Check in the pristine copy of ICU 4.6...

icu46/source/common/unicode/utext.h

+/*
+*******************************************************************************
+*
+*   Copyright (C) 2004-2010, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  utext.h
+*   encoding:   US-ASCII
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 2004oct06
+*   created by: Markus W. Scherer
+*/
+
+#ifndef __UTEXT_H__
+#define __UTEXT_H__
+
+/**
+ * \file
+ * \brief C API: Abstract Unicode Text API
+ *
+ * The Text Access API provides a means to allow text that is stored in alternative
+ * formats to work with ICU services.  ICU normally operates on text that is
+ * stored in UTF-16 format, in (UChar *) arrays for the C APIs or as type
+ * UnicodeString for C++ APIs.
+ *
+ * ICU Text Access allows other formats, such as UTF-8 or non-contiguous
+ * UTF-16 strings, to be placed in a UText wrapper and then passed to ICU services.
+ *
+ * There are three general classes of usage for UText:
+ *
+ *     Application Level Use.  This is the simplest usage - applications would
+ *     use one of the utext_open() functions on their input text, and pass
+ *     the resulting UText to the desired ICU service.
+ *
+ *     Second is usage in ICU Services, such as break iteration, that will need to
+ *     operate on input presented to them as a UText.  These implementations
+ *     will need to use the iteration and related UText functions to gain
+ *     access to the actual text.
+ *
+ *     The third class of UText users are "text providers."  These are the
+ *     UText implementations for the various text storage formats.  An application
+ *     or system with a unique text storage format can implement a set of
+ *     UText provider functions for that format, which will then allow
+ *     ICU services to operate on that format.
+ *
+ *
+ * <em>Iterating over text</em>
+ *
+ * Here is sample code for a forward iteration over the contents of a UText
+ *
+ * \code
+ *    UChar32  c;
+ *    UText    *ut = whatever();
+ *
+ *    for (c=utext_next32From(ut, 0); c>=0; c=utext_next32(ut)) {
+ *       // do whatever with the codepoint c here.
+ *    }
+ * \endcode
+ *
+ * And here is similar code to iterate in the reverse direction, from the end
+ * of the text towards the beginning.
+ *
+ * \code
+ *    UChar32  c;
+ *    UText    *ut = whatever();
+ *    int      textLength = utext_nativeLength(ut);
+ *    for (c=utext_previous32From(ut, textLength); c>=0; c=utext_previous32(ut)) {
+ *       // do whatever with the codepoint c here.
+ *    }
+ * \endcode
+ *
+ * <em>Characters and Indexing</em>
+ *
+ * Indexing into text by UText functions is nearly always in terms of the native
+ * indexing of the underlying text storage.  The storage format could be UTF-8
+ * or UTF-32, for example.  When coding to the UText access API, no assumptions
+ * can be made regarding the size of characters, or how far an index
+ * may move when iterating between characters.
+ *
+ * All indices supplied to UText functions are pinned to the length of the
+ * text.  An out-of-bounds index is not considered to be an error, but is
+ * adjusted to be in the range  0 <= index <= length of input text.
+ *
+ *
+ * When an index position is returned from a UText function, it will be
+ * a native index to the underlying text.  In the case of multi-unit characters,
+ * it will  always refer to the first position of the character,
+ * never to the interior.  This is essentially the same thing as saying that
+ * a returned index will always point to a boundary between characters.
+ *
+ * When a native index is supplied to a UText function, all indices that
+ * refer to any part of a multi-unit character representation are considered
+ * to be equivalent.  In the case of multi-unit characters, an incoming index
+ * will be logically normalized to refer to the start of the character.
+ * 
+ * It is possible to test whether a native index is on a code point boundary
+ * by doing a utext_setNativeIndex() followed by a utext_getNativeIndex().
+ * If the index is returned unchanged, it was on a code point boundary.  If
+ * an adjusted index is returned, the original index referred to the
+ * interior of a character.
+ *
+ * <em>Conventions for calling UText functions</em>
+ *
+ * Most UText access functions have as their first parameter a (UText *) pointer,
+ * which specifies the UText to be used.  Unless otherwise noted, the
+ * pointer must refer to a valid, open UText.  Attempting to
+ * use a closed UText or passing a NULL pointer is a programming error and
+ * will produce undefined results or NULL pointer exceptions.
+ * 
+ * The UText_Open family of functions can either open an existing (closed)
+ * UText, or heap allocate a new UText.  Here is sample code for creating
+ * a stack-allocated UText.
+ *
+ * \code
+ *    char     *s = whatever();  // A utf-8 string 
+ *    U_ErrorCode status = U_ZERO_ERROR;
+ *    UText    ut = UTEXT_INITIALIZER;
+ *    utext_openUTF8(ut, s, -1, &status);
+ *    if (U_FAILURE(status)) {
+ *        // error handling
+ *    } else {
+ *        // work with the UText
+ *    }
+ * \endcode
+ *
+ * Any existing UText passed to an open function _must_ have been initialized, 
+ * either by the UTEXT_INITIALIZER, or by having been originally heap-allocated
+ * by an open function.  Passing NULL will cause the open function to
+ * heap-allocate and fully initialize a new UText.
+ *
+ */
+
+
+
+#include "unicode/utypes.h"
+#include "unicode/uchar.h"
+#if U_SHOW_CPLUSPLUS_API
+#include "unicode/localpointer.h"
+#include "unicode/rep.h"
+#include "unicode/unistr.h"
+#include "unicode/chariter.h"
+#endif
+
+
+U_CDECL_BEGIN
+
+struct UText;
+typedef struct UText UText; /**< C typedef for struct UText. @stable ICU 3.6 */
+
+
+/***************************************************************************************
+ *
+ *   C Functions for creating UText wrappers around various kinds of text strings.
+ *
+ ****************************************************************************************/
+
+
+/**
+  * Close function for UText instances.
+  * Cleans up, releases any resources being held by an open UText.
+  * <p>
+  *   If the UText was originally allocated by one of the utext_open functions,
+  *   the storage associated with the utext will also be freed.
+  *   If the UText storage originated with the application, as it would with
+  *   a local or static instance, the storage will not be deleted.
+  *
+  *   An open UText can be reset to refer to new string by using one of the utext_open()
+  *   functions without first closing the UText.  
+  *
+  * @param ut  The UText to be closed.
+  * @return    NULL if the UText struct was deleted by the close.  If the UText struct
+  *            was originally provided by the caller to the open function, it is
+  *            returned by this function, and may be safely used again in
+  *            a subsequent utext_open.
+  *
+  * @stable ICU 3.4
+  */
+U_STABLE UText * U_EXPORT2
+utext_close(UText *ut);
+
+#if U_SHOW_CPLUSPLUS_API
+
+U_NAMESPACE_BEGIN
+
+/**
+ * \class LocalUTextPointer
+ * "Smart pointer" class, closes a UText via utext_close().
+ * For most methods see the LocalPointerBase base class.
