icuSources/common/unicode/ubiditransform.h

   1 /*
   2 ******************************************************************************
   3 *
   4 * © 2016 and later: Unicode, Inc. and others.
   5 * License & terms of use: http://www.unicode.org/copyright.html
   6 *
   7 ******************************************************************************
   8 *   file name:  ubiditransform.h
   9 *   encoding:   UTF-8
  10 *   tab size:   8 (not used)
  11 *   indentation:4
  12 *
  13 *   created on: 2016jul24
  14 *   created by: Lina Kemmel
  15 *
  16 */
  17
  18 #ifndef UBIDITRANSFORM_H
  19 #define UBIDITRANSFORM_H
  20
  21 #include "unicode/utypes.h"
  22 #include "unicode/ubidi.h"
  23 #include "unicode/uchar.h"
  24 #include "unicode/localpointer.h"
  25
  26 /**
  27  * \file
  28  * \brief Bidi Transformations
  29  *
  30  * <code>UBiDiOrder</code> indicates the order of text.<p>
  31  * This bidi transformation engine supports all possible combinations (4 in
  32  * total) of input and output text order:
  33  * <ul>
  34  * <li><logical input, visual output>: unless the output direction is RTL, this
  35  * corresponds to a normal operation of the Bidi algorithm as described in the
  36  * Unicode Technical Report and implemented by <code>UBiDi</code> when the
  37  * reordering mode is set to <code>UBIDI_REORDER_DEFAULT</code>. Visual RTL
  38  * mode is not supported by <code>UBiDi</code> and is accomplished through
  39  * reversing a visual LTR string,</li>
  40  * <li><visual input, logical output>: unless the input direction is RTL, this
  41  * corresponds to an "inverse bidi algorithm" in <code>UBiDi</code> with the
  42  * reordering mode set to <code>UBIDI_REORDER_INVERSE_LIKE_DIRECT</code>.
  43  * Visual RTL mode is not not supported by <code>UBiDi</code> and is
  44  * accomplished through reversing a visual LTR string,</li>
  45  * <li><logical input, logical output>: if the input and output base directions
  46  * mismatch, this corresponds to the <code>UBiDi</code> implementation with the
  47  * reordering mode set to <code>UBIDI_REORDER_RUNS_ONLY</code>; and if the
  48  * input and output base directions are identical, the transformation engine
  49  * will only handle character mirroring and Arabic shaping operations without
  50  * reordering,</li>
  51  * <li><visual input, visual output>: this reordering mode is not supported by
  52  * the <code>UBiDi</code> engine; it implies character mirroring, Arabic
  53  * shaping, and - if the input/output base directions mismatch -  string
  54  * reverse operations.</li>
  55  * </ul>
  56  * @see ubidi_setInverse
  57  * @see ubidi_setReorderingMode
  58  * @see UBIDI_REORDER_DEFAULT
  59  * @see UBIDI_REORDER_INVERSE_LIKE_DIRECT
  60  * @see UBIDI_REORDER_RUNS_ONLY
  61  * @stable ICU 58
  62  */
  63 typedef enum {
  64     /** 0: Constant indicating a logical order.
  65       * This is the default for input text.
  66       * @stable ICU 58
  67       */
  68     UBIDI_LOGICAL = 0,
  69     /** 1: Constant indicating a visual order.
  70       * This is a default for output text.
  71       * @stable ICU 58
  72       */
  73     UBIDI_VISUAL
  74 } UBiDiOrder;
  75
  76 /**
  77  * <code>UBiDiMirroring</code> indicates whether or not characters with the
  78  * "mirrored" property in RTL runs should be replaced with their mirror-image
  79  * counterparts.
  80  * @see UBIDI_DO_MIRRORING
  81  * @see ubidi_setReorderingOptions
  82  * @see ubidi_writeReordered
  83  * @see ubidi_writeReverse
  84  * @stable ICU 58
  85  */
  86 typedef enum {
  87     /** 0: Constant indicating that character mirroring should not be
  88       * performed.
  89       * This is the default.
