@Beta @GwtCompatible public abstract class ArrayBasedUnicodeEscaper extends UnicodeEscaper
UnicodeEscaper that uses an array to quickly look up replacement characters for a given
code point. An additional safe range is provided that determines whether code points without
specific replacements are to be considered safe and left unescaped or should be escaped in a
general way.
A good example of usage of this class is for HTML escaping where the replacement array
contains information about the named HTML entities such as & and " while
escapeUnsafe(int) is overridden to handle general escaping of the form &#NNNNN;.
The size of the data structure used by ArrayBasedUnicodeEscaper is proportional to the
highest valued code point that requires escaping. For example a replacement map containing the
single character '\u1000' will require approximately 16K of memory. If you need
to create multiple escaper instances that have the same character replacement mapping consider
using ArrayBasedEscaperMap.
| Modifier | Constructor and Description |
|---|---|
protected |
ArrayBasedUnicodeEscaper(ArrayBasedEscaperMap escaperMap,
int safeMin,
int safeMax,
@Nullable String unsafeReplacement)
Creates a new ArrayBasedUnicodeEscaper instance with the given replacement map and specified
safe range.
|
protected |
ArrayBasedUnicodeEscaper(Map<Character,String> replacementMap,
int safeMin,
int safeMax,
@Nullable String unsafeReplacement)
Creates a new ArrayBasedUnicodeEscaper instance with the given replacement map and specified
safe range.
|
| Modifier and Type | Method and Description |
|---|---|
protected char[] |
escape(int cp)
Escapes a single Unicode code point using the replacement array and safe range values.
|
String |
escape(String s)
Returns the escaped form of a given literal string.
|
protected abstract char[] |
escapeUnsafe(int cp)
Escapes a code point that has no direct explicit value in the replacement array and lies
outside the stated safe range.
|
protected int |
nextEscapeIndex(CharSequence csq,
int index,
int end)
Scans a sub-sequence of characters from a given
CharSequence, returning the index of
the next character that requires escaping. |
codePointAt, escapeSlowasFunctionprotected ArrayBasedUnicodeEscaper(Map<Character,String> replacementMap, int safeMin, int safeMax, @Nullable String unsafeReplacement)
safeMax < safeMin then no code points are considered safe.
If a code point has no mapped replacement then it is checked against the safe range. If it
lies outside that, then escapeUnsafe(int) is called, otherwise no escaping is performed.
replacementMap - a map of characters to their escaped representationssafeMin - the lowest character value in the safe rangesafeMax - the highest character value in the safe rangeunsafeReplacement - the default replacement for unsafe characters or null if no default
replacement is requiredprotected ArrayBasedUnicodeEscaper(ArrayBasedEscaperMap escaperMap, int safeMin, int safeMax, @Nullable String unsafeReplacement)
safeMax < safeMin then no code points are considered safe. This
initializer is useful when explicit instances of ArrayBasedEscaperMap are used to allow the
sharing of large replacement mappings.
If a code point has no mapped replacement then it is checked against the safe range. If it
lies outside that, then escapeUnsafe(int) is called, otherwise no escaping is performed.
escaperMap - the map of replacementssafeMin - the lowest character value in the safe rangesafeMax - the highest character value in the safe rangeunsafeReplacement - the default replacement for unsafe characters or null if no default
replacement is requiredpublic final String escape(String s)
UnicodeEscaperIf you are escaping input in arbitrary successive chunks, then it is not generally safe to
use this method. If an input string ends with an unmatched high surrogate character, then this
method will throw IllegalArgumentException. You should ensure your input is valid UTF-16 before calling this method.
Note: When implementing an escaper it is a good idea to override this method for
efficiency by inlining the implementation of UnicodeEscaper.nextEscapeIndex(CharSequence, int, int)
directly. Doing this for PercentEscaper more than doubled the
performance for unescaped strings (as measured by CharEscapersBenchmark).
escape in class UnicodeEscapers - the literal string to be escapedstringprotected final char[] escape(int cp)
escapeUnsafe(int) is called.escape in class UnicodeEscapercp - the Unicode code point to escape if necessarynull if no escaping was neededprotected final int nextEscapeIndex(CharSequence csq, int index, int end)
UnicodeEscaperCharSequence, returning the index of
the next character that requires escaping.
Note: When implementing an escaper, it is a good idea to override this method for
efficiency. The base class implementation determines successive Unicode code points and invokes
UnicodeEscaper.escape(int) for each of them. If the semantics of your escaper are such that code
points in the supplementary range are either all escaped or all unescaped, this method can be
implemented more efficiently using CharSequence.charAt(int).
Note however that if your escaper does not escape characters in the supplementary range, you should either continue to validate the correctness of any surrogate characters encountered or provide a clear warning to users that your escaper does not validate its input.
See PercentEscaper for an example.
nextEscapeIndex in class UnicodeEscapercsq - a sequence of charactersindex - the index of the first character to be scannedend - the index immediately after the last character to be scannedprotected abstract char[] escapeUnsafe(int cp)
Note that arrays returned by this method must not be modified once they have been returned. However it is acceptable to return the same array multiple times (even for different input characters).
cp - the Unicode code point to escapenull if no escaping was requiredCopyright © 2010–2018. All rights reserved.