+ *
+ * @see LocalPointerBase
+ * @see LocalPointer
+ * @stable ICU 4.4
+ */
+U_DEFINE_LOCAL_OPEN_POINTER(LocalUTextPointer, UText, utext_close);
+
+U_NAMESPACE_END
+
+#endif
+
+/**
+ * Open a read-only UText implementation for UTF-8 strings.
+ * 
+ * \htmlonly
+ * Any invalid UTF-8 in the input will be handled in this way:
+ * a sequence of bytes that has the form of a truncated, but otherwise valid,
+ * UTF-8 sequence will be replaced by a single unicode replacement character, \uFFFD. 
+ * Any other illegal bytes will each be replaced by a \uFFFD.
+ * \endhtmlonly
+ * 
+ * @param ut     Pointer to a UText struct.  If NULL, a new UText will be created.
+ *               If non-NULL, must refer to an initialized UText struct, which will then
+ *               be reset to reference the specified UTF-8 string.
+ * @param s      A UTF-8 string.  Must not be NULL.
+ * @param length The length of the UTF-8 string in bytes, or -1 if the string is
+ *               zero terminated.
+ * @param status Errors are returned here.
+ * @return       A pointer to the UText.  If a pre-allocated UText was provided, it
+ *               will always be used and returned.
+ * @stable ICU 3.4
+ */
+U_STABLE UText * U_EXPORT2
+utext_openUTF8(UText *ut, const char *s, int64_t length, UErrorCode *status);
+
+
+/**
+ * Open a read-only UText for UChar * string.
+ * 
+ * @param ut     Pointer to a UText struct.  If NULL, a new UText will be created.
+ *               If non-NULL, must refer to an initialized UText struct, which will then
+ *               be reset to reference the specified UChar string.
+ * @param s      A UChar (UTF-16) string
+ * @param length The number of UChars in the input string, or -1 if the string is
+ *               zero terminated.
+ * @param status Errors are returned here.
+ * @return       A pointer to the UText.  If a pre-allocated UText was provided, it
+ *               will always be used and returned.
+ * @stable ICU 3.4
+ */
+U_STABLE UText * U_EXPORT2
+utext_openUChars(UText *ut, const UChar *s, int64_t length, UErrorCode *status);
+
+
+#if U_SHOW_CPLUSPLUS_API
+/**
+ * Open a writable UText for a non-const UnicodeString. 
+ * 
+ * @param ut      Pointer to a UText struct.  If NULL, a new UText will be created.
+ *                 If non-NULL, must refer to an initialized UText struct, which will then
+ *                 be reset to reference the specified input string.
+ * @param s       A UnicodeString.
+ * @param status Errors are returned here.
+ * @return        Pointer to the UText.  If a UText was supplied as input, this
+ *                 will always be used and returned.
+ * @stable ICU 3.4
+ */
+U_STABLE UText * U_EXPORT2
+utext_openUnicodeString(UText *ut, U_NAMESPACE_QUALIFIER UnicodeString *s, UErrorCode *status);
+
+
+/**
+ * Open a UText for a const UnicodeString.   The resulting UText will not be writable.
+ * 
+ * @param ut    Pointer to a UText struct.  If NULL, a new UText will be created.
+ *               If non-NULL, must refer to an initialized UText struct, which will then
+ *               be reset to reference the specified input string.
+ * @param s      A const UnicodeString to be wrapped.
+ * @param status Errors are returned here.
+ * @return       Pointer to the UText.  If a UText was supplied as input, this
+ *               will always be used and returned.
+ * @stable ICU 3.4
+ */
+U_STABLE UText * U_EXPORT2
+utext_openConstUnicodeString(UText *ut, const U_NAMESPACE_QUALIFIER UnicodeString *s, UErrorCode *status);
+
+
+/**
+ * Open a writable UText implementation for an ICU Replaceable object.
+ * @param ut    Pointer to a UText struct.  If NULL, a new UText will be created.
+ *               If non-NULL, must refer to an already existing UText, which will then
+ *               be reset to reference the specified replaceable text.
+ * @param rep    A Replaceable text object.
+ * @param status Errors are returned here.
+ * @return       Pointer to the UText.  If a UText was supplied as input, this
+ *               will always be used and returned.
+ * @see Replaceable
+ * @stable ICU 3.4
+ */
+U_STABLE UText * U_EXPORT2
+utext_openReplaceable(UText *ut, U_NAMESPACE_QUALIFIER Replaceable *rep, UErrorCode *status);
+
+/**
+ * Open a  UText implementation over an ICU CharacterIterator.
+ * @param ut    Pointer to a UText struct.  If NULL, a new UText will be created.
+ *               If non-NULL, must refer to an already existing UText, which will then
+ *               be reset to reference the specified replaceable text.
+ * @param ci     A Character Iterator.
+ * @param status Errors are returned here.
+ * @return       Pointer to the UText.  If a UText was supplied as input, this
+ *               will always be used and returned.
+ * @see Replaceable
+ * @stable ICU 3.4
+ */
+U_STABLE UText * U_EXPORT2
+utext_openCharacterIterator(UText *ut, U_NAMESPACE_QUALIFIER CharacterIterator *ic, UErrorCode *status);
+
+#endif
+
+
+/**
+  *  Clone a UText.  This is much like opening a UText where the source text is itself
+  *  another UText.
+  *
+  *  A deep clone will copy both the UText data structures and the underlying text.
+  *  The original and cloned UText will operate completely independently; modifications
+  *  made to the text in one will not affect the other.  Text providers are not
+  *  required to support deep clones.  The user of clone() must check the status return
+  *  and be prepared to handle failures.
+  *
+  *  The standard UText implementations for UTF8, UChar *, UnicodeString and
+  *  Replaceable all support deep cloning.
+  *
+  *  The UText returned from a deep clone will be writable, assuming that the text
+  *  provider is able to support writing, even if the source UText had been made
+  *  non-writable by means of UText_freeze().
+  *
+  *  A shallow clone replicates only the UText data structures; it does not make
+  *  a copy of the underlying text.  Shallow clones can be used as an efficient way to 
+  *  have multiple iterators active in a single text string that is not being
+  *  modified.
+  *
+  *  A shallow clone operation will not fail, barring truly exceptional conditions such
+  *  as memory allocation failures.
+  *
+  *  Shallow UText clones should be avoided if the UText functions that modify the
+  *  text are expected to be used, either on the original or the cloned UText.
+  *  Any such modifications  can cause unpredictable behavior.  Read Only
+  *  shallow clones provide some protection against errors of this type by
+  *  disabling text modification via the cloned UText.
+  *
+  *  A shallow clone made with the readOnly parameter == FALSE will preserve the 
+  *  utext_isWritable() state of the source object.  Note, however, that
+  *  write operations must be avoided while more than one UText exists that refer
+  *  to the same underlying text.
+  *
+  *  A UText and its clone may be safely concurrently accessed by separate threads.
+  *  This is true for read access only with shallow clones, and for both read and
+  *  write access with deep clones.
+  *  It is the responsibility of the Text Provider to ensure that this thread safety
+  *  constraint is met.
