saleae-logic: new package

Add Saleae Logic - analyzer software for Saleae logic analyzators.

Also, add a small LD_PRELOAD library that is needed to make it work from
a read-only installation directory.

1 files changed, 114 insertions, 0 deletions

diff --git a/pkgs/development/tools/misc/saleae-logic/preload.c b/pkgs/development/tools/misc/saleae-logic/preload.c
new file mode 100644
index 00000000000..6b3632db97b
--- /dev/null
+++ b/pkgs/development/tools/misc/saleae-logic/preload.c
@@ -0,0 +1,114 @@
+/*
+ * LD_PRELOAD trick to make Saleae Logic work from a read-only installation
+ * directory.
+ *
+ * Saleae Logic tries to write to the ./Settings/settings.xml file, relative to
+ * its installation directory. Because the nix store is read-only, we have to
+ * redirect access to this file somewhere else. Here's the map:
+ *
+ *   $out/Settings/settings.xml => $HOME/.saleae-logic-settings.xml
+ *
+ * This also makes the software multi-user aware :-)
+ *
+ * NOTE: The next Logic version is supposed to have command line parameters for
+ * configuring where the Settings/ directory is located, but until then we have
+ * to use this.
+ *
+ * Usage:
+ *   gcc -shared -fPIC -DOUT="$out" preload.c -o preload.so -ldl
+ *   LD_PRELOAD=$PWD/preload.so ./result/Logic
+ *
+ * To see the paths that are modified at runtime, set the environment variable
+ * PRELOAD_DEBUG to 1 (or anything really; debugging is on as long as the
+ * variable exists).
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <dlfcn.h>
+#include <limits.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#ifndef OUT
+#error Missing OUT define - path to the installation directory.
+#endif
+
+typedef FILE *(*fopen_func_t)(const char *path, const char *mode);
+typedef FILE *(*fopen64_func_t)(const char *path, const char *mode);
+
+/*
+ * Redirect $out/Settings/settings.xml => $HOME/.saleae-logic-settings.xml. No
+ * other paths are changed. Path is truncated if bigger than PATH_MAX.
+ *
+ * @param pathname Original file path.
+ * @param buffer Pointer to a buffer of size PATH_MAX bytes that this function
+ * will write the new redirected path to (if needed).
+ *
+ * @return Pointer to the resulting path. It will either be equal to the
+ * pathname or buffer argument.
+ */
+static const char *redirect(const char *pathname, char *buffer)
+{
+	const char *homepath;
+	const char *new_path;
+	static char have_warned;
+
+	homepath = getenv("HOME");
+	if (!homepath) {
+		homepath = "/";
+		if (!have_warned && getenv("PRELOAD_DEBUG")) {
+			fprintf(stderr, "preload_debug: WARNING: HOME is unset, using \"/\" (root) instead.\n");
+			have_warned = 1;
+		}
+	}
+
+	new_path = pathname;
+	if (strcmp(OUT "/Settings/settings.xml", pathname) == 0) {
+		snprintf(buffer, PATH_MAX, "%s/.saleae-logic-settings.xml", homepath);
+		buffer[PATH_MAX-1] = '\0';
+		new_path = buffer;
+	}
+
+	return new_path;
+}
+
+FILE *fopen(const char *pathname, const char *mode)
+{
+	FILE *fp;
+	const char *path;
+	char buffer[PATH_MAX];
+	fopen_func_t orig_fopen;
+
+	orig_fopen = (fopen_func_t)dlsym(RTLD_NEXT, "fopen");
+	path = redirect(pathname, buffer);
+	fp = orig_fopen(path, mode);
+
+	if (path != pathname && getenv("PRELOAD_DEBUG")) {
+		fprintf(stderr, "preload_debug: fopen(\"%s\", \"%s\") => \"%s\": fp=%p\n", pathname, mode, path, fp);
+	}
+
+	return fp;
+}
+
+FILE *fopen64(const char *pathname, const char *mode)
+{
+	FILE *fp;
+	const char *path;
+	char buffer[PATH_MAX];
+	fopen64_func_t orig_fopen64;
+
+	orig_fopen64 = (fopen64_func_t)dlsym(RTLD_NEXT, "fopen64");
+	path = redirect(pathname, buffer);
+	fp = orig_fopen64(path, mode);
+
+	if (path != pathname && getenv("PRELOAD_DEBUG")) {
+		fprintf(stderr, "preload_debug: fopen64(\"%s\", \"%s\") => \"%s\": fp=%p\n", pathname, mode, path, fp);
+	}
+
+	return fp;
+}