Java tutorial
/* * Copyright (C) 2010 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.android.tradefed.util; import com.android.tradefed.result.InputStreamSource; import com.google.common.io.ByteStreams; import java.io.BufferedInputStream; import java.io.BufferedReader; import java.io.ByteArrayOutputStream; import java.io.Closeable; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.PrintStream; import java.io.Reader; import java.io.Writer; import java.security.DigestInputStream; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.util.Objects; import java.util.zip.GZIPOutputStream; import java.util.zip.ZipOutputStream; /** * Utility class for managing input streams. */ public class StreamUtil { // 16K buffer size private static final int BUF_SIZE = 16 * 1024; private StreamUtil() { } /** * Retrieves a {@link String} from an {@link InputStreamSource}. * * @param source the {@link InputStreamSource} * @return a {@link String} containing the stream contents * @throws IOException if failure occurred reading the stream */ public static String getStringFromSource(InputStreamSource source) throws IOException { final InputStream stream = source.createInputStream(); final String contents; try { contents = getStringFromStream(stream); } finally { close(stream); } return contents; } /** * Count number of lines in an {@link InputStreamSource} * @param source the {@link InputStreamSource} * @return number of lines * @throws IOException if failure occurred reading the stream */ public static int countLinesFromSource(InputStreamSource source) throws IOException { int lineCount = 0; try (BufferedReader br = new BufferedReader(new InputStreamReader(source.createInputStream()))) { while (br.readLine() != null) { lineCount++; } } return lineCount; } /** * Retrieves a {@link ByteArrayList} from an {@link InputStreamSource}. * * @param source the {@link InputStreamSource} * @return a {@link ByteArrayList} containing the stream contents * @throws IOException if failure occurred reading the stream */ public static ByteArrayList getByteArrayListFromSource(InputStreamSource source) throws IOException { final InputStream stream = source.createInputStream(); final ByteArrayList contents; try { contents = getByteArrayListFromStream(stream); } finally { close(stream); } return contents; } /** * Retrieves a {@link String} from a character stream. * * @param stream the {@link InputStream} * @return a {@link String} containing the stream contents * @throws IOException if failure occurred reading the stream */ public static String getStringFromStream(InputStream stream) throws IOException { int irChar = -1; StringBuilder builder = new StringBuilder(); try (Reader ir = new BufferedReader(new InputStreamReader(stream))) { while ((irChar = ir.read()) != -1) { builder.append((char) irChar); } } return builder.toString(); } /** * Retrieves a {@link ByteArrayList} from a byte stream. * * @param stream the {@link InputStream} * @return a {@link ByteArrayList} containing the stream contents * @throws IOException if failure occurred reading the stream */ public static ByteArrayList getByteArrayListFromStream(InputStream stream) throws IOException { InputStream is = new BufferedInputStream(stream); int inputByte = -1; ByteArrayList list = new ByteArrayList(); while ((inputByte = is.read()) != -1) { list.add((byte) inputByte); } list.trimToSize(); return list; } /** * Copies contents of origStream to destStream. * <p/> * Recommended to provide a buffered stream for input and output * * @param inStream the {@link InputStream} * @param outStream the {@link OutputStream} * @throws IOException */ public static void copyStreams(InputStream inStream, OutputStream outStream) throws IOException { byte[] buf = new byte[BUF_SIZE]; int size = -1; while ((size = inStream.read(buf)) != -1) { outStream.write(buf, 0, size); } } /** * Copies contents of inStream to writer. * <p/> * Recommended to provide a buffered stream for input and output * * @param inStream the {@link InputStream} * @param writer the {@link Writer} destination * @throws IOException */ public static void copyStreamToWriter(InputStream inStream, Writer writer) throws IOException { byte[] buf = new byte[BUF_SIZE]; int size = -1; while ((size = inStream.read(buf)) != -1) { writer.write(new String(buf, 0, size)); } } /** * Gets the stack trace as a {@link String}. * * @param throwable the {@link Throwable} to convert. * @return a {@link String} stack trace */ public static String getStackTrace(Throwable throwable) { // dump the print stream results to the ByteArrayOutputStream, so contents can be evaluated ByteArrayOutputStream outputStream = new ByteArrayOutputStream(); PrintStream bytePrintStream = new PrintStream(outputStream); throwable.printStackTrace(bytePrintStream); return outputStream.toString(); } /** * @deprecated use {@link #close(Closeable)} instead. */ @Deprecated public static void closeStream(OutputStream out) { close(out); } /** * @deprecated use {@link #close(Closeable)} instead. */ @Deprecated public static void closeStream(InputStream in) { close(in); } /** * Attempts to flush the given output stream, and then closes it. * * @param outStream the {@link OutputStream}. No action taken if outStream is null. */ public static void flushAndCloseStream(OutputStream outStream) { if (outStream != null) { try { outStream.flush(); } catch (IOException e) { // ignore } try { outStream.close(); } catch (IOException e) { // ignore } } } /** * Closes given zip output stream. * * @param outStream the {@link ZipOutputStream}. No action taken if outStream is null. */ public static void closeZipStream(ZipOutputStream outStream) { if (outStream != null) { try { outStream.closeEntry(); outStream.close(); } catch (IOException e) { // ignore } } } /** * Closes given gzip output stream. * * @param outStream the {@link ZipOutputStream}. No action taken if outStream is null. */ public static void closeGZipStream(GZIPOutputStream outStream) { if (outStream != null) { try { outStream.finish(); outStream.close(); } catch (IOException e) { // ignore } } } /** * Closes the given {@link Closeable}. * * @param closeable the {@link Closeable}. No action taken if <code>null</code>. */ public static void close(Closeable closeable) { if (closeable != null) { try { closeable.close(); } catch (IOException e) { // ignore } } } /** * Cancels the given {@link InputStreamSource} if non-null. */ public static void cancel(InputStreamSource outputSource) { if (outputSource != null) { outputSource.close(); } } /** * Create a {@link OutputStream} that discards all writes. */ public static OutputStream nullOutputStream() { return ByteStreams.nullOutputStream(); } /** * Helper method to calculate md5 for a inputStream. The inputStream will be consumed and * closed. * * @param inputSource used to create inputStream * @return md5 of the stream * @throws IOException */ public static String calculateMd5(InputStream inputSource) throws IOException { MessageDigest md = null; try { md = MessageDigest.getInstance("md5"); } catch (NoSuchAlgorithmException e) { // This should not happen throw new RuntimeException(e); } InputStream input = new BufferedInputStream(new DigestInputStream(inputSource, md)); byte[] buf = new byte[BUF_SIZE]; while (input.read(buf) != -1) { // Read through the stream to update digest. } input.close(); String md5 = bytesToHexString(md.digest()); return md5; } private static final char[] HEX_CHARS = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f' }; /** * Converts a byte array into a String of hexadecimal characters. * * @param bytes an array of bytes * @return hex string representation of bytes array */ private static String bytesToHexString(byte[] bytes) { Objects.requireNonNull(bytes); StringBuilder sb = new StringBuilder(2 * bytes.length); for (int i = 0; i < bytes.length; i++) { int b = 0x0f & (bytes[i] >> 4); sb.append(HEX_CHARS[b]); b = 0x0f & bytes[i]; sb.append(HEX_CHARS[b]); } return sb.toString(); } }