+  *
+  *  @param dest   A UText struct to be filled in with the result of the clone operation,
+  *                or NULL if the clone function should heap-allocate a new UText struct.
+  *                If non-NULL, must refer to an already existing UText, which will then
+  *                be reset to become the clone.
+  *  @param src    The UText to be cloned.
+  *  @param deep   TRUE to request a deep clone, FALSE for a shallow clone.
+  *  @param readOnly TRUE to request that the cloned UText have read only access to the 
+  *                underlying text.  
+
+  *  @param status Errors are returned here.  For deep clones, U_UNSUPPORTED_ERROR
+  *                will be returned if the text provider is unable to clone the
+  *                original text.
+  *  @return       The newly created clone, or NULL if the clone operation failed.
+  *  @stable ICU 3.4
+  */
+U_STABLE UText * U_EXPORT2
+utext_clone(UText *dest, const UText *src, UBool deep, UBool readOnly, UErrorCode *status);
+
+
+/**
+  *  Compare two UText objects for equality.
+  *  UTexts are equal if they are iterating over the same text, and
+  *    have the same iteration position within the text.
+  *    If either or both of the parameters are NULL, the comparison is FALSE.
+  *
+  *  @param a   The first of the two UTexts to compare.
+  *  @param b   The other UText to be compared.
+  *  @return    TRUE if the two UTexts are equal.
+  *  @stable ICU 3.6
+  */
+U_STABLE UBool U_EXPORT2
+utext_equals(const UText *a, const UText *b);
+
+
+/*****************************************************************************
+ *
+ *   Functions to work with the text represeted by a UText wrapper
+ *
+ *****************************************************************************/
+
+/**
+  * Get the length of the text.  Depending on the characteristics
+  * of the underlying text representation, this may be expensive.  
+  * @see  utext_isLengthExpensive()
+  *
+  *
+  * @param ut  the text to be accessed.
+  * @return the length of the text, expressed in native units.
+  *
+  * @stable ICU 3.4
+  */
+U_STABLE int64_t U_EXPORT2
+utext_nativeLength(UText *ut);
+
+/**
+ *  Return TRUE if calculating the length of the text could be expensive.
+ *  Finding the length of NUL terminated strings is considered to be expensive.
+ *
+ *  Note that the value of this function may change
+ *  as the result of other operations on a UText.
+ *  Once the length of a string has been discovered, it will no longer
+ *  be expensive to report it.
+ *
+ * @param ut the text to be accessed.
+ * @return TRUE if determining the length of the text could be time consuming.
+ * @stable ICU 3.4
+ */
+U_STABLE UBool U_EXPORT2
+utext_isLengthExpensive(const UText *ut);
+
+/**
+ * Returns the code point at the requested index,
+ * or U_SENTINEL (-1) if it is out of bounds.
+ *
+ * If the specified index points to the interior of a multi-unit
+ * character - one of the trail bytes of a UTF-8 sequence, for example -
+ * the complete code point will be returned.
+ *
+ * The iteration position will be set to the start of the returned code point.
+ *
+ * This function is roughly equivalent to the the sequence
+ *    utext_setNativeIndex(index);
+ *    utext_current32();
+ * (There is a subtle difference if the index is out of bounds by being less than zero - 
+ * utext_setNativeIndex(negative value) sets the index to zero, after which utext_current()
+ * will return the char at zero.  utext_char32At(negative index), on the other hand, will
+ * return the U_SENTINEL value of -1.)
+ * 
+ * @param ut the text to be accessed
+ * @param nativeIndex the native index of the character to be accessed.  If the index points
+ *        to other than the first unit of a multi-unit character, it will be adjusted
+ *        to the start of the character.
+ * @return the code point at the specified index.
+ * @stable ICU 3.4
+ */
+U_STABLE UChar32 U_EXPORT2
+utext_char32At(UText *ut, int64_t nativeIndex);
+
+
+/**
+ *
+ * Get the code point at the current iteration position,
+ * or U_SENTINEL (-1) if the iteration has reached the end of
+ * the input text.
+ *
+ * @param ut the text to be accessed.
+ * @return the Unicode code point at the current iterator position.
+ * @stable ICU 3.4
+ */
+U_STABLE UChar32 U_EXPORT2
+utext_current32(UText *ut);
+
+
+/**
+ * Get the code point at the current iteration position of the UText, and
+ * advance the position to the first index following the character.
+ *
+ * If the position is at the end of the text (the index following
+ * the last character, which is also the length of the text), 
+ * return U_SENTINEL (-1) and do not advance the index. 
+ *
+ * This is a post-increment operation.
+ *
+ * An inline macro version of this function, UTEXT_NEXT32(), 
+ * is available for performance critical use.
+ *
+ * @param ut the text to be accessed.
+ * @return the Unicode code point at the iteration position.
+ * @see UTEXT_NEXT32
+ * @stable ICU 3.4
+ */
+U_STABLE UChar32 U_EXPORT2
+utext_next32(UText *ut);
+
+
+/**
+ *  Move the iterator position to the character (code point) whose
+ *  index precedes the current position, and return that character.
+ *  This is a pre-decrement operation.
+ *
+ *  If the initial position is at the start of the text (index of 0) 
+ *  return U_SENTINEL (-1), and leave the position unchanged.
+ *
+ *  An inline macro version of this function, UTEXT_PREVIOUS32(), 
+ *  is available for performance critical use.
+ *
+ *  @param ut the text to be accessed.
+ *  @return the previous UChar32 code point, or U_SENTINEL (-1) 
+ *          if the iteration has reached the start of the text.
+ *  @see UTEXT_PREVIOUS32
+ *  @stable ICU 3.4
+ */
+U_STABLE UChar32 U_EXPORT2
+utext_previous32(UText *ut);
+
+
+/**
+  * Set the iteration index and return the code point at that index. 
+  * Leave the iteration index at the start of the following code point.
+  *
+  * This function is the most efficient and convenient way to
+  * begin a forward iteration.  The results are identical to the those
+  * from the sequence
+  * \code
+  *    utext_setIndex();
+  *    utext_next32();
+  * \endcode
+  *
+  *  @param ut the text to be accessed.
+  *  @param nativeIndex Iteration index, in the native units of the text provider.
+  *  @return Code point which starts at or before index,
+  *         or U_SENTINEL (-1) if it is out of bounds.
+  * @stable ICU 3.4
+  */
+U_STABLE UChar32 U_EXPORT2
+utext_next32From(UText *ut, int64_t nativeIndex);
+
+
+
+/**
+  * Set the iteration index, and return the code point preceding the
+  * one specified by the initial index.  Leave the iteration position
+  * at the start of the returned code point.
+  *
+  * This function is the most efficient and convenient way to
+  * begin a backwards iteration.
+  *
+  * @param ut the text to be accessed.
+  * @param nativeIndex Iteration index in the native units of the text provider.
+  * @return Code point preceding the one at the initial index,
+  *         or U_SENTINEL (-1) if it is out of bounds.
