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package com.fasterxml.jackson.core;
import java.io.*;
import com.fasterxml.jackson.core.io.NumberInput;
/**
* Implementation of
* JSON Pointer
* specification.
* Pointer instances can be used to locate logical JSON nodes for things like
* tree traversal (see {@link TreeNode#at}).
* It may be used in future for filtering of streaming JSON content
* as well (not implemented yet for 2.3).
*
* Note that the implementation was largely rewritten for Jackson 2.14 to
* reduce memory usage by sharing backing "full path" representation for
* nested instances.
*
* Instances are fully immutable and can be cached, shared between threads.
*
* @author Tatu Saloranta
*
* @since 2.3
*/
public class JsonPointer implements Serializable
{
private static final long serialVersionUID = 1L;
/**
* Character used to separate segments.
*
* @since 2.9
*/
public final static char SEPARATOR = '/';
/**
* Marker instance used to represent segment that matches current
* node or position (that is, returns true for
* {@link #matches()}).
*/
protected final static JsonPointer EMPTY = new JsonPointer();
/**
* Reference to rest of the pointer beyond currently matching
* segment (if any); null if this pointer refers to the matching
* segment.
*/
protected final JsonPointer _nextSegment;
/**
* Reference from currently matching segment (if any) to node
* before leaf.
* Lazily constructed if/as needed.
*
* NOTE: we'll use `volatile` here assuming that this is unlikely to
* become a performance bottleneck. If it becomes one we can probably
* just drop it and things still should work (despite warnings as per JMM
* regarding visibility (and lack thereof) of unguarded changes).
*
* @since 2.5
*/
protected volatile JsonPointer _head;
/**
* We will retain representation of the pointer, as a String,
* so that {@link #toString} should be as efficient as possible.
*
* NOTE: starting with 2.14, there is no accompanying
* {@link #_asStringOffset} that MUST be considered with this String;
* this {@code String} may contain preceding path, as it is now full path
* of parent pointer, except for the outermost pointer instance.
*/
protected final String _asString;
/**
* @since 2.14
*/
protected final int _asStringOffset;
protected final String _matchingPropertyName;
protected final int _matchingElementIndex;
/**
* Lazily-calculated hash code: need to retain hash code now that we can no
* longer rely on {@link #_asString} being the exact full representation (it
* is often "more", including parent path).
*
* @since 2.14
*/
protected int _hashCode;
/*
/**********************************************************
/* Construction
/**********************************************************
*/
/**
* Constructor used for creating "empty" instance, used to represent
* state that matches current node.
*/
protected JsonPointer() {
_nextSegment = null;
// [core#788]: must be `null` to distinguish from Property with "" as key
_matchingPropertyName = null;
_matchingElementIndex = -1;
_asString = "";
_asStringOffset = 0;
}
// Constructor used for creating non-empty Segments
protected JsonPointer(String fullString, int fullStringOffset,
String segment, JsonPointer next)
{
_asString = fullString;
_asStringOffset = fullStringOffset;
_nextSegment = next;
// Ok; may always be a property
_matchingPropertyName = segment;
// but could be an index, if parsable
_matchingElementIndex = _parseIndex(segment);
}
protected JsonPointer(String fullString, int fullStringOffset,
String segment, int matchIndex, JsonPointer next) {
_asString = fullString;
_asStringOffset = fullStringOffset;
_nextSegment = next;
_matchingPropertyName = segment;
_matchingElementIndex = matchIndex;
}
/*
/**********************************************************
/* Factory methods
/**********************************************************
*/
/**
* Factory method that parses given input and construct matching pointer
* instance, if it represents a valid JSON Pointer: if not, a
* {@link IllegalArgumentException} is thrown.
*
* @param expr Pointer expression to compile
*
* @return Compiled {@link JsonPointer} path expression
*
* @throws IllegalArgumentException Thrown if the input does not present a valid JSON Pointer
* expression: currently the only such expression is one that does NOT start with
* a slash ('/').
*/
public static JsonPointer compile(String expr) throws IllegalArgumentException
{
// First quick checks for well-known 'empty' pointer
if ((expr == null) || expr.length() == 0) {
return EMPTY;
}
// And then quick validity check:
if (expr.charAt(0) != '/') {
throw new IllegalArgumentException("Invalid input: JSON Pointer expression must start with '/': "+"\""+expr+"\"");
}
return _parseTail(expr);
}
/**
* Alias for {@link #compile}; added to make instances automatically
* deserializable by Jackson databind.
