ICU Overview:
The Open Source Unicode Library
Markus Scherer
IBM Globalization Center of Competency
29th Internationalization and Unicode Conference
© 2006 IBM Corporation
ICU Overview: The Open Source Unicode Library
Agenda
 Background Information
 What is ICU?
 Architecture Overview
– Significant New ICU Features
 References
 Q and A
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ICU Overview: The Open Source Unicode Library
Why Globalization?
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Unicode
 Handles all modern world languages
 Efficient and effective processing
 Lossless data exchange
 Enables single-binary global software
 But… all languages ⇒ large, complex standard
– 1,400 pages + Annexes + additional standards
– Almost 100,000 characters
– Major update every 3 years; minor update about once a year
– 70 character properties, many multi-valued
– Affects many processes: display, line-break, regular expressions,
…
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Internationalization, Localization & Locales
 Requirements vary widely across languages & countries
– Sorting
– Text searching
– Line breaks
– Date/time/number/currency formatting
– Codepage conversion
– …and so on
 Performance is key
– It is easy to do the right thing
– It is hard to do it fast
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ICU Overview: The Open Source Unicode Library
What is ICU?
 International Components for Unicode
 Globalization / Unicode / Locales
 Mature, widely used set of C/C++ and Java libraries
– Basis for Java 1.1 internationalization, but goes far beyond Java 1.1
 Very portable – identical results on all platforms / programming
languages
– C/C++ (ICU4C): 30+ platforms/compilers
– Java (ICU4J): IBM & Sun JDK
– C/C++ with Java (ICU4JNI)
 Full threading model
 Customizable & Modular
 Open source – but non-restrictive
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ICU Overview: The Open Source Unicode Library
Who uses ICU?
 Products Within IBM
– All 5 major software brands
– Many other related software applications
– Used on all IBM operating systems
 Other Companies and Organizations
– Adobe, Apple (Mac OS X), Avaya, BEA, BroadJump, Business
Objects, Caris, CERN, Cognos, Debian Linux, Gentoo Linux, HP,
Home Depot, Inktomi, JD Edwards, Macromedia, Mathworks, MKS,
Mozilla, NCR, OpenOffice, Parrot, PayPal, Python, QNX, Rogue
Wave, SAP, Siebel, SIL, Software AG, Sun Microsystems (Solaris,
Java), SuSE Linux, Sybase, Virage, webMethods, Wine, Leica
Geosystems GIS & Mapping LLC., Xerox, Yahoo!
...and many more
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ICU Overview: The Open Source Unicode Library
ICU Features
 Unicode text handling
 Breaks: word, line, …
 Charset conversions (700+)
 Formatting
– Date & time
 Collation & Searching
– Messages
 Locales from CLDR (250+)
– Numbers & currencies
 Resource Bundles
 Transforms
 Calendar & Time zones
– Normalization
 Complex-text layout engine
– Casing
 Unicode Regular Expressions
– Transliterations
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ICU Overview: The Open Source Unicode Library
Architecture Overview 1
 Locale Based Services
– Locale is an identifier, not a container
– Keywords for variants: [email protected]=phonebook
 Resource inheritance: shared resources
root
Language
en
de
zh
Script
Region
US
IE
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DE
CH
9
Hant
Hans
TW
CN
CN
TW
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ICU Overview: The Open Source Unicode Library
Architecture Overview 2
 Open and Close Service Model
– Open a service object, use it many times, close it when done
– Better performance by avoiding setup costs per operation
 ICU Threading Model
– Multiple service objects in use simultaneously
with same or different attributes
– Large resources shared in read-only cache
– Compatible with Java threading model
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Architecture Overview 3
