elna/source/Parser.elna

implementation module Parser;

from SYSTEM import TSIZE;

from MemUtils import MemZero;
from Storage import ALLOCATE, REALLOCATE;

from Lexer import LexerKind, LexerToken, lexer_current, lexer_lex;

(* Calls lexer_lex() but skips the comments. *)
proc transpiler_lex(lexer: PLexer) -> LexerToken;
var
  result: LexerToken;
begin
  result := lexer_lex(lexer);

  while result.kind = lexerKindComment do
    result := lexer_lex(lexer)
  end;

  return result
end;

proc parse_type_fields(lexer: PLexer) -> PAstFieldDeclaration;
var
  token: LexerToken;
  field_declarations: PAstFieldDeclaration;
  field_count: CARDINAL;
  current_field: PAstFieldDeclaration;
begin
  ALLOCATE(field_declarations, TSIZE(AstFieldDeclaration));
  token := transpiler_lex(lexer);
  field_count := 0;

  while token.kind <> lexerKindEnd do
    INC(field_count);
	REALLOCATE(field_declarations, TSIZE(AstFieldDeclaration) * (field_count + 1));
    current_field := field_declarations;
    INC(current_field , TSIZE(AstFieldDeclaration) * (field_count - 1));

    token := transpiler_lex(lexer);

    current_field^.field_name := token.identifierKind;

    token := transpiler_lex(lexer);
    current_field^.field_type := parse_type_expression(lexer);
    token := transpiler_lex(lexer);

    if token.kind = lexerKindSemicolon then
      token := transpiler_lex(lexer)
    end
  end;
  INC(current_field, TSIZE(AstFieldDeclaration));
  MemZero(current_field, TSIZE(AstFieldDeclaration));

  return field_declarations
end;

proc parse_record_type(lexer: PLexer) -> PAstTypeExpression;
var
  result: PAstTypeExpression;
begin
  ALLOCATE(result, TSIZE(AstTypeExpression));
  result^.kind := astTypeExpressionKindRecord;
  result^.fields := parse_type_fields(lexer);

  return result
end;

proc parse_pointer_type(lexer: PLexer) -> PAstTypeExpression;
var
  token: LexerToken;
  result: PAstTypeExpression;
begin
  ALLOCATE(result, TSIZE(AstTypeExpression));
  result^.kind := astTypeExpressionKindPointer;

  token := lexer_current(lexer);

  if token.kind = lexerKindPointer then
    token := transpiler_lex(lexer)
  end;
  token := lexer_current(lexer);
  result^.target := parse_type_expression(lexer);

  return result
end;

proc parse_array_type(lexer: PLexer) -> PAstTypeExpression;
var
  token: LexerToken;
  buffer: [20]CHAR;
  result: PAstTypeExpression;
begin
  ALLOCATE(result, TSIZE(AstTypeExpression));
  result^.kind := astTypeExpressionKindArray;
  result^.length := 0;

  token := lexer_current(lexer);

  if token.kind = lexerKindArray then
    token := transpiler_lex(lexer)
  end;
  if token.kind <> lexerKindOf then
    token := transpiler_lex(lexer);

    result^.length := token.integerKind;

    token := transpiler_lex(lexer);
  end;
  token := transpiler_lex(lexer);
  result^.base := parse_type_expression(lexer);

  return result
end;

proc parse_enumeration_type(lexer: PLexer) -> PAstTypeExpression;
var
  token: LexerToken;
  result: PAstTypeExpression;
  current_case: PIdentifier;
  case_count: CARDINAL;
begin
  ALLOCATE(result, TSIZE(AstTypeExpression));
  result^.kind := astTypeExpressionKindEnumeration;

  case_count := 1;
  ALLOCATE(result^.cases, TSIZE(Identifier) * 2);
  token := transpiler_lex(lexer);
  current_case := result^.cases;
  current_case^ := token.identifierKind;

  token := transpiler_lex(lexer);

  while token.kind = lexerKindComma do
    token := transpiler_lex(lexer);

    INC(case_count);
    REALLOCATE(result^.cases, TSIZE(Identifier) * (case_count + 1));
    current_case := result^.cases;
	INC(current_case, TSIZE(Identifier) * (case_count - 1));
	current_case^ := token.identifierKind;

    token := transpiler_lex(lexer)
  end;
  INC(current_case, TSIZE(Identifier));
  MemZero(current_case, TSIZE(Identifier));

  return result
end;

proc parse_named_type(lexer: PLexer) -> PAstTypeExpression;
var
  token: LexerToken;
  result: PAstTypeExpression;
  written_bytes: CARDINAL;
begin
  token := lexer_current(lexer);
  ALLOCATE(result, TSIZE(AstTypeExpression));

  result^.kind := astTypeExpressionKindNamed;
  result^.name := token.identifierKind;

  return result
end;

proc parse_procedure_type(lexer: PLexer) -> PAstTypeExpression;
var
  token: LexerToken;
  result: PAstTypeExpression;
  current_parameter: PPAstTypeExpression;
  parameter_count: CARDINAL;
begin
  parameter_count := 0;
  ALLOCATE(result, TSIZE(AstTypeExpression));
  result^.kind := astTypeExpressionKindProcedure;

  ALLOCATE(result^.parameters, 1);

  token := transpiler_lex(lexer);
  token := transpiler_lex(lexer);

  while token.kind <> lexerKindRightParen do
    INC(parameter_count);
    REALLOCATE(result^.parameters, TSIZE(PAstTypeExpression) * (parameter_count + 1));
    current_parameter := result^.parameters;
	INC(current_parameter, TSIZE(PAstTypeExpression) * (parameter_count - 1));

    current_parameter^ := parse_type_expression(lexer);

    token := transpiler_lex(lexer);
    if token.kind = lexerKindComma then
      token := transpiler_lex(lexer)
    end
  end;
  current_parameter := result^.parameters;
  INC(current_parameter, TSIZE(PAstTypeExpression) * parameter_count);
  current_parameter^ := nil;

  return result
end;

proc parse_type_expression(lexer: PLexer) -> PAstTypeExpression;
var
  token: LexerToken;
  result: PAstTypeExpression;
begin
  result := nil;
  token := lexer_current(lexer);

  if token.kind = lexerKindRecord then
    result := parse_record_type(lexer)
  end;
  if token.kind = lexerKindLeftParen then
    result := parse_enumeration_type(lexer)
  end;
  if (token.kind = lexerKindArray) or (token.kind = lexerKindLeftSquare) then
    result := parse_array_type(lexer)
  end;
  if token.kind = lexerKindHat then
    result := parse_pointer_type(lexer)
  end;
  if token.kind = lexerKindProc then
    result := parse_procedure_type(lexer)
  end;
  if token.kind = lexerKindIdentifier then
    result := parse_named_type(lexer)
  end;
  return result
end;

end.