+  *
+  * @stable ICU 3.4
+  */
+U_STABLE UChar32 U_EXPORT2
+utext_previous32From(UText *ut, int64_t nativeIndex);
+
+/**
+  * Get the current iterator position, which can range from 0 to 
+  * the length of the text.
+  * The position is a native index into the input text, in whatever format it
+  * may have (possibly UTF-8 for example), and may not always be the same as
+  * the corresponding UChar (UTF-16) index.
+  * The returned position will always be aligned to a code point boundary. 
+  *
+  * @param ut the text to be accessed.
+  * @return the current index position, in the native units of the text provider.
+  * @stable ICU 3.4
+  */
+U_STABLE int64_t U_EXPORT2
+utext_getNativeIndex(const UText *ut);
+
+/**
+ * Set the current iteration position to the nearest code point
+ * boundary at or preceding the specified index.
+ * The index is in the native units of the original input text.
+ * If the index is out of range, it will be pinned to be within
+ * the range of the input text.
+ * <p>
+ * It will usually be more efficient to begin an iteration
+ * using the functions utext_next32From() or utext_previous32From()
+ * rather than setIndex().
+ * <p>
+ * Moving the index position to an adjacent character is best done
+ * with utext_next32(), utext_previous32() or utext_moveIndex32().
+ * Attempting to do direct arithmetic on the index position is
+ * complicated by the fact that the size (in native units) of a
+ * character depends on the underlying representation of the character
+ * (UTF-8, UTF-16, UTF-32, arbitrary codepage), and is not
+ * easily knowable.
+ *
+ * @param ut the text to be accessed.
+ * @param nativeIndex the native unit index of the new iteration position.
+ * @stable ICU 3.4
+ */
+U_STABLE void U_EXPORT2
+utext_setNativeIndex(UText *ut, int64_t nativeIndex);
+
+/**
+ * Move the iterator postion by delta code points.  The number of code points
+ * is a signed number; a negative delta will move the iterator backwards,
+ * towards the start of the text.
+ * <p>
+ * The index is moved by <code>delta</code> code points
+ * forward or backward, but no further backward than to 0 and
+ * no further forward than to utext_nativeLength().
+ * The resulting index value will be in between 0 and length, inclusive.
+ *
+ * @param ut the text to be accessed.
+ * @param delta the signed number of code points to move the iteration position.
+ * @return TRUE if the position could be moved the requested number of positions while
+ *              staying within the range [0 - text length].
+ * @stable ICU 3.4
+ */
+U_STABLE UBool U_EXPORT2
+utext_moveIndex32(UText *ut, int32_t delta);
+
+/**
+ * Get the native index of the character preceeding the current position.
+ * If the iteration position is already at the start of the text, zero
+ * is returned.
+ * The value returned is the same as that obtained from the following sequence,
+ * but without the side effect of changing the iteration position.
+ *   
+ * \code
+ *    UText  *ut = whatever;
+ *      ...
+ *    utext_previous(ut)
+ *    utext_getNativeIndex(ut);
+ * \endcode
+ *
+ * This function is most useful during forwards iteration, where it will get the
+ *   native index of the character most recently returned from utext_next().
+ *
+ * @param ut the text to be accessed
+ * @return the native index of the character preceeding the current index position,
+ *         or zero if the current position is at the start of the text.
+ * @stable ICU 3.6
+ */
+U_STABLE int64_t U_EXPORT2
+utext_getPreviousNativeIndex(UText *ut); 
+
+
+/**
+ *
+ * Extract text from a UText into a UChar buffer.  The range of text to be extracted
+ * is specified in the native indices of the UText provider.  These may not necessarily
+ * be UTF-16 indices.
+ * <p>
+ * The size (number of 16 bit UChars) of the data to be extracted is returned.  The
+ * full number of UChars is returned, even when the extracted text is truncated
+ * because the specified buffer size is too small.
+ * <p>
+ * The extracted string will (if you are a user) / must (if you are a text provider)
+ * be NUL-terminated if there is sufficient space in the destination buffer.  This
+ * terminating NUL is not included in the returned length.
+ * <p>
+ * The iteration index is left at the position following the last extracted character.
+ *
+ * @param  ut    the UText from which to extract data.
+ * @param  nativeStart the native index of the first character to extract.\
+ *               If the specified index is out of range,
+ *               it will be pinned to to be within 0 <= index <= textLength
+ * @param  nativeLimit the native string index of the position following the last
+ *               character to extract.  If the specified index is out of range,
+ *               it will be pinned to to be within 0 <= index <= textLength.
+ *               nativeLimit must be >= nativeStart.
+ * @param  dest  the UChar (UTF-16) buffer into which the extracted text is placed
+ * @param  destCapacity  The size, in UChars, of the destination buffer.  May be zero
+ *               for precomputing the required size.
+ * @param  status receives any error status.
+ *         U_BUFFER_OVERFLOW_ERROR: the extracted text was truncated because the 
+ *         buffer was too small.  Returns number of UChars for preflighting.
+ * @return Number of UChars in the data to be extracted.  Does not include a trailing NUL.
+ *
+ * @stable ICU 3.4
+ */
+U_STABLE int32_t U_EXPORT2
+utext_extract(UText *ut,
+             int64_t nativeStart, int64_t nativeLimit,
+             UChar *dest, int32_t destCapacity,
+             UErrorCode *status);
+
+
+/**
+ * Compare two UTexts (binary order). The comparison begins at each source text's
+ * iteration position. The iteration position of each UText will be left following
+ * the last character compared.
+ *
+ * The comparison is done in code point order; unlike u_strCompare, you
+ * cannot choose to use code unit order. This is because the characters
+ * in a UText are accessed one code point at a time, and may not be from a UTF-16
+ * context.
+ *
+ * This functions works with strings of different explicitly specified lengths
+ * unlike the ANSI C-like u_strcmp() and u_memcmp() etc.
+ * A length argument of -1 signifies that as much of the string should be used as
+ * is necessary to compare with the other string. If both length arguments are -1,
+ * the entire remaining portionss of both strings are used.
+ *
+ * @param s1 First source string.
+ * @param length1 Length of first source string in UTF-32 code points.
+ *
+ * @param s2 Second source string.
+ * @param length2 Length of second source string in UTF-32 code points.
+ *
+ * @return <0 or 0 or >0 as usual for string comparisons
+ *
+ * @internal ICU 4.4 technology preview
+ */
+U_INTERNAL int32_t U_EXPORT2
+utext_compare(UText *s1, int32_t length1,
+              UText *s2, int32_t length2);    
+
+/**
+ * Compare two UTexts (binary order). The comparison begins at each source text's
+ * iteration position. The iteration position of each UText will be left following
+ * the last character compared. This method differs from utext_compare in that
+ * it accepts native limits rather than lengths for each string.
+ *
+ * The comparison is done in code point order; unlike u_strCompare, you
+ * cannot choose to use code unit order. This is because the characters
+ * in a UText are accessed one code point at a time, and may not be from a UTF-16
+ * context.
+ *
+ * This functions works with strings of different explicitly specified lengths
+ * unlike the ANSI C-like u_strcmp() and u_memcmp() etc.
