net.mograsim.machine/src/net/mograsim/machine/standard/memory/WordAddressableMemory.java

   1 package net.mograsim.machine.standard.memory;
   2
   3 import java.util.Arrays;
   4 import java.util.HashMap;
   5
   6 import net.mograsim.logic.core.types.Bit;
   7 import net.mograsim.logic.core.types.BitVector;
   8
   9 public class WordAddressableMemory
  10 {
  11         private final int cellWidth;
  12         private final long minimalAddress, maximalAddress;
  13         private final int pageSize = 64;
  14
  15         private HashMap<Long, Page> pages;
  16
  17         public WordAddressableMemory(int cellWidth, long minimalAddress, long maximalAddress)
  18         {
  19                 super();
  20                 this.cellWidth = cellWidth;
  21                 this.minimalAddress = minimalAddress;
  22                 this.maximalAddress = maximalAddress;
  23                 this.pages = new HashMap<>();
  24         }
  25
  26         public void setCell(long address, BitVector b)
  27         {
  28                 if (address < minimalAddress || address > maximalAddress)
  29                         throw new IndexOutOfBoundsException(String.format("Memory address out of bounds! Minimum: %d Maximum: %d Actual: %d",
  30                                         minimalAddress, maximalAddress, address));
  31                 long page = address / pageSize;
  32                 int offset = (int) (address % pageSize);
  33                 Page p = pages.get(Long.valueOf(page));
  34                 if (p == null)
  35                         pages.put(page, p = new Page());
  36                 p.setCell(offset, b);
  37         }
  38
  39         public BitVector getCell(long address)
  40         {
  41                 long page = address / pageSize;
  42                 int offset = (int) (address % pageSize);
  43                 Page p = pages.get(Long.valueOf(page));
  44                 if (p == null)
  45                         return BitVector.of(Bit.U, cellWidth);
  46                 return p.getCell(offset);
  47         }
  48
  49         private class Page
  50         {
  51                 private BitVector[] memory;
  52
  53                 public Page()
  54                 {
  55                         memory = new BitVector[pageSize];
  56                 }
  57
  58                 public BitVector getCell(int index)
  59                 {
  60                         BitVector b = memory[index];
  61                         if (b == null)
  62                                 return BitVector.of(Bit.U, cellWidth);
  63                         return memory[index];
  64                 }
  65
  66                 public void setCell(int index, BitVector bits)
  67                 {
  68                         if (bits.length() != cellWidth)
  69                                 throw new IllegalArgumentException(String.format(
  70                                                 "BitVector to be saved in memory cell has unexpected length. Expected: %d Actual: %d", cellWidth, bits.length()));
  71                         memory[index] = bits;
  72                 }
  73
  74                 @Override
  75                 public String toString()
  76                 {
  77                         return Arrays.deepToString(memory);
  78                 }
  79         }
  80 }