  90       * @stable ICU 58
  91       */
  92     UBIDI_MIRRORING_OFF = 0,
  93     /** 1: Constant indicating that character mirroring should be performed.
  94       * This corresponds to calling <code>ubidi_writeReordered</code> or
  95       * <code>ubidi_writeReverse</code> with the
  96       * <code>UBIDI_DO_MIRRORING</code> option bit set.
  97       * @stable ICU 58
  98       */
  99     UBIDI_MIRRORING_ON
 100 } UBiDiMirroring;
 101
 102 /**
 103  * Forward declaration of the <code>UBiDiTransform</code> structure that stores
 104  * information used by the layout transformation engine.
 105  * @stable ICU 58
 106  */
 107 typedef struct UBiDiTransform UBiDiTransform;
 108
 109 /**
 110  * Performs transformation of text from the bidi layout defined by the input
 111  * ordering scheme to the bidi layout defined by the output ordering scheme,
 112  * and applies character mirroring and Arabic shaping operations.<p>
 113  * In terms of <code>UBiDi</code>, such a transformation implies:
 114  * <ul>
 115  * <li>calling <code>ubidi_setReorderingMode</code> as needed (when the
 116  * reordering mode is other than normal),</li>
 117  * <li>calling <code>ubidi_setInverse</code> as needed (when text should be
 118  * transformed from a visual to a logical form),</li>
 119  * <li>resolving embedding levels of each character in the input text by
 120  * calling <code>ubidi_setPara</code>,</li>
 121  * <li>reordering the characters based on the computed embedding levels, also
 122  * performing character mirroring as needed, and streaming the result to the
 123  * output, by calling <code>ubidi_writeReordered</code>,</li>
 124  * <li>performing Arabic digit and letter shaping on the output text by calling
 125  * <code>u_shapeArabic</code>.</li>
 126  * </ul>
 127  * An "ordering scheme" encompasses the base direction and the order of text,
 128  * and these characteristics must be defined by the caller for both input and
 129  * output explicitly .<p>
 130  * There are 36 possible combinations of <input, output> ordering schemes,
 131  * which are partially supported by <code>UBiDi</code> already. Examples of the
 132  * currently supported combinations:
 133  * <ul>
 134  * <li><Logical LTR, Visual LTR>: this is equivalent to calling
 135  * <code>ubidi_setPara</code> with <code>paraLevel == UBIDI_LTR</code>,</li>
 136  * <li><Logical RTL, Visual LTR>: this is equivalent to calling
 137  * <code>ubidi_setPara</code> with <code>paraLevel == UBIDI_RTL</code>,</li>
 138  * <li><Logical Default ("Auto") LTR, Visual LTR>: this is equivalent to
 139  * calling <code>ubidi_setPara</code> with
 140  * <code>paraLevel == UBIDI_DEFAULT_LTR</code>,</li>
 141  * <li><Logical Default ("Auto") RTL, Visual LTR>: this is equivalent to
 142  * calling <code>ubidi_setPara</code> with
 143  * <code>paraLevel == UBIDI_DEFAULT_RTL</code>,</li>
 144  * <li><Visual LTR, Logical LTR>: this is equivalent to
 145  * calling <code>ubidi_setInverse(UBiDi*, TRUE)</code> and then
 146  * <code>ubidi_setPara</code> with <code>paraLevel == UBIDI_LTR</code>,</li>
 147  * <li><Visual LTR, Logical RTL>: this is equivalent to
 148  * calling <code>ubidi_setInverse(UBiDi*, TRUE)</code> and then
 149  * <code>ubidi_setPara</code> with <code>paraLevel == UBIDI_RTL</code>.</li>
 150  * </ul>
 151  * All combinations that involve the Visual RTL scheme are unsupported by
 152  * <code>UBiDi</code>, for instance:
 153  * <ul>
 154  * <li><Logical LTR, Visual RTL>,</li>
 155  * <li><Visual RTL, Logical RTL>.</li>
 156  * </ul>
 157  * <p>Example of usage of the transformation engine:<br>
 158  * <pre>
 159  * \code
 160  * UChar text1[] = {'a', 'b', 'c', 0x0625, '1', 0};
 161  * UChar text2[] = {'a', 'b', 'c', 0x0625, '1', 0};
 162  * UErrorCode errorCode = U_ZERO_ERROR;
 163  * // Run a transformation.
 164  * ubiditransform_transform(pBidiTransform,
 165  *          text1, -1, text2, -1,
 166  *          UBIDI_LTR, UBIDI_VISUAL,
 167  *          UBIDI_RTL, UBIDI_LOGICAL,
 168  *          UBIDI_MIRRORING_OFF,
 169  *          U_SHAPE_DIGITS_AN2EN | U_SHAPE_DIGIT_TYPE_AN_EXTENDED,
 170  *          &errorCode);
 171  * // Do something with text2.
 172  *  text2[4] = '2';
 173  * // Run a reverse transformation.
 174  * ubiditransform_transform(pBidiTransform,
 175  *          text2, -1, text1, -1,
 176  *          UBIDI_RTL, UBIDI_LOGICAL,
 177  *          UBIDI_LTR, UBIDI_VISUAL,
 178  *          UBIDI_MIRRORING_OFF,
 179  *          U_SHAPE_DIGITS_EN2AN | U_SHAPE_DIGIT_TYPE_AN_EXTENDED,
 180  *          &errorCode);
 181  *\endcode
 182  * </pre>
 183  * </p>
 184  *
 185  * @param pBiDiTransform A pointer to a <code>UBiDiTransform</code> object
 186  *        allocated with <code>ubiditransform_open()</code> or
 187  *        <code>NULL</code>.<p>
 188  *        This object serves for one-time setup to amortize initialization
 189  *        overheads. Use of this object is not thread-safe. All other threads
 190  *        should allocate a new <code>UBiDiTransform</code> object by calling
 191  *        <code>ubiditransform_open()</code> before using it. Alternatively,
 192  *        a caller can set this parameter to <code>NULL</code>, in which case
 193  *        the object will be allocated by the engine on the fly.</p>
 194  * @param src A pointer to the text that the Bidi layout transformations will
 195  *        be performed on.
 196  *        <p><strong>Note:</strong> the text must be (at least)
 197  *        <code>srcLength</code> long.</p>
 198  * @param srcLength The length of the text, in number of UChars. If
 199  *        <code>length == -1</code> then the text must be zero-terminated.
 200  * @param dest A pointer to where the processed text is to be copied.
 201  * @param destSize The size of the <code>dest</code> buffer, in number of
 202  *        UChars. If the <code>U_SHAPE_LETTERS_UNSHAPE</code> option is set,
 203  *        then the destination length could be as large as
 204  *        <code>srcLength * 2</code>. Otherwise, the destination length will
 205  *        not exceed <code>srcLength</code>. If the caller reserves the last
 206  *        position for zero-termination, it should be excluded from
 207  *        <code>destSize</code>.
 208  *        <p><code>destSize == -1</code> is allowed and makes sense when
 209  *        <code>dest</code> was holds some meaningful value, e.g. that of
 210  *        <code>src</code>. In this case <code>dest</code> must be
 211  *        zero-terminated.</p>
 212  * @param inParaLevel A base embedding level of the input as defined in
 213  *        <code>ubidi_setPara</code> documentation for the
 214  *        <code>paraLevel</code> parameter.
 215  * @param inOrder An order of the input, which can be one of the
 216  *        <code>UBiDiOrder</code> values.
 217  * @param outParaLevel A base embedding level of the output as defined in
 218  *        <code>ubidi_setPara</code> documentation for the
 219  *        <code>paraLevel</code> parameter.
 220  * @param outOrder An order of the output, which can be one of the
 221  *        <code>UBiDiOrder</code> values.
 222  * @param doMirroring Indicates whether or not to perform character mirroring,
 223  *        and can accept one of the <code>UBiDiMirroring</code> values.
 224  * @param shapingOptions Arabic digit and letter shaping options defined in the
 225  *        ushape.h documentation.
