Don't crash if mmap fails to map memory

Author: Mallory Paine

FastImageCache/FICImageTable.m

@@ -235,6 +235,11 @@ - (FICImageTableChunk *)_chunkAtIndex:(NSInteger)index {
         }
     }
 
+    if (!chunk) {
+        NSString *message = [NSString stringWithFormat:@"*** FIC Error: %s failed to get chunk for index %d.", __PRETTY_FUNCTION__, index];
+        [[FICImageCache sharedImageCache] _logMessage:message];
+    }
+    
     return chunk;
 }
 
@@ -262,30 +267,32 @@ - (void)setEntryForEntityUUID:(NSString *)entityUUID sourceImageUUID:(NSString *
 
             // Create context whose backing store *is* the mapped file data
             FICImageTableEntry *entryData = [self _entryDataAtIndex:newEntryIndex];
-            CGContextRef context = CGBitmapContextCreate([entryData bytes], pixelSize.width, pixelSize.height, bitsPerComponent, _imageRowLength, colorSpace, bitmapInfo);
-            CGColorSpaceRelease(colorSpace);
-            
-            CGContextTranslateCTM(context, 0, pixelSize.height);
-            CGContextScaleCTM(context, _screenScale, -_screenScale);
-            
-            // Call drawing block to allow client to draw into the context
-            imageDrawingBlock(context, [_imageFormat imageSize]);
-            CGContextRelease(context);
-            
-            [entryData setEntityUUIDBytes:FICUUIDBytesWithString(entityUUID)];
-            [entryData setSourceImageUUIDBytes:FICUUIDBytesWithString(sourceImageUUID)];
-            
-            // Update our book-keeping
-            [_indexMap setObject:[NSNumber numberWithUnsignedInteger:newEntryIndex] forKey:entityUUID];
-            [_occupiedIndexes addIndex:newEntryIndex];
-            [_sourceImageMap setObject:sourceImageUUID forKey:entityUUID];
-            
-            // Update MRU array
-            [self _entryWasAccessedWithEntityUUID:entityUUID];
-            [self saveMetadata];
-            
-            // Write the data back to the filesystem
-            [entryData flush];
+            if (entryData) {
+                CGContextRef context = CGBitmapContextCreate([entryData bytes], pixelSize.width, pixelSize.height, bitsPerComponent, _imageRowLength, colorSpace, bitmapInfo);
+                CGColorSpaceRelease(colorSpace);
+                
+                CGContextTranslateCTM(context, 0, pixelSize.height);
+                CGContextScaleCTM(context, _screenScale, -_screenScale);
+                
+                // Call drawing block to allow client to draw into the context
+                imageDrawingBlock(context, [_imageFormat imageSize]);
+                CGContextRelease(context);
+                
+                [entryData setEntityUUIDBytes:FICUUIDBytesWithString(entityUUID)];
+                [entryData setSourceImageUUIDBytes:FICUUIDBytesWithString(sourceImageUUID)];
+                
+                // Update our book-keeping
+                [_indexMap setObject:[NSNumber numberWithUnsignedInteger:newEntryIndex] forKey:entityUUID];
+                [_occupiedIndexes addIndex:newEntryIndex];
+                [_sourceImageMap setObject:sourceImageUUID forKey:entityUUID];
+                
+                // Update MRU array
+                [self _entryWasAccessedWithEntityUUID:entityUUID];
+                [self saveMetadata];
+                
+                // Write the data back to the filesystem
+                [entryData flush];
+            }
         }
 
         [_lock unlock];
@@ -458,6 +465,11 @@ - (FICImageTableEntry *)_entryDataAtIndex:(NSInteger)index {
 
     [_lock unlock];
 
+    if (!entryData) {
+        NSString *message = [NSString stringWithFormat:@"*** FIC Error: %s failed to get entry for index %d.", __PRETTY_FUNCTION__, index];
+        [[FICImageCache sharedImageCache] _logMessage:message];
+    }
+    
     return entryData;
 }
 

FastImageCache/FICImageTableChunk.m

@@ -40,7 +40,9 @@ - (instancetype)initWithFileDescriptor:(int)fileDescriptor index:(NSInteger)inde
         _bytes = mmap(NULL, _length, (PROT_READ|PROT_WRITE), (MAP_FILE|MAP_SHARED), fileDescriptor, _fileOffset);
 
         if (_bytes == MAP_FAILED) {
+            NSLog(@"Failed to map chunk. errno=%d", errno);
             _bytes = NULL;
+            self = nil;
         }
     }