 Data Driven Services
– Customize at build-time or run-time
– Interchange with other platforms;
• same results on each
– Rule-based
• Collation, Word-breaks, Transforms
– Pattern-based
• Date/Time/Number/Message formatting
– Table-based
• Character Conversion
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Architecture Overview – ICU4C
 Simple Error Handling
– Thread safe
– Works in C and C++
 C/C++ subset for portability
 Version Management
– Multiple versions of ICU4C in the same process memory space
– Data and library versioning
 String Buffer Management
– Preflighting and overflow protection
 Flexible
– Allows Loading and Unloading ICU4C libraries
– Runtime settable memory allocation and mutex functions
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Architecture Overview – ICU4J
 Supplement for Java
 Core globalization (no character conversion or
regular expressions)
– We do supply complex text support for Sun
 Modularized: products may add just needed
functionality
 Usually drop-in replacement for JDK functionality
– Changing the import statements is usually all that is needed
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ICU Overview: The Open Source Unicode Library
ICU4J: Supplement for Java
 CLDR (Common Locale Data Repository)
– More fully supported locales than Java
 Up-to-date globalization: standards-compliant; latest Unicode
– Supplementary character (GB 18030, JIS X 213, HKSCS)
• Java 5 adds handling of supplementary characters
– Full properties – JDK has only a fraction
– Unicode Collation Algorithm
– Local calendars (Islamic, Japan,…); more time zone localizations
– Currencies, String Search, Internationalized Domain Names
– Transforms: Case, Scripts, Normalization
 Much shorter release cycle and quicker support for Unicode standard
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ICU Overview: The Open Source Unicode Library
Recent Additions for ICU4J
 ICU4J in Eclipse Rich Client Platform
– Take advantage of advanced globalization and support for
more locales and more recent Unicode
– Consistent behavior between application code and
framework code
– ICU4J 3.4+ in Eclipse 3.2
– No-op jar for JDK behavior and low-memory devices
 Improved portability & JRE independence
– Back-ported to Java 1.3 (via preprocessor)
– Carries own Time Zone data
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Unicode Text Handling
 All UTF-16 processing
C
– UChar*: null-terminated or with length
 C++
– UnicodeString: full featured string class
 Java
– Uses java.lang.String and adds utilities
 All handle supplementary characters
– Required for GB 18030, HKSCS and JIS X 213 repertoires
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Abstract Text Access
 Work with non-UTF-16 text
UText
– UTF-16 text in discontinuous buffers
– UTF-8/32 APIs (char/wchar_t compatibility)
– Non-Unicode APIs, SBCS or MBCS
UTF-8,
SBCS, …
Line
Break
 UText API: Efficient interface
– Provider implementation converts to UTF-16
– Fast inline code for text access within blocks
– Storage-native indexes avoid index translation
– Writable
 For now only C/C++, used in few services
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ICU Overview: The Open Source Unicode Library
Unicode Character Handling
 All Unicode properties (except Unihan)
– Direct API
Ideographic
• Values, names, enumerations
– UnicodeSet
Uppercase
不与 aξँై
AΞ
Alphabetic
• Fast, compact set operations (union, intersection, …)
• Pattern-based (both Perl & POSIX syntax for properties)
– \p{greek} vs. [:greek:]
• All properties:
– [\p{lowercase}-[a-z]]
– [\p{greek} & \p{uppercase}]
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Recent Additions
 Conforms to CLDR 1.3/1.4
– Adds and confirms many translated terms for languages, scripts,
regions, currencies, and time zones
– Access to more CLDR items
 Support for Unicode interpretation of POSIX properties
 Charset detection API (ICU4J only)
 Load Java resource bundles from ULocale, support zh_Hant etc.
