Fix for lack of basic error checking in writing compressed .blend files

(which is enabled by default). If there was a problem reading or writing
in the compression process, the original .blend file could get lost. Now
errors are checked, and writing is done as follows:

write .blend@ -> compress .blend@ to .blend@.gz ->
rename .blend@.gz to .blend -> remove .blend@

We've had blender crash here, lose the original .blend and leave an
empty .blend@. It is not clear to me where this would happen in practice 
if there is enough disk space and permissions are correct, so the actual
crash is likely not fixed by this commit.

2 files changed, 51 insertions, 27 deletions

diff --git a/source/blender/blenlib/intern/fileops.c b/source/blender/blenlib/intern/fileops.c
index ae20eda5a59..52ebab9b1ff 100644
--- a/source/blender/blenlib/intern/fileops.c
+++ b/source/blender/blenlib/intern/fileops.c
@@ -153,29 +153,39 @@ int BLI_gzip(char *from, char *to) {
 	char buffer[10240];
 	int file;
 	int readsize = 0;
+	int rval= 0, err;
+	gzFile gzfile;
 	
-	gzFile gzfile = gzopen(to,"wb"); 
-	if (NULL == gzfile) return -1;
+	gzfile = gzopen(to, "wb"); 
+	if(gzfile == NULL)
+		return -1;
 	
-	file = open(from,O_BINARY|O_RDONLY);
-	
-	if (file < 0)	return -2;
+	file = open(from, O_BINARY|O_RDONLY);
+	if(file < 0)
+		return -2;
 
-	while ( 1 )
-	{
+	while(1) {
 		readsize = read(file, buffer, 10240);
+
+		if(readsize < 0) {
+			rval= -2; /* error happened in reading */
+			fprintf(stderr, "Error reading file %s: %s.\n", from, strerror(errno));
+			break;
+		}
+		else if(readsize == 0)
+			break; /* done reading */
 		
-		if (readsize <= 0) break;
-		
-		gzwrite(gzfile,buffer,readsize);
+		if(gzwrite(gzfile, buffer, readsize) <= 0) {
+			rval= -1; /* error happened in writing */
+			fprintf(stderr, "Error writing gz file %s: %s.\n", to, gzerror(gzfile, &err));
+			break;
+		}
 	}
 	
 	gzclose(gzfile);
 	close(file);
-	
-	remove(from);
 
-	return 0;
+	return rval;
 }
 
 /* return 1 when file can be written */
diff --git a/source/blender/blenloader/intern/writefile.c b/source/blender/blenloader/intern/writefile.c
index 06b01a8be0d..06af7cb20d3 100644
--- a/source/blender/blenloader/intern/writefile.c
+++ b/source/blender/blenloader/intern/writefile.c
@@ -2445,10 +2445,11 @@ static int write_file_handle(Main *mainvar, int handle, MemFile *compare, MemFil
 int BLO_write_file(Main *mainvar, char *dir, int write_flags, ReportList *reports)
 {
 	char userfilename[FILE_MAXDIR+FILE_MAXFILE];
-	char tempname[FILE_MAXDIR+FILE_MAXFILE];
+	char tempname[FILE_MAXDIR+FILE_MAXFILE+1];
 	int file, err, write_user_block;
 
-	sprintf(tempname, "%s@", dir);
+	/* open temporary file, so we preserve the original in case we crash */
+	BLI_snprintf(tempname, sizeof(tempname), "%s@", dir);
 
 	file = open(tempname,O_BINARY+O_WRONLY+O_CREAT+O_TRUNC, 0666);
 	if(file == -1) {
@@ -2456,6 +2457,7 @@ int BLO_write_file(Main *mainvar, char *dir, int write_flags, ReportList *report
 		return 0;
 	}
 
+	/* remapping of relative paths to new file location */
 	if(write_flags & G_FILE_RELATIVE_REMAP) {
 		char dir1[FILE_MAXDIR+FILE_MAXFILE];
 		char dir2[FILE_MAXDIR+FILE_MAXFILE];
@@ -2470,7 +2472,6 @@ int BLO_write_file(Main *mainvar, char *dir, int write_flags, ReportList *report
 			write_flags &= ~G_FILE_RELATIVE_REMAP;
 		else
 			makeFilesAbsolute(G.sce, NULL);
-
 	}
 
 	BLI_make_file_string(G.sce, userfilename, BLI_gethome(), ".B25.blend");
@@ -2479,33 +2480,46 @@ int BLO_write_file(Main *mainvar, char *dir, int write_flags, ReportList *report
 	if(write_flags & G_FILE_RELATIVE_REMAP)
 		makeFilesRelative(dir, NULL); /* note, making relative to something OTHER then G.sce */
 
+	/* actual file writing */
 	err= write_file_handle(mainvar, file, NULL,NULL, write_user_block, write_flags);
 	close(file);
 
+	/* rename/compress */
 	if(!err) {
-		if(write_flags & G_FILE_COMPRESS)
-		{	
-			// compressed files have the same ending as regular files... only from 2.4!!!
-			
-			int ret = BLI_gzip(tempname, dir);
+		if(write_flags & G_FILE_COMPRESS) {
+			/* compressed files have the same ending as regular files... only from 2.4!!! */
+			char gzname[FILE_MAXDIR+FILE_MAXFILE+4];
+			int ret;
+
+			/* first write compressed to separate @.gz */
+			BLI_snprintf(gzname, sizeof(gzname), "%s@.gz", dir);
+			ret = BLI_gzip(tempname, gzname);
 			
-			if(-1==ret) {
+			if(0==ret) {
+				/* now rename to real file name, and delete temp @ file too */
+				if(BLI_rename(gzname, dir) != 0) {
+					BKE_report(reports, RPT_ERROR, "Can't change old file. File saved with @.");
+					return 0;
+				}
+
+				BLI_delete(tempname, 0, 0);
+			}
+			else if(-1==ret) {
 				BKE_report(reports, RPT_ERROR, "Failed opening .gz file.");
 				return 0;
 			}
-			if(-2==ret) {
+			else if(-2==ret) {
 				BKE_report(reports, RPT_ERROR, "Failed opening .blend file for compression.");
 				return 0;
 			}
 		}
-		else
-		if(BLI_rename(tempname, dir) != 0) {
+		else if(BLI_rename(tempname, dir) != 0) {
 			BKE_report(reports, RPT_ERROR, "Can't change old file. File saved with @");
 			return 0;
 		}
-
 		
-	} else {
+	}
+	else {
 		BKE_report(reports, RPT_ERROR, strerror(errno));
 		remove(tempname);