Initial source files

acs_interface/ZMEMORY.acs

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+#library "ZMEMORY"
+#include "zcommon.acs"
+
+//Simple linked list implementation of malloc
+
+//Memory space
+global int 63:memory[];
+
+//NULL "pointer"
+#libdefine nullptr 0
+
+//Allocated size bytes in the memory space
+function int malloc (int size) {return 0;}
+
+//Frees an allocated block in the memory space.
+//There are no safeguards in this function to guess whether or not the free is 
+// valid, so be careful.
+function int free (int p_ptr) {return 0;}

src/LOADACS.txt

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+ZMEMORY

src/acs_source/ZMEMORY.acs

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+#library "ZMEMORY"
+#include "zcommon.acs"
+
+//Simple linked list implementation of malloc
+
+global int 63:memory[];
+
+#libdefine nullptr 0
+
+#define malloc_allocated 0
+#define malloc_size 1
+#define malloc_next_header 2
+#define malloc_prev_header 3
+#define malloc_num_header_properties 4
+
+#define p_malloc_init_flag_location 0
+#define p_malloc_first_header_location 1
+
+function int malloc (int size) {
+  log(s:"Invoked malloc");
+  //Do the setup on the first run of this function.
+  if(memory[p_malloc_init_flag_location] == FALSE) { //Default values for global values is 0, so this is true.
+    memory[p_malloc_init_flag_location] = TRUE;
+    memory[p_malloc_first_header_location+malloc_allocated] = FALSE;
+    memory[p_malloc_first_header_location+malloc_size] = -1; //"infinite"
+    memory[p_malloc_first_header_location+malloc_next_header] = nullptr; //nullptr
+    memory[p_malloc_first_header_location+malloc_prev_header] = nullptr; //nullptr
+  }
+  
+  int p_previous_header = nullptr;
+  int p_current_header = p_malloc_first_header_location;
+  int p_retval = nullptr;
+  
+  while(p_retval == nullptr) {
+    int memalloced = memory[p_current_header+malloc_allocated];
+    int memsize = memory[p_current_header+malloc_size];
+    if(memsize == -1) { //The end of the list.
+      memory[p_current_header+malloc_allocated] = TRUE;
+      memory[p_current_header+malloc_size] = size;
+      memory[p_current_header+malloc_next_header] = p_current_header+malloc_num_header_properties+size; //New EOL
+      memory[p_current_header+malloc_prev_header] = p_previous_header;
+      
+      //Retrieve the return value while we are at the allocated space.
+      p_retval = p_current_header+malloc_num_header_properties;
+      
+      //Remember to initialize the new end list node.
+      p_previous_header = p_current_header; //This is the header previous to the EOL.
+      p_current_header = memory[p_current_header+malloc_next_header];
+      //Set the tail node constants.
+      memory[p_current_header+malloc_allocated] = FALSE;
+      memory[p_current_header+malloc_size] = -1;
+      memory[p_current_header+malloc_next_header] = nullptr;
+      memory[p_current_header+malloc_prev_header] = p_previous_header;
+    } else if(memsize >= size && memalloced == FALSE) { //There is room here AND it isn't in use,
+      memory[p_current_header+malloc_allocated] = TRUE;
+      //The size isn't modified because we are re-using an existing space.
+      // It would be a good idea to check just how large this space is and act accordingly rather
+      //  than using a 500 indexes large space for a 4 indexes large object.
+      // Objects allocated in a doom mod probably won't be outside the 1-16 indexes range so it
+      //  should still be fine for most applications.
+      //The next header isn't changed either for the same reason.
+      if(memsize >= (size+malloc_num_header_properties+5)) { //Assume that 5 is the smallest useful allocation size.
+        int p_split_newheader = p_current_header+malloc_num_header_properties+size; //Just to the end of the allocation.
+        memory[p_split_newheader+malloc_allocated] = FALSE;
