)
 		return -1;
+	if (test_rte_strlcat() < 0)
+		return -1;
 	return 0;
 }
 
-- 
2.20.1