 226  *        <p><strong>Note:</strong> Direction indicator options are computed by
 227  *        the transformation engine based on the effective ordering schemes, so
 228  *        user-defined direction indicators will be ignored.</p>
 229  * @param pErrorCode A pointer to an error code value.
 230  *
 231  * @return The destination length, i.e. the number of UChars written to
 232  *         <code>dest</code>. If the transformation fails, the return value
 233  *         will be 0 (and the error code will be written to
 234  *         <code>pErrorCode</code>).
 235  *
 236  * @see UBiDiLevel
 237  * @see UBiDiOrder
 238  * @see UBiDiMirroring
 239  * @see ubidi_setPara
 240  * @see u_shapeArabic
 241  * @stable ICU 58
 242  */
 243 U_STABLE uint32_t U_EXPORT2
 244 ubiditransform_transform(UBiDiTransform *pBiDiTransform,
 245             const UChar *src, int32_t srcLength,
 246             UChar *dest, int32_t destSize,
 247             UBiDiLevel inParaLevel, UBiDiOrder inOrder,
 248             UBiDiLevel outParaLevel, UBiDiOrder outOrder,
 249             UBiDiMirroring doMirroring, uint32_t shapingOptions,
 250             UErrorCode *pErrorCode);
 251
 252 /**
 253  * Allocates a <code>UBiDiTransform</code> object. This object can be reused,
 254  * e.g. with different ordering schemes, mirroring or shaping options.<p>
 255  * <strong>Note:</strong>The object can only be reused in the same thread.
 256  * All other threads should allocate a new <code>UBiDiTransform</code> object
 257  * before using it.<p>
 258  * Example of usage:<p>
 259  * <pre>
 260  * \code
 261  * UErrorCode errorCode = U_ZERO_ERROR;
 262  * // Open a new UBiDiTransform.
 263  * UBiDiTransform* transform = ubiditransform_open(&errorCode);
 264  * // Run a transformation.
 265  * ubiditransform_transform(transform,
 266  *          text1, -1, text2, -1,
 267  *          UBIDI_RTL, UBIDI_LOGICAL,
 268  *          UBIDI_LTR, UBIDI_VISUAL,
 269  *          UBIDI_MIRRORING_ON,
 270  *          U_SHAPE_DIGITS_EN2AN,
 271  *          &errorCode);
 272  * // Do something with the output text and invoke another transformation using
 273  * //   that text as input.
 274  * ubiditransform_transform(transform,
 275  *          text2, -1, text3, -1,
 276  *          UBIDI_LTR, UBIDI_VISUAL,
 277  *          UBIDI_RTL, UBIDI_VISUAL,
 278  *          UBIDI_MIRRORING_ON,
 279  *          0, &errorCode);
 280  *\endcode
 281  * </pre>
 282  * <p>
 283  * The <code>UBiDiTransform</code> object must be deallocated by calling
 284  * <code>ubiditransform_close()</code>.
 285  *
 286  * @return An empty <code>UBiDiTransform</code> object.
 287  * @stable ICU 58
 288  */
 289 U_STABLE UBiDiTransform* U_EXPORT2
 290 ubiditransform_open(UErrorCode *pErrorCode);
 291
 292 /**
 293  * Deallocates the given <code>UBiDiTransform</code> object.
 294  * @stable ICU 58
 295  */
 296 U_STABLE void U_EXPORT2
 297 ubiditransform_close(UBiDiTransform *pBidiTransform);
 298
 299 #if U_SHOW_CPLUSPLUS_API
 300
 301 U_NAMESPACE_BEGIN
 302
 303 /**
 304  * \class LocalUBiDiTransformPointer
 305  * "Smart pointer" class, closes a UBiDiTransform via ubiditransform_close().
 306  * For most methods see the LocalPointerBase base class.
 307  *
 308  * @see LocalPointerBase
 309  * @see LocalPointer
 310  * @stable ICU 58
 311  */
 312 U_DEFINE_LOCAL_OPEN_POINTER(LocalUBiDiTransformPointer, UBiDiTransform, ubiditransform_close);
 313
 314 U_NAMESPACE_END
 315
 316 #endif // U_SHOW_CPLUSPLUS_API
 317
 318 #endif