1 files changed, 170 insertions, 0 deletions
diff --git a/pkgs/applications/graphics/sane/backends/brscan4/preload.c b/pkgs/applications/graphics/sane/backends/brscan4/preload.c
new file mode 100644
index 00000000000..01616277093
--- /dev/null
+++ b/pkgs/applications/graphics/sane/backends/brscan4/preload.c
@@ -0,0 +1,170 @@
+/* Brgen4 search for configuration under `/etc/opt/brother/scanner/brscan4`. This
+   LD_PRELOAD library intercepts execvp(), open and open64 calls to redirect them to
+   the corresponding location in $out. Also support specifying an alternate
+   file name for `brsanenetdevice4.cfg` which otherwise is invariable
+   created at `/etc/opt/brother/scanner/brscan4`*/
+
+#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>
+#include <string.h>
+#include <dirent.h>
+
+char origDir [] = "/etc/opt/brother/scanner/brscan4";
+char realDir [] = OUT "/opt/brother/scanner/brscan4";
+
+char devCfgFileNameEnvVar [] = "BRSANENETDEVICE4_CFG_FILENAME";
+char devCfgFileName [] = "/etc/opt/brother/scanner/brscan4//brsanenetdevice4.cfg";
+
+const char * rewrite(const char * path, char * buf)
+{
+    if (strncmp(path, devCfgFileName, sizeof(devCfgFileName)) == 0) {
+
+      const char* newCfgFileName = getenv(devCfgFileNameEnvVar);
+      if (!newCfgFileName) return path;
+
+      if (snprintf(buf, PATH_MAX, "%s", newCfgFileName) >= PATH_MAX)
+          abort();
+      return buf;
+    }
+
+    if (strncmp(path, origDir, sizeof(origDir) - 1) != 0) return path;
+    if (snprintf(buf, PATH_MAX, "%s%s", realDir, path + sizeof(origDir) - 1) >= PATH_MAX)
+        abort();
+    return buf;
+}
+
+const char* findAndReplaceFirstOccurence(const char* inStr, const char* subStr, 
+                                         const char* replaceStr, 
+                                         char* buf, unsigned maxBuf)
+{
+    const char* foundStr = strstr(inStr, subStr);
+    if (!foundStr)
+      return inStr;
+
+    const unsigned inStrLen = strlen(inStr);
+    const unsigned subStrLen = strlen(subStr);
+    const unsigned replaceStrLen = strlen(replaceStr);
+
+    const unsigned precedingStrLen = foundStr - inStr;
+    if (precedingStrLen + 1 > maxBuf)
+      return NULL;
+
+    const unsigned followingStrPos = precedingStrLen + subStrLen;
+    const unsigned followingStrLen = inStrLen - followingStrPos;
+
+    strncpy(buf, inStr, precedingStrLen);
+    unsigned outLength = precedingStrLen;
+
+    if (outLength + replaceStrLen + 1 > maxBuf)
+      return NULL;
+
+    strncpy(buf + outLength, replaceStr, replaceStrLen);
+    outLength += replaceStrLen;
+    
+    if (outLength + followingStrLen + 1 > maxBuf)
+      return NULL;
+
+    strncpy(buf + outLength, inStr + followingStrPos, followingStrLen);
+    outLength += followingStrLen;
+    
+    buf[outLength] = '\0';
+
+    return buf;
+}
+
+const char* rewriteSystemCall(const char* command, char* buf, unsigned maxBuf)
+{
+
+    const char* foundStr = strstr(command, devCfgFileName);
+    if (!foundStr)
+      return command;
+
+    const char* replaceStr = getenv(devCfgFileNameEnvVar);
+    if (!replaceStr) return command;
+
+    const char* result = 
+      findAndReplaceFirstOccurence(command, devCfgFileName, replaceStr, buf, maxBuf);
+
+    if (!result)
+      abort();
+
+    return result;
+}
+
+int execvp(const char * path, char * const argv[])
+{
+    int (*_execvp) (const char *, char * const argv[]) = dlsym(RTLD_NEXT, "execvp");
+    char buf[PATH_MAX];
+    return _execvp(rewrite(path, buf), argv);
+}
+
+
+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);
+}
+
+FILE* fopen(const char* path, const char* mode)
+{
+  char buf[PATH_MAX];
+	FILE* (*_fopen) (const char*, const char*) = dlsym(RTLD_NEXT, "fopen");
+
+	return _fopen(rewrite(path, buf), mode);
+}
+
+FILE *fopen64(const char *path, const char *mode)
+{
+  char buf[PATH_MAX];
+	FILE* (*_fopen64) (const char*, const char*) = dlsym(RTLD_NEXT, "fopen64");
+
+	return _fopen64(rewrite(path, buf), mode);
+}
+
+DIR* opendir(const char* path)
+{
+  char buf[PATH_MAX];
+	DIR* (*_opendir) (const char*) = dlsym(RTLD_NEXT, "opendir");
+
+	return _opendir(rewrite(path, buf));
+}
+
+#define SYSTEM_CMD_MAX 512
+
+int system(const char *command)
+{
+    char buf[SYSTEM_CMD_MAX];
+    int (*_system) (const char*) = dlsym(RTLD_NEXT, "system");
+
+    const char* newCommand = rewriteSystemCall(command, buf, SYSTEM_CMD_MAX);
+    return _system(newCommand);
+}