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6502bench/PluginCommon/AddressTranslate.cs
Andy McFadden b3dacc2613 Switch to left-handed coordinate system
There's no "standard" coordinate system, so the choice is arbitrary.
However, an examination of the Transporter mesh in Elite revealed
that the mesh was designed for a left-handed coordinate system.  We
can compensate for that trivially in the Elite visualizer, but we
might as well match what they're doing.  (The only change required
in the code is a couple of sign changes on the Z coordinate, and an
update to the rotation matrix.)

This also downsizes Matrix44 to Matrix33, exposes the rotation mode
enum, and adds a left-handed ZYX rotation mode.

This does mean that meshes that put the front at +Z will show their
backsides initially, since we're now oriented as if we're flying
the ships rather than facing them.  I considered adding a 180-degree
Y rotation (with a tweak to the rotation matrix handedness to correct
the first rotation axis) to have them facing by default, but figured
that might be confusing since +Z is supposed to be away.

Anybody who really wants it to be the other way can trivially flip
the coordinates in their visualizer (negate xc/zc).

The Z coordinates in the visualization test project were flipped so
that the design is still facing the viewer at rotation (0,0,0).
2020-03-14 13:59:08 -07:00

101 lines
4.2 KiB
C#

/*
* Copyright 2019 faddenSoft
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
using System;
using CommonUtil;
namespace PluginCommon {
/// <summary>
/// Read-only wrapper around AddressMap.
///
/// Instance is immutable, though in theory the underlying AddressMap could change if
/// some other code has a reference to it.
/// </summary>
/// <remarks>
/// This is currently simple enough that it could just be an interface, but I don't want
/// to rely on that remaining true.
///
/// TODO(maybe): add a "IsAddressRangeValid(int srcOffset, int addr, int length)" method
/// that verifies an entire address range is in memory. This would allow subsequent access
/// to skip error checks. (You still have to do the address-to-offset translation on every
/// byte though, which is where most of the expense is.)
/// TODO(maybe): add a "CopyAddressRange(byte[] data, int srcOffset, int addr, int length)"
/// that returns a newly-allocated buffer with the data copied out. This would allow fast
/// access to data that is split into multiple regions.
/// </remarks>
public class AddressTranslate {
private AddressMap mAddrMap;
public AddressTranslate(AddressMap addrMap) {
mAddrMap = addrMap;
}
/// <summary>
/// Converts a file offset to an address.
/// </summary>
/// <param name="offset">File offset.</param>
/// <returns>24-bit address.</returns>
public int OffsetToAddress(int offset) {
return mAddrMap.OffsetToAddress(offset);
}
/// <summary>
/// Determines the file offset that best contains the specified target address.
/// </summary>
/// <param name="srcOffset">Offset of the address reference. Only matters when
/// multiple file offsets map to the same address.</param>
/// <param name="targetAddr">Address to look up.</param>
/// <returns>The file offset, or -1 if the address falls outside the file.</returns>
public int AddressToOffset(int srcOffset, int targetAddr) {
return mAddrMap.AddressToOffset(srcOffset, targetAddr);
}
/// <summary>
/// Returns the data found at the specified address. If the address is out
/// of bounds this throws an AddressException.
/// </summary>
/// <param name="data">Data array.</param>
/// <param name="srcOffset">Offset of the address reference. Only matters when
/// multiple file offsets map to the same address.</param>
/// <param name="address">Data address.</param>
/// <returns>Data found.</returns>
public byte GetDataAtAddress(byte[] data, int srcOffset, int address) {
int offset = AddressToOffset(srcOffset, address);
if (offset == -1) {
Exception ex = new AddressTranslateException("Address $" + address.ToString("X4") +
" is outside the file bounds");
ex.Data.Add("Address", address);
throw ex;
}
try {
byte foo = data[offset];
} catch (Exception) {
throw new AddressTranslateException("FAILED at srcOff=$" + srcOffset.ToString("x4") +
" addr=$" + address.ToString("x4"));
}
return data[offset];
}
}
/// <summary>
/// Exception thrown by AddressTranslate's GetDataAtAddress().
/// </summary>
public class AddressTranslateException : Exception {
public AddressTranslateException() : base() { }
public AddressTranslateException(string msg) : base(msg) { }
}
}