1 files changed, 191 insertions, 0 deletions
diff --git a/src/common/linear_disk_cache.h b/src/common/linear_disk_cache.h
new file mode 100644
index 000000000..da5d6b9b4
--- /dev/null
+++ b/src/common/linear_disk_cache.h
@@ -0,0 +1,191 @@
+// Copyright 2013 Dolphin Emulator Project
+// Licensed under GPLv2
+// Refer to the license.txt file included.
+
+
+#ifndef _LINEAR_DISKCACHE
+#define _LINEAR_DISKCACHE
+
+#include "common.h"
+#include <fstream>
+
+// defined in Version.cpp
+extern const char *scm_rev_git_str;
+
+// On disk format:
+//header{
+// u32 'DCAC';
+// u32 version;  // svn_rev
+// u16 sizeof(key_type);
+// u16 sizeof(value_type);
+//}
+
+//key_value_pair{
+// u32 value_size;
+// key_type   key;
+// value_type[value_size]   value;
+//}
+
+template <typename K, typename V>
+class LinearDiskCacheReader
+{
+public:
+    virtual void Read(const K &key, const V *value, u32 value_size) = 0;
+};
+
+// Dead simple unsorted key-value store with append functionality.
+// No random read functionality, all reading is done in OpenAndRead.
+// Keys and values can contain any characters, including \0.
+//
+// Suitable for caching generated shader bytecode between executions.
+// Not tuned for extreme performance but should be reasonably fast.
+// Does not support keys or values larger than 2GB, which should be reasonable.
+// Keys must have non-zero length; values can have zero length.
+
+// K and V are some POD type
+// K : the key type
+// V : value array type
+template <typename K, typename V>
+class LinearDiskCache
+{
+public:
+    // return number of read entries
+    u32 OpenAndRead(const char *filename, LinearDiskCacheReader<K, V> &reader)
+    {
+        using std::ios_base;
+
+        // close any currently opened file
+        Close();
+        m_num_entries = 0;
+
+        // try opening for reading/writing
+        OpenFStream(m_file, 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
+            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) && 
+                    Read(&entry_number) &&
+                    entry_number == m_num_entries+1)
+                 {
+                    reader.Read(key, value, value_size);
+                }
+                else
+                {
+                    break;
+                }
+
+                m_num_entries++;
+                last_pos = m_file.tellg();
+            }
+            m_file.seekp(last_pos);
+            m_file.clear();
+
+            delete[] value;
+            return m_num_entries;
+        }
+
+        // failed to open file for reading or bad header
+        // close and recreate file
+        Close();
+        m_file.open(filename, ios_base::out | ios_base::trunc | ios_base::binary);
+        WriteHeader();
+        return 0;
+    }
+    
+    void Sync()
+    {
+        m_file.flush();
+    }
+
+    void Close()
+    {
+        if (m_file.is_open())
+            m_file.close();
+        // clear any error flags
+        m_file.clear();
+    }
+
+    // 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"? (I think each caller does that already.)
+        Write(&value_size);
+        Write(&key);
+        Write(value, value_size);
+        m_num_entries++;
+        Write(&m_num_entries);
+    }
+
+private:
+    void WriteHeader()
+    {
+        Write(&m_header);
+    }
+
+    bool ValidateHeader()
+    {
+        char file_header[sizeof(Header)];
+
+        return (Read(file_header, sizeof(Header))
+            && !memcmp((const char*)&m_header, file_header, sizeof(Header)));
+    }
+
+    template <typename D>
+    bool Write(const D *data, u32 count = 1)
+    {
+        return m_file.write((const char*)data, count * sizeof(D)).good();
+    }
+
+    template <typename D>
+    bool Read(const D *data, u32 count = 1)
+    {
+        return m_file.read((char*)data, count * sizeof(D)).good();
+    }
+
+    struct Header
+    {
+        Header()
+            : id(*(u32*)"DCAC")
+            , key_t_size(sizeof(K))
+            , value_t_size(sizeof(V))
+        {
+            memcpy(ver, scm_rev_git_str, 40);
+        }
+
+        const u32 id;
+        const u16 key_t_size, value_t_size;
+        char ver[40];
+
+    } m_header;
+
+    std::fstream m_file;
+    u32 m_num_entries;
+};
+
+#endif  // _LINEAR_DISKCACHE