+ * A limit argument of -1 signifies that as much of the string should be used as
+ * is necessary to compare with the other string. If both limit arguments are -1,
+ * the entire remaining portionss of both strings are used.
+ *
+ * @param s1 First source string.
+ * @param limit1 Native index of the last character in the first source string to be considered.
+ *
+ * @param s2 Second source string.
+ * @param limit2 Native index of the last character in the second source string to be considered.
+ *
+ * @return <0 or 0 or >0 as usual for string comparisons
+ *
+ * @internal ICU 4.4 technology preview
+ */
+U_INTERNAL int32_t U_EXPORT2
+utext_compareNativeLimit(UText *s1, int64_t limit1,
+                         UText *s2, int64_t limit2);    
+
+/**
+ * Compare two UTexts case-insensitively using full case folding. The comparison
+ * begins at each source text's iteration position. The iteration position of each
+ * UText will be left following the last character compared.
+ *
+ * The comparison is done in code point order; this is because the characters
+ * in a UText are accessed one code point at a time, and may not be from a UTF-16
+ * context.
+ *
+ * This functions works with strings of different explicitly specified lengths
+ * unlike the ANSI C-like u_strcmp() and u_memcmp() etc.
+ * A length argument of -1 signifies that as much of the string should be used as
+ * is necessary to compare with the other string. If both length arguments are -1,
+ * the entire remaining portionss of both strings are used.
+ *
+ * @param s1 First source string.
+ * @param length1 Length of first source string in UTF-32 code points.
+ *
+ * @param s2 Second source string.
+ * @param length2 Length of second source string in UTF-32 code points.
+ *
+ * @param options A bit set of options:
+ *   - U_FOLD_CASE_DEFAULT or 0 is used for default options:
+ *     Comparison in code point order with default case folding.
+ *
+ *   - U_FOLD_CASE_EXCLUDE_SPECIAL_I
+ *
+ * @param pErrorCode Must be a valid pointer to an error code value,
+ *                  which must not indicate a failure before the function call.
+ *
+ * @return <0 or 0 or >0 as usual for string comparisons
+ *
+ * @internal ICU 4.4 technology preview
+ */
+U_INTERNAL int32_t U_EXPORT2
+utext_caseCompare(UText *s1, int32_t length1,
+                  UText *s2, int32_t length2,
+                  uint32_t options, UErrorCode *pErrorCode);    
+
+/**
+ * Compare two UTexts case-insensitively using full case folding. The comparison
+ * begins at each source text's iteration position. The iteration position of each
+ * UText will be left following the last character compared. This method differs from
+ * utext_caseCompare in that it accepts native limits rather than lengths for each
+ * string.
+ *
+ * The comparison is done in code point order; this is because the characters
+ * in a UText are accessed one code point at a time, and may not be from a UTF-16
+ * context.
+ *
+ * This functions works with strings of different explicitly specified lengths
+ * unlike the ANSI C-like u_strcmp() and u_memcmp() etc.
+ * A limit argument of -1 signifies that as much of the string should be used as
+ * is necessary to compare with the other string. If both length arguments are -1,
+ * the entire remaining portionss of both strings are used.
+ *
+ * @param s1 First source string.
+ * @param limit1 Native index of the last character in the first source string to be considered.
+ *
+ * @param s2 Second source string.
+ * @param limit2 Native index of the last character in the second source string to be considered.
+ *
+ * @param options A bit set of options:
+ *   - U_FOLD_CASE_DEFAULT or 0 is used for default options:
+ *     Comparison in code point order with default case folding.
+ *
+ *   - U_FOLD_CASE_EXCLUDE_SPECIAL_I
+ *
+ * @param pErrorCode Must be a valid pointer to an error code value,
+ *                  which must not indicate a failure before the function call.
+ *
+ * @return <0 or 0 or >0 as usual for string comparisons
+ *
+ * @internal ICU 4.4 technology preview
+ */
+U_INTERNAL int32_t U_EXPORT2
+utext_caseCompareNativeLimit(UText *s1, int64_t limit1,
+                             UText *s2, int64_t limit2,
+                             uint32_t options, UErrorCode *pErrorCode);    
+
+
+/************************************************************************************
+ *
+ *  #define inline versions of selected performance-critical text access functions
+ *          Caution:  do not use auto increment++ or decrement-- expressions
+ *                    as parameters to these macros.
+ *
+ *          For most use, where there is no extreme performance constraint, the
+ *          normal, non-inline functions are a better choice.  The resulting code
+ *          will be smaller, and, if the need ever arises, easier to debug.
+ *
+ *          These are implemented as #defines rather than real functions
+ *          because there is no fully portable way to do inline functions in plain C.
+ *
+ ************************************************************************************/
+
+/**
+ * inline version of utext_current32(), for performance-critical situations.
+ *
+ * Get the code point at the current iteration position of the UText.
+ * Returns U_SENTINEL (-1) if the position is at the end of the
+ * text.
+ *
+ * @internal ICU 4.4 technology preview
+ */
+#define UTEXT_CURRENT32(ut)  \
+    ((ut)->chunkOffset < (ut)->chunkLength && ((ut)->chunkContents)[(ut)->chunkOffset]<0xd800 ? \
+    ((ut)->chunkContents)[((ut)->chunkOffset)] : utext_current32(ut))
+
+/**
+ * inline version of utext_next32(), for performance-critical situations.
+ *
+ * Get the code point at the current iteration position of the UText, and
+ * advance the position to the first index following the character.
+ * This is a post-increment operation.
+ * Returns U_SENTINEL (-1) if the position is at the end of the
+ * text.
+ *
+ * @stable ICU 3.4
+ */
+#define UTEXT_NEXT32(ut)  \
+    ((ut)->chunkOffset < (ut)->chunkLength && ((ut)->chunkContents)[(ut)->chunkOffset]<0xd800 ? \
+    ((ut)->chunkContents)[((ut)->chunkOffset)++] : utext_next32(ut))
+
+/**
+ * inline version of utext_previous32(), for performance-critical situations.
+ *
+ *  Move the iterator position to the character (code point) whose
+ *  index precedes the current position, and return that character.
+ *  This is a pre-decrement operation.
+ *  Returns U_SENTINEL (-1) if the position is at the start of the  text.
+ *
+ * @stable ICU 3.4
+ */
+#define UTEXT_PREVIOUS32(ut)  \
+    ((ut)->chunkOffset > 0 && \
+     (ut)->chunkContents[(ut)->chunkOffset-1] < 0xd800 ? \
+          (ut)->chunkContents[--((ut)->chunkOffset)]  :  utext_previous32(ut))
+
+/**
+  *  inline version of utext_getNativeIndex(), for performance-critical situations.
+  *
+  * Get the current iterator position, which can range from 0 to 
+  * the length of the text.
+  * The position is a native index into the input text, in whatever format it
+  * may have (possibly UTF-8 for example), and may not always be the same as
+  * the corresponding UChar (UTF-16) index.
+  * The returned position will always be aligned to a code point boundary. 
