Patch: various Syscall changes

[Tom Tromey <tromey at redhat dot com>]

This patch makes a few changes to Syscall:

* Updates javadoc of syscallByNum
* Fixed typo in syscallByNum
* Changes syscallByNum to cache requested unknown syscalls, so that
  each Syscall object is unique
* Adds equals() method.  We don't really need this but it is a
  convenient place to add a comment
* Adds syscallByName.  This is needed for 'ftrace -e' (or "--trace" as
  I spell it in my impl...)

Tom

Index: ChangeLog
from  Tom Tromey  <tromey@redhat.com>

	* Syscall.java (syscallByNum): Updated javadoc.  Fixed typo.
	Cache unknown syscalls.
	(unknownSyscalls): New field.
	(equals): New method.
	(syscallByName): Likewise.

Index: Syscall.java
===================================================================
RCS file: /cvs/frysk/frysk-core/frysk/proc/Syscall.java,v
retrieving revision 1.11
diff -u -r1.11 Syscall.java
--- Syscall.java 24 Aug 2006 03:13:05 -0000 1.11
+++ Syscall.java 7 Sep 2006 01:29:16 -0000
@@ -38,6 +38,7 @@
 // exception.
 package frysk.proc;
 
+import java.util.HashMap;
 import inua.util.PrintWriter;
 
 /**
@@ -53,6 +54,10 @@
     String argList;
     boolean noreturn;
 
+    // This is used to keep track of syscalls whose number we do not
+    // know.
+    static HashMap unknownSyscalls;
+
     Syscall (String name, int number, int numArgs, 
 	     String argList, boolean noreturn)
     {
@@ -62,6 +67,7 @@
 	this.argList = argList;
 	this.noreturn = noreturn;
     }
+
     Syscall (String name, int number, int numArgs, String argList)
     {
 	this.name = name;
@@ -97,6 +103,13 @@
         return number;
     }
 
+    /** Return true if this object equals the argument.  */
+    public boolean equals(Object other)
+    {
+        // Syscall objects are unique.
+        return this == other;
+    }
+
     private void printStringArg (PrintWriter writer,
 				 frysk.proc.Task task,
 				 long addr)
@@ -215,17 +228,48 @@
     /**
      * Given a system call's number, this will return the corresponding
      * Syscall object.  Note that system call numbers are platform
-     * dependent.
+     * dependent.  This will return a Syscall object in all cases; if
+     * there is no predefined system call with the given number, a unique
+     * "unknown" system call with the indicated number will be
+     * returned.
      * XXX: Eventually this will be moved down to Linux, or even
      * further.
      * @param num the number of the system call
+     * @return the Syscall object
      */
     public static Syscall syscallByNum (int num)
     {
-      if(num >= syscallList.length || num < 0){
-        return new Syscall("UKNOWN SYSCALL", num);
-      }
-      return syscallList[num];
+      if (num >= 0 && num < syscallList.length)
+	return syscallList[num];
+      synchronized (Syscall.class)
+	{
+	  Integer key = new Integer(num);
+	  if (unknownSyscalls == null)
+	    unknownSyscalls = new HashMap();
+	  else if (unknownSyscalls.containsKey(key))
+	    return (Syscall) unknownSyscalls.get(key);
+	  Syscall result = new Syscall("UNKNOWN SYSCALL", num);
+	  unknownSyscalls.put(key, result);
+	  return result;
+	}
+    }
+
+    /**
+     * Given a system call's name, this will return the corresponding
+     * Syscall object.  If no predefined system call with that name
+     * is available, this will return null.
+     * XXX: Eventually this will be moved down to Linux, or even
+     * further.
+     * @param name the name of the system call
+     * @return the Syscall object, or null
+     * @throws NullPointerException if name is null
+     */
+    public static Syscall syscallByName (String name)
+    {
+      for (int i = 0; i < syscallList.length; ++i)
+	if (name.equals(syscallList[i].name))
+	  return syscallList[i];
+      return null;
     }
 
     private static Syscall[] syscallList = {