com.google.common.io.CharStreams Maven / Gradle / Ivy
/*
* Copyright (C) 2007 The Guava Authors
*
* 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.google.common.io;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.annotations.Beta;
import com.google.common.base.Charsets;
import com.google.common.base.Splitter;
import com.google.common.collect.AbstractIterator;
import com.google.common.collect.ImmutableList;
import java.io.Closeable;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.Writer;
import java.nio.CharBuffer;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.regex.Pattern;
/**
* Provides utility methods for working with character streams.
*
* All method parameters must be non-null unless documented otherwise.
*
*
Some of the methods in this class take arguments with a generic type of
* {@code Readable & Closeable}. A {@link java.io.Reader} implements both of
* those interfaces. Similarly for {@code Appendable & Closeable} and
* {@link java.io.Writer}.
*
* @author Chris Nokleberg
* @author Bin Zhu
* @author Colin Decker
* @since 1.0
*/
@Beta
public final class CharStreams {
private static final int BUF_SIZE = 0x800; // 2K chars (4K bytes)
private CharStreams() {}
/**
* Returns a factory that will supply instances of {@link StringReader} that
* read a string value.
*
* @param value the string to read
* @return the factory
*/
public static InputSupplier newReaderSupplier(
final String value) {
return CharStreams.asInputSupplier(asCharSource(value));
}
/**
* Returns a {@link CharSource} that reads the given string value.
*
* @since 14.0
*/
public static CharSource asCharSource(String string) {
return new StringCharSource(string);
}
private static final class StringCharSource extends CharSource {
private static final Splitter LINE_SPLITTER
= Splitter.on(Pattern.compile("\r\n|\n|\r"));
private final String string;
private StringCharSource(String string) {
this.string = checkNotNull(string);
}
@Override
public Reader openStream() {
return new StringReader(string);
}
@Override
public String read() {
return string;
}
/**
* Returns an iterable over the lines in the string. If the string ends in
* a newline, a final empty string is not included to match the behavior of
* BufferedReader/LineReader.readLine().
*/
private Iterable lines() {
return new Iterable() {
@Override
public Iterator iterator() {
return new AbstractIterator() {
Iterator lines = LINE_SPLITTER.split(string).iterator();
@Override
protected String computeNext() {
if (lines.hasNext()) {
String next = lines.next();
// skip last line if it's empty
if (lines.hasNext() || !next.isEmpty()) {
return next;
}
}
return endOfData();
}
};
}
};
}
@Override
public String readFirstLine() {
Iterator lines = lines().iterator();
return lines.hasNext() ? lines.next() : null;
}
@Override
public ImmutableList readLines() {
return ImmutableList.copyOf(lines());
}
@Override
public String toString() {
String limited = (string.length() <= 15)
? string
: string.substring(0, 12) + "...";
return "CharStreams.asCharSource(" + limited + ")";
}
}
/**
* Returns a factory that will supply instances of {@link InputStreamReader},
* using the given {@link InputStream} factory and character set.
*
* @param in the factory that will be used to open input streams
* @param charset the charset used to decode the input stream; see {@link
* Charsets} for helpful predefined constants
* @return the factory
*/
public static InputSupplier newReaderSupplier(
final InputSupplier in, final Charset charset) {
return CharStreams.asInputSupplier(
ByteStreams.asByteSource(in).asCharSource(charset));
}
/**
* Returns a factory that will supply instances of {@link OutputStreamWriter},
* using the given {@link OutputStream} factory and character set.
*
* @param out the factory that will be used to open output streams
* @param charset the charset used to encode the output stream; see {@link
* Charsets} for helpful predefined constants
* @return the factory
*/
public static OutputSupplier newWriterSupplier(
final OutputSupplier out, final Charset charset) {
return CharStreams.asOutputSupplier(
ByteStreams.asByteSink(out).asCharSink(charset));
}
/**
* Writes a character sequence (such as a string) to an appendable
* object from the given supplier.
*
* @param from the character sequence to write
* @param to the output supplier
* @throws IOException if an I/O error occurs
*/
public static void write(CharSequence from,
OutputSupplier to) throws IOException {
asCharSink(to).write(from);
}
/**
* Opens {@link Readable} and {@link Appendable} objects from the
* given factories, copies all characters between the two, and closes
* them.
