SignatureResolver.java

package gb.svnfilter.findbugs;

import org.eclipse.jdt.core.IMethod;
import org.eclipse.jdt.core.IType;
import org.eclipse.jdt.core.ITypeParameter;
import org.eclipse.jdt.core.JavaModelException;
import org.eclipse.jdt.core.Signature;

/**
 * Utility to get a resolved binary signature from a given method.
 *
 * @author Marc R. Hoffmann
 * @version $Revision: $
 */
public final class SignatureResolver {

  private static final String EMPTY = ""; //$NON-NLS-1$

  private static final String OBJECT = "Ljava/lang/Object;"; //$NON-NLS-1$

  private static final char SLASH = '/';

  /**
   * Extracts the parameter part from the given signature, i.e. the substring
   * contained in braces.
   *
   * @param signature
   *          method signature
   * @return parameter part only
   */
  public static String getParameters(final String signature) {
    final int pos = signature.lastIndexOf(')');
    // avoid String instances for methods without parameters
    return pos == 1 ? EMPTY : signature.substring(1, pos);
  }

  /**
   * Extracts the resolved binary parameters from the given method
   *
   * @param method
   *          method to resolve
   * @return binary parameter specification
   * @throws JavaModelException
   */
  public static String getParameters(final IMethod method)
      throws JavaModelException {
    if (method.isBinary()) {
      return getParameters(method.getSignature());
    }
    final StringBuffer buffer = new StringBuffer();
    final String[] parameterTypes = method.getParameterTypes();
    for (int i = 0; i < parameterTypes.length; i++) {
      resolveArrayParameterType(method, parameterTypes[i], buffer);
    }
    return buffer.toString();
  }

  private static final void resolveArrayParameterType(final IMethod method,
      final String parameterType, final StringBuffer result)
      throws JavaModelException {
    final int arrayCount = Signature.getArrayCount(parameterType);
    for (int i = 0; i < arrayCount; i++) {
      result.append(Signature.C_ARRAY);
    }
    resolveParameterType(method, parameterType.substring(arrayCount), result);
  }

  private static final void resolveParameterType(final IMethod method,
      final String parameterType, final StringBuffer result)
      throws JavaModelException {
    final char kind = parameterType.charAt(0);
    switch (kind) {
    case Signature.C_UNRESOLVED:
      final String identifier = parameterType.substring(1, parameterType
          .length() - 1);
      if (resolveType(method.getDeclaringType(), identifier, result)) {
        return;
      }
      if (resolveTypeParameter(method, identifier, result)) {
        return;
      }
      break;
    }
    result.append(parameterType);
  }

  private static final boolean resolveType(final IType scope,
      final String identifier, final StringBuffer result)
      throws JavaModelException {
    final String[][] types = scope.resolveType(Signature
        .getTypeErasure(identifier));
    if (types == null || types.length != 1) {
      return false;
    }
    result.append(Signature.C_RESOLVED);
    final String qualifier = types[0][0];
    if (qualifier.length() > 0) {
      replace(qualifier, Signature.C_DOT, SLASH, result);
      result.append(SLASH);
    }
    replace(types[0][1], Signature.C_DOT, Signature.C_DOLLAR, result);
    result.append(Signature.C_SEMICOLON);
    return true;
  }

  private static final boolean resolveTypeParameter(final IMethod method,
      final String identifier, final StringBuffer result)
      throws JavaModelException {
    IType type = method.getDeclaringType();
    if (resolveTypeParameter(type, method.getTypeParameters(), identifier,
        result)) {
      return true;
    }
    while (type != null) {
      if (resolveTypeParameter(type, type.getTypeParameters(), identifier,
          result)) {
        return true;
      }
      type = type.getDeclaringType();
    }
    return false;
  }

  private static final boolean resolveTypeParameter(final IType context,
      final ITypeParameter[] typeParameters, final String identifier,
      final StringBuffer result) throws JavaModelException {
    for (int i = 0; i < typeParameters.length; i++) {
      final ITypeParameter p = typeParameters[i];
      if (identifier.equals(p.getElementName())) {
        final String[] bounds = p.getBounds();
        if (bounds.length == 0) {
          result.append(OBJECT);
          return true;
        }
        return resolveType(context, bounds[0], result);
      }
    }
    return false;
  }

  private static final void replace(final String source, final char oldChar,
      final char newChar, final StringBuffer result) {
    final int len = source.length();
    for (int i = 0; i < len; i++) {
      final char c = source.charAt(i);
      result.append(c == oldChar ? newChar : c);
    }
  }

}