*
* @param expr Pointer expression to compile
*
* @return Compiled {@link JsonPointer} path expression
*/
public static JsonPointer valueOf(String expr) { return compile(expr); }
/**
* Accessor for an "empty" expression, that is, one you can get by
* calling {@link #compile} with "" (empty String).
*
* NOTE: this is different from expression for {@code "/"} which would
* instead match Object node property with empty String ("") as name.
*
* @return "Empty" pointer expression instance that matches given root value
*
* @since 2.10
*/
public static JsonPointer empty() { return EMPTY; }
/**
* Factory method that will construct a pointer instance that describes
* path to location given {@link JsonStreamContext} points to.
*
* @param context Context to build pointer expression for
* @param includeRoot Whether to include number offset for virtual "root context"
* or not.
*
* @return {@link JsonPointer} path to location of given context
*
* @since 2.9
*/
public static JsonPointer forPath(JsonStreamContext context,
boolean includeRoot)
{
// First things first: last segment may be for START_ARRAY/START_OBJECT,
// in which case it does not yet point to anything, and should be skipped
if (context == null) {
return EMPTY;
}
// Otherwise if context was just created but is not advanced -- like,
// opening START_ARRAY/START_OBJECT returned -- drop the empty context.
if (!context.hasPathSegment()) {
// Except one special case: do not prune root if we need it
if (!(includeRoot && context.inRoot() && context.hasCurrentIndex())) {
context = context.getParent();
}
}
PointerSegment next = null;
int approxLength = 0;
for (; context != null; context = context.getParent()) {
if (context.inObject()) {
String propName = context.getCurrentName();
if (propName == null) { // is this legal?
propName = "";
}
approxLength += 2 + propName.length();
next = new PointerSegment(next, propName, -1);
} else if (context.inArray() || includeRoot) {
int ix = context.getCurrentIndex();
approxLength += 6;
next = new PointerSegment(next, null, ix);
}
// NOTE: this effectively drops ROOT node(s); should have 1 such node,
// as the last one, but we don't have to care (probably some paths have
// no root, for example)
}
if (next == null) {
return EMPTY;
}
// And here the fun starts! We have the head, need to traverse
// to compose full path String
StringBuilder pathBuilder = new StringBuilder(approxLength);
PointerSegment last = null;
for (; next != null; next = next.next) {
// Let's find the last segment as well, for reverse traversal
last = next;
next.pathOffset = pathBuilder.length();
pathBuilder.append('/');
if (next.property != null) {
_appendEscaped(pathBuilder, next.property);
} else {
pathBuilder.append(next.index);
}
}
final String fullPath = pathBuilder.toString();
// and then iteratively construct JsonPointer chain in reverse direction
// (from innermost back to outermost)
PointerSegment currSegment = last;
JsonPointer currPtr = EMPTY;
for (; currSegment != null; currSegment = currSegment.prev) {
if (currSegment.property != null) {
currPtr = new JsonPointer(fullPath, currSegment.pathOffset,
currSegment.property, currPtr);
} else {
int index = currSegment.index;
currPtr = new JsonPointer(fullPath, currSegment.pathOffset,
String.valueOf(index), index, currPtr);
}
}
return currPtr;
}
private static void _appendEscaped(StringBuilder sb, String segment)
{
for (int i = 0, end = segment.length(); i < end; ++i) {
char c = segment.charAt(i);
if (c == '/') {
sb.append("~1");
continue;
}
if (c == '~') {
sb.append("~0");
continue;
}
sb.append(c);
}
}
/*
/**********************************************************
/* Public API
/**********************************************************
*/
/**
* Functionally same as:
*
* toString().length()
*
* but more efficient as it avoids likely String allocation.
*
* @since 2.14
*/
public int length() {
return _asString.length() - _asStringOffset;
}
public boolean matches() { return _nextSegment == null; }
public String getMatchingProperty() { return _matchingPropertyName; }
public int getMatchingIndex() { return _matchingElementIndex; }
/**
* @return True if the root selector matches property name (that is, could
* match field value of JSON Object node)
*/
public boolean mayMatchProperty() { return _matchingPropertyName != null; }
/**
* @return True if the root selector matches element index (that is, could
* match an element of JSON Array node)
*/
public boolean mayMatchElement() { return _matchingElementIndex >= 0; }
/**
* @return the leaf of current JSON Pointer expression: leaf is the last
* non-null segment of current JSON Pointer.
*
* @since 2.5
*/
public JsonPointer last() {
JsonPointer current = this;
if (current == EMPTY) {
return null;
}
JsonPointer next;
while ((next = current._nextSegment) != JsonPointer.EMPTY) {
current = next;
}
return current;
}
/**
* Mutant factory method that will return
*
* - `tail` if `this` instance is "empty" pointer, OR
*
* - `this` instance if `tail` is "empty" pointer, OR
*
* - Newly constructed {@link JsonPointer} instance that starts with all segments
* of `this`, followed by all segments of `tail`.