+  *
+  * @stable ICU 3.6
+  */
+#define UTEXT_GETNATIVEINDEX(ut)                       \
+    ((ut)->chunkOffset <= (ut)->nativeIndexingLimit?   \
+        (ut)->chunkNativeStart+(ut)->chunkOffset :     \
+        (ut)->pFuncs->mapOffsetToNative(ut))    
+
+/**
+  *  inline version of utext_setNativeIndex(), for performance-critical situations.
+  *
+  * Set the current iteration position to the nearest code point
+  * boundary at or preceding the specified index.
+  * The index is in the native units of the original input text.
+  * If the index is out of range, it will be pinned to be within
+  * the range of the input text.
+  *
+  * @stable ICU 3.8
+  */
+#define UTEXT_SETNATIVEINDEX(ut, ix)                       \
+    { int64_t __offset = (ix) - (ut)->chunkNativeStart; \
+      if (__offset>=0 && __offset<=(int64_t)(ut)->nativeIndexingLimit) { \
+          (ut)->chunkOffset=(int32_t)__offset; \
+      } else { \
+          utext_setNativeIndex((ut), (ix)); } }
+
+
+
+/************************************************************************************
+ *
+ *   Functions related to writing or modifying the text.
+ *   These will work only with modifiable UTexts.  Attempting to
+ *   modify a read-only UText will return an error status.
+ *
+ ************************************************************************************/
+
+
+/**
+ *  Return TRUE if the text can be written (modified) with utext_replace() or
+ *  utext_copy().  For the text to be writable, the text provider must
+ *  be of a type that supports writing and the UText must not be frozen.
+ *
+ *  Attempting to modify text when utext_isWriteable() is FALSE will fail -
+ *  the text will not be modified, and an error will be returned from the function
+ *  that attempted the modification.
+ *
+ * @param  ut   the UText to be tested.
+ * @return TRUE if the text is modifiable.
+ *
+ * @see    utext_freeze()
+ * @see    utext_replace()
+ * @see    utext_copy()
+ * @stable ICU 3.4
+ *
+ */
+U_STABLE UBool U_EXPORT2
+utext_isWritable(const UText *ut);
+
+
+/**
+  * Test whether there is meta data associated with the text.
+  * @see Replaceable::hasMetaData()
+  *
+  * @param ut The UText to be tested
+  * @return TRUE if the underlying text includes meta data.
+  * @stable ICU 3.4
+  */
+U_STABLE UBool U_EXPORT2
+utext_hasMetaData(const UText *ut);
+
+
+/**
+ * Replace a range of the original text with a replacement text.
+ *
+ * Leaves the current iteration position at the position following the
+ *  newly inserted replacement text.
+ *
+ * This function is only available on UText types that support writing,
+ * that is, ones where utext_isWritable() returns TRUE.
+ *
+ * When using this function, there should be only a single UText opened onto the
+ * underlying native text string.  Behavior after a replace operation
+ * on a UText is undefined for any other additional UTexts that refer to the
+ * modified string.
+ *
+ * @param ut               the UText representing the text to be operated on.
+ * @param nativeStart      the native index of the start of the region to be replaced
+ * @param nativeLimit      the native index of the character following the region to be replaced.
+ * @param replacementText  pointer to the replacement text
+ * @param replacementLength length of the replacement text, or -1 if the text is NUL terminated.
+ * @param status           receives any error status.  Possible errors include
+ *                         U_NO_WRITE_PERMISSION
+ *
+ * @return The signed number of (native) storage units by which
+ *         the length of the text expanded or contracted.
+ *
+ * @stable ICU 3.4
+ */
+U_STABLE int32_t U_EXPORT2
+utext_replace(UText *ut,
+             int64_t nativeStart, int64_t nativeLimit,
+             const UChar *replacementText, int32_t replacementLength,
+             UErrorCode *status);
+
+
+
+/**
+ *
+ * Copy or move a substring from one position to another within the text,
+ * while retaining any metadata associated with the text.
+ * This function is used to duplicate or reorder substrings.
+ * The destination index must not overlap the source range.
+ *
+ * The text to be copied or moved is inserted at destIndex;
+ * it does not replace or overwrite any existing text.
+ *
+ * The iteration position is left following the newly inserted text
+ * at the destination position.
+ *
+ * This function is only available on UText types that support writing,
+ * that is, ones where utext_isWritable() returns TRUE.
+ *
+ * When using this function, there should be only a single UText opened onto the
+ * underlying native text string.  Behavior after a copy operation
+ * on a UText is undefined in any other additional UTexts that refer to the
+ * modified string.
+ *
+ * @param ut           The UText representing the text to be operated on.
+ * @param nativeStart  The native index of the start of the region to be copied or moved
+ * @param nativeLimit  The native index of the character position following the region
+ *                     to be copied.
+ * @param destIndex    The native destination index to which the source substring is
+ *                     copied or moved.
+ * @param move         If TRUE, then the substring is moved, not copied/duplicated.
+ * @param status       receives any error status.  Possible errors include U_NO_WRITE_PERMISSION
+ *                       
+ * @stable ICU 3.4
+ */
+U_STABLE void U_EXPORT2
+utext_copy(UText *ut,
+          int64_t nativeStart, int64_t nativeLimit,
+          int64_t destIndex,
+          UBool move,
+          UErrorCode *status);
+
+
+/**
+  *  <p>
+  *  Freeze a UText.  This prevents any modification to the underlying text itself
+  *  by means of functions operating on this UText.
+  *  </p>
+  *  <p>
+  *  Once frozen, a UText can not be unfrozen.  The intent is to ensure
+  *  that a the text underlying a frozen UText wrapper cannot be modified via that UText.
+  *  </p>
+  *  <p>
+  *  Caution:  freezing a UText will disable changes made via the specific
+  *   frozen UText wrapper only; it will not have any effect on the ability to
+  *   directly modify the text by bypassing the UText.  Any such backdoor modifications
+  *   are always an error while UText access is occuring because the underlying
+  *   text can get out of sync with UText's buffering.
+  *  </p>
+  *
+  *  @param ut  The UText to be frozen.
+  *  @see   utext_isWritable()
+  *  @stable ICU 3.6
+  */
+U_STABLE void U_EXPORT2
+utext_freeze(UText *ut);
+
+
+/**
+ * UText provider properties (bit field indexes).
+ *
+ * @see UText
+ * @stable ICU 3.4
+ */
+enum {
+    /**
+     * It is potentially time consuming for the provider to determine the length of the text.
+     * @stable ICU 3.4
+     */
+    UTEXT_PROVIDER_LENGTH_IS_EXPENSIVE = 1,
+    /**
+     * Text chunks remain valid and usable until the text object is modified or
+     * deleted, not just until the next time the access() function is called
+     * (which is the default).
+     * @stable ICU 3.4
+     */
+    UTEXT_PROVIDER_STABLE_CHUNKS = 2,
+    /**
+     * The provider supports modifying the text via the replace() and copy()
+     * functions.