*
* @param from the input factory
* @param to the output factory
* @return the number of characters copied
* @throws IOException if an I/O error occurs
*/
public static long copy(InputSupplier from,
OutputSupplier to) throws IOException {
return asCharSource(from).copyTo(asCharSink(to));
}
/**
* Opens a {@link Readable} object from the supplier, copies all characters
* to the {@link Appendable} object, and closes the input. Does not close
* or flush the output.
*
* @param from the input factory
* @param to the object to write to
* @return the number of characters copied
* @throws IOException if an I/O error occurs
*/
public static long copy(
InputSupplier from, Appendable to) throws IOException {
return asCharSource(from).copyTo(to);
}
/**
* Copies all characters between the {@link Readable} and {@link Appendable}
* objects. Does not close or flush either object.
*
* @param from the object to read from
* @param to the object to write to
* @return the number of characters copied
* @throws IOException if an I/O error occurs
*/
public static long copy(Readable from, Appendable to) throws IOException {
checkNotNull(from);
checkNotNull(to);
CharBuffer buf = CharBuffer.allocate(BUF_SIZE);
long total = 0;
while (from.read(buf) != -1) {
buf.flip();
to.append(buf);
total += buf.remaining();
buf.clear();
}
return total;
}
/**
* Reads all characters from a {@link Readable} object into a {@link String}.
* Does not close the {@code Readable}.
*
* @param r the object to read from
* @return a string containing all the characters
* @throws IOException if an I/O error occurs
*/
public static String toString(Readable r) throws IOException {
return toStringBuilder(r).toString();
}
/**
* Returns the characters from a {@link Readable} & {@link Closeable} object
* supplied by a factory as a {@link String}.
*
* @param supplier the factory to read from
* @return a string containing all the characters
* @throws IOException if an I/O error occurs
*/
public static String toString(
InputSupplier supplier) throws IOException {
return asCharSource(supplier).read();
}
/**
* Reads all characters from a {@link Readable} object into a new
* {@link StringBuilder} instance. Does not close the {@code Readable}.
*
* @param r the object to read from
* @return a {@link StringBuilder} containing all the characters
* @throws IOException if an I/O error occurs
*/
private static StringBuilder toStringBuilder(Readable r) throws IOException {
StringBuilder sb = new StringBuilder();
copy(r, sb);
return sb;
}
/**
* Reads the first line from a {@link Readable} & {@link Closeable} object
* supplied by a factory. The line does not include line-termination
* characters, but does include other leading and trailing whitespace.
*
* @param supplier the factory to read from
* @return the first line, or null if the reader is empty
* @throws IOException if an I/O error occurs
*/
public static String readFirstLine(
InputSupplier supplier) throws IOException {
return asCharSource(supplier).readFirstLine();
}
/**
* Reads all of the lines from a {@link Readable} & {@link Closeable} object
* supplied by a factory. The lines do not include line-termination
* characters, but do include other leading and trailing whitespace.
*
* @param supplier the factory to read from
* @return a mutable {@link List} containing all the lines
* @throws IOException if an I/O error occurs
*/
public static List readLines(
InputSupplier supplier) throws IOException {
Closer closer = Closer.create();
try {
R r = closer.register(supplier.getInput());
return readLines(r);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* Reads all of the lines from a {@link Readable} object. The lines do
* not include line-termination characters, but do include other
* leading and trailing whitespace.
*
* Does not close the {@code Readable}. If reading files or resources you
* should use the {@link Files#readLines} and {@link Resources#readLines}
* methods.
*
* @param r the object to read from
* @return a mutable {@link List} containing all the lines
* @throws IOException if an I/O error occurs
*/
public static List readLines(Readable r) throws IOException {
List result = new ArrayList();
LineReader lineReader = new LineReader(r);
String line;
while ((line = lineReader.readLine()) != null) {
result.add(line);
}
return result;
}
/**
* Streams lines from a {@link Readable} object, stopping when the processor
* returns {@code false} or all lines have been read and returning the result
* produced by the processor. Does not close {@code readable}. Note that this
* method may not fully consume the contents of {@code readable} if the
* processor stops processing early.
