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/*
 * Copyright (C) 2009 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.base;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

/**
 * Extracts non-overlapping substrings from an input string, typically by recognizing appearances of
 * a separator sequence. This separator can be specified as a single {@linkplain #on(char)
 * character}, fixed {@linkplain #on(String) string}, {@linkplain #onPattern regular expression} or
 * {@link #on(CharMatcher) CharMatcher} instance. Or, instead of using a separator at all, a
 * splitter can extract adjacent substrings of a given {@linkplain #fixedLength fixed length}.
 *
 * 

For example, this expression: * *

{@code
 * Splitter.on(',').split("foo,bar,qux")
 * }
* * ... produces an {@code Iterable} containing {@code "foo"}, {@code "bar"} and {@code "qux"}, in * that order. * *

By default, {@code Splitter}'s behavior is simplistic and unassuming. The following * expression: * *

{@code
 * Splitter.on(',').split(" foo,,,  bar ,")
 * }
* * ... yields the substrings {@code [" foo", "", "", " bar ", ""]}. If this is not the desired * behavior, use configuration methods to obtain a new splitter instance with modified * behavior: * *
{@code
 * private static final Splitter MY_SPLITTER = Splitter.on(',')
 *     .trimResults()
 *     .omitEmptyStrings();
 * }
* *

Now {@code MY_SPLITTER.split("foo,,, bar ,")} returns just {@code ["foo", "bar"]}. Note that * the order in which these configuration methods are called is never significant. * *

Warning: Splitter instances are immutable. Invoking a configuration method has no * effect on the receiving instance; you must store and use the new splitter instance it returns * instead. * *

{@code
 * // Do NOT do this
 * Splitter splitter = Splitter.on('/');
 * splitter.trimResults(); // does nothing!
 * return splitter.split("wrong / wrong / wrong");
 * }
* *

For separator-based splitters that do not use {@code omitEmptyStrings}, an input string * containing {@code n} occurrences of the separator naturally yields an iterable of size {@code n + * 1}. So if the separator does not occur anywhere in the input, a single substring is returned * containing the entire input. Consequently, all splitters split the empty string to {@code [""]} * (note: even fixed-length splitters). * *

Splitter instances are thread-safe immutable, and are therefore safe to store as {@code static * final} constants. * *

The {@link Joiner} class provides the inverse operation to splitting, but note that a * round-trip between the two should be assumed to be lossy. * *

