Java tutorial
/******************************************************************************* * Copyright (c) 2000, 2003 IBM Corporation and others. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Common Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/cpl-v10.html * * Contributors: * IBM Corporation - initial API and implementation *******************************************************************************/ package org.eclipse.core.runtime; import java.io.File; import org.eclipse.core.internal.runtime.Assert; /** * The standard implementation of the <code>IPath</code> interface. * Paths are always maintained in canonicalized form. That is, parent * references (i.e., <code>../../</code>) and duplicate separators are * resolved. For example, * <pre> new Path("/a/b").append("../foo/bar")</pre> * will yield the path * <pre> /a/foo/bar</pre> * <p> * This class is not intended to be subclassed by clients but * may be instantiated. * </p> * @see IPath */ public class Path implements IPath, Cloneable { /** The path segments */ private String[] segments; /** The device id string. May be null if there is no device. */ private String device = null; /** flags indicating separators (has leading, is UNC, has trailing) */ private int separators; /** masks for separator values */ private static final int HAS_LEADING = 1; private static final int IS_UNC = 2; private static final int HAS_TRAILING = 4; private static final int ALL_SEPARATORS = HAS_LEADING | IS_UNC | HAS_TRAILING; /** Mask for all bits that are involved in the hashcode */ private static final int HASH_MASK = ~HAS_TRAILING; /** Constant value indicating no segments */ private static final String[] NO_SEGMENTS = new String[0]; /** Constant root path string (<code>"/"</code>). */ private static final String ROOT_STRING = "/"; //$NON-NLS-1$ /** Constant value containing the root path with no device. */ public static final Path ROOT = new Path(ROOT_STRING); /** Constant empty string value. */ private static final String EMPTY_STRING = ""; //$NON-NLS-1$ /** Constant value containing the empty path with no device. */ public static final Path EMPTY = new Path(EMPTY_STRING); //Private implementation note: the segments and separators //arrays are never modified, so that they can be shared between //path instances ///* (Intentionally not included in javadoc) // * Private constructor. // */ //private Path() { //} /* (Intentionally not included in javadoc) * Private constructor. */ private Path(String device, String[] segments, int _separators) { // no segment validations are done for performance reasons this.segments = segments; this.device = device; //hashcode is cached in all but the bottom three bits of the separators field this.separators = (computeHashCode() << 3) | (_separators & ALL_SEPARATORS); } /** * Constructs a new path from the given string path. * The given string path must be valid. * The path is canonicalized and double slashes are removed * except at the beginning. (to handle UNC paths) All backslashes ('\') * are replaced with forward slashes. ('/') * * @param fullPath the string path * @see #isValidPath */ public Path(String fullPath) { // no segment validations are done for performance reasons initialize(null, fullPath); } /** * Constructs a new path from the given device id and string path. * The given string path must be valid. * The path is canonicalized and double slashes are removed except * at the beginning (to handle UNC paths). All backslashes ('\') * are replaced with forward slashes. ('/') * * @param device the device id * @param path the string path * @see #isValidPath * @see #setDevice */ public Path(String device, String path) { // no segment validations are done for performance reasons initialize(device, path); } /* (Intentionally not included in javadoc) * @see IPath#addFileExtension */ public IPath addFileExtension(String extension) { if (isRoot() || isEmpty() || hasTrailingSeparator()) return this; int len = segments.length; String[] newSegments = new String[len]; System.arraycopy(segments, 0, newSegments, 0, len - 1); newSegments[len - 1] = segments[len - 1] + "." + extension; //$NON-NLS-1$ return new Path(device, newSegments, separators); } /* (Intentionally not included in javadoc) * @see IPath#addTrailingSeparator */ public IPath addTrailingSeparator() { if (hasTrailingSeparator() || isRoot()) { return this; } //XXX workaround, see 1GIGQ9V if (isEmpty()) { return new Path(device, segments, HAS_LEADING); } return new Path(device, segments, separators | HAS_TRAILING); } /* (Intentionally not included in javadoc) * @see IPath#append(java.lang.String) */ public IPath append(String tail) { //optimize addition of a single segment if (tail.indexOf(SEPARATOR) == -1 && tail.indexOf("\\") == -1) { //$NON-NLS-1$ int tailLength = tail.length(); if (tailLength < 3) { //some special cases if (tailLength == 0 || ".".equals(tail)) { //$NON-NLS-1$ return this; } if ("..".equals(tail)) //$NON-NLS-1$ return removeLastSegments(1); } //just add the segment int myLen = segments.length; String[] newSegments = new String[myLen + 1]; System.arraycopy(segments, 0, newSegments, 0, myLen); newSegments[myLen] = tail; return new Path(device, newSegments, separators & ~HAS_TRAILING); } if (this.isEmpty()) return new Path(device, tail).makeRelative(); if (this.isRoot()) return new Path(device, tail).makeAbsolute(); //go with easy implementation for now return append(new Path(tail)); } /* (Intentionally not included in javadoc) * @see IPath#append(IPath) */ public IPath append(IPath tail) { //optimize some easy cases if (tail == null || tail.isEmpty() || tail.isRoot()) return this; if (this.isEmpty()) return tail.setDevice(device).makeRelative(); if (this.isRoot()) return tail.setDevice(device).makeAbsolute(); //concatenate the two segment arrays int myLen = segments.length; int tailLen = tail.segmentCount(); String[] newSegments = new String[myLen + tailLen]; System.arraycopy(segments, 0, newSegments, 0, myLen); for (int i = 0; i < tailLen; i++) { newSegments[myLen + i] = tail.segment(i); } //use my leading separators and the tail's trailing separator Path result = new Path(device, newSegments, (separators & (HAS_LEADING | IS_UNC)) | (tail.hasTrailingSeparator() ? HAS_TRAILING : 0)); String tailFirstSegment = newSegments[myLen]; if (tailFirstSegment.equals("..") || tailFirstSegment.equals(".")) { //$NON-NLS-1$ //$NON-NLS-2$ result.canonicalize(); } return result; } /** * Destructively converts this path to its canonical form. * <p> * In its canonical form, a path does not have any * "." segments, and parent references ("..") are collapsed * where possible. * </p> * @return true if the path was modified, and false otherwise. */ private boolean canonicalize() { //look for segments that need canonicalizing for (int i = 0, max = segments.length; i < max; i++) { String segment = segments[i]; if (segment.charAt(0) == '.' && (segment.equals("..") || segment.equals("."))) { //$NON-NLS-1$ //$NON-NLS-2$ //path needs to be canonicalized collapseParentReferences(); //paths of length 0 have no trailing separator if (segments.length == 0) separators &= (HAS_LEADING | IS_UNC); //recompute hash because canonicalize affects hash separators = (separators & ALL_SEPARATORS) | (computeHashCode() << 3); return true; } } return false; } /* (Intentionally not included in javadoc) * Clones this object. */ public Object clone() { try { return super.clone(); } catch (CloneNotSupportedException e) { return null; } } /** * Destructively removes all occurrences of ".." segments from this path. */ private void collapseParentReferences() { int segmentCount = segments.length; String[] stack = new String[segmentCount]; int stackPointer = 0; for (int i = 0; i < segmentCount; i++) { String segment = segments[i]; if (segment.equals("..")) { //$NON-NLS-1$ if (stackPointer == 0) { // if the stack is empty we are going out of our scope // so we need to accumulate segments. But only if the original // path is relative. If it is absolute then we can't go any higher than // root so simply toss the .. references. if (!isAbsolute()) stack[stackPointer++] = segment;//stack push } else { // if the top is '..' then we are accumulating segments so don't pop if ("..".equals(stack[stackPointer - 1])) //$NON-NLS-1$ stack[stackPointer++] = ".."; //$NON-NLS-1$ else stackPointer--;//stack pop } //collapse current references } else if (!segment.equals(".") || (i == 0 && !isAbsolute())) //$NON-NLS-1$ stack[stackPointer++] = segment;//stack push } //if the number of segments hasn't changed, then no modification needed if (stackPointer == segmentCount) return; //build the new segment array backwards by popping the stack String[] newSegments = new String[stackPointer]; System.arraycopy(stack, 0, newSegments, 0, stackPointer); this.segments = newSegments; } /** * Removes duplicate slashes from the given path, with the exception * of leading double slash which represents a UNC path. */ private String collapseSlashes(String path) { int length = path.length(); // if the path is only 0, 1 or 2 chars long then it could not possibly have illegal // duplicate slashes. if (length < 3) return path; // check for an occurence of // in the path. Start at index 1 to ensure we skip leading UNC // // If there are no // then there is nothing to collapse so just return. if (path.indexOf("//", 1) == -1) //$NON-NLS-1$ return path; // We found an occurence of // in the path so do the slow collapse. char[] result = new char[path.length()]; int count = 0; boolean hasPrevious = false; char[] characters = path.toCharArray(); for (int index = 0; index < characters.length; index++) { char c = characters[index]; if (c == SEPARATOR) { if (hasPrevious) { // skip double slashes, except for beginning of UNC. // note that a UNC path can't have a device. if (device == null && index == 1) { result[count] = c; count++; } } else { hasPrevious = true; result[count] = c; count++; } } else { hasPrevious = false; result[count] = c; count++; } } return new String(result, 0, count); } /* (Intentionally not included in javadoc) * Computes the hash code for this object. */ private int computeHashCode() { int hash = device == null ? 17 : device.hashCode(); int segmentCount = segments.length; for (int i = 0; i < segmentCount; i++) { //this function tends to given a fairly even distribution hash = hash * 37 + segments[i].hashCode(); } return hash; } /* (Intentionally not included in javadoc) * Returns the size of the string that will be created by toString or toOSString. */ private int computeLength() { int length = 0; if (device != null) length += device.length(); if ((separators & HAS_LEADING) != 0) length++; if ((separators & IS_UNC) != 0) length++; //add the segment lengths int max = segments.length; if (max > 0) { for (int i = 0; i < max; i++) { length += segments[i].length(); } //add the separator lengths length += max - 1; } if ((separators & HAS_TRAILING) != 0) length++; return length; } /* (Intentionally not included in javadoc) * Returns the number of segments in the given path */ private int computeSegmentCount(String path) { int len = path.length(); if (len == 0 || (len == 1 && path.charAt(0) == SEPARATOR)) { return 0; } int count = 1; int prev = -1; int i; while ((i = path.indexOf(SEPARATOR, prev + 1)) != -1) { if (i != prev + 1 && i != len) { ++count; } prev = i; } if (path.charAt(len - 1) == SEPARATOR) { --count; } return count; } /** * Computes the segment array for the given canonicalized path. */ private String[] computeSegments(String path) { // performance sensitive --- avoid creating garbage int segmentCount = computeSegmentCount(path); if (segmentCount == 0) return NO_SEGMENTS; String[] newSegments = new String[segmentCount]; int len = path.length(); // check for initial slash int firstPosition = (path.charAt(0) == SEPARATOR) ? 1 : 0; // check for UNC if (firstPosition == 1 && len > 1 && (path.charAt(1) == SEPARATOR)) firstPosition = 2; int lastPosition = (path.charAt(len - 1) != SEPARATOR) ? len - 1 : len - 2; // for non-empty paths, the number of segments is // the number of slashes plus 1, ignoring any leading // and trailing slashes int next = firstPosition; for (int i = 0; i < segmentCount; i++) { int start = next; int end = path.indexOf(SEPARATOR, next); if (end == -1) { newSegments[i] = path.substring(start, lastPosition + 1); } else { newSegments[i] = path.substring(start, end); } next = end + 1; } return newSegments; } /* (Intentionally not included in javadoc) * Compares objects for equality. */ public boolean equals(Object obj) { if (this == obj) return true; if (!