*
*
*
* @param tail {@link JsonPointer} instance to append to this one, to create a new pointer instance
*
* @return Either `this` instance, `tail`, or a newly created combination, as per description above.
*/
public JsonPointer append(JsonPointer tail) {
if (this == EMPTY) {
return tail;
}
if (tail == EMPTY) {
return this;
}
// 21-Mar-2017, tatu: Not superbly efficient; could probably improve by not concatenating,
// re-decoding -- by stitching together segments -- but for now should be fine.
String currentJsonPointer = _asString;
if (currentJsonPointer.endsWith("/")) {
//removes final slash
currentJsonPointer = currentJsonPointer.substring(0, currentJsonPointer.length()-1);
}
return compile(currentJsonPointer + tail._asString);
}
/**
* ATTENTION! {@link JsonPointer} is head centric, tail appending is much costlier than head appending.
* It is not recommended to overuse the method.
*
* Mutant factory method that will return
*
* - `this` instance if `property` is null or empty String, OR
*
* - Newly constructed {@link JsonPointer} instance that starts with all segments
* of `this`, followed by new segment of 'property' name.
*
*
*
* 'property' format is starting separator (optional, added automatically if not provided) and new segment name.
*
* @param property new segment property name
*
* @return Either `this` instance, or a newly created combination, as per description above.
*/
public JsonPointer appendProperty(String property) {
if (property == null || property.isEmpty()) {
return this;
}
if (property.charAt(0) != SEPARATOR) {
property = SEPARATOR + property;
}
String currentJsonPointer = _asString;
if (currentJsonPointer.endsWith("/")) {
//removes final slash
currentJsonPointer = currentJsonPointer.substring(0, currentJsonPointer.length()-1);
}
return compile(currentJsonPointer + property);
}
/**
* ATTENTION! {@link JsonPointer} is head centric, tail appending is much costlier than head appending.
* It is not recommended to overuse the method.
*
* Mutant factory method that will return newly constructed {@link JsonPointer} instance that starts with all
* segments of `this`, followed by new segment of element 'index'. Element 'index' should be non-negative.
*
* @param index new segment element index
*
* @return Newly created combination, as per description above.
* @throws IllegalArgumentException if element index is negative
*/
public JsonPointer appendIndex(int index) {
if (index < 0) {
throw new IllegalArgumentException("Negative index cannot be appended");
}
String currentJsonPointer = _asString;
if (currentJsonPointer.endsWith("/")) {
//removes final slash
currentJsonPointer = currentJsonPointer.substring(0, currentJsonPointer.length()-1);
}
return compile(currentJsonPointer + SEPARATOR + index);
}
/**
* Method that may be called to see if the pointer head (first segment)
* would match property (of a JSON Object) with given name.
*
* @param name Name of Object property to match
*
* @return {@code True} if the pointer head matches specified property name
*
* @since 2.5
*/
public boolean matchesProperty(String name) {
return (_nextSegment != null) && _matchingPropertyName.equals(name);
}
/**
* Method that may be called to check whether the pointer head (first segment)
* matches specified Object property (by name) and if so, return
* {@link JsonPointer} that represents rest of the path after match.
* If there is no match, {@code null} is returned.
*
* @param name Name of Object property to match
*
* @return Remaining path after matching specified property, if there is match;
* {@code null} otherwise
*/
public JsonPointer matchProperty(String name) {
if ((_nextSegment != null) && _matchingPropertyName.equals(name)) {
return _nextSegment;
}
return null;
}
/**
* Method that may be called to see if the pointer would match
* Array element (of a JSON Array) with given index.
*
* @param index Index of Array element to match
*
* @return {@code True} if the pointer head matches specified Array index
*
* @since 2.5
*/
public boolean matchesElement(int index) {
return (index == _matchingElementIndex) && (index >= 0);
}
/**
* Method that may be called to check whether the pointer head (first segment)
* matches specified Array index and if so, return
* {@link JsonPointer} that represents rest of the path after match.
* If there is no match, {@code null} is returned.
*
* @param index Index of Array element to match
*
* @return Remaining path after matching specified index, if there is match;
* {@code null} otherwise
*
* @since 2.6
*/
public JsonPointer matchElement(int index) {
if ((index != _matchingElementIndex) || (index < 0)) {
return null;
}
return _nextSegment;
}
/**
* Accessor for getting a "sub-pointer" (or sub-path), instance where current segment
* has been removed and pointer includes rest of the segments.