See the Guava User Guide article on {@code Splitter}. * * @author Julien Silland * @author Jesse Wilson * @author Kevin Bourrillion * @author Louis Wasserman * @since 1.0 */ @GwtCompatible(emulated = true) public final class Splitter { private final CharMatcher trimmer; private final boolean omitEmptyStrings; private final Strategy strategy; private final int limit; private Splitter(Strategy strategy) { this(strategy, false, CharMatcher.none(), Integer.MAX_VALUE); } private Splitter(Strategy strategy, boolean omitEmptyStrings, CharMatcher trimmer, int limit) { this.strategy = strategy; this.omitEmptyStrings = omitEmptyStrings; this.trimmer = trimmer; this.limit = limit; } /** * Returns a splitter that uses the given single-character separator. For example, {@code * Splitter.on(',').split("foo,,bar")} returns an iterable containing {@code ["foo", "", "bar"]}. * * @param separator the character to recognize as a separator * @return a splitter, with default settings, that recognizes that separator */ public static Splitter on(char separator) { return on(CharMatcher.is(separator)); } /** * Returns a splitter that considers any single character matched by the given {@code CharMatcher} * to be a separator. For example, {@code * Splitter.on(CharMatcher.anyOf(";,")).split("foo,;bar,quux")} returns an iterable containing * {@code ["foo", "", "bar", "quux"]}. * * @param separatorMatcher a {@link CharMatcher} that determines whether a character is a * separator * @return a splitter, with default settings, that uses this matcher */ public static Splitter on(final CharMatcher separatorMatcher) { checkNotNull(separatorMatcher); return new Splitter( new Strategy() { @Override public SplittingIterator iterator(Splitter splitter, final CharSequence toSplit) { return new SplittingIterator(splitter, toSplit) { @Override int separatorStart(int start) { return separatorMatcher.indexIn(toSplit, start); } @Override int separatorEnd(int separatorPosition) { return separatorPosition + 1; } }; } }); } /** * Returns a splitter that uses the given fixed string as a separator. For example, {@code * Splitter.on(", ").split("foo, bar,baz")} returns an iterable containing {@code ["foo", * "bar,baz"]}. * * @param separator the literal, nonempty string to recognize as a separator * @return a splitter, with default settings, that recognizes that separator */ public static Splitter on(final String separator) { checkArgument(separator.length() != 0, "The separator may not be the empty string."); if (separator.length() == 1) { return Splitter.on(separator.charAt(0)); } return new Splitter( new Strategy() { @Override public SplittingIterator iterator(Splitter splitter, CharSequence toSplit) { return new SplittingIterator(splitter, toSplit) { @Override public int separatorStart(int start) { int separatorLength = separator.length(); positions: for (int p = start, last = toSplit.length() - separatorLength; p <= last; p++) { for (int i = 0; i < separatorLength; i++) { if (toSplit.charAt(i + p) != separator.charAt(i)) { continue positions; } } return p; } return -1; } @Override public int separatorEnd(int separatorPosition) { return separatorPosition + separator.length(); } }; } }); } /** * Returns a splitter that considers any subsequence matching {@code pattern} to be a separator. * For example, {@code Splitter.on(Pattern.compile("\r?\n")).split(entireFile)} splits a string * into lines whether it uses DOS-style or UNIX-style line terminators. * * @param separatorPattern the pattern that determines whether a subsequence is a separator. This * pattern may not match the empty string. * @return a splitter, with default settings, that uses this pattern * @throws IllegalArgumentException if {@code separatorPattern} matches the empty string */ @GwtIncompatible // java.util.regex public static Splitter on(Pattern separatorPattern) { return on(new JdkPattern(separatorPattern)); } private static Splitter on(final CommonPattern separatorPattern) { checkArgument( !separatorPattern.matcher("").matches(), "The pattern may not match the empty string: %s", separatorPattern); return new Splitter( new Strategy() { @Override public SplittingIterator iterator(final Splitter splitter, CharSequence toSplit) { final CommonMatcher matcher = separatorPattern.matcher(toSplit); return new SplittingIterator(splitter, toSplit) { @Override public int separatorStart(int start) { return matcher.find(start) ? matcher.start() : -1; } @Override public int separatorEnd(int separatorPosition) { return matcher.end(); } }; } }); } /** * Returns a splitter that considers any subsequence matching a given pattern (regular expression) * to be a separator. For example, {@code Splitter.onPattern("\r?\n").split(entireFile)} splits a * string into lines whether it uses DOS-style or UNIX-style line terminators. This is equivalent * to {@code Splitter.on(Pattern.compile(pattern))}. * * @param separatorPattern the pattern that determines whether a subsequence is a separator. This * pattern may not match the empty string. * @return a splitter, with default settings, that uses this pattern * @throws IllegalArgumentException if {@code separatorPattern} matches the empty string or is a * malformed expression */ @GwtIncompatible // java.util.regex public static Splitter onPattern(String separatorPattern) { return on(Platform.compilePattern(separatorPattern)); } /** * Returns a splitter that divides strings into pieces of the given length. For example, {@code * Splitter.fixedLength(2).split("abcde")} returns an iterable containing {@code ["ab", "cd", * "e"]}. The last piece can be smaller than {@code length} but will never be empty. * *

Note: if {@link #fixedLength} is used in conjunction with {@link #limit}, the final * split piece may be longer than the specified fixed length. This is because the splitter * will stop splitting when the limit is reached, and just return the final piece as-is. * *

Exception: for consistency with separator-based splitters, {@code split("")} does not * yield an empty iterable, but an iterable containing {@code ""}. This is the only case in which * {@code Iterables.size(split(input))} does not equal {@code IntMath.divide(input.length(), * length, CEILING)}. To avoid this behavior, use {@code omitEmptyStrings}. * * @param length the desired length of pieces after splitting, a positive integer * @return a splitter, with default settings, that can split into fixed sized pieces * @throws IllegalArgumentException if {@code length} is zero or negative */ public static Splitter fixedLength(final int length) { checkArgument(length > 0, "The length may not be less than 1"); return new Splitter( new Strategy() { @Override public SplittingIterator iterator(final Splitter splitter, CharSequence toSplit) { return new SplittingIterator(splitter, toSplit) { @Override public int separatorStart(int start) { int nextChunkStart = start + length; return (nextChunkStart < toSplit.length() ? nextChunkStart : -1); } @Override public int separatorEnd(int separatorPosition) { return separatorPosition; } }; } }); } /** * Returns a splitter that behaves equivalently to {@code this} splitter, but automatically omits * empty strings from the results. For example, {@code * Splitter.on(',').omitEmptyStrings().split(",a,,,b,c,,")} returns an iterable containing only * {@code ["a", "b", "c"]}. * *

If either {@code trimResults} option is also specified when creating a splitter, that * splitter always trims results first before checking for emptiness. So, for example, {@code * Splitter.on(':').omitEmptyStrings().trimResults().split(": : : ")} returns an empty iterable. * *

