Allow user to use their chosen WINEPREFIX for each bridge

Additionally, I cleaned up and secured templating a bit.

README

@@ -12,6 +12,8 @@ First you have to create a directory for your bridges:
 Then you can create your first bridge:
  $ ~/local/bin/vst-bridge-maker ~/.wine/drive_c/VST/Synth1/Synth1.dll ~/.vst-bridges/Synth1.so
 
+Optionally, you can add a third argument — a path to a WINEPREFIX you want the plugin to use.
+
 Now edit ~/.bashrc and add $HOME/.vst-bridges/ to VST_PATH. Mine looks like:
 export VST_PATH=/usr/lib/vst/:$HOME/.vst-bridges/
 

common/common.h

@@ -14,7 +14,9 @@
       const typeof( ((type *)0)->member ) *__mptr = (ptr);              \
       (type *)( (char *)__mptr - offsetof(type,member) );})
 
-# define VST_BRIDGE_TPL_MAGIC "VST-BRIDGE-TPL-PATH"
+# define VST_BRIDGE_TPL_DLL "VST-BRIDGE-TPL-DLL"
+# define VST_BRIDGE_TPL_HOST "VST-BRIDGE-TPL-HOST"
+# define VST_BRIDGE_TPL_WINEPREFIX "VST-BRIDGE-TPL-WINEPREFIX"
 # define VST_BRIDGE_TPL_PATH INSTALL_PREFIX "/lib/vst-bridge/vst-bridge-plugin-tpl.so"
 # define VST_BRIDGE_HOST32_PATH INSTALL_PREFIX "/lib/vst-bridge/vst-bridge-host-32.exe"
 # define VST_BRIDGE_HOST64_PATH INSTALL_PREFIX "/lib/vst-bridge/vst-bridge-host-64.exe"

maker/maker.c

@@ -8,23 +8,30 @@
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
+#include <errno.h>
 
 #include <magic.h>
 
 #include "../config.h"
 #include "../common/common.h"
 
+void replace_magic(void *mem_so, size_t mem_sz,
+                   const char *magic, const char *replacement);
+
 int main(int argc, char **argv)
 {
   int arch = 32;
   magic_t magic;
   char dll_real_path[PATH_MAX];
+  char wineprefix_real_path[PATH_MAX];
 
-  if (argc != 3) {
-    fprintf(stderr, "usage: %s <vst.dll> <vst.so>\n", argv[0]);
+  if (argc != 3 && argc != 4) {
+    fprintf(stderr, "usage: %s <vst.dll> <vst.so> [<wine-prefix>]\n", argv[0]);
     return 2;
   }
 
+  int has_wineprefix = argc == 4;
+
   struct stat st_dll;
   if (stat(argv[1], &st_dll) ||
       !realpath(argv[1], dll_real_path)) {
@@ -38,6 +45,21 @@ int main(int argc, char **argv)
     return 1;
   }
 
+  if (has_wineprefix) {
+    struct stat st_wineprefix;
+
+    if (stat(argv[3], &st_wineprefix) ||
+        !realpath(argv[3], wineprefix_real_path)) {
+      fprintf(stderr, "%s: %m\n", argv[3]);
+      return 1;
+    }
+
+    if (!S_ISDIR(st_wineprefix.st_mode)) {
+      fprintf(stderr, "%s: %s\n", argv[3], strerror(ENOTDIR));
+      return 1;
+    }
+  }
+
   magic = magic_open(MAGIC_NONE);
   if (!magic)
     fprintf(stderr, "failed to initialize magic\n");
@@ -81,28 +103,36 @@ int main(int argc, char **argv)
     return 1;
   }
 
-  void *dll_path = memmem(mem_so, st_tpl.st_size, VST_BRIDGE_TPL_MAGIC,
-                          sizeof (VST_BRIDGE_TPL_MAGIC));
-  if (!dll_path) {
-    fprintf(stderr, "template magic not found in plugin\n");
-    return 1;
-  }
-  strncpy(dll_path, dll_real_path, PATH_MAX);
+  replace_magic(mem_so, st_tpl.st_size, VST_BRIDGE_TPL_DLL, dll_real_path);
+  replace_magic(mem_so, st_tpl.st_size, VST_BRIDGE_TPL_HOST, arch == 32 ? VST_BRIDGE_HOST32_PATH : VST_BRIDGE_HOST64_PATH);
+  if (has_wineprefix)
+    replace_magic(mem_so, st_tpl.st_size, VST_BRIDGE_TPL_WINEPREFIX, wineprefix_real_path);
 
-  void *host_path = memmem(mem_so, st_tpl.st_size, VST_BRIDGE_HOST32_PATH,
-                           sizeof (VST_BRIDGE_HOST32_PATH));
-  if (!host_path) {
-    fprintf(stderr, "host path not found in plugin\n");
-    return 1;
-  }
-
-  if (arch == 32)
-    memcpy(host_path, VST_BRIDGE_HOST32_PATH, sizeof (VST_BRIDGE_HOST32_PATH));
-  else
-    memcpy(host_path, VST_BRIDGE_HOST64_PATH, sizeof (VST_BRIDGE_HOST64_PATH));
   munmap(mem_so, st_tpl.st_size);
 
   close(fd_so);
 
   return 0;
 }
+
+void replace_magic(void *mem_so, size_t mem_sz,
+                   const char *magic, const char *replacement)
+{
+  char pattern[PATH_MAX];
+
+  // Just to make sure we replace only values of PATH_MAX length.
+  memset(pattern, 0, sizeof(pattern));
+  strcpy(pattern, magic);
+
+  void *pos = memmem(mem_so, mem_sz, pattern, sizeof(pattern));
+  if (!pos) {
+    fprintf(stderr, "`%s' magic not found in plugin\n", magic);
+    exit(1);
+  }
+
+  // Remove all the rubbish. Probably will never matter.
+  memset(pattern, 0, sizeof(pattern));
+  strcpy(pattern, replacement);
+
+  memcpy(pos, pattern, sizeof(pattern));
+}

plugin/plugin.cc

@@ -19,8 +19,9 @@
 #include "../config.h"
 #include "../common/common.h"
 
-const char g_plugin_path[PATH_MAX] = VST_BRIDGE_TPL_MAGIC;
-const char g_host_path[PATH_MAX] = VST_BRIDGE_HOST32_PATH;
+const char g_plugin_path[PATH_MAX] = VST_BRIDGE_TPL_DLL;
+const char g_host_path[PATH_MAX] = VST_BRIDGE_TPL_HOST;
+const char g_plugin_wineprefix[PATH_MAX] = VST_BRIDGE_TPL_WINEPREFIX;
 
 #ifdef DEBUG
 
@@ -798,6 +799,16 @@ AEffect* VSTPluginMain(audioMasterCallback audio_master)
 
   if (!vbe->child) {
     // in the child
+
+    // A hack to cheat GCC optimisation. If we'd simply compare
+    // g_plugin_wineprefix to VST_BRIDGE_TPL_WINEPREFIX, the
+    // whole if(strcmp(...)) {} will disappear in the assembly.
+
+    char *local_plugin_wineprefix = strdup(g_plugin_wineprefix);
+    if (strcmp(local_plugin_wineprefix, VST_BRIDGE_TPL_WINEPREFIX) != 0)
+      setenv("WINEPREFIX", local_plugin_wineprefix, 1); // Should we really override an existing var?
+    free(local_plugin_wineprefix);
+
     char buff[8];
     close(fds[0]);
     snprintf(buff, sizeof (buff), "%d", fds[1]);