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Rename and parameterize crc function to crc32

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This commit is contained in:
Dominic Höglinger 2026-04-25 11:57:15 +02:00
parent a05903df4d
commit 4d9ce95f6f
2 changed files with 69 additions and 20 deletions
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41
Parser/XnParser.cs
View File

@ -35,7 +35,7 @@ namespace XNeedle.Parser
static Parser<Expression> Function(Context ctx)
{
return
from name in Parse.Letter.AtLeastOnce().Text()
from name in Identifier
from lparen in Parse.Char('(')
from expr in Parse.Ref(() => Expr(ctx)).DelimitedBy(Parse.Char(',').Token()).Optional()
from rparen in Parse.Char(')')
@ -46,23 +46,44 @@ namespace XNeedle.Parser
{
var mathMethodInfo = typeof(Math).GetTypeInfo().GetMethod(name, parameters.Select(e => e.Type).ToArray());
if (mathMethodInfo != null)
{
return Expression.Call(mathMethodInfo, parameters);
}
var ctxMethodInfo = typeof(ContextFunctions).GetTypeInfo().GetMethod(name, parameters.Select(e => e.Type).Prepend(typeof(Context)).ToArray());
// Find by name and fill in optional parameters with their default values
var ctxMethodInfo = typeof(ContextFunctions).GetTypeInfo()
.GetMethods()
.FirstOrDefault(m =>
{
if (m.Name != name) return false;
var mp = m.GetParameters();
if (mp.Length == 0 || mp[0].ParameterType != typeof(Context)) return false;
int required = mp.Skip(1).Count(p => !p.HasDefaultValue);
return parameters.Length >= required && parameters.Length <= mp.Length - 1;
});
if (ctxMethodInfo != null)
{
return Expression.Call(ctxMethodInfo, parameters.Prepend(CtxParam).ToArray());
var mp = ctxMethodInfo.GetParameters();
var args = mp.Skip(1).Select((p, i) =>
i < parameters.Length
? parameters[i]
: Expression.Constant(p.DefaultValue, p.ParameterType)
).ToArray();
return Expression.Call(ctxMethodInfo, args.Prepend(CtxParam).ToArray());
}
throw new ParseException(string.Format("Function '{0}({1})' does not exist.", name,
string.Join(",", parameters.Select(e => e.Type.Name))));
}
public static readonly Parser<string> HexNumber =
from prefix in Parse.String("0x").Token()
from number in Parse.Char(char.IsAsciiHexDigit, "hexadecimal digit").AtLeastOnce().Text()
select number;
static readonly Parser<Expression> NumberConstant =
Parse.Decimal
.Select(x => Expression.Constant(double.Parse(x)))
.Named("number");
HexNumber.Select(x => Expression.Constant(int.Parse(x, System.Globalization.NumberStyles.HexNumber)))
.XOr(Parse.Decimal.Select(x => Expression.Constant(double.Parse(x))))
.Named("number");
private static readonly Parser<Expression> StringConstant =
from open in Parse.Char('"')
@ -183,10 +204,6 @@ namespace XNeedle.Parser
from arguments in Argument.DelimitedBy(Parse.Char(',').Token())
from close in Parse.Char(')')
select new Call{Identifier = new string(identifier.ToArray()), Arguments = arguments};
/*public static readonly Parser<Expression> ExpressionObject =
from expression in CallObject
*/
public static CommentParser Comment = new CommentParser { Single = "#", NewLine = Environment.NewLine };

48
Transformation/ContextFunctions.cs
View File

@ -26,7 +26,41 @@ namespace XNeedle.Transformation
level++;
return level;
}
public static double crc(Context ctx)
private static uint ComputeCrc32(byte[] data, uint poly, uint init, uint xorOut, bool reflected)
{
uint crc = init;
uint polyReflected = ReflectBits(poly, 32);
foreach (byte b in data)
{
if (reflected)
{
crc ^= b;
for (int i = 0; i < 8; i++)
crc = (crc & 1) != 0 ? (crc >> 1) ^ polyReflected : crc >> 1;
}
else
{
crc ^= (uint)b << 24;
for (int i = 0; i < 8; i++)
crc = (crc & 0x80000000u) != 0 ? (crc << 1) ^ poly : crc << 1;
}
}
return crc ^ xorOut;
}
private static uint ReflectBits(uint value, int bits)
{
uint reflected = 0;
for (int i = 0; i < bits; i++)
{
if ((value & (1u << i)) != 0)
reflected |= 1u << (bits - 1 - i);
}
return reflected;
}
public static double crc32(Context ctx, int poly = 0x04C11DB7, int init = 0, int xorOut = 0, bool reflected = false)
{
if (ctx.Node is null)
return 0;
@ -36,17 +70,15 @@ namespace XNeedle.Transformation
ctx.Node.WriteTo(writer);
writer.Flush();
string xml = buffer.ToString();
// Step 2: Extract all text after the opening tag through and including the closing tag
string tagName = ctx.Node.Name.LocalName;
string data = XmlFragParser.ChecksumData(tagName).Parse(xml);
//byte[] fragBytes = ctx.SLoc.Encoding.GetBytes(data);
byte[] fragBytes = Encoding.UTF8.GetBytes(data);
// Step 3: Digest into CRC32 using the source encoding
var crc32 = new System.IO.Hashing.Crc32();
crc32.Append(ctx.SLoc.Encoding.GetBytes(data));
uint result = BitConverter.ToUInt32(crc32.GetCurrentHash());
return (double)result;
// Step 3: Digest into CRC32 using parameterized CRC32 - by default MPEG-2
return (double)ComputeCrc32(fragBytes, (uint)poly, (uint)init, (uint)xorOut, reflected);
}
public static string text(Context ctx)