(obj instanceof Path)) return false; Path target = (Path) obj; //check leading separators and hashcode if ((separators & HASH_MASK) != (target.separators & HASH_MASK)) return false; String[] targetSegments = target.segments; int i = segments.length; //check segment count if (i != targetSegments.length) return false; //check segments in reverse order - later segments more likely to differ while (--i >= 0) if (!segments[i].equals(targetSegments[i])) return false; //check device last (least likely to differ) return device == target.device || (device != null && device.equals(target.device)); } /* (Intentionally not included in javadoc) * @see IPath#getDevice */ public String getDevice() { return device; } /* (Intentionally not included in javadoc) * @see IPath#getFileExtension */ public String getFileExtension() { if (hasTrailingSeparator()) { return null; } String lastSegment = lastSegment(); if (lastSegment == null) { return null; } int index = lastSegment.lastIndexOf("."); //$NON-NLS-1$ if (index == -1) { return null; } return lastSegment.substring(index + 1); } /* (Intentionally not included in javadoc) * Computes the hash code for this object. */ public int hashCode() { return separators & HASH_MASK; } /* (Intentionally not included in javadoc) * @see IPath#hasTrailingSeparator */ public boolean hasTrailingSeparator() { return (separators & HAS_TRAILING) != 0; } /* * Initialize the current path with the given string. */ private void initialize(String device, String fullPath) { Assert.isNotNull(fullPath); this.device = device; //indexOf is much faster than replace String path = fullPath.indexOf('\\') == -1 ? fullPath : fullPath.replace('\\', SEPARATOR); int i = path.indexOf(DEVICE_SEPARATOR); if (i != -1) { // if the specified device is null then set it to // be whatever is defined in the path string if (device == null) this.device = path.substring(0, i + 1); path = path.substring(i + 1, path.length()); } path = collapseSlashes(path); int len = path.length(); //compute the separators array if (len < 2) { if (len == 1 && path.charAt(0) == SEPARATOR) { this.separators = HAS_LEADING; } else { this.separators = 0; } } else { boolean hasLeading = path.charAt(0) == SEPARATOR; boolean isUNC = hasLeading && path.charAt(1) == SEPARATOR; //UNC path of length two has no trailing separator boolean hasTrailing = !(isUNC && len == 2) && path.charAt(len - 1) == SEPARATOR; separators = hasLeading ? HAS_LEADING : 0; if (isUNC) separators |= IS_UNC; if (hasTrailing) separators |= HAS_TRAILING; } //compute segments and ensure canonical form segments = computeSegments(path); if (!canonicalize()) { //compute hash now because canonicalize didn't need to do it separators = (separators & ALL_SEPARATORS) | (computeHashCode() << 3); } } /* (Intentionally not included in javadoc) * @see IPath#isAbsolute */ public boolean isAbsolute() { //it's absolute if it has a leading separator return (separators & HAS_LEADING) != 0; } /* (Intentionally not included in javadoc) * @see IPath#isEmpty */ public boolean isEmpty() { //true if no segments and no leading prefix return segments.length == 0 && ((separators & HAS_LEADING) == 0); } /* (Intentionally not included in javadoc) * @see IPath#isPrefixOf */ public boolean isPrefixOf(IPath anotherPath) { Assert.isNotNull(anotherPath); if (device == null) { if (anotherPath.getDevice() != null) { return false; } } else { if (!device.equalsIgnoreCase(anotherPath.getDevice())) { return false; } } if (isEmpty() || (isRoot() && anotherPath.isAbsolute())) { return true; } int len = segments.length; if (len > anotherPath.segmentCount()) { return false; } for (int i = 0; i < len; i++) { if (!segments[i].equals(anotherPath.segment(i))) return false; } return true; } /* (Intentionally not