org.unbescape.css
Class CssEscape

Object
  org.unbescape.css.CssEscape

public final class CssEscape
extends Object

Utility class for performing CSS escape/unescape operations.

This class supports both escaping of CSS identifiers and CSS Strings (or literals).

Configuration of escape/unescape operations

Escape operations can be (optionally) configured by means of:

• Level, which defines how deep the escape operation must be (what chars are to be considered eligible for escaping, depending on the specific needs of the scenario). Its values are defined by the CssIdentifierEscapeLevel and CssStringEscapeLevel enums.
• Type, which defines whether escaping should be performed by means of backslash escapes or by means of hexadecimal numerical escape sequences. Its values are defined by the CssIdentifierEscapeType and CssStringEscapeType enums.

Unescape operations need no configuration parameters. Unescape operations will always perform complete unescape of backslash and hexadecimal escapes, including all required tweaks (i.e. optional whitespace characters) needed for unescaping.

Features

Specific features of the CSS escape/unescape operations performed by means of this class:

• Complete set of CSS Backslash Escapes supported (e.g. \+, \(, \), etc.).
• Full set of escape syntax rules supported, both for CSS identifiers and CSS Strings (or literals).
• Non-standard tweaks supported: \: not used because of lacking support in Internet Explorer < 8, \_ escaped at the beginning of identifiers for better Internet Explorer 6 support, etc.
• Hexadecimal escapes (a.k.a. unicode escapes) are supported both in escape and unescape operations, and both in compact (\E1 ) and six-digit forms (\0000E1).
• Support for the whole Unicode character set: \u0000 to \u10FFFF, including characters not representable by only one char in Java (>\uFFFF).
• Support for unescaping unicode characters > U+FFFF both when represented in standard form (one char, \20000) and non-standard (surrogate pair, \D840\DC00, used by older WebKit browsers).

Input/Output

There are two different input/output modes that can be used in escape/unescape operations:

• String input, String output: Input is specified as a String object and output is returned as another. In order to improve memory performance, all escape and unescape operations will return the exact same input object as output if no escape/unescape modifications are required.
• char[] input, java.io.Writer output: Input will be read from a char array (char[]) and output will be written into the specified java.io.Writer. Two int arguments called offset and len will be used for specifying the part of the char[] that should be escaped/unescaped. These methods should be called with offset = 0 and len = text.length in order to process the whole char[].

Glossary

Backslash escapes

Escape sequences performed by means of prefixing a backslash (\) to the escaped char: \+, \(, \)

HEXA escapes

Complete representation of unicode codepoints up to U+10FFFF, in two forms:

• Compact: non-zero-padded hexadecimal representation (\E1 ), followed by an optional whitespace (U+0020), required if after the escaped character comes a hexadecimal digit ([0-9A-Fa-f]) or another whitespace (&nbps;).
• Six-digit: zero-padded hexadecimal representation (\0000E1), followed by an optional whitespace (U+0020), required if after the escaped character comes another whitespace ( ).

Unicode Codepoint

Each of the int values conforming the Unicode code space. Normally corresponding to a Java char primitive value (codepoint <= \uFFFF), but might be two chars for codepoints \u10000 to \u10FFFF if the first char is a high surrogate (\uD800 to \uDBFF) and the second is a low surrogate (\uDC00 to \uDFFF).

References

The following references apply:

• Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification [w3.org]
• CSS character escape sequences [mathiasbynens.be]
• CSS escapes tester [mothereff.in]

Since:

1.0

Author:

Daniel Fernández

Method Summary

static void	escapeCssIdentifier(char[] text, int offset, int len, Writer writer) Perform a CSS Identifier level 2 (basic set and all non-ASCII chars) escape operation on a char[] input.
static void	escapeCssIdentifier(char[] text, int offset, int len, Writer writer, CssIdentifierEscapeType type, CssIdentifierEscapeLevel level) Perform a (configurable) CSS Identifier escape operation on a char[] input.
static String	escapeCssIdentifier(String text) Perform a CSS Identifier level 2 (basic set and all non-ASCII chars) escape operation on a String input.
static String	escapeCssIdentifier(String text, CssIdentifierEscapeType type, CssIdentifierEscapeLevel level) Perform a (configurable) CSS Identifier escape operation on a String input.
static void	escapeCssIdentifierMinimal(char[] text, int offset, int len, Writer writer) Perform a CSS Identifier level 1 (only basic set) escape operation on a char[] input.
static String	escapeCssIdentifierMinimal(String text) Perform a CSS Identifier level 1 (only basic set) escape operation on a String input.
static void	escapeCssString(char[] text, int offset, int len, Writer writer) Perform a CSS String level 2 (basic set and all non-ASCII chars) escape operation on a char[] input.
static void	escapeCssString(char[] text, int offset, int len, Writer writer, CssStringEscapeType type, CssStringEscapeLevel level) Perform a (configurable) CSS String escape operation on a char[] input.
static String	escapeCssString(String text) Perform a CSS String level 2 (basic set and all non-ASCII chars) escape operation on a String input.
static String	escapeCssString(String text, CssStringEscapeType type, CssStringEscapeLevel level) Perform a (configurable) CSS String escape operation on a String input.
static void	escapeCssStringMinimal(char[] text, int offset, int len, Writer writer) Perform a CSS String level 1 (only basic set) escape operation on a char[] input.
static String	escapeCssStringMinimal(String text) Perform a CSS String level 1 (only basic set) escape operation on a String input.
static void	unescapeCss(char[] text, int offset, int len, Writer writer) Perform a CSS unescape operation on a char[] input.
static String	unescapeCss(String text) Perform a CSS unescape operation on a String input.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

escapeCssStringMinimal

public static String escapeCssStringMinimal(String text)

Perform a CSS String level 1 (only basic set) escape operation on a String input.

Level 1 means this method will only escape the CSS String basic escape set:

• The Backslash Escapes: \" (U+0022) and \' (U+0027).
• Two ranges of non-displayable, control characters: U+0000 to U+001F and U+007F to U+009F.

This escape will be performed by using Backslash escapes whenever possible. For escaped characters that do not have an associated Backslash, default to \FF Hexadecimal Escapes.

This method calls escapeCssString(String, CssStringEscapeType, CssStringEscapeLevel) with the following preconfigured values:

• type: CssStringEscapeType.BACKSLASH_ESCAPES_DEFAULT_TO_COMPACT_HEXA
• level: CssStringEscapeLevel.LEVEL_1_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the String to be escaped.

Returns:

The escaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no escaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

escapeCssString

public static String escapeCssString(String text)

Perform a CSS String level 2 (basic set and all non-ASCII chars) escape operation on a String input.

Level 2 means this method will escape:

• The CSS String basic escape set:
  • The Backslash Escapes: \" (U+0022) and \' (U+0027).
  • Two ranges of non-displayable, control characters: U+0000 to U+001F and U+007F to U+009F.
• All non ASCII characters.

This escape will be performed by using Backslash escapes whenever possible. For escaped characters that do not have an associated Backslash, default to \FF Hexadecimal Escapes.

This method calls escapeCssString(String, CssStringEscapeType, CssStringEscapeLevel) with the following preconfigured values:

• type: CssStringEscapeType.BACKSLASH_ESCAPES_DEFAULT_TO_COMPACT_HEXA
• level: CssStringEscapeLevel.LEVEL_2_ALL_NON_ASCII_PLUS_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the String to be escaped.

Returns:

The escaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no escaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

escapeCssString

public static String escapeCssString(String text,
                                     CssStringEscapeType type,
                                     CssStringEscapeLevel level)

Perform a (configurable) CSS String escape operation on a String input.

This method will perform an escape operation according to the specified CssStringEscapeType and CssStringEscapeLevel argument values.

All other String-based escapeCssString*(...) methods call this one with preconfigured type and level values.

This method is thread-safe.

Parameters:

text - the String to be escaped.

type - the type of escape operation to be performed, see CssStringEscapeType.

level - the escape level to be applied, see CssStringEscapeLevel.

Returns:

The escaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no escaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

escapeCssStringMinimal

public static void escapeCssStringMinimal(char[] text,
                                          int offset,
                                          int len,
                                          Writer writer)
                                   throws IOException

Perform a CSS String level 1 (only basic set) escape operation on a char[] input.

Level 1 means this method will only escape the CSS String basic escape set:

• The Backslash Escapes: \" (U+0022) and \' (U+0027).
• Two ranges of non-displayable, control characters: U+0000 to U+001F and U+007F to U+009F.

This escape will be performed by using Backslash escapes whenever possible. For escaped characters that do not have an associated Backslash, default to \FF Hexadecimal Escapes.

This method calls escapeCssString(char[], int, int, java.io.Writer, CssStringEscapeType, CssStringEscapeLevel) with the following preconfigured values:

• type: CssStringEscapeType.BACKSLASH_ESCAPES_DEFAULT_TO_COMPACT_HEXA
• level: CssStringEscapeLevel.LEVEL_1_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the char[] to be escaped.

offset - the position in text at which the escape operation should start.

len - the number of characters in text that should be escaped.

writer - the java.io.Writer to which the escaped result will be written. Nothing will be written at all to this writer if text is null.

