increased fault tolerance of shader cache files.

more specifically: if the emulator stops unexpectedly, it is quite possible that one of the shader cache files will have some bytes near the end that never got their values filled in. this change adds an index number at the end of each entry as extra verification that the entry is valid, so that invalid entries can be ignored (and eventually overwritten) instead of causing crashes.

Source/Core/Common/Src/LinearDiskCache.h

@@ -24,7 +24,7 @@
 // Increment this every time you change shader generation code.
 enum
 {
-	LINEAR_DISKCACHE_VER = 6967
+	LINEAR_DISKCACHE_VER = 6969
 };
 
 // On disk format:
@@ -71,36 +71,58 @@ public:
 
 		// close any currently opened file
 		Close();
+		m_num_entries = 0;
 
 		// try opening for reading/writing
-		m_file.open(filename, ios_base::in | ios_base::out | ios_base::binary | ios_base::app);
+		m_file.open(filename, ios_base::in | ios_base::out | ios_base::binary);
+
+		m_file.seekg(0, std::ios::end);
+		std::fstream::pos_type end_pos = m_file.tellg();
+		m_file.seekg(0, std::ios::beg);
+		std::fstream::pos_type start_pos = m_file.tellg();
+		std::streamoff file_size = end_pos - start_pos;
 		
 		if (m_file.is_open() && ValidateHeader())
 		{
 			// good header, read some key/value pairs
-			u32 num_entries = 0;
 			K key;
 
 			V *value = NULL;
 			u32 value_size;
+			u32 entry_number;
+
+			std::fstream::pos_type last_pos = m_file.tellg();
 
 			while (Read(&value_size))
 			{
+				std::streamoff next_extent = (last_pos - start_pos) + sizeof(value_size) + value_size;
+				if (next_extent > file_size)
+					break;
+
 				delete[] value;
 				value = new V[value_size];
 
 				// read key/value and pass to reader
-				if (Read(&key) && Read(value, value_size))
+				if (Read(&key) &&
+					Read(value, value_size) && 
+					Read(&entry_number) &&
+					entry_number == m_num_entries+1)
+ 				{
 					reader.Read(key, value, value_size);
+				}
 				else
+				{
 					break;
+				}
 
-				++num_entries;
+				m_num_entries++;
+				last_pos = m_file.tellg();
 			}
+			m_file.seekp(last_pos);
 			m_file.clear();
 
 			delete[] value;
-			return num_entries;
+			return m_num_entries;
 		}
 
 		// failed to open file for reading or bad header
@@ -127,10 +149,12 @@ public:
 	// Appends a key-value pair to the store.
 	void Append(const K &key, const V *value, u32 value_size)
 	{
-		// TODO: Should do a check that we don't already have "key"?
+		// TODO: Should do a check that we don't already have "key"? (I think each caller does that already.)
 		Write(&value_size);
 		Write(&key);
 		Write(value, value_size);
+		m_num_entries++;
+		Write(&m_num_entries);
 	}
 
 private:
@@ -174,6 +198,7 @@ private:
 	} m_header;
 
 	std::fstream m_file;
+	u32 m_num_entries;
 };
 
 #endif  // _LINEAR_DISKCACHE