Application: gvSIG desktop

package org.gvsig.expressionevaluator.impl;

import java.io.BufferedReader;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.InputStreamReader;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

import org.apache.commons.lang3.StringUtils;

/**

 *

 * @author jjdelcerro

 */

public class EncodingUtils {

  private static final Pattern RE_ENCODING = Pattern.compile(".*encoding[:]\\s*\"?([a-zA-Z_][a-zA-Z0-9_-]*)\"?.*");

  public static String getEncoding(File f) {

    String line = getFirstLine(f);

    String encoding = getEncoding(line);

    return encoding;

  }

  public static String getEncoding(InputStream is) {

    String line = getFirstLine(is);

    String encoding = getEncoding(line);

    return encoding;

  }

  public static String getEncoding(String line) {

    if( StringUtils.isBlank(line) ) {

      return null;

    }

    String encoding = null;

    Matcher m = RE_ENCODING.matcher(line);

    if (m != null && m.matches() && m.groupCount() == 1) {

      String s = m.group(1);

      if (!StringUtils.isBlank(s)) {

        encoding = s;

      }

    }

    return encoding;

  }

  public static String getFirstLine(File f) {

    String line;

    try (FileInputStream is = new FileInputStream(f)) {

      line = getFirstLine(is);

    } catch (Exception ex) {

      return null;

    }

    return line;

  }

  public static String getFirstLine(InputStream is) {

    String line;

    try (InputStreamReader isr = new InputStreamReader(is); BufferedReader br = new BufferedReader(isr)) {

      line = br.readLine();

      while (line != null) {

        if (!StringUtils.isBlank(line)) {

          break;

        }

        line = br.readLine();

      }

    } catch (IOException ex) {

      return null;

    }

    return line;

  }

}