Throws:

IOException

escapeCssString

public static void escapeCssString(char[] text,
                                   int offset,
                                   int len,
                                   Writer writer)
                            throws IOException

Perform a CSS String level 2 (basic set and all non-ASCII chars) escape operation on a char[] input.

Level 2 means this method will escape:

• The CSS String basic escape set:
  • The Backslash Escapes: \" (U+0022) and \' (U+0027).
  • Two ranges of non-displayable, control characters: U+0000 to U+001F and U+007F to U+009F.
• All non ASCII characters.

This escape will be performed by using Backslash escapes whenever possible. For escaped characters that do not have an associated Backslash, default to \FF Hexadecimal Escapes.

This method calls escapeCssString(char[], int, int, java.io.Writer, CssStringEscapeType, CssStringEscapeLevel) with the following preconfigured values:

• type: CssStringEscapeType.BACKSLASH_ESCAPES_DEFAULT_TO_COMPACT_HEXA
• level: CssStringEscapeLevel.LEVEL_2_ALL_NON_ASCII_PLUS_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the char[] to be escaped.

offset - the position in text at which the escape operation should start.

len - the number of characters in text that should be escaped.

writer - the java.io.Writer to which the escaped result will be written. Nothing will be written at all to this writer if text is null.

Throws:

IOException

escapeCssString

public static void escapeCssString(char[] text,
                                   int offset,
                                   int len,
                                   Writer writer,
                                   CssStringEscapeType type,
                                   CssStringEscapeLevel level)
                            throws IOException

Perform a (configurable) CSS String escape operation on a char[] input.

This method will perform an escape operation according to the specified CssStringEscapeType and CssStringEscapeLevel argument values.

All other char[]-based escapeCssString*(...) methods call this one with preconfigured type and level values.

This method is thread-safe.

Parameters:

text - the char[] to be escaped.

offset - the position in text at which the escape operation should start.

len - the number of characters in text that should be escaped.

writer - the java.io.Writer to which the escaped result will be written. Nothing will be written at all to this writer if text is null.

type - the type of escape operation to be performed, see CssStringEscapeType.

level - the escape level to be applied, see CssStringEscapeLevel.

Throws:

IOException

escapeCssIdentifierMinimal

public static String escapeCssIdentifierMinimal(String text)

Perform a CSS Identifier level 1 (only basic set) escape operation on a String input.

Level 1 means this method will only escape the CSS Identifier basic escape set:

• The Backslash Escapes: \ (U+0020), \! (U+0021), \" (U+0022), \# (U+0023), \$ (U+0024), \% (U+0025), \& (U+0026), \' (U+0027), \( (U+0028), \) (U+0029), \* (U+002A), \+ (U+002B), \, (U+002C), \. (U+002E), \/ (U+002F), \; (U+003B), \< (U+003C), \= (U+003D), \> (U+003E), \? (U+003F), \@ (U+0040), \[ (U+005B), \\ (U+005C), \] (U+005D), \^ (U+005E), \` (U+0060), \{ (U+007B), \| (U+007C), \} (U+007D) and \~ (U+007E). Note that the \- (U+002D) escape sequence exists, but will only be used when an identifier starts with two hypens or hyphen + digit. Also, the \_ (U+005F) escape will only be used at the beginning of an identifier to avoid problems with Internet Explorer 6. In the same sense, note that the \: (U+003A) escape sequence is also defined in the standard, but will not be used for escaping as Internet Explorer < 8 does not recognize it.
• Two ranges of non-displayable, control characters: U+0000 to U+001F and U+007F to U+009F.

This escape will be performed by using Backslash escapes whenever possible. For escaped characters that do not have an associated Backslash, default to \FF Hexadecimal Escapes.

This method calls escapeCssIdentifier(String, CssIdentifierEscapeType, CssIdentifierEscapeLevel) with the following preconfigured values:

• type: CssIdentifierEscapeType.BACKSLASH_ESCAPES_DEFAULT_TO_COMPACT_HEXA
• level: CssIdentifierEscapeLevel.LEVEL_1_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the String to be escaped.

Returns:

The escaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no escaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

escapeCssIdentifier

public static String escapeCssIdentifier(String text)

Perform a CSS Identifier level 2 (basic set and all non-ASCII chars) escape operation on a String input.

