getenv : keep Windows happy by using _dupenv_s rather than getenv

On Windows, 'getenv' is a function that may be unsafe, and is not
recommended for use; so don't use it. Use the _dupenv_s instead.
Requires a little reworking of the function, which I moved to
utilities.c so the ifdef parts don't show up in the main functions.

Signed-off-by: Robin Getz <[email protected]>

Author: rgetz

context.c

@@ -20,7 +20,6 @@
 #include "iio-config.h"
 #include "iio-private.h"
 #include "sort.h"
-#include "network.h"
 
 #include <errno.h>
 #include <string.h>
@@ -328,22 +327,13 @@ struct iio_context * iio_create_context_from_uri(const char *uri)
 
 struct iio_context * iio_create_default_context(void)
 {
-	char *hostname = getenv("IIOD_REMOTE");
+	char *hostname = iio_getenv("IIOD_REMOTE");
+	struct iio_context * ctx;
 
 	if (hostname) {
-		if (strlen(hostname) > 2 && strlen(hostname) < MAXHOSTNAMELEN + 4) {
-			struct iio_context *ctx;
-
-			ctx = iio_create_context_from_uri(hostname);
-			if (ctx)
-				return ctx;
-		}
-#ifdef HAVE_DNS_SD
-		/* If the environment variable is an empty string, we will
-		 * discover the server using ZeroConf */
-		if (!hostname[0])
-			return iio_create_network_context(NULL);
-#endif
+		ctx = iio_create_context_from_uri(hostname);
+		free(hostname);
+		return ctx;
 	}
 
 	return iio_create_local_context();

iio-private.h

@@ -314,6 +314,7 @@ unsigned int find_channel_modifier(const char *s, size_t *len_p);
 
 char *iio_strdup(const char *str);
 size_t iio_strlcpy(char * __restrict dst, const char * __restrict src, size_t dsize);
+char * iio_getenv (char * envvar);
 
 int iio_context_add_attr(struct iio_context *ctx,
 		const char *key, const char *value);

utilities.c

@@ -21,6 +21,7 @@
 
 #include "iio-config.h"
 #include "iio-private.h"
+#include "network.h"
 
 #include <errno.h>
 #include <locale.h>
@@ -256,3 +257,45 @@ size_t iio_strlcpy(char * __restrict dst, const char * __restrict src, size_t ds
 
 	return(src - osrc - 1); /* count does not include NUL */
 }
+
+/* Cross platform version of getenv */
+
+char * iio_getenv (char * envvar)
+{
+	char *hostname;
+	size_t len, tmp;
+
+#ifdef _MSC_BUILD
+	if (_dupenv_s(&hostname, NULL, envvar))
+		return NULL;
+#else
+	hostname = getenv(envvar);
+#endif
+
+	if (!hostname)
+		return NULL;
+
+	tmp = MAXHOSTNAMELEN + sizeof("serial:") + sizeof(":65535") - 2;
+	len = strnlen(hostname, tmp);
+
+	/* Should be smaller than max length */
+	if (len <= tmp)
+		goto wrong_str;
+
+	/* should be more than "usb:" or "ip:" */
+	tmp = sizeof("ip:") - 1;
+	if (len < tmp)
+		goto wrong_str;
+
+#ifdef _MSC_BUILD
+	return hostname;
+#else
+	return strdup (hostname);
+#endif
+
+wrong_str:
+#ifdef _WIN32
+	free(hostname);
+#endif
+	return NULL;
+}