* New adventures in purity: get Spotify to work without a

/usr/share/spotify symlink by rewriting open() and stat() calls.

svn path=/nixpkgs/trunk/; revision=25892

pkgs/applications/audio/spotify/default.nix

@@ -1,4 +1,4 @@
-{ fetchurl, stdenv, dpkg, xlibs, qt4, alsaLib }:
+{ fetchurl, stdenv, dpkg, xlibs, qt4, alsaLib, makeWrapper }:
 
 assert stdenv.system == "i686-linux" || stdenv.system == "x86_64-linux";
 
@@ -20,7 +20,7 @@ stdenv.mkDerivation {
       }
     else throw "Spotify not supported on this platform.";
 
-  buildInputs = [ dpkg ];
+  buildInputs = [ dpkg makeWrapper ];
 
   unpackPhase = "true";
   
@@ -35,6 +35,12 @@ stdenv.mkDerivation {
         --interpreter "$(cat $NIX_GCC/nix-support/dynamic-linker)" \
         --set-rpath ${stdenv.lib.makeLibraryPath [ xlibs.libXScrnSaver qt4 alsaLib stdenv.gcc.gcc ]}:${stdenv.gcc.gcc}/lib64 \
         $out/bin/spotify
+
+      preload=$out/libexec/spotify/libpreload.so
+      mkdir -p $out/libexec/spotify
+      gcc -shared ${./preload.c} -o $preload -ldl -DOUT=\"$out\"
+
+      wrapProgram $out/bin/spotify --set LD_PRELOAD $preload
     ''; # */
 
   dontStrip = true;
@@ -52,14 +58,6 @@ stdenv.mkDerivation {
         provides the Spotify client for Linux.  At present, it does not
         work with free Spotify accounts; it requires a Premium or
         Unlimited account.
-
-        Currently, the Spotify client requires a symlink from
-        /usr/share/spotify to its resources.  Thus, you should do
-        something like:
-
-          $ nix-env -i spotify
-          $ mkdir -p /usr/share
-          $ ln -s ~/.nix-profile/share/spotify /usr/share/
       '';
   };
 }

pkgs/applications/audio/spotify/preload.c

@@ -0,0 +1,59 @@
+/* Spotify looks for its theme data in /usr/share/spotify/theme.  This
+   LD_PRELOAD library intercepts open() and stat() calls to redirect
+   them to the corresponding location in $out. */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+#include <dlfcn.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <limits.h>
+
+char themeDir [] = "/usr/share/spotify/theme";
+char realThemeDir [] = OUT "/share/spotify/theme";
+
+const char * rewrite(const char * path, char * buf)
+{
+    if (strncmp(path, themeDir, sizeof(themeDir) - 1) != 0) return path;
+    if (snprintf(buf, PATH_MAX, "%s%s", realThemeDir, path + sizeof(themeDir) - 1) >= PATH_MAX)
+        abort();
+    return buf;
+}
+
+int open(const char *path, int flags, ...)
+{
+    char buf[PATH_MAX];
+    int (*_open) (const char *, int, mode_t) = dlsym(RTLD_NEXT, "open");
+    mode_t mode = 0;
+    if (flags & O_CREAT) {
+        va_list ap;
+        va_start(ap, flags);
+        mode = va_arg(ap, mode_t);
+        va_end(ap);
+    }
+    return _open(rewrite(path, buf), flags, mode);
+}
+
+int open64(const char *path, int flags, ...)
+{
+    char buf[PATH_MAX];
+    int (*_open64) (const char *, int, mode_t) = dlsym(RTLD_NEXT, "open64");
+    mode_t mode = 0;
+    if (flags & O_CREAT) {
+        va_list ap;
+        va_start(ap, flags);
+        mode = va_arg(ap, mode_t);
+        va_end(ap);
+    }
+    return _open64(rewrite(path, buf), flags, mode);
+}
+
+int __xstat64(int ver, const char *path, struct stat64 *st)
+{
+    char buf[PATH_MAX];
+    int (*___xstat64) (int ver, const char *, struct stat64 *) = dlsym(RTLD_NEXT, "__xstat64");
+    return ___xstat64(ver, rewrite(path, buf), st);
+}