Level 2 means this method will escape:

• The CSS Identifier basic escape set:
  • The Backslash Escapes: \ (U+0020), \! (U+0021), \" (U+0022), \# (U+0023), \$ (U+0024), \% (U+0025), \& (U+0026), \' (U+0027), \( (U+0028), \) (U+0029), \* (U+002A), \+ (U+002B), \, (U+002C), \. (U+002E), \/ (U+002F), \; (U+003B), \< (U+003C), \= (U+003D), \> (U+003E), \? (U+003F), \@ (U+0040), \[ (U+005B), \\ (U+005C), \] (U+005D), \^ (U+005E), \` (U+0060), \{ (U+007B), \| (U+007C), \} (U+007D) and \~ (U+007E). Note that the \- (U+002D) escape sequence exists, but will only be used when an identifier starts with two hypens or hyphen + digit. Also, the \_ (U+005F) escape will only be used at the beginning of an identifier to avoid problems with Internet Explorer 6. In the same sense, note that the \: (U+003A) escape sequence is also defined in the standard, but will not be used for escaping as Internet Explorer < 8 does not recognize it.
  • Two ranges of non-displayable, control characters: U+0000 to U+001F and U+007F to U+009F.
• All non ASCII characters.

This escape will be performed by using Backslash escapes whenever possible. For escaped characters that do not have an associated Backslash, default to \FF Hexadecimal Escapes.

This method calls escapeCssIdentifier(String, CssIdentifierEscapeType, CssIdentifierEscapeLevel) with the following preconfigured values:

• type: CssIdentifierEscapeType.BACKSLASH_ESCAPES_DEFAULT_TO_COMPACT_HEXA
• level: CssIdentifierEscapeLevel.LEVEL_2_ALL_NON_ASCII_PLUS_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the String to be escaped.

Returns:

The escaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no escaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

escapeCssIdentifier

public static String escapeCssIdentifier(String text,
                                         CssIdentifierEscapeType type,
                                         CssIdentifierEscapeLevel level)

Perform a (configurable) CSS Identifier escape operation on a String input.

This method will perform an escape operation according to the specified CssIdentifierEscapeType and CssIdentifierEscapeLevel argument values.

All other String-based escapeCssIdentifier*(...) methods call this one with preconfigured type and level values.

This method is thread-safe.

Parameters:

text - the String to be escaped.

type - the type of escape operation to be performed, see CssIdentifierEscapeType.

level - the escape level to be applied, see CssIdentifierEscapeLevel.

Returns:

The escaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no escaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

escapeCssIdentifierMinimal

public static void escapeCssIdentifierMinimal(char[] text,
                                              int offset,
                                              int len,
                                              Writer writer)
                                       throws IOException

Perform a CSS Identifier level 1 (only basic set) escape operation on a char[] input.

Level 1 means this method will only escape the CSS Identifier basic escape set:

• The Backslash Escapes: \ (U+0020), \! (U+0021), \" (U+0022), \# (U+0023), \$ (U+0024), \% (U+0025), \& (U+0026), \' (U+0027), \( (U+0028), \) (U+0029), \* (U+002A), \+ (U+002B), \, (U+002C), \. (U+002E), \/ (U+002F), \; (U+003B), \< (U+003C), \= (U+003D), \> (U+003E), \? (U+003F), \@ (U+0040), \[ (U+005B), \\ (U+005C), \] (U+005D), \^ (U+005E), \` (U+0060), \{ (U+007B), \| (U+007C), \} (U+007D) and \~ (U+007E). Note that the \- (U+002D) escape sequence exists, but will only be used when an identifier starts with two hypens or hyphen + digit. Also, the \_ (U+005F) escape will only be used at the beginning of an identifier to avoid problems with Internet Explorer 6. In the same sense, note that the \: (U+003A) escape sequence is also defined in the standard, but will not be used for escaping as Internet Explorer < 8 does not recognize it.
• Two ranges of non-displayable, control characters: U+0000 to U+001F and U+007F to U+009F.

This escape will be performed by using Backslash escapes whenever possible. For escaped characters that do not have an associated Backslash, default to \FF Hexadecimal Escapes.

This method calls escapeCssIdentifier(char[], int, int, java.io.Writer, CssIdentifierEscapeType, CssIdentifierEscapeLevel) with the following preconfigured values:

• type: CssIdentifierEscapeType.BACKSLASH_ESCAPES_DEFAULT_TO_COMPACT_HEXA
• level: CssIdentifierEscapeLevel.LEVEL_1_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the char[] to be escaped.

offset - the position in text at which the escape operation should start.

len - the number of characters in text that should be escaped.

writer - the java.io.Writer to which the escaped result will be written. Nothing will be written at all to this writer if text is null.