* For example, for JSON Pointer "/root/branch/leaf", this method would
* return pointer "/branch/leaf".
* For matching state (last segment), will return {@code null}.
*
* Note that this is a very cheap method to call as it simply returns "next" segment
* (which has been constructed when pointer instance was constructed).
*
* @return Tail of this pointer, if it has any; {@code null} if this pointer only
* has the current segment
*/
public JsonPointer tail() {
return _nextSegment;
}
/**
* Accessor for getting a pointer instance that is identical to this
* instance except that the last segment has been dropped.
* For example, for JSON Pointer "/root/branch/leaf", this method would
* return pointer "/root/branch" (compared to {@link #tail()} that
* would return "/branch/leaf").
*
* Note that whereas {@link #tail} is a very cheap operation to call (as "tail" already
* exists for single-linked forward direction), this method has to fully
* construct a new instance by traversing the chain of segments.
*
* @return Pointer expression that contains same segments as this one, except for
* the last segment.
*
* @since 2.5
*/
public JsonPointer head() {
JsonPointer h = _head;
if (h == null) {
if (this != EMPTY) {
h = _constructHead();
}
_head = h;
}
return h;
}
/*
/**********************************************************
/* Standard method overrides (since 2.14)
/**********************************************************
*/
@Override public String toString() {
if (_asStringOffset <= 0) {
return _asString;
}
return _asString.substring(_asStringOffset);
}
@Override public int hashCode() {
int h = _hashCode;
if (h == 0) {
// Alas, this is bit wasteful, creating temporary String, but
// without JDK exposing hash code calculation for a sub-string
// can't do much
h = toString().hashCode();
if (h == 0) {
h = -1;
}
_hashCode = h;
}
return h;
}
@Override public boolean equals(Object o) {
if (o == this) return true;
if (o == null) return false;
if (!(o instanceof JsonPointer)) return false;
JsonPointer other = (JsonPointer) o;
// 07-Oct-2022, tatu: Ugh.... this gets way more complicated as we MUST
// compare logical representation so cannot simply compare offset
// and String
return _compare(_asString, _asStringOffset,
other._asString, other._asStringOffset);
}
private final boolean _compare(String str1, int offset1,
String str2, int offset2) {
final int end1 = str1.length();
// Different lengths? Not equal
if ((end1 - offset1) != (str2.length() - offset2)) {
return false;
}
for (; offset1 < end1; ) {
if (str1.charAt(offset1++) != str2.charAt(offset2++)) {
return false;
}
}
return true;
}
/*
/**********************************************************
/* Internal methods
/**********************************************************
*/
private final static int _parseIndex(String str) {
final int len = str.length();
// [core#133]: beware of super long indexes; assume we never
// have arrays over 2 billion entries so ints are fine.
if (len == 0 || len > 10) {
return -1;
}
// [core#176]: no leading zeroes allowed
char c = str.charAt(0);
if (c <= '0') {
return (len == 1 && c == '0') ? 0 : -1;
}
if (c > '9') {
return -1;
}
for (int i = 1; i < len; ++i) {
c = str.charAt(i);
if (c > '9' || c < '0') {
return -1;
}
}
if (len == 10) {
long l = NumberInput.parseLong(str);
if (l > Integer.MAX_VALUE) {
return -1;
}
}
return NumberInput.parseInt(str);
}
protected static JsonPointer _parseTail(final String fullPath)
{
PointerParent parent = null;
// first char is the contextual slash, skip
int i = 1;
final int end = fullPath.length();
int startOffset = 0;
while (i < end) {
char c = fullPath.charAt(i);
if (c == '/') { // common case, got a segment
parent = new PointerParent(parent, startOffset,
fullPath.substring(startOffset + 1, i));
startOffset = i;
++i;
continue;
}
++i;
// quoting is different; offline this case
if (c == '~' && i < end) { // possibly, quote
// 04-Oct-2022, tatu: Let's decode escaped segment
// instead of recursive call
StringBuilder sb = new StringBuilder(32);
i = _extractEscapedSegment(fullPath, startOffset+1, i, sb);
final String segment = sb.toString();
if (i < 0) { // end!
return _buildPath(fullPath, startOffset, segment, parent);
}
parent = new PointerParent(parent, startOffset, segment);
startOffset = i;
++i;
continue;
}
// otherwise, loop on
}
// end of the road, no escapes
return _buildPath(fullPath, startOffset, fullPath.substring(startOffset + 1), parent);
}
private static JsonPointer _buildPath(final String fullPath, int fullPathOffset,
String segment, PointerParent parent) {
JsonPointer curr = new JsonPointer(fullPath, fullPathOffset, segment, EMPTY);
for (; parent != null; parent = parent.parent) {
curr = new JsonPointer(fullPath, parent.fullPathOffset, parent.segment, curr);
}
return curr;
}
/**
* Method called to extract the next segment of the path, in case
* where we seem to have encountered a (tilde-)escaped character
* within segment.
