private string HandleTimesDirective(IReadOnlyList <string> aSegments,
ref int aArgIndex,
ref DirectiveCodes aDirCode)
{
// Skip the TIMES directive term as it will
// trigger an early loop break below.
++aArgIndex;
object?dirCode = null;
string timesExprStr = string.Empty;
var hasValidDir = false;
var len = aSegments.Count;
for (; aArgIndex < len; aArgIndex++)
{
if (!Enum.TryParse(typeof(DirectiveCodes),
aSegments[aArgIndex].ToUpper(),
out dirCode))
{
// We have not found a valid directive.
// Add this argument to the expression string.
timesExprStr += aSegments[aArgIndex];
continue;
}
// Ensure that this directive can use the times
// prefix.
hasValidDir = dirCode switch
{
DirectiveCodes.DB => true,
_ => false
};
break;
}
// We did not find a valid directive after the times
// prefix. This syntax is invalid.
// We have to null check dirCode here as the compiler
// doesn't understand that it cannot ever be null here.
if (!hasValidDir || dirCode is null)
{
AsmParser.Assert(true,
AsmParser.ExIDs.InvalidDirectiveType);
return(string.Empty);
}
// Update the directive code.
aDirCode = (DirectiveCodes)dirCode;
return(timesExprStr);
}
public CompilerDir?ParseDirLine(ReadOnlySpan <char> aLine)
{
// Fast path return for lines that are comments.
if (aLine[0] == ';')
{
return(null);
}
var len = aLine.Length;
var buffer = new StringBuilder(len);
var segments = new List <string>();
var skipNext = false;
var inString = false;
var skipUntilEnd = false;
var pushString = false;
for (var i = 0; i <= len; i++)
{
// Always ensure that we push the last segment to
// the list.
// This needs to be done here otherwise we might end
// up skipping the entire last segment of the line.
if (i == len)
{
// We should not be attempting to push a line
// that has an unmatched string.
AsmParser.Assert(inString,
AsmParser.ExIDs.MismatchedString,
segments.Count + 1,
i);
if (buffer.Length > 0)
{
segments.Add(buffer.ToString());
}
break;
}
var c = aLine[i];
switch (c)
{
case '"':
case '\'':
inString = !inString;
break;
case ';':
skipUntilEnd = !inString;
break;
case ',':
skipNext = !inString;
pushString = !inString;
break;
case { } when c == AsmParser.LineContinuation:
skipNext = !inString;
break;
case { } when char.IsWhiteSpace(c):
pushString = !inString;
skipNext = !inString;
break;
}
// Do we need to push the contents of the buffer
// into the segment list?
if (pushString)
{
if (buffer.Length > 0)
{
segments.Add(buffer.ToString());
buffer.Clear();
}
pushString = false;
}
// Do we need to skip this character?
if (skipNext || skipUntilEnd)
{
skipNext = false;
continue;
}
buffer.Append(c);
}
return(BuildDirective(segments.ToArray()));
}
private CompilerDir?BuildDirective(IReadOnlyList <string> aSegments,
int aStartIndex = 0)
{
// The line could not be a valid directive with
// less than three segments.
if (aSegments.Count < 3)
{
return(null);
}
// If this is the first segment (startIndex == 0)
// then the directive label will be the first entry
// of the segment array. Otherwise it will be empty.
// This will be the case in sub directives.
var dirLabel =
aStartIndex == 0 ? aSegments[0] : string.Empty;
object?dirCodeObj = null;
var foundDirective = false;
var len = aSegments.Count;
var argIndex = aStartIndex == 0 ? 1 : aStartIndex;
for (; argIndex < len; argIndex++)
{
// Did we find a known directive identifier?
foundDirective =
Enum.TryParse(typeof(DirectiveCodes),
aSegments[argIndex].ToUpper(),
out dirCodeObj);
if (foundDirective)
{
break;
}
}
// We did not find a valid directive within the
// input arguments. The data must be invalid.
if (!foundDirective || dirCodeObj is null)
{
AsmParser.Assert(true,
AsmParser.ExIDs.InvalidDirectiveType);
return(null);
}
var dirCode = (DirectiveCodes)dirCodeObj;
// Are we working with a times directive?
string?timesPreExprStr = null;
if (dirCode == DirectiveCodes.TIMES)
{
timesPreExprStr =
HandleTimesDirective(aSegments,
ref argIndex,
ref dirCode);
}
// Advance to the next segment.
++argIndex;
// Which type of directive are we parsing?
var canHaveSubDirective = false;
string?directiveStrData = null;
byte[]? directiveData = null;
switch (dirCode)
{
case DirectiveCodes.DB:
canHaveSubDirective = true;
directiveData =
ParseDbDirectiveArgs(aSegments, ref argIndex);
break;
case DirectiveCodes.EQU:
// We only expect a single argument with
// the EQU directive, any additional arguments
// will simply be disregarded.
directiveStrData = aSegments[2];
break;
case DirectiveCodes.TIMES:
default:
AsmParser.Assert(true,
AsmParser.ExIDs.InvalidDirectiveType);
break;
}
// Do we need to handle a sub directive here?
CompilerDir?subDir = null;
if (canHaveSubDirective && argIndex < len)
{
// We do not handle nested sub directives.
AsmParser.Assert((aStartIndex > 0),
AsmParser.ExIDs.NestedSubQuery);
// We have a sub directive to handle.
// This will usually be a "TIMES" directive.
// We will start processing the sub directive
// from the current argument index.
subDir = BuildDirective(aSegments, argIndex);
}
// We are done! Construct and return the
// compiler directive object.
return
(new CompilerDir(dirCode,
dirLabel,
directiveData,
directiveStrData,
timesPreExprStr,
subDir));
}