Throws:

IOException

escapeCssIdentifier

public static void escapeCssIdentifier(char[] text,
                                       int offset,
                                       int len,
                                       Writer writer)
                                throws IOException

Perform a CSS Identifier level 2 (basic set and all non-ASCII chars) escape operation on a char[] input.

Level 2 means this method will escape:

• The CSS Identifier basic escape set:
  • The Backslash Escapes: \ (U+0020), \! (U+0021), \" (U+0022), \# (U+0023), \$ (U+0024), \% (U+0025), \& (U+0026), \' (U+0027), \( (U+0028), \) (U+0029), \* (U+002A), \+ (U+002B), \, (U+002C), \. (U+002E), \/ (U+002F), \; (U+003B), \< (U+003C), \= (U+003D), \> (U+003E), \? (U+003F), \@ (U+0040), \[ (U+005B), \\ (U+005C), \] (U+005D), \^ (U+005E), \` (U+0060), \{ (U+007B), \| (U+007C), \} (U+007D) and \~ (U+007E). Note that the \- (U+002D) escape sequence exists, but will only be used when an identifier starts with two hypens or hyphen + digit. Also, the \_ (U+005F) escape will only be used at the beginning of an identifier to avoid problems with Internet Explorer 6. In the same sense, note that the \: (U+003A) escape sequence is also defined in the standard, but will not be used for escaping as Internet Explorer < 8 does not recognize it.
  • Two ranges of non-displayable, control characters: U+0000 to U+001F and U+007F to U+009F.
• All non ASCII characters.

This escape will be performed by using Backslash escapes whenever possible. For escaped characters that do not have an associated Backslash, default to \FF Hexadecimal Escapes.

This method calls escapeCssIdentifier(char[], int, int, java.io.Writer, CssIdentifierEscapeType, CssIdentifierEscapeLevel) with the following preconfigured values:

• type: CssIdentifierEscapeType.BACKSLASH_ESCAPES_DEFAULT_TO_COMPACT_HEXA
• level: CssIdentifierEscapeLevel.LEVEL_2_ALL_NON_ASCII_PLUS_BASIC_ESCAPE_SET

This method is thread-safe.

Parameters:

text - the char[] to be escaped.

offset - the position in text at which the escape operation should start.

len - the number of characters in text that should be escaped.

writer - the java.io.Writer to which the escaped result will be written. Nothing will be written at all to this writer if text is null.

Throws:

IOException

escapeCssIdentifier

public static void escapeCssIdentifier(char[] text,
                                       int offset,
                                       int len,
                                       Writer writer,
                                       CssIdentifierEscapeType type,
                                       CssIdentifierEscapeLevel level)
                                throws IOException

Perform a (configurable) CSS Identifier escape operation on a char[] input.

This method will perform an escape operation according to the specified CssIdentifierEscapeType and CssIdentifierEscapeLevel argument values.

All other char[]-based escapeCssIdentifier*(...) methods call this one with preconfigured type and level values.

This method is thread-safe.

Parameters:

text - the char[] to be escaped.

offset - the position in text at which the escape operation should start.

len - the number of characters in text that should be escaped.

writer - the java.io.Writer to which the escaped result will be written. Nothing will be written at all to this writer if text is null.

type - the type of escape operation to be performed, see CssIdentifierEscapeType.

level - the escape level to be applied, see CssIdentifierEscapeLevel.

Throws:

IOException

unescapeCss

public static String unescapeCss(String text)

Perform a CSS unescape operation on a String input.

No additional configuration arguments are required. Unescape operations will always perform complete CSS unescape of backslash and hexadecimal escape sequences.

This method is thread-safe.

Parameters:

text - the String to be unescaped.

Returns:

The unescaped result String. As a memory-performance improvement, will return the exact same object as the text input argument if no unescaping modifications were required (and no additional String objects will be created during processing). Will return null if text is null.

unescapeCss

public static void unescapeCss(char[] text,
                               int offset,
                               int len,
                               Writer writer)
                        throws IOException

Perform a CSS unescape operation on a char[] input.

No additional configuration arguments are required. Unescape operations will always perform complete CSS unescape of backslash and hexadecimal escape sequences.

This method is thread-safe.

Parameters:

text - the char[] to be unescaped.

offset - the position in text at which the unescape operation should start.

len - the number of characters in text that should be unescaped.

writer - the java.io.Writer to which the unescaped result will be written. Nothing will be written at all to this writer if text is null.

Throws:

IOException