+        memory[p_split_newheader+malloc_size] = memory[p_current_header+malloc_size]-malloc_num_header_properties-size;
+        memory[p_split_newheader+malloc_next_header] = memory[p_current_header+malloc_next_header];
+        memory[p_split_newheader+malloc_prev_header] = p_current_header;
+        memory[p_current_header+malloc_next_header] = p_split_newheader; //The header whose block was split should have its next pointer set to its other half.
+        memory[p_current_header+malloc_size] = size; //Set the size of the allocation to reflect the split.
+      }
+      
+      //Retrieve the return value while we are at the allocated space.
+      p_retval = p_current_header+malloc_num_header_properties;
+    } else {
+      //The observed node isn't useful for allocating the request. Go to the next node.
+      p_previous_header = p_current_header;
+      p_current_header = memory[p_current_header+malloc_next_header];
+    }
+  }
+  
+  log(s:"Malloc allocated ", d:size, s:" indexes at location ", d:p_retval, s:" with header location ", d:p_current_header);
+  
+  return p_retval;
+}
+
+function int free (int p_ptr) {
+  log(s:"Invoked free");
+  
+  int p_header = p_ptr - malloc_num_header_properties;
+  
+  memory[p_header+malloc_allocated] = FALSE;
+  
+  int p_next = memory[p_header+malloc_next_header];
+  int p_prev = memory[p_header+malloc_prev_header];
+  
+  //Below is the merging of free blocks.
+  //It merges to the left (lower indexes) first becaue the right (larger 
+  // indexes) has a special case. (the end of the list)
+  
+  //the previous block is unused. Merge.
+  if(p_prev != nullptr //This doesn't make sense if the previous block doesn't exist.
+  && memory[p_prev+malloc_allocated] == FALSE) {
+    log(s:"Free attempting merge of header ", d:p_header, s: " to the left with header ", d:p_prev);
+    memory[p_prev+malloc_size] += memory[p_header+malloc_size] + malloc_num_header_properties;
+    memory[p_prev+malloc_next_header] = p_next; //The prev header needs to know the new next.
+    memory[p_next+malloc_prev_header] = p_prev; //The next header needs to know the new prev.
+    
+    //Now the two blocks are the same block. requires new initializations of the
+    // variables for the other check to function correctly.
+    //The header is the result of the merge, and the prev is the one before it.
+    p_header = p_prev;
+    p_prev = memory[p_header+malloc_prev_header];
+  }
+  
+  //The next block is unused. Merge.
+  //Note that p_next will never be a nullptr with correct usage.
+  if(memory[p_next+malloc_allocated] == FALSE) {
+    if(memory[p_next+malloc_size] == -1) { //EOL
+      memory[p_header+malloc_size] = -1;
+      memory[p_header+malloc_next_header] = nullptr;
+    } else {
+      int p_next_next = memory[p_next+malloc_next_header];
+      memory[p_header+malloc_size] += memory[p_next+malloc_size] + malloc_num_header_properties;
+      memory[p_header+malloc_next_header] = p_next_next; //The header on the other side of the next header needs to know its new prev.
+      memory[p_next_next+malloc_prev_header] = p_header; //This header needs to know its new next.
+    }
+  }
+  
+  
+  return -1;
+}
+
+//These are for debugging
+script "memory_write" (int index, int value) {
+  memory[index] = value;
+}
+
+script "memory_read" (int index) {
+  log(d:memory[index]);
+}
+
+script "memory_print_allocation_list" (void) {
+  int p_current_header = p_malloc_first_header_location;
+  
+  while(p_current_header != nullptr) {
+    log(s:  "Header location: ", d:p_current_header,
+        s:"\n Allocated flag: ", d:memory[p_current_header+malloc_allocated],
+        s:"\n Allocation size: ", d:memory[p_current_header+malloc_size],
+        s:"\n Prev header pointer: ", d:memory[p_current_header+malloc_prev_header],
+        s:"\n Next header pointer: ", d:memory[p_current_header+malloc_next_header],
+        s:"\n"
+        );
+    
+    p_current_header = memory[p_current_header+malloc_next_header];
+  }
+}