Java pass1汇编器的符号表
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Symbol table of pass1 assembler
提问by chinu
I want to design a simple assembler for IBM360 assembly language.so i'm implementing symbol table first. i'm storing my symbols/labels in a separate file so as to compare it while generating the symbol table.the problem im facing is ,the incorrect location counter(LC) value due to unwanted comparisions.I'm able to detect the symbols but with the wrong LC value. can anyone guide me in modifying my code?
我想为 IBM360 汇编语言设计一个简单的汇编器。所以我首先实现符号表。我将我的符号/标签存储在一个单独的文件中，以便在生成符号表时进行比较。我面临的问题是，由于不需要的比较，位置计数器（LC）值不正确。我能够检测到符号但 LC 值错误。谁能指导我修改我的代码？
Here is my program :
这是我的程序：
import java.io.*;
import java.lang.*;
class SymbolTable
{
public static void main(String args[]) throws Exception
{
FileReader fr = new FileReader("program.asm");
BufferedReader br = new BufferedReader(fr);
String s,l;
String code[]=new String[100];
String label[]=new String[100];
int N=0,i,LOC=0,n=0,j;
System.out.println("Assembly lang program :\n--------------------------");
while((s = br.readLine()) != null)
{
code[N++]=s;
System.out.println(s);
}
fr.close();
FileReader labels = new FileReader("label.txt");
BufferedReader buff = new BufferedReader(labels);
while((s = buff.readLine()) != null)
{
label[n++]=s;
}
labels.close();
System.out.println("\n\n SYMBOL TABLE :\n-------------------------------------------\nLABEL\tLC\tLENGTH\tRELATIVE/ABSOLUTE\n-------------------------------------------");
for(i=0;i<N;i++)
{
for(j=0;j<n;j++)
{
char codearr[]=new char[15];
codearr=code[i].toCharArray();
if(code[i].startsWith("USING"))
{
break;
}
else if(code[i].startsWith(label[j]))
{
System.out.println(label[j]+"\t"+LOC+"\t4\tR");
if(i==0)
{}
else
LOC=LOC+4;
break;
}
else if(codearr[1]=='R') // for register addressing mode
LOC=LOC+2;
else
LOC=LOC+4;
}
}
}
}
program.asm:
程序.asm：
JOHN START
USING *,15
L 1,FIVE
A 1,FOUR
ST 1,TEMP
FOUR DC F '4'
FIVE DC F '5'
TEMP DS 1F
END
label.txt
标签.txt
JOHN
FOUR
FIVE
TEMP
output :
输出 ：
G:\programs>javac SymbolTable.java
G:\programs>java SymbolTable
Assembly lang program :
--------------------------
JOHN START
USING *,15
LR 1,FIVE
A 1,FOUR
ST 1,TEMP
FOUR DC F '4'
FIVE DC F '5'
TEMP DS 1F
END
SYMBOL TABLE :
-------------------------------------------
LABEL LC LENGTH RELATIVE/ABSOLUTE
-------------------------------------------
JOHN 0 4 R
FOUR 44 4 R
FIVE 56 4 R
TEMP 72 4 R
回答by blackcompe
Here's an example to help you see your way through. I'm not aware of the language ins and outs, but based on the input you provided, this example should help. It builds the symbol table from labels matched at the beginning of the opcode, which I assume is the correct syntax for demarcating code sections associated with a label. The code makes assumptions and doesn't check against possible conflicts, but you can figure all that out. Feel free to build off it.
这是一个示例，可帮助您了解自己的方法。我不知道语言的来龙去脉，但根据您提供的输入，此示例应该会有所帮助。它根据在操作码开头匹配的标签构建符号表，我认为这是划分与标签关联的代码部分的正确语法。该代码进行假设并且不检查可能的冲突，但您可以弄清楚所有这些。随意构建它。
Input
输入
The exact input you provided.
您提供的确切输入。
Output
输出
JOHN 0 true
FOUR 50 true
TEMP 78 true
FIVE 64 true
Code
代码
import java.io.File;
import java.io.IOException;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Objects;
class SymbolTableBuilder
{
public static SymbolTable build(String asm, String lbls)
{
return build(asm.split("\n"), lbls.split("\n"));
}
public static SymbolTable build(String[] asm, String[] lbls)
{
return build(Arrays.asList(asm), Arrays.asList(lbls));
}
public static SymbolTable build(File asm, File lbls)
{
//TODO
return null;
}
public static SymbolTable build(List<String> asm, List<String> lbls)
{
SymbolTable tbl = new SymbolTable();
int pos = 0;
for (String opCode : asm) {
String tok = opCode.split("\s+")[0];
if (lbls.contains(tok))
tbl.addSymbol(tok, new Symbol(tok, pos, true));
pos += opCode.length() + 1; //account for newline
}
return tbl;
}
public static void main(String[] args) throws IOException
{
final String asm
= "JOHN START\nUSING *,15\nL 1,FIVE\nA 1,FOUR\n"
+ "ST 1,TEMP\nFOUR DC F '4'\nFIVE DC F '5'\nTEMP DS 1F\nEND";
final String lbls = "JOHN\nFOUR\nFIVE\nTEMP";
for (Entry<String, Symbol> e : SymbolTableBuilder.build(asm, lbls))
System.out.println(e.getValue());
}
}
class SymbolTable implements Iterable<Entry<String, Symbol>>
{
private Map<String, Symbol> syms;
public SymbolTable()
{
syms = new HashMap<>();
}
public void addSymbol(String key, Symbol sym)
{
syms.put(key, sym);
}
public Symbol getSymbol(String key)
{
return syms.get(key);
}
@Override
public Iterator<Entry<String, Symbol>> iterator()
{
return syms.entrySet().iterator();
}
}
class Symbol
{
String label;
int loc;
boolean relative;
public Symbol(String label, int loc, boolean relative)
{
this.label = label;
this.loc = loc;
this.relative = relative;
}
@Override
public int hashCode()
{
int hash = 3;
hash = 29 * hash + Objects.hashCode(this.label);
return hash;
}
@Override
public boolean equals(Object obj)
{
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
final Symbol other = (Symbol) obj;
if (!Objects.equals(this.label, other.label)) return false;
return true;
}
@Override
public String toString()
{
return label + "\t" + loc + "\t" + relative;
}
}