 Better modularization for memory constrained environments
(ICU4C only)
 New icupkg tool for data customization
– Easily update pre-built or installed data packages (.dat files)
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ICU Overview: The Open Source Unicode Library
Character Set Conversion
 Precise alias information:
– When you ask for “Shift-JIS”, you can request the precise definition by
platform (e.g. Windows, IBM, Java, … )
 Buffer management
– API automatically handles characters that cross buffers
– Can provide offset mappings between byte buffer and UChar buffer
 Runtime customizations allowed for:
– Illegal sequences
– Undefined characters
 Unicode Text Compression – SCSU, BOCU-1
 Consistent conversion results across platforms
 You can use more character sets at runtime or build time
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Collation: Sorting, Searching and Matching
 Fast international comparison for string search; fully UCA
compliant
– Compressed sort keys, optimized string comparison, sublinear
string search
– Incremental sortkeys used for radix sorting
 Precise binary sortkey stability over time (library versioning)
 Fully data driven
– Many common rules provided
 Runtime and build time rule customizations
– Strength, normalization, upper vs. lowercase first, ignore
punctuation, numeric, …
– Only delta from UCA is needed for rule customization
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ICU Overview: The Open Source Unicode Library
Calendar & Time Zones
 International Calendars – Islamic, Buddhist, Hebrew, Japanese
– Required for correct presentation of dates in some countries
 Olson timezone support with localizations
 Recent Additions:
– Many more time zone localizations
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ICU Overview: The Open Source Unicode Library
Formatting
 Date & time: 8 formats per locale by default
 Messages
– Completely localizable, plural support
 Numbers & currencies
– Scientific Notation, Spelled-out (checks, etc.)
– Full Orthogonal Currency support (any currency × any language)
• INR
• INR
• INR
In Hindi:
In English:
In German:
रु१,२३४.५७
Rs. 1,234.57
Rs. 1.234,57
 Recent Additions
– Flexible date/time formatting: Select format for desired set of fields
– List available currencies API
– Short and stand-alone month/day names
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ICU Overview: The Open Source Unicode Library
Globalization Preferences
Example
Standard
Language
en_US (or en-US)
RFC 3066 (or successor)
Region
AU
ISO 3166
Currency
EUR
ISO 4217
Time zone
Australia/Melbourne
TZ DB
Calendar
islamic-civil
CLDR Calendar ID
Custom Date
yyyy-mmm-dd
CLDR Pattern Format
VAT
08.23% (books), 15.73% (food)
App/Country-Specific
…
Exact Composition Depends on System Requirements!
 ICU: Convenient container for globalization preference values
 Provides defaults for missing values
 Convenient instantiation of related formatters
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Transforms
 Unicode Normalization
– Highly optimized for performance
– performance utilities: concatenation, detection, comparison
 Casing (upper, lower, title, folding)
 General Transforms
– Script transliterations
– Half-width/Full-width, Hex, etc.
– Chain transforms together, filter source characters
– Rule-based, customizable at runtime.
 StringPrep: Internationalized Domain Names (IDN), NFS
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ICU Overview: The Open Source Unicode Library
Segmentation: word, line & sentence
 Fast state-table implementation
 Customizable
– Rule-based – customizable at runtime
– Special customizations, e.g. Thai
 Recent Additions:
– Uses new UText API
– ICU4J rule syntax aligned with ICU4C
– Tracks Unicode Line Break changes
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ICU Overview: The Open Source Unicode Library
Unicode Regular Expressions
 Full Regex Implementation
– C/C++ only: Java 1.4 has own package (though not as
powerful)
 All Unicode Properties
– Supported through UnicodeSet
 Good performance
– Competitive with non-Unicode regex
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ICU Overview: The Open Source Unicode Library
Complex-text layout engine
 Glyph processing, positioning & adjustment
– Ligature substitution, contextual forms, kerning, accent placement, bidi
scripts, etc.
 Support for:
–
–
–
–
–
–
–
–
Information for drawing
Caret Display
Hit Testing
Selection Highlighting
Caret Movement
Layout Metrics
Line Break
Canonical Equivalence: a + ´ or á
 Recent Additions:
– Tibetan, Sinhala, Indic ZWJ/ZWNJ, Kerning
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References
 ICU main site:
– http://www.ibm.com/software/globalization/icu/
– Links to
• Download ICU
• User Guide, Technical FAQ, Support, Bug Reports, Demonstrations
 ICU support site:
– http://icu.sourceforge.net/
 Unicode Consortium
– http://www.unicode.org/
• Unicode glossary, Unicode character database
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Questions and Answers
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ICU Overview - International Components for Unicode