*
* @throws IOException if an I/O error occurs
* @since 14.0
*/
public static T readLines(
Readable readable, LineProcessor processor) throws IOException {
checkNotNull(readable);
checkNotNull(processor);
LineReader lineReader = new LineReader(readable);
String line;
while ((line = lineReader.readLine()) != null) {
if (!processor.processLine(line)) {
break;
}
}
return processor.getResult();
}
/**
* Streams lines from a {@link Readable} and {@link Closeable} object
* supplied by a factory, stopping when our callback returns false, or we
* have read all of the lines.
*
* @param supplier the factory to read from
* @param callback the LineProcessor to use to handle the lines
* @return the output of processing the lines
* @throws IOException if an I/O error occurs
*/
public static T readLines(
InputSupplier supplier, LineProcessor callback) throws IOException {
checkNotNull(supplier);
checkNotNull(callback);
Closer closer = Closer.create();
try {
R r = closer.register(supplier.getInput());
return readLines(r, callback);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
/**
* Joins multiple {@link Reader} suppliers into a single supplier.
* Reader returned from the supplier will contain the concatenated data
* from the readers of the underlying suppliers.
*
* Reading from the joined reader will throw a {@link NullPointerException}
* if any of the suppliers are null or return null.
*
*
Only one underlying reader will be open at a time. Closing the
* joined reader will close the open underlying reader.
*
* @param suppliers the suppliers to concatenate
* @return a supplier that will return a reader containing the concatenated
* data
*/
public static InputSupplier join(
final Iterable> suppliers) {
checkNotNull(suppliers);
return new InputSupplier() {
@Override public Reader getInput() throws IOException {
return new MultiReader(suppliers.iterator());
}
};
}
/** Varargs form of {@link #join(Iterable)}. */
public static InputSupplier join(
InputSupplier... suppliers) {
return join(Arrays.asList(suppliers));
}
/**
* Discards {@code n} characters of data from the reader. This method
* will block until the full amount has been skipped. Does not close the
* reader.
*
* @param reader the reader to read from
* @param n the number of characters to skip
* @throws EOFException if this stream reaches the end before skipping all
* the bytes
* @throws IOException if an I/O error occurs
*/
public static void skipFully(Reader reader, long n) throws IOException {
checkNotNull(reader);
while (n > 0) {
long amt = reader.skip(n);
if (amt == 0) {
// force a blocking read
if (reader.read() == -1) {
throw new EOFException();
}
n--;
} else {
n -= amt;
}
}
}
/**
* Returns a Writer that sends all output to the given {@link Appendable}
* target. Closing the writer will close the target if it is {@link
* Closeable}, and flushing the writer will flush the target if it is {@link
* java.io.Flushable}.
*
* @param target the object to which output will be sent
* @return a new Writer object, unless target is a Writer, in which case the
* target is returned
*/
public static Writer asWriter(Appendable target) {
if (target instanceof Writer) {
return (Writer) target;
}
return new AppendableWriter(target);
}
// TODO(user): Remove these once Input/OutputSupplier methods are removed
static Reader asReader(final R readable) {
checkNotNull(readable);
if (readable instanceof Reader) {
return (Reader) readable;
}
return new Reader() {
@Override
public int read(char[] cbuf, int off, int len) throws IOException {
return read(CharBuffer.wrap(cbuf, off, len));
}
@Override
public int read(CharBuffer target) throws IOException {
return readable.read(target);
}
@Override
public void close() throws IOException {
readable.close();
}
};
}
static InputSupplier asInputSupplier(
final CharSource source) {
checkNotNull(source);
return new InputSupplier() {
@Override
public R getInput() throws IOException {
return (R) source.openStream();
}
};
}
static OutputSupplier asOutputSupplier(
final CharSink sink) {
checkNotNull(sink);
return new OutputSupplier() {
@Override
public W getOutput() throws IOException {
return (W) sink.openStream();
}
};
}
static CharSource asCharSource(
final InputSupplier supplier) {
checkNotNull(supplier);
return new CharSource() {
@Override
public Reader openStream() throws IOException {
return asReader(supplier.getInput());
}
};
}
static CharSink asCharSink(
final OutputSupplier supplier) {
checkNotNull(supplier);
return new CharSink() {
@Override
public Writer openStream() throws IOException {
return asWriter(supplier.getOutput());
}
};
}
}