Note that it is ordinarily not possible for {@link #split(CharSequence)} to return an empty * iterable, but when using this option, it can (if the input sequence consists of nothing but * separators). * * @return a splitter with the desired configuration */ public Splitter omitEmptyStrings() { return new Splitter(strategy, true, trimmer, limit); } /** * Returns a splitter that behaves equivalently to {@code this} splitter but stops splitting after * it reaches the limit. The limit defines the maximum number of items returned by the iterator, * or the maximum size of the list returned by {@link #splitToList}. * *

For example, {@code Splitter.on(',').limit(3).split("a,b,c,d")} returns an iterable * containing {@code ["a", "b", "c,d"]}. When omitting empty strings, the omitted strings do not * count. Hence, {@code Splitter.on(',').limit(3).omitEmptyStrings().split("a,,,b,,,c,d")} returns * an iterable containing {@code ["a", "b", "c,d"}. When trim is requested, all entries are * trimmed, including the last. Hence {@code Splitter.on(',').limit(3).trimResults().split(" a , b * , c , d ")} results in {@code ["a", "b", "c , d"]}. * * @param maxItems the maximum number of items returned * @return a splitter with the desired configuration * @since 9.0 */ public Splitter limit(int maxItems) { checkArgument(maxItems > 0, "must be greater than zero: %s", maxItems); return new Splitter(strategy, omitEmptyStrings, trimmer, maxItems); } /** * Returns a splitter that behaves equivalently to {@code this} splitter, but automatically * removes leading and trailing {@linkplain CharMatcher#whitespace whitespace} from each returned * substring; equivalent to {@code trimResults(CharMatcher.whitespace())}. For example, {@code * Splitter.on(',').trimResults().split(" a, b ,c ")} returns an iterable containing {@code ["a", * "b", "c"]}. * * @return a splitter with the desired configuration */ public Splitter trimResults() { return trimResults(CharMatcher.whitespace()); } /** * Returns a splitter that behaves equivalently to {@code this} splitter, but removes all leading * or trailing characters matching the given {@code CharMatcher} from each returned substring. For * example, {@code Splitter.on(',').trimResults(CharMatcher.is('_')).split("_a ,_b_ ,c__")} * returns an iterable containing {@code ["a ", "b_ ", "c"]}. * * @param trimmer a {@link CharMatcher} that determines whether a character should be removed from * the beginning/end of a subsequence * @return a splitter with the desired configuration */ // TODO(kevinb): throw if a trimmer was already specified! public Splitter trimResults(CharMatcher trimmer) { checkNotNull(trimmer); return new Splitter(strategy, omitEmptyStrings, trimmer, limit); } /** * Splits {@code sequence} into string components and makes them available through an {@link * Iterator}, which may be lazily evaluated. If you want an eagerly computed {@link List}, use * {@link #splitToList(CharSequence)}. Java 8 users may prefer {@link #splitToStream} instead. * * @param sequence the sequence of characters to split * @return an iteration over the segments split from the parameter */ public Iterable split(final CharSequence sequence) { checkNotNull(sequence); return new Iterable() { @Override public Iterator iterator() { return splittingIterator(sequence); } @Override public String toString() { return Joiner.on(", ") .appendTo(new StringBuilder().append('['), this) .append(']') .toString(); } }; } private Iterator splittingIterator(CharSequence sequence) { return strategy.iterator(this, sequence); } /** * Splits {@code sequence} into string components and returns them as an immutable list. If you * want an {@link Iterable} which may be lazily evaluated, use {@link #split(CharSequence)}. * * @param sequence the sequence of characters to split * @return an immutable list of the segments split from the parameter * @since 15.0 */ public List splitToList(CharSequence sequence) { checkNotNull(sequence); Iterator iterator = splittingIterator(sequence); List result = new ArrayList<>(); while (iterator.hasNext()) { result.add(iterator.next()); } return Collections.unmodifiableList(result); } /** * Splits {@code sequence} into string components and makes them available through an {@link * Stream}, which may be lazily evaluated. If you want an eagerly computed {@link List}, use * {@link #splitToList(CharSequence)}. * * @param sequence the sequence of characters to split * @return a stream over the segments split from the parameter * @since 28.2 */ @Beta public Stream splitToStream(CharSequence sequence) { // Can't use Streams.stream() from base return StreamSupport.stream(split(sequence).spliterator(), false); } /** * Returns a {@code MapSplitter} which splits entries based on this splitter, and splits entries * into keys and values using the specified separator. * * @since 10.0 */ @Beta public MapSplitter withKeyValueSeparator(String separator) { return withKeyValueSeparator(on(separator)); } /** * Returns a {@code MapSplitter} which splits entries based on this splitter, and splits entries * into keys and values using the specified separator. * * @since 14.0 */ @Beta public MapSplitter withKeyValueSeparator(char separator) { return withKeyValueSeparator(on(separator)); } /** * Returns a {@code MapSplitter} which splits entries based on this splitter, and splits entries * into keys and values using the specified key-value splitter. * *

Note: Any configuration option configured on this splitter, such as {@link #trimResults}, * does not change the behavior of the {@code keyValueSplitter}. * *

Example: * *

{@code
   * String toSplit = " x -> y, z-> a ";
   * Splitter outerSplitter = Splitter.on(',').trimResults();
   * MapSplitter mapSplitter = outerSplitter.withKeyValueSeparator(Splitter.on("->"));
   * Map result = mapSplitter.split(toSplit);
   * assertThat(result).isEqualTo(ImmutableMap.of("x ", " y", "z", " a"));
   * }
* * @since 10.0 */ @Beta public MapSplitter withKeyValueSeparator(Splitter keyValueSplitter) { return new MapSplitter(this, keyValueSplitter); } /** * An object that splits strings into maps as {@code Splitter} splits iterables and lists. Like * {@code Splitter}, it is thread-safe and immutable. The common way to build instances is by * providing an additional {@linkplain Splitter#withKeyValueSeparator key-value separator} to * {@link Splitter}. * * @since 10.0 */ @Beta public static final class MapSplitter { private static final String INVALID_ENTRY_MESSAGE = "Chunk [%s] is not a valid entry"; private final Splitter outerSplitter; private final Splitter entrySplitter; private MapSplitter(Splitter outerSplitter, Splitter entrySplitter) { this.outerSplitter = outerSplitter; // only "this" is passed this.entrySplitter = checkNotNull(entrySplitter); } /** * Splits {@code sequence} into substrings, splits each substring into an entry, and returns an * unmodifiable map with each of the entries. For example, {@code * Splitter.on(';').trimResults().withKeyValueSeparator("=>").split("a=>b ; c=>b")} will return * a mapping from {@code "a"} to {@code "b"} and {@code "c"} to {@code "b"}. * *

The returned map preserves the order of the entries from {@code sequence}. * * @throws IllegalArgumentException if the specified sequence does not split into valid map * entries, or if there are duplicate keys */ public Map split(CharSequence sequence) { Map map = new LinkedHashMap<>(); for (String entry : outerSplitter.split(sequence)) { Iterator entryFields = entrySplitter.splittingIterator(entry); checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry); String key = entryFields.next(); checkArgument(!map.containsKey(key), "Duplicate key [%s] found.", key); checkArgument(entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry); String value = entryFields.next(); map.put(key, value); checkArgument(!entryFields.hasNext(), INVALID_ENTRY_MESSAGE, entry); } return Collections.unmodifiableMap(map); } } private interface Strategy { Iterator iterator(Splitter splitter, CharSequence toSplit); } private abstract static class SplittingIterator extends AbstractIterator { final CharSequence toSplit; final CharMatcher trimmer; final boolean omitEmptyStrings; /** * Returns the first index in {@code toSplit} at or after {@code start} that contains the * separator. */ abstract int separatorStart(int start); /** * Returns the first index in {@code toSplit} after {@code separatorPosition} that does not * contain a separator. This method is only invoked after a call to {@code separatorStart}. */ abstract int separatorEnd(int separatorPosition); int offset = 0; int limit; protected SplittingIterator(Splitter splitter, CharSequence toSplit) { this.trimmer = splitter.trimmer; this.omitEmptyStrings = splitter.omitEmptyStrings; this.limit = splitter.limit; this.toSplit = toSplit; } @Override protected String computeNext() { /* * The returned string will be from the end of the last match to the beginning of the next * one. nextStart is the start position of the returned substring, while offset is the place * to start looking for a separator. */ int nextStart = offset; while (offset != -1) { int start = nextStart; int end; int separatorPosition = separatorStart(offset); if (separatorPosition == -1) { end = toSplit.length(); offset = -1; } else { end = separatorPosition; offset = separatorEnd(separatorPosition); } if (offset == nextStart) { /* * This occurs when some pattern has an empty match, even if it doesn't match the empty * string -- for example, if it requires lookahead or the like. The offset must be * increased to look for separators beyond this point, without changing the start position * of the next returned substring -- so nextStart stays the same. */ offset++; if (offset > toSplit.length()) { offset = -1; } continue; } while (start < end && trimmer.matches(toSplit.charAt(start))) { start++; } while (end > start && trimmer.matches(toSplit.charAt(end - 1))) { end--; } if (omitEmptyStrings && start == end) { // Don't include the (unused) separator in next split string. nextStart = offset; continue; } if (limit == 1) { // The limit has been reached, return the rest of the string as the // final item. This is tested after empty string removal so that // empty strings do not count towards the limit. end = toSplit.length(); offset = -1; // Since we may have changed the end, we need to trim it again. while (end > start && trimmer.matches(toSplit.charAt(end - 1))) { end--; } } else { limit--; } return toSplit.subSequence(start, end).toString(); } return endOfData(); } } }





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