*
* @param input Full input for the tail being parsed
* @param firstCharOffset Offset of the first character of segment (one
* after slash)
* @param i Offset to character after tilde
* @param sb StringBuilder into which unquoted segment is added
*
* @return Offset at which slash was encountered, if any, or -1
* if expression ended without seeing unescaped slash
*/
protected static int _extractEscapedSegment(String input, int firstCharOffset,
int i,
StringBuilder sb)
{
final int end = input.length();
final int toCopy = i - 1 - firstCharOffset;
if (toCopy > 0) {
sb.append(input, firstCharOffset, i-1);
}
_appendEscape(sb, input.charAt(i++));
while (i < end) {
char c = input.charAt(i);
if (c == '/') { // end is nigh!
return i;
}
++i;
if (c == '~' && i < end) {
_appendEscape(sb, input.charAt(i++));
continue;
}
sb.append(c);
}
// end of the road, last segment
return -1;
}
private static void _appendEscape(StringBuilder sb, char c) {
if (c == '0') {
c = '~';
} else if (c == '1') {
c = '/';
} else {
sb.append('~');
}
sb.append(c);
}
protected JsonPointer _constructHead()
{
// ok; find out who we are to drop
JsonPointer last = last();
if (last == this) {
return EMPTY;
}
// and from that, length of suffix to drop
int suffixLength = last.length();
JsonPointer next = _nextSegment;
// !!! TODO 07-Oct-2022, tatu: change to iterative, not recursive
String fullString = toString();
return new JsonPointer(fullString.substring(0, fullString.length() - suffixLength), 0,
_matchingPropertyName,
_matchingElementIndex, next._constructHead(suffixLength, last));
}
protected JsonPointer _constructHead(int suffixLength, JsonPointer last)
{
if (this == last) {
return EMPTY;
}
JsonPointer next = _nextSegment;
String str = toString();
// !!! TODO 07-Oct-2022, tatu: change to iterative, not recursive
return new JsonPointer(str.substring(0, str.length() - suffixLength), 0,
_matchingPropertyName,
_matchingElementIndex, next._constructHead(suffixLength, last));
}
/*
/**********************************************************
/* Helper class used to replace call stack (2.14+)
/**********************************************************
*/
/**
* Helper class used to replace call stack when parsing JsonPointer
* expressions.
*/
private static class PointerParent {
public final PointerParent parent;
public final int fullPathOffset;
public final String segment;
PointerParent(PointerParent pp, int fpo, String sgm) {
parent = pp;
fullPathOffset = fpo;
segment = sgm;
}
}
/**
* Helper class used to contain a single segment when constructing JsonPointer
* from context.
*/
private static class PointerSegment {
public final PointerSegment next;
public final String property;
public final int index;
// Offset within external buffer, updated when constructing
public int pathOffset;
// And we actually need 2-way traversal, it turns out so:
public PointerSegment prev;
public PointerSegment(PointerSegment next, String pn, int ix) {
this.next = next;
property = pn;
index = ix;
// Ok not the cleanest thing but...
if (next != null) {
next.prev = this;
}
}
}
/*
/**********************************************************
/* Support for JDK serialization (2.14+)
/**********************************************************
*/
// Since 2.14: needed for efficient JDK serializability
private Object writeReplace() {
// 11-Oct-2022, tatu: very important, must serialize just contents!
return new Serialization(toString());
}
/**
* This must only exist to allow both final properties and implementation of
* Externalizable/Serializable for JsonPointer.
* Note that here we do not store offset but simply use (and expect use)
* full path, from which we need to decode actual structure.
*
* @since 2.14
*/
static class Serialization implements Externalizable
{
private String _fullPath;
public Serialization() { }
Serialization(String fullPath) {
_fullPath = fullPath;
}
@Override
public void writeExternal(ObjectOutput out) throws IOException {
out.writeUTF(_fullPath);
}
@Override
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
_fullPath = in.readUTF();
}
private Object readResolve() throws ObjectStreamException {
// NOTE: method handles canonicalization of "empty", as well as other
// aspects of decoding.
return compile(_fullPath);
}
}
}