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https://github.com/Tehreer/SheenBidi

A sophisticated implementation of Unicode Bidirectional Algorithm
https://github.com/Tehreer/SheenBidi

ansi-c bidi c c-plus-plus c89 i18n internationalization library script text uax-24 uax-9 uba unicode unicode-bidirectional-algorithm writing

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A sophisticated implementation of Unicode Bidirectional Algorithm

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SheenBidi

=========

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SheenBidi implements Unicode Bidirectional Algorithm available at http://www.unicode.org/reports/tr9. It is a sophisticated implementation which provides the developers an easy way to use UBA in their applications.



Here are some of the advantages of SheenBidi.



* Object based.

* Optimized to the core.

* Designed to be thread safe.

* Lightweight API for interaction.

* Supports UTF-8, UTF-16 and UTF-32 encodings.



## API



The above screenshot depicts a visual representation of the API on a sample text.



### SBCodepointSequence

It works as a code point decoder by accepting a string buffer in specified encoding.



### SBAlgorithm

It provides bidirectional type of each code unit in source string. Paragraph boundaries can be queried from it as determined by rule [P1](https://www.unicode.org/reports/tr9/#P1). Individual paragraph objects can be created from it by explicitly specifying the base level or deriving it from rules [P2](https://www.unicode.org/reports/tr9/#P2)-[P3](https://www.unicode.org/reports/tr9/#P3).



### SBParagraph

It represents a single paragraph of text processed with rules [X1](https://www.unicode.org/reports/tr9/#X1)-[I2](https://www.unicode.org/reports/tr9/#I2). It provides resolved embedding levels of all the code units of a paragraph.



### SBLine

It represents a single line of text processed with rules [L1](https://www.unicode.org/reports/tr9/#L1)-[L2](https://www.unicode.org/reports/tr9/#L2). However, it provides reordered level runs instead of reordered characters.



### SBRun

It represents a sequence of characters which have the same embedding level. The direction of a run would be right-to-left, if its embedding level is odd.



### SBMirrorLocator

It provides the facility to find out the mirrored characters in a line as determined by rule [L4](https://www.unicode.org/reports/tr9/#L4).



### SBScriptLocator

Not directly related to UBA but can be useful for text shaping. It provides the facility to find out the script runs as specified in [UAX #24](https://www.unicode.org/reports/tr24/).



## Dependency

SheenBidi does not depend on any external library. It only uses standard C library headers ```stddef.h```, ```stdint.h``` and ```stdlib.h```.



## Configuration

The configuration options are available in `Headers/SBConfig.h`.



* ```SB_CONFIG_LOG``` logs every activity performed in order to apply bidirectional algorithm.

* ```SB_CONFIG_UNITY``` builds the library as a single module and lets the compiler make decisions to inline functions.



## Compiling

SheenBidi can be compiled with any C compiler. The best way for compiling is to add all the files in an IDE and hit build. The only thing to consider however is that if ```SB_CONFIG_UNITY``` is enabled then only ```Source/SheenBidi.c``` should be compiled.



## Example

Here is a simple example written in C11.



```c

#include 

#include 

#include 



#include 



int main(int argc, const char * argv[]) {

    /* Create code point sequence for a sample bidirectional text. */

    const char *bidiText = "یہ ایک )car( ہے۔";

    SBCodepointSequence codepointSequence = { SBStringEncodingUTF8, (void *)bidiText, strlen(bidiText) };



    /* Extract the first bidirectional paragraph. */

    SBAlgorithmRef bidiAlgorithm = SBAlgorithmCreate(&codepointSequence);

    SBParagraphRef firstParagraph = SBAlgorithmCreateParagraph(bidiAlgorithm, 0, INT32_MAX, SBLevelDefaultLTR);

    SBUInteger paragraphLength = SBParagraphGetLength(firstParagraph);



    /* Create a line consisting of whole paragraph and get its runs. */

    SBLineRef paragraphLine = SBParagraphCreateLine(firstParagraph, 0, paragraphLength);

    SBUInteger runCount = SBLineGetRunCount(paragraphLine);

    const SBRun *runArray = SBLineGetRunsPtr(paragraphLine);



    /* Log the details of each run in the line. */

    for (SBUInteger i = 0; i < runCount; i++) {

        printf("Run Offset: %ld\n", (long)runArray[i].offset);

        printf("Run Length: %ld\n", (long)runArray[i].length);

        printf("Run Level: %ld\n\n", (long)runArray[i].level);

    }



    /* Create a mirror locator and load the line in it. */

    SBMirrorLocatorRef mirrorLocator = SBMirrorLocatorCreate();

    SBMirrorLocatorLoadLine(mirrorLocator, paragraphLine, (void *)bidiText);

    const SBMirrorAgent *mirrorAgent = SBMirrorLocatorGetAgent(mirrorLocator);



    /* Log the details of each mirror in the line. */

    while (SBMirrorLocatorMoveNext(mirrorLocator)) {

        printf("Mirror Index: %ld\n", (long)mirrorAgent->index);

        printf("Actual Code Point: %ld\n", (long)mirrorAgent->codepoint);

        printf("Mirrored Code Point: %ld\n\n", (long)mirrorAgent->mirror);

    }



    /* Release all objects. */

    SBMirrorLocatorRelease(mirrorLocator);

    SBLineRelease(paragraphLine);

    SBParagraphRelease(firstParagraph);

    SBAlgorithmRelease(bidiAlgorithm);



    return 0;

}

```



## License

```

Copyright (C) 2014-2022 Muhammad Tayyab Akram



Licensed under the Apache License, Version 2.0 (the "License");

you may not use this file except in compliance with the License.

You may obtain a copy of the License at



  http://www.apache.org/licenses/LICENSE-2.0



Unless required by applicable law or agreed to in writing, software

distributed under the License is distributed on an "AS IS" BASIS,

WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

See the License for the specific language governing permissions and

limitations under the License.

```