+     * @see Replaceable
+     * @stable ICU 3.4
+     */
+    UTEXT_PROVIDER_WRITABLE = 3,
+    /**
+     * There is meta data associated with the text.
+     * @see Replaceable::hasMetaData()
+     * @stable ICU 3.4
+     */ 
+    UTEXT_PROVIDER_HAS_META_DATA = 4,
+    /**
+     * Text provider owns the text storage.
+     *  Generally occurs as the result of a deep clone of the UText.
+     *  When closing the UText, the associated text must
+     *  also be closed/deleted/freed/ whatever is appropriate.
+     * @stable ICU 3.6
+     */
+     UTEXT_PROVIDER_OWNS_TEXT = 5
+};
+
+/**
+  * Function type declaration for UText.clone().
+  *
+  *  clone a UText.  Much like opening a UText where the source text is itself
+  *  another UText.
+  *
+  *  A deep clone will copy both the UText data structures and the underlying text.
+  *  The original and cloned UText will operate completely independently; modifications
+  *  made to the text in one will not effect the other.  Text providers are not
+  *  required to support deep clones.  The user of clone() must check the status return
+  *  and be prepared to handle failures.
+  *
+  *  A shallow clone replicates only the UText data structures; it does not make
+  *  a copy of the underlying text.  Shallow clones can be used as an efficient way to 
+  *  have multiple iterators active in a single text string that is not being
+  *  modified.
+  *
+  *  A shallow clone operation must not fail except for truly exceptional conditions such
+  *  as memory allocation failures.
+  *
+  *  A UText and its clone may be safely concurrently accessed by separate threads.
+  *  This is true for both shallow and deep clones.
+  *  It is the responsibility of the Text Provider to ensure that this thread safety
+  *  constraint is met.
+
+  *
+  *  @param dest   A UText struct to be filled in with the result of the clone operation,
+  *                or NULL if the clone function should heap-allocate a new UText struct.
+  *  @param src    The UText to be cloned.
+  *  @param deep   TRUE to request a deep clone, FALSE for a shallow clone.
+  *  @param status Errors are returned here.  For deep clones, U_UNSUPPORTED_ERROR
+  *                should be returned if the text provider is unable to clone the
+  *                original text.
+  *  @return       The newly created clone, or NULL if the clone operation failed.
+  *
+  * @stable ICU 3.4
+  */
+typedef UText * U_CALLCONV
+UTextClone(UText *dest, const UText *src, UBool deep, UErrorCode *status);
+
+
+/**
+ * Function type declaration for UText.nativeLength().
+ *
+ * @param ut the UText to get the length of.
+ * @return the length, in the native units of the original text string.
+ * @see UText
+ * @stable ICU 3.4
+ */
+typedef int64_t U_CALLCONV
+UTextNativeLength(UText *ut);
+
+/**
+ * Function type declaration for UText.access().  Get the description of the text chunk
+ *  containing the text at a requested native index.  The UText's iteration
+ *  position will be left at the requested index.  If the index is out
+ *  of bounds, the iteration position will be left at the start or end
+ *  of the string, as appropriate.
+ *
+ *  Chunks must begin and end on code point boundaries.  A single code point
+ *  comprised of multiple storage units must never span a chunk boundary.
+ *
+ *
+ * @param ut          the UText being accessed.
+ * @param nativeIndex Requested index of the text to be accessed.
+ * @param forward     If TRUE, then the returned chunk must contain text
+ *                    starting from the index, so that start<=index<limit.
+ *                    If FALSE, then the returned chunk must contain text
+ *                    before the index, so that start<index<=limit.
+ * @return            True if the requested index could be accessed.  The chunk
+ *                    will contain the requested text.
+ *                    False value if a chunk cannot be accessed
+ *                    (the requested index is out of bounds).
+ *
+ * @see UText
+ * @stable ICU 3.4
+ */
+typedef UBool U_CALLCONV
+UTextAccess(UText *ut, int64_t nativeIndex, UBool forward);
+
+/**
+ * Function type declaration for UText.extract().
+ *
+ * Extract text from a UText into a UChar buffer.  The range of text to be extracted
+ * is specified in the native indices of the UText provider.  These may not necessarily
+ * be UTF-16 indices.
+ * <p>
+ * The size (number of 16 bit UChars) in the data to be extracted is returned.  The
+ * full amount is returned, even when the specified buffer size is smaller.
+ * <p>
+ * The extracted string will (if you are a user) / must (if you are a text provider)
+ * be NUL-terminated if there is sufficient space in the destination buffer.
+ *
+ * @param  ut            the UText from which to extract data.
+ * @param  nativeStart   the native index of the first characer to extract.
+ * @param  nativeLimit   the native string index of the position following the last
+ *                       character to extract.
+ * @param  dest          the UChar (UTF-16) buffer into which the extracted text is placed
+ * @param  destCapacity  The size, in UChars, of the destination buffer.  May be zero
+ *                       for precomputing the required size.
+ * @param  status        receives any error status.
+ *                       If U_BUFFER_OVERFLOW_ERROR: Returns number of UChars for
+ *                       preflighting.
+ * @return Number of UChars in the data.  Does not include a trailing NUL.
+ *
+ * @stable ICU 3.4
+ */
+typedef int32_t U_CALLCONV
+UTextExtract(UText *ut,
+             int64_t nativeStart, int64_t nativeLimit,
+             UChar *dest, int32_t destCapacity,
+             UErrorCode *status);
+
+/**
+ * Function type declaration for UText.replace().
+ *
+ * Replace a range of the original text with a replacement text.
+ *
+ * Leaves the current iteration position at the position following the
+ *  newly inserted replacement text.
+ *
+ * This function need only be implemented on UText types that support writing.
+ *
+ * When using this function, there should be only a single UText opened onto the
+ * underlying native text string.  The function is responsible for updating the
+ * text chunk within the UText to reflect the updated iteration position,
+ * taking into account any changes to the underlying string's structure caused
+ * by the replace operation.
+ *
+ * @param ut               the UText representing the text to be operated on.
+ * @param nativeStart      the index of the start of the region to be replaced
+ * @param nativeLimit      the index of the character following the region to be replaced.
+ * @param replacementText  pointer to the replacement text
+ * @param replacmentLength length of the replacement text in UChars, or -1 if the text is NUL terminated.
+ * @param status           receives any error status.  Possible errors include
+ *                         U_NO_WRITE_PERMISSION
+ *
+ * @return The signed number of (native) storage units by which
+ *         the length of the text expanded or contracted.
+ *
+ * @stable ICU 3.4
+ */
+typedef int32_t U_CALLCONV
+UTextReplace(UText *ut,
+             int64_t nativeStart, int64_t nativeLimit,
+             const UChar *replacementText, int32_t replacmentLength,
+             UErrorCode *status);
+
+/**
+ * Function type declaration for UText.copy().
+ *
+ * Copy or move a substring from one position to another within the text,
+ * while retaining any metadata associated with the text.
+ * This function is used to duplicate or reorder substrings.
+ * The destination index must not overlap the source range.
+ *
+ * The text to be copied or moved is inserted at destIndex;
+ * it does not replace or overwrite any existing text.
