/**
* 解析标识符
*
* @param token
* @return 对应符号表项
* @throws Exception
*/
private SymTabEntry parseIdentifier(Token token) throws Exception {
SymTabEntry id = null;
if (token.getType() == IDENTIFIER) {
String name = token.getText().toLowerCase();
id = symTabStack.lookupLocal(name);
// 申明必须得没有，否则重定义了
if (id == null) {
id = symTabStack.enterLocal(name);
id.setDefinition(definition);
id.appendLineNumber(token.getLineNumber());
} else {
errorHandler.flag(token, IDENTIFIER_REDEFINED, this);
}
token = nextToken();
} else {
errorHandler.flag(token, MISSING_IDENTIFIER, this);
}
return id;
}
/**
* 解析标识符子表及类型说明
*
* @param token the current token.
* @return 一个申明中的子表标识符列表
* @throws Exception
*/
protected ArrayList<SymTabEntry> parseIdentifierSublist(Token token) throws Exception {
ArrayList<SymTabEntry> sublist = new ArrayList<SymTabEntry>();
do {
token = synchronize(IDENTIFIER_START_SET);
SymTabEntry id = parseIdentifier(token);
if (id != null) {
sublist.add(id);
}
token = synchronize(COMMA_SET);
TokenType tokenType = token.getType();
// 找逗号
if (tokenType == COMMA) {
token = nextToken(); // 有逗号吞掉以便下一个
if (IDENTIFIER_FOLLOW_SET.contains(token.getType())) {
errorHandler.flag(token, MISSING_IDENTIFIER, this);
}
} else if (IDENTIFIER_START_SET.contains(tokenType)) {
errorHandler.flag(token, MISSING_COMMA, this);
}
} while (!IDENTIFIER_FOLLOW_SET.contains(token.getType()));
// 冒号后面的类型
TypeSpec type = parseTypeSpec(token);
// 将子表中的每个变量的类型设置上，比如a,b,c:int，先解析了a,b,c，然后解析了int类型
// 那么这儿就会给a,b,c设置上int类型
for (SymTabEntry variableId : sublist) {
variableId.setTypeSpec(type);
}
return sublist;
}
/**
* Parse type definitions.
*
* @param token the initial token.
* @throws Exception if an error occurred.
*/
public void parse(Token token) throws Exception {
token = synchronize(IDENTIFIER_SET);
// Loop to parse a sequence of type definitions
// separated by semicolons.
while (token.getType() == IDENTIFIER) {
String name = token.getText().toLowerCase();
SymTabEntry typeId = symTabStack.lookupLocal(name);
// Enter the new identifier into the symbol table
// but don't set how it's defined yet.
if (typeId == null) {
typeId = symTabStack.enterLocal(name);
typeId.appendLineNumber(token.getLineNumber());
} else {
errorHandler.flag(token, IDENTIFIER_REDEFINED, this);
typeId = null;
}
token = nextToken(); // consume the identifier token
// Synchronize on the = token.
token = synchronize(EQUALS_SET);
if (token.getType() == EQUALS) {
token = nextToken(); // consume the =
} else {
errorHandler.flag(token, MISSING_EQUALS, this);
}
// Parse the type specification.
TypeSpecificationParser typeSpecificationParser = new TypeSpecificationParser(this);
TypeSpec type = typeSpecificationParser.parse(token);
// Set identifier to be a type and set its type specificationt.
if (typeId != null) {
typeId.setDefinition(TYPE);
}
// Cross-link the type identifier and the type specification.
if (type != null && typeId != null) {
if (type.getIdentifier() == null) {
type.setIdentifier(typeId);
}
typeId.setTypeSpec(type);
} else {
token = synchronize(FOLLOW_SET);
}
token = currentToken();
TokenType tokenType = token.getType();
// Look for one or more semicolons after a definition.
if (tokenType == SEMICOLON) {
while (token.getType() == SEMICOLON) {
token = nextToken(); // consume the ;
}
}
// If at the start of the next definition or declaration,
// then missing a semicolon.
else if (NEXT_START_SET.contains(tokenType)) {
errorHandler.flag(token, MISSING_SEMICOLON, this);
}
token = synchronize(IDENTIFIER_SET);
}
}