NativeString.java
/*
** Module : NativeString.java
** Abstract : descriptor for text data as an argument or return value to a native function
**
** Copyright (c) 2014-2017, Golden Code Development Corporation.
**
** -#- -I- --Date-- ---------------------------------Description---------------------------------
** 001 GES 20140107 First version.
** 002 GES 20140201 Complete rewrite of the render() method to override the parent's version. It
** is important to write strings into their own memory buffer and then write the
** pointer into the given buffer. On restore(), the parent's version is fine.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
** Under Section 7 of the GNU Affero GPL version 3, the following additional
** terms apply to the works covered under the License. These additional terms
** are non-permissive additional terms allowed under Section 7 of the GNU
** Affero GPL version 3 and may not be removed by you.
**
** 0. Attribution Requirement.
**
** You must preserve all legal notices or author attributions in the covered
** work or Appropriate Legal Notices displayed by works containing the covered
** work. You may not remove from the covered work any author or developer
** credit already included within the covered work.
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**
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*/
package com.goldencode.p2j.library;
import java.io.*;
import java.math.*;
import com.goldencode.p2j.util.*;
/**
* A descriptor for text data as an argument or return value to a native function.
*/
public class NativeString
extends NativePrimitive
{
/** Amount of extra bytes allocated to reduce the change of buffer overflows. */
private static int BUFFER_PADDING = 128;
/** The stored value (defaults to empty string). */
protected String value = "";
/**
* Default constructor.
*/
public NativeString()
{
super();
type = LibraryManager.TYPE_POINTER;
}
/**
* Access the data element.
*
* @return The doubleing point data element.
*/
public String getValue()
{
return value;
}
/**
* Assign the data element.
*
* @param value
* The new text data element. Ignored if <code>null</code>.
*/
public void setValue(String value)
{
if (value != null)
this.value = value;
}
/**
* Replacement for the default object reading method. The latest
* state is read from the input source. The parent's state is
* read first.
*
* @param in
* The input source from which fields will be restored.
*
* @throws IOException
* In case of I/O errors.
* @throws ClassNotFoundException
* If payload can't be instantiated.
*/
public void readExternal(ObjectInput in)
throws IOException,
ClassNotFoundException
{
super.readExternal(in);
value = (String) in.readObject();
}
/**
* Replacement for the default object writing method. The latest
* state is written to the output destination. The parent's state is
* written first.
*
* @param out
* The output destination to which fields will be saved.
*
* @throws IOException
* In case of I/O errors.
*/
public void writeExternal(ObjectOutput out)
throws IOException
{
super.writeExternal(out);
out.writeObject(value);
}
/**
* Report the size (in bytes) of the native memory needed to store this instance.
* <p>
* This should never be called on the server, only on the client side.
*
* @return This is always the size of a pointer on the client platform.
*/
public int size()
{
return LibraryManager.ptrSize();
}
/**
* Copy our data into a large-enough buffer in native memory and then render the buffer's
* address into native memory if an explicit address is provided and return the data's
* address to the caller.
* <p>
* This should never be called on the server, only on the client side.
*
* @param addr
* The memory address into which the address should be rendered, if the caller
* is supplying a buffer or 0 if the internally created buffer's address should be
* returned directly.
*
* @return The memory address of the buffer or 0 if there is no data to output.
*/
public long render(long addr)
{
// make sure there is room for the null terminator and the value itself
int sz = value.length() + 1 + BUFFER_PADDING;
// save off the buffer for restore later
ref = new memptr();
ref.setLength(sz);
// since we are always passed as a pointer, we always copy our data into the
// native buffer; this will always result in at least the empty string (a null
// terminator in the first position of the buffer)
writeNative(ref);
// - return parms (always scalar) do not call through here
// - non-return scalar parm types will have addr == 0 and we just need to return the
// target address of our newly created buffer memptr
// - array elements will be called with addr != 0 because the address needs to be
// written to memory controlled by the caller
// return our buffer's address
long target = ref.getPointerValue().longValue();
// write it into the caller's buffer if specified
if (addr != 0)
{
memptr local = new memptr();
local.setPointerValue(addr);
if (size() == 4)
{
local.setLong(target, 1);
}
else
{
local.setInt64(target, 1);
}
}
return target;
}
/**
* Worker method to read the primitive value from the first index position of the given
* memory buffer.
*
* @param ptr
* The memory buffer to reference.
*/
protected void readNative(memptr ptr)
{
character txt = ptr.getString(1);
if (!txt.isUnknown())
{
value = txt.toStringMessage();
}
}
/**
* Worker method to write the primitive value to the first index position of the given
* memory buffer.
*
* @param ptr
* The memory buffer to reference.
*/
protected void writeNative(memptr ptr)
{
ptr.setString(value, 1);
}
}