+ *
+ * This function need only be implemented for UText types that support writing.
+ *
+ * When using this function, there should be only a single UText opened onto the
+ * underlying native text string.  The function is responsible for updating the
+ * text chunk within the UText to reflect the updated iteration position,
+ * taking into account any changes to the underlying string's structure caused
+ * by the replace operation.
+ *
+ * @param ut           The UText representing the text to be operated on.
+ * @param nativeStart  The index of the start of the region to be copied or moved
+ * @param nativeLimit  The index of the character following the region to be replaced.
+ * @param nativeDest   The destination index to which the source substring is copied or moved.
+ * @param move         If TRUE, then the substring is moved, not copied/duplicated.
+ * @param status       receives any error status.  Possible errors include U_NO_WRITE_PERMISSION
+ *
+ * @stable ICU 3.4
+ */
+typedef void U_CALLCONV
+UTextCopy(UText *ut,
+          int64_t nativeStart, int64_t nativeLimit,
+          int64_t nativeDest,
+          UBool move,
+          UErrorCode *status);
+
+/**
+ * Function type declaration for UText.mapOffsetToNative().
+ * Map from the current UChar offset within the current text chunk to
+ *  the corresponding native index in the original source text.
+ *
+ * This is required only for text providers that do not use native UTF-16 indexes.
+ *
+ * @param ut     the UText.
+ * @return Absolute (native) index corresponding to chunkOffset in the current chunk.
+ *         The returned native index should always be to a code point boundary.
+ *
+ * @stable ICU 3.4
+ */
+typedef int64_t U_CALLCONV
+UTextMapOffsetToNative(const UText *ut);
+
+/**
+ * Function type declaration for UText.mapIndexToUTF16().
+ * Map from a native index to a UChar offset within a text chunk.
+ * Behavior is undefined if the native index does not fall within the
+ *   current chunk.
+ *
+ * This function is required only for text providers that do not use native UTF-16 indexes.
+ *
+ * @param ut          The UText containing the text chunk.
+ * @param nativeIndex Absolute (native) text index, chunk->start<=index<=chunk->limit.
+ * @return            Chunk-relative UTF-16 offset corresponding to the specified native
+ *                    index.
+ *
+ * @stable ICU 3.4
+ */
+typedef int32_t U_CALLCONV
+UTextMapNativeIndexToUTF16(const UText *ut, int64_t nativeIndex);
+
+
+/**
+ * Function type declaration for UText.utextClose().
+ *
+ * A Text Provider close function is only required for provider types that make
+ *  allocations in their open function (or other functions) that must be 
+ *  cleaned when the UText is closed.
+ *
+ * The allocation of the UText struct itself and any "extra" storage
+ * associated with the UText is handled by the common UText implementation
+ * and does not require provider specific cleanup in a close function.
+ *
+ * Most UText provider implementations do not need to implement this function.
+ *
+ * @param ut A UText object to be closed.
+ *
+ * @stable ICU 3.4
+ */
+typedef void U_CALLCONV
+UTextClose(UText *ut);
+
+
+/**
+  *   (public)  Function dispatch table for UText.
+  *             Conceptually very much like a C++ Virtual Function Table.
+  *             This struct defines the organization of the table.
+  *             Each text provider implementation must provide an
+  *              actual table that is initialized with the appropriate functions
+  *              for the type of text being handled.
+  *   @stable ICU 3.6
+  */
+struct UTextFuncs {
+    /**
+     *   (public)  Function table size, sizeof(UTextFuncs)
+     *             Intended for use should the table grow to accomodate added
+     *             functions in the future, to allow tests for older format
+     *             function tables that do not contain the extensions.
+     *
+     *             Fields are placed for optimal alignment on
+     *             32/64/128-bit-pointer machines, by normally grouping together
+     *             4 32-bit fields,
+     *             4 pointers,
+     *             2 64-bit fields
+     *             in sequence.
+     *   @stable ICU 3.6
+     */
+    int32_t       tableSize;
+
+    /**
+      *   (private)  Alignment padding.
+      *              Do not use, reserved for use by the UText framework only.
+      *   @internal
+      */
+    int32_t       reserved1, /** @internal */ reserved2, /** @internal */ reserved3;
+
+
+    /**
+     * (public) Function pointer for UTextClone
+     *
+     * @see UTextClone
+     * @stable ICU 3.6
+     */
+    UTextClone *clone;
+
+    /**
+     * (public) function pointer for UTextLength
+     * May be expensive to compute!
+     *
+     * @see UTextLength
+     * @stable ICU 3.6
+     */
+    UTextNativeLength *nativeLength;
+
+    /**
+     * (public) Function pointer for UTextAccess.
+     *
+     * @see UTextAccess
+     * @stable ICU 3.6
+     */
+    UTextAccess *access;
+
+    /**
+     * (public) Function pointer for UTextExtract.
+     *
+     * @see UTextExtract
+     * @stable ICU 3.6
+     */
+    UTextExtract *extract;
+
+    /**
+     * (public) Function pointer for UTextReplace.
+     *
+     * @see UTextReplace
+     * @stable ICU 3.6
+     */
+    UTextReplace *replace;
+
+    /**
+     * (public) Function pointer for UTextCopy.
+     *
+     * @see UTextCopy
+     * @stable ICU 3.6
+     */
+    UTextCopy *copy;
+
+    /**
+     * (public) Function pointer for UTextMapOffsetToNative.
+     *
+     * @see UTextMapOffsetToNative
+     * @stable ICU 3.6
+     */
+    UTextMapOffsetToNative *mapOffsetToNative;
+
+    /**
+     * (public) Function pointer for UTextMapNativeIndexToUTF16.
+     *
+     * @see UTextMapNativeIndexToUTF16
+     * @stable ICU 3.6
+     */
+    UTextMapNativeIndexToUTF16 *mapNativeIndexToUTF16;
+
+    /**
+     * (public) Function pointer for UTextClose.
+      *
+      * @see UTextClose
+      * @stable ICU 3.6
+      */
+    UTextClose  *close;
+
+    /**
+      * (private)  Spare function pointer
+      * @internal
+      */
+    UTextClose  *spare1;
+    
+    /**
+      * (private)  Spare function pointer
+      * @internal
+      */
+    UTextClose  *spare2;
+
+    /**
+      * (private)  Spare function pointer
+      * @internal
+      */
+    UTextClose  *spare3;
+
+};
+/**
+ * Function dispatch table for UText
+ * @see UTextFuncs
+ */
+typedef struct UTextFuncs UTextFuncs;
+
+ /**
+  *   UText struct.  Provides the interface between the generic UText access code
+  *                  and the UText provider code that works on specific kinds of
+  *                  text  (UTF-8, noncontiguous UTF-16, whatever.)
+  *
+  *                  Applications that are using predefined types of text providers
+  *                  to pass text data to ICU services will have no need to view the
+  *                  internals of the UText structs that they open.
+  *
+  * @stable ICU 3.6
+  */
+struct UText {
+    /**
+     *     (private)  Magic