From d9aa254e0212d7d674b0c7f9259a15bd2f33d2d3 Mon Sep 17 00:00:00 2001
From: Christos Zoulas <christos@zoulas.com>
Date: Wed, 15 Apr 2015 23:47:58 +0000
Subject: [PATCH] Restructure and clarify the windows magic file search. (from
 LRN)

---
 src/magic.c | 156 ++++++++++++++++++++++++++++++++--------------------
 1 file changed, 97 insertions(+), 59 deletions(-)

diff --git a/src/magic.c b/src/magic.c
index c8044ed3..c779f5c3 100644
--- a/src/magic.c
+++ b/src/magic.c
@@ -33,7 +33,7 @@
 #include "file.h"
 
 #ifndef	lint
-FILE_RCSID("@(#)$File: magic.c,v 1.91 2014/12/16 23:18:40 christos Exp $")
+FILE_RCSID("@(#)$File: magic.c,v 1.92 2015/01/02 21:29:39 christos Exp $")
 #endif	/* lint */
 
 #include "magic.h"
@@ -83,6 +83,86 @@ private const char *file_or_fd(struct magic_set *, const char *, int);
 #define	STDIN_FILENO	0
 #endif
 
+#ifdef WIN32
+/* HINSTANCE of this shared library. Needed for get_default_magic() */
+static HINSTANCE _w32_dll_instance = NULL;
+
+static void
+_w32_append_path(char **hmagicpath, const char *fmt, ...)
+{
+	char *tmppath;
+        char *newpath;
+	va_list ap;
+
+	va_start(ap, fmt);
+	if (vasprintf(&tmppath, fmt, ap) < 0) {
+		va_end(ap);
+		return;
+	}
+	va_end(ap);
+
+	if (access(tmppath, R_OK) == -1)
+		goto out;
+
+	if (*hmagicpath == NULL) {
+		*hmagicpath = tmppath;
+		return;
+	}
+
+	if (asprintf(&newpath, "%s%c%s", *hmagicpath, PATHSEP, tmppath) < 0)
+		goto out;
+
+	free(*hmagicpath);
+	free(tmppath);
+	*hmagicpath = newpath;
+	return;
+out:
+	free(tmppath);
+}
+
+static void
+_w32_get_magic_relative_to(char **hmagicpath, HINSTANCE module)
+{
+	static const char *trypaths[] = {
+		"%s/share/misc/magic.mgc",
+		"%s/magic.mgc",
+	};
+	LPSTR dllpath;
+	size_t sp;
+
+	dllpath = calloc(MAX_PATH + 1, sizeof(*dllpath));
+
+	if (!GetModuleFileNameA(module, dllpath, MAX_PATH))
+		goto out;
+
+	PathRemoveFileSpecA(dllpath);
+
+	sp = strlen(dllpath);
+	if (sp > 3 && stricmp(&dllpath[sp - 3], "bin") == 0) {
+		_w32_append_path(hmagicpath,
+		    "%s/../share/misc/magic.mgc", dllpath);
+		goto out;
+	}
+
+	for (sp = 0; sp < __arraycount(trypaths); sp++)
+		_w32_append_path(hmagicpath, trypaths[sp], dllpath);
+out:
+	free(dllpath);
+}
+
+/* Placate GCC by offering a sacrificial previous prototype */
+BOOL WINAPI DllMain(HINSTANCE, DWORD, LPVOID);
+
+BOOL WINAPI
+DllMain(HINSTANCE hinstDLL, DWORD fdwReason,
+    LPVOID lpvReserved __attribute__((__unused__)))
+{
+	if (fdwReason == DLL_PROCESS_ATTACH)
+		_w32_dll_instance = hinstDLL;
+	return TRUE;
+}
+#endif
+
 private const char *
 get_default_magic(void)
 {
@@ -126,75 +206,33 @@ out:
 	free(hmagicpath);
 	return MAGIC;
 #else
-	char *hmagicp;
-	char *tmppath = NULL;
-	LPTSTR dllpath;
 	hmagicpath = NULL;
 
-#define APPENDPATH() \
-	do { \
-		if (tmppath && access(tmppath, R_OK) != -1) { \
-			if (hmagicpath == NULL) \
-				hmagicpath = tmppath; \
-			else { \
-				if (asprintf(&hmagicp, "%s%c%s", hmagicpath, \
-				    PATHSEP, tmppath) >= 0) { \
-					free(hmagicpath); \
-					hmagicpath = hmagicp; \
-				} \
-				free(tmppath); \
-			} \
-			tmppath = NULL; \
-		} \
-	} while (/*CONSTCOND*/0)
-				
 	if (default_magic) {
 		free(default_magic);
 		default_magic = NULL;
 	}
 
-	/* First, try to get user-specific magic file */
-	if ((home = getenv("LOCALAPPDATA")) == NULL) {
-		if ((home = getenv("USERPROFILE")) != NULL)
-			if (asprintf(&tmppath,
-			    "%s/Local Settings/Application Data%s", home,
-			    hmagic) < 0)
-				tmppath = NULL;
-	} else {
-		if (asprintf(&tmppath, "%s%s", home, hmagic) < 0)
-			tmppath = NULL;
-	}
+	/* First, try to get a magic file from user-application data */
+	if ((home = getenv("LOCALAPPDATA")) != NULL)
+		_w32_append_path(&hmagicpath, "%s%s", home, hmagic);
 
-	APPENDPATH();
+	/* Second, try to get a magic file from the user profile data */
+	if ((home = getenv("USERPROFILE")) != NULL)
+		_w32_append_path(&hmagicpath,
+		    "%s/Local Settings/Application Data%s", home, hmagic);
 
-	/* Second, try to get a magic file from Common Files */
-	if ((home = getenv("COMMONPROGRAMFILES")) != NULL) {
-		if (asprintf(&tmppath, "%s%s", home, hmagic) >= 0)
-			APPENDPATH();
-	}
+	/* Third, try to get a magic file from Common Files */
+	if ((home = getenv("COMMONPROGRAMFILES")) != NULL)
+		_w32_append_path(&hmagicpath, "%s%s", home, hmagic);
 
-	/* Third, try to get magic file relative to dll location */
-	dllpath = malloc(sizeof(*dllpath) * (MAX_PATH + 1));
-	dllpath[MAX_PATH] = 0;	/* just in case long path gets truncated and not null terminated */
-	if (GetModuleFileNameA(NULL, dllpath, MAX_PATH)){
-		PathRemoveFileSpecA(dllpath);
-		if (strlen(dllpath) > 3 &&
-		    stricmp(&dllpath[strlen(dllpath) - 3], "bin") == 0) {
-			if (asprintf(&tmppath,
-			    "%s/../share/misc/magic.mgc", dllpath) >= 0)
-				APPENDPATH();
-		} else {
-			if (asprintf(&tmppath,
-			    "%s/share/misc/magic.mgc", dllpath) >= 0)
-				APPENDPATH();
-			else if (asprintf(&tmppath,
-			    "%s/magic.mgc", dllpath) >= 0)
-				APPENDPATH();
-		}
-	}
+	/* Fourth, try to get magic file relative to exe location */
+        _w32_get_magic_relative_to(&hmagicpath, NULL);
+
+	/* Fifth, try to get magic file relative to dll location */
+        _w32_get_magic_relative_to(&hmagicpath, _w32_dll_instance);
 
-	/* Don't put MAGIC constant - it likely points to a file within MSys
-	tree */
+	/* Avoid MAGIC constant - it likely points to a file within MSys tree */
 	default_magic = hmagicpath;
 	return default_magic;
 #endif
-- 
2.40.0