included in javadoc) * @see IPath#isRoot */ public boolean isRoot() { //must have no segments, a leading separator, and not be a UNC path. return this == ROOT || (segments.length == 0 && ((separators & ALL_SEPARATORS) == HAS_LEADING)); } /* (Intentionally not included in javadoc) * @see IPath#isUNC */ public boolean isUNC() { if (device != null) return false; return (separators & IS_UNC) != 0; } /* (Intentionally not included in javadoc) * @see IPath#isValidPath */ public boolean isValidPath(String path) { // We allow "//" at the beginning for UNC paths if (path.indexOf("//") > 0) { //$NON-NLS-1$ return false; } Path test = new Path(path); int segmentCount = test.segmentCount(); for (int i = 0; i < segmentCount; i++) { if (!test.isValidSegment(test.segment(i))) { return false; } } return true; } /* (Intentionally not included in javadoc) * @see IPath#isValidSegment */ public boolean isValidSegment(String segment) { int size = segment.length(); if (size == 0) { return false; } if (Character.isWhitespace(segment.charAt(0)) || Character.isWhitespace(segment.charAt(size - 1))) { return false; } for (int i = 0; i < size; i++) { char c = segment.charAt(i); if (c == '/' || c == '\\' || c == ':') { return false; } } return true; } /* (Intentionally not included in javadoc) * @see IPath#lastSegment */ public String lastSegment() { int len = segments.length; return len == 0 ? null : segments[len - 1]; } /* (Intentionally not included in javadoc) * @see IPath#makeAbsolute */ public IPath makeAbsolute() { if (isAbsolute()) { return this; } Path result = new Path(device, segments, separators | HAS_LEADING); //may need canonicalizing if it has leading ".." or "." segments if (result.segmentCount() > 0) { String first = result.segment(0); if (first.equals("..") || first.equals(".")) { //$NON-NLS-1$ //$NON-NLS-2$ result.canonicalize(); } } return result; } /* (Intentionally not included in javadoc) * @see IPath#makeRelative */ public IPath makeRelative() { if (!isAbsolute()) { return this; } return new Path(device, segments, separators & HAS_TRAILING); } /* (Intentionally not included in javadoc) * @see IPath#makeUNC */ public IPath makeUNC(boolean toUNC) { // if we are already in the right form then just return if (!(toUNC ^ isUNC())) return this; int newSeparators = this.separators; if (toUNC) { newSeparators |= HAS_LEADING | IS_UNC; } else { //mask out the UNC bit newSeparators &= HAS_LEADING | HAS_TRAILING; } return new Path(toUNC ? null : device, segments, newSeparators); } /* (Intentionally not included in javadoc) * @see IPath#matchingFirstSegments */ public int matchingFirstSegments(IPath anotherPath) { Assert.isNotNull(anotherPath); int anotherPathLen = anotherPath.segmentCount(); int max = Math.min(segments.length, anotherPathLen); int count = 0; for (int i = 0; i < max; i++) { if (!segments[i].equals(anotherPath.segment(i))) { return count; } count++; } return count; } /* (Intentionally not included in javadoc) * @see IPath#removeFileExtension */ public IPath removeFileExtension() { String extension = getFileExtension(); if (extension == null || extension.equals("")) { //$NON-NLS-1$ return this; } String lastSegment = lastSegment(); int index = lastSegment.lastIndexOf(extension) - 1; return removeLastSegments(1).append(lastSegment.substring(0, index)); } /* (Intentionally not included in javadoc) * @see IPath#removeFirstSegments */ public IPath removeFirstSegments(int count) { if (count == 0) return this; if (count >= segments.length) { return new Path(device, NO_SEGMENTS, 0); } Assert.isLegal(count > 0); int newSize = segments.length - count; String[] newSegments = new String[newSize]; System.arraycopy(this.segments, count, newSegments, 0, newSize); //result is always a relative path return new Path(device, newSegments, separators & HAS_TRAILING); } /* (Intentionally not included in javadoc) * @see IPath#removeLastSegments */ public IPath removeLastSegments(int count) { if (count == 0) return this; if (count >= segments.length) { //result will have no trailing separator return new Path(device, NO_SEGMENTS, separators & (HAS_LEADING | IS_UNC)); } Assert.isLegal(count > 0); int newSize = segments.length - count; String[] newSegments = new String[newSize]; System.arraycopy(this.segments, 0, newSegments, 0, newSize); return new Path(device, newSegments, separators); } /* (Intentionally not included in javadoc) * @see IPath#removeTrailingSeparator */ public IPath removeTrailingSeparator() { if (!hasTrailingSeparator()) { return this; } return new Path(device, segments, separators & (HAS_LEADING | IS_UNC)); } /* (Intentionally not included in javadoc) * @see IPath#segment */ public String segment(int index) { if (index >= segments.length) return null; return segments[index]; } /* (Intentionally not included in javadoc) * @see IPath#segmentCount */ public int segmentCount() { return segments.length; } /* (Intentionally not included in javadoc) * @see IPath#segments */ public String[] segments() { String[] segmentCopy = new String[segments.length]; System.arraycopy(segments, 0, segmentCopy, 0, segments.length); return segmentCopy; } /* (Intentionally not included in javadoc) * @see IPath#setDevice */ public IPath setDevice(String value) { if (value != null) { Assert.isTrue(value.indexOf(IPath.DEVICE_SEPARATOR) == (value.length() - 1), "Last character should be the device separator"); //$NON-NLS-1$ } //return the reciever if the device is the same if (value == device || (value != null && value.equals(device))) return this; return new Path(value, segments, separators); } /* (Intentionally not included in javadoc) * @see IPath#toFile */ public File toFile() { return new File(toOSString()); } /* (Intentionally not included in javadoc) * @see IPath#toOSString */ public String toOSString() { //Note that this method is identical to toString except //it uses the OS file separator instead of the path separator int resultSize = computeLength(); if (resultSize <= 0) return EMPTY_STRING; char FILE_SEPARATOR = File.separatorChar; char[] result = new char[resultSize]; int offset = 0; if (device != null) { int size = device.length(); device.getChars(0, size, result, offset); offset += size; } if ((separators & HAS_LEADING) != 0) result[offset++] = FILE_SEPARATOR; if ((separators & IS_UNC) != 0) result[offset++] = FILE_SEPARATOR; int len = segments.length - 1; if (len >= 0) { //append all but the last segment, with separators for (int i = 0; i < len; i++) { int size = segments[i].length(); segments[i].getChars(0, size, result, offset); offset += size; result[offset++] = FILE_SEPARATOR; } //append the last segment int size = segments[len].length(); segments[len].getChars(0, size, result, offset); offset += size; } if ((separators & HAS_TRAILING) != 0) result[offset++] = FILE_SEPARATOR; return new String(result); } /* (Intentionally not included in javadoc) * @see IPath#toString */ public String toString() { int resultSize = computeLength(); if (resultSize <= 0) return EMPTY_STRING; char[] result = new char[resultSize]; int offset = 0; if (device != null) { int size = device.length(); device.getChars(0, size, result, offset); offset += size; } if ((separators & HAS_LEADING) != 0) result[offset++] = SEPARATOR; if ((separators & IS_UNC) != 0) result[offset++] = SEPARATOR; int len = segments.length - 1; if (len >= 0) { //append all but the last segment, with separators for (int i = 0; i < len; i++) { int size = segments[i].length(); segments[i].getChars(0, size, result, offset); offset += size; result[offset++] = SEPARATOR; } //append the last segment int size = segments[len].length(); segments[len].getChars(0, size, result, offset); offset += size; } if ((separators & HAS_TRAILING) != 0) result[offset++] = SEPARATOR; return new String(result); } /* (Intentionally not included in javadoc) * @see IPath#uptoSegment */ public IPath uptoSegment(int count) { if (count == 0) return Path.EMPTY; if (count >= segments.length) return this; Assert.isTrue(count > 0, "Invalid parameter to Path.uptoSegment"); //$NON-NLS-1$ String[] newSegments = new String[count]; System.arraycopy(segments, 0, newSegments, 0, count); return new Path(device, newSegments, separators); } }