1 files changed, 134 insertions, 0 deletions
diff --git a/nixpkgs/pkgs/applications/science/electronics/eagle/eagle7_fixer.c b/nixpkgs/pkgs/applications/science/electronics/eagle/eagle7_fixer.c
new file mode 100644
index 000000000000..da9da4dcbd3a
--- /dev/null
+++ b/nixpkgs/pkgs/applications/science/electronics/eagle/eagle7_fixer.c
@@ -0,0 +1,134 @@
+/*
+ * LD_PRELOAD trick to make Eagle (schematic editor and PCB layout tool from
+ * CadSoft) work from a read-only installation directory.
+ *
+ * When Eagle starts, it looks for the license file in <eagle>/bin/eagle.key
+ * (where <eagle> is the install path). If eagle.key is not found, Eagle checks
+ * for write access to <eagle>/bin/, shows a license dialog to the user and
+ * then attempts to write a license file to <eagle>/bin/.
+ *
+ * This will of course fail when Eagle is installed in the read-only Nix store.
+ * Hence this library that redirects accesses to the those paths in the
+ * following way:
+ *
+ *   <eagle>/bin              => $HOME
+ *   <eagle>/bin/eagle.key    => $HOME/.eagle.key
+ *
+ * Also, if copying an example project to ~/eagle/ (in the Eagle GUI), Eagle
+ * chmod's the destination with read-only permission bits (presumably because
+ * the source is read-only) and fails to complete the copy operation.
+ * Therefore, the mode argument in calls to chmod() is OR'ed with the S_IWUSR
+ * bit (write by owner).
+ *
+ * Usage:
+ *   gcc -shared -fPIC -DEAGLE_PATH="$out/eagle-${version}" eagle_fixer.c -o eagle_fixer.so -ldl
+ *   LD_PRELOAD=$PWD/eagle_fixer.so ./result/bin/eagle
+ *
+ * To see the paths that are modified at runtime, set the environment variable
+ * EAGLE_FIXER_DEBUG to 1.
+ */
+
+#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>
+
+#ifndef EAGLE_PATH
+#error Missing EAGLE_PATH, path to the eagle-${version} installation directory.
+#endif
+
+typedef FILE *(*fopen_func_t)(const char *path, const char *mode);
+typedef int (*access_func_t)(const char *pathname, int mode);
+typedef int (*chmod_func_t)(const char *path, mode_t mode);
+
+/*
+ * Map <eagle>/bin to $HOME and <eagle>/bin/eagle.key to $HOME/.eagle.key
+ *
+ * Path is truncated if bigger than PATH_MAX. It's not threadsafe, but that's
+ * OK.
+ */
+static const char *redirect(const char *pathname)
+{
+	static char buffer[PATH_MAX];
+	const char *homepath;
+	const char *new_path;
+	static int have_warned;
+
+	homepath = getenv("HOME");
+	if (!homepath) {
+		homepath = "/";
+		if (!have_warned && getenv("EAGLE_FIXER_DEBUG")) {
+			fprintf(stderr, "eagle_fixer: HOME is unset, using \"/\" (root) instead.\n");
+			have_warned = 1;
+		}
+	}
+
+	new_path = pathname;
+	if (strcmp(EAGLE_PATH "/bin", pathname) == 0) {
+		/* redirect to $HOME */
+		new_path = homepath;
+	} else if (strcmp(EAGLE_PATH "/bin/eagle.key", pathname) == 0) {
+		/* redirect to $HOME/.eagle.key */
+		snprintf(buffer, PATH_MAX, "%s/.eagle.key", 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;
+	fopen_func_t orig_fopen;
+
+	orig_fopen = (fopen_func_t)dlsym(RTLD_NEXT, "fopen");
+	path = redirect(pathname);
+	fp = orig_fopen(path, mode);
+
+	if (path != pathname && getenv("EAGLE_FIXER_DEBUG")) {
+		fprintf(stderr, "eagle_fixer: fopen(\"%s\", \"%s\") => \"%s\": fp=%p\n", pathname, mode, path, fp);
+	}
+
+	return fp;
+}
+
+int access(const char *pathname, int mode)
+{
+	int ret;
+	const char *path;
+	access_func_t orig_access;
+
+	orig_access = (access_func_t)dlsym(RTLD_NEXT, "access");
+	path = redirect(pathname);
+	ret = orig_access(path, mode);
+
+	if (path != pathname && getenv("EAGLE_FIXER_DEBUG")) {
+		fprintf(stderr, "eagle_fixer: access(\"%s\", %d) => \"%s\": ret=%d\n", pathname, mode, path, ret);
+	}
+
+	return ret;
+}
+
+int chmod(const char *pathname, mode_t mode)
+{
+	int ret;
+	mode_t new_mode;
+	chmod_func_t orig_chmod;
+
+	orig_chmod = (chmod_func_t)dlsym(RTLD_NEXT, "chmod");
+	new_mode = mode | S_IWUSR;
+	ret = orig_chmod(pathname, new_mode);
+
+	if (getenv("EAGLE_FIXER_DEBUG")) {
+		fprintf(stderr, "eagle_fixer: chmod(\"%s\", %o) => %o: ret=%d\n", pathname, mode, new_mode, ret);
+	}
+
+	return ret;
+}