PL/0编译器(java version) – SymbolTable.java

   1:  package compiler;

   2:  //竟然没有对符号表检查大小，会溢出的。

   3:   

   4:  import java.io.IOException;

   5:   

   6:  public class SymbolTable {

   7:   

   8:      /**

   9:       * 当前名字表项指针(有效的符号表大小)table size

  10:       */

  11:      public int tablePtr = 0;

  12:      /**

  13:       * 符号表的大小

  14:       */

  15:      public static final int tableMax = 100;

  16:      public static final int symMax = 10;            //符号的最大长度

  17:      public static final int addrMax = 1000000;        //最大允许的数值

  18:      public static final int levMax = 3;            //最大允许过程嵌套声明层数[0,levmax]

  19:      public static final int numMax = 14;           //number的最大位数

  20:      public static boolean tableswitch;           //显示名字表与否

  21:      //名字表

  22:      public Item[] table = new Item[tableMax];

  23:   

  24:      public class Item {

  25:   

  26:          public static final int constant = 0;

  27:          public static final int variable = 1;

  28:          public static final int procedure = 2;

  29:          String name;                                             //名字

  30:          int type;                                               //类型，const var or procedur

  31:          int value;                                                 //数值，const使用

  32:          int lev;                                                 //所处层，var和procedur使用

  33:          int addr;                                                //地址，var和procedur使用

  34:          int size;                                               //需要分配的数据区空间，仅procedure使用

  35:   

  36:          public Item() {

  37:              super();

  38:              this.name = "";

  39:          }

  40:   

  41:      }

  42:   

  43:      /**

  44:       * 获得名字表某一项的内容

  45:       *

  46:       * @param i 名字表中的位置

  47:       * @return 名字表第i项的内容

  48:       */

  49:      public Item get(int i) {

  50:          if (table[i] == null) {

  51:              table[i] = new Item();

  52:          }

  53:          return table[i];

  54:      }

  55:   

  56:      /**

  57:       * 把某个符号登录到名字表中 名字表从1开始填，0表示不存在该项符号

  58:       *

  59:       * @param sym 要登记到名字表的符号

  60:       * @param k 该符号的类型：const,var,procedure

  61:       * @param lev 名字所在的层次

  62:       * @param dx 当前应分配的变量的相对地址，注意调用enter()后dx要加一

  63:       */

  64:      public void enter(Symbol sym, int type, int lev, int dx) {

  65:          tablePtr++;

  66:          Item item = get(tablePtr);

  67:          item.name = sym.id;

  68:          item.type = type;

  69:          switch (type) {

  70:              case Item.constant:                                     //常量名字

  71:                  item.value = sym.num;                               //记录下常数值的大小

  72:                  break;

  73:              case Item.variable:                                      //变量名字

  74:                  item.lev = lev;                                          //变量所在的层

  75:                  item.addr = dx;                                            //变量的偏移地址

  76:                  break;

  77:              case Item.procedure:                                    //过程名字

  78:                  item.lev = lev;

  79:   

  80:          }

  81:      }

  82:   

  83:      /**

  84:       * 在名字表中查找某个名字的位置 查找符号表是从后往前查， 这样符合嵌套分程序名字定义和作用域的规定

  85:       *

  86:       * @param idt 要查找的名字

  87:       * @return 如果找到则返回名字项的下标，否则返回0

  88:       */

  89:      public int position(String idt) {

  90:          for (int i = tablePtr; i > 0; i--) //必须从后往前找

  91:          {

  92:              if (get(i).name.equals(idt)) {

  93:                  return i;

  94:              }

  95:          }

  96:          return 0;

  97:      }

  98:   

  99:      /**

 100:       * 输出符号表内容，摘自block()函数

 101:       *

 102:       * @param start 当前符号表区间的左端

 103:       */

 104:      void debugTable(int start) {

 105:          if (tableswitch) //显示名字表与否

 106:          {

 107:              return;

 108:          }

 109:          System.out.println("**** Symbol Table ****");

 110:          if (start > tablePtr) {

 111:              System.out.println("  NULL");

 112:          }

 113:          for (int i = start + 1; i <= tablePtr; i++) {

 114:              try {

 115:                  String msg = "unknown table item !";

 116:                  switch (table[i].type) {

 117:                      case Item.constant:

 118:                          msg = "   " + i + "  const: " + table[i].name + "  val: " + table[i].value;

 119:                          break;

 120:                      case Item.variable:

 121:                          msg = "    " + i + "  var: " + table[i].name + "  lev: " + table[i].lev + "  addr: " + table[i].addr;

 122:                          break;

 123:                      case Item.procedure:

 124:                          msg = "    " + i + " proc: " + table[i].name + "  lev: " + table[i].lev + "  addr: " + table[i].size;

 125:                          break;

 126:                  }

 127:                  System.out.println(msg);

 128:                  PL0.tableWriter.write(msg + '\n');

 129:              } catch (IOException ex) {

 130:                  ex.printStackTrace();

 131:                  System.out.println("***write table intfo meet with error***");

 132:              }

 133:          }

 134:      }

 135:  }

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }