Snapshots now store raw size to speed up decompression

Author: dirkwhoffmann

Emulator/Media/Snapshot.cpp

@@ -73,6 +73,7 @@ Snapshot::Snapshot(isize capacity)
     header->minor = SNP_MINOR;
     header->subminor = SNP_SUBMINOR;
     header->beta = SNP_BETA;
+    header->rawSize = i32(data.size);
 }
 
 Snapshot::Snapshot(Amiga &amiga) : Snapshot(amiga.size())
@@ -175,14 +176,22 @@ Snapshot::uncompress()
 {
     if (isCompressed()) {
 
+        isize expectedSize = getHeader()->rawSize;
+        
         debug(SNP_DEBUG, "Uncompressing %ld bytes...", data.size);
 
         {   auto watch = util::StopWatch(SNP_DEBUG, "");
 
-            data.uncompress(2, sizeof(SnapshotHeader));
+            data.uncompress(2, sizeof(SnapshotHeader), expectedSize);
             getHeader()->compressed = false;
         }
         debug(SNP_DEBUG, "Uncompressed size: %ld bytes (hash: 0x%x)\n", data.size, data.fnv32());
+        
+        if (getHeader()->rawSize != expectedSize) {
+         
+            warn("Snaphot size: %ld. Expected: %ld\n", data.size, expectedSize);
+            fatalError;
+        }
     }
 }
 

Emulator/Media/Snapshot.h

@@ -43,6 +43,9 @@ struct SnapshotHeader {
     // Indicates if the snapshot contents is stored in compressed form
     bool compressed;
 
+    // Size of this snapshot when uncompressed
+    i32 rawSize;
+    
     // Preview image
     Thumbnail screenshot;
 };

Emulator/Utilities/Buffer.cpp

@@ -251,12 +251,14 @@ Allocator<T>::compress(isize n, isize offset)
 }
 
 template <class T> void
-Allocator<T>::uncompress(isize n, isize offset)
+Allocator<T>::uncompress(isize n, isize offset, isize expectedSize)
 {
     T prev = 0;
     isize repetitions = 0;
     std::vector<T> vec;
-    vec.reserve(size);
+
+    // Speed up by starting with a big enough container
+    if (expectedSize) vec.reserve(expectedSize);
 
     auto decode = [&](T element, isize count) {
 
@@ -304,7 +306,7 @@ template void Allocator<T>::copy(T *buf, isize offset, isize len) const; \
 template void Allocator<T>::patch(const u8 *seq, const u8 *subst); \
 template void Allocator<T>::patch(const char *seq, const char *subst); \
 template void Allocator<T>::compress(isize, isize); \
-template void Allocator<T>::uncompress(isize, isize);
+template void Allocator<T>::uncompress(isize, isize, isize);
 
 INSTANTIATE_ALLOCATOR(u8)
 INSTANTIATE_ALLOCATOR(u32)

Emulator/Utilities/Buffer.h

@@ -70,7 +70,7 @@ template <class T> struct Allocator {
 
     // Compresses or uncompresses a buffer
     void compress(isize n = 2, isize offset = 0);
-    void uncompress(isize n = 2, isize offset = 0);
+    void uncompress(isize n = 2, isize offset = 0, isize expectedSize = 0);
 };
 
 template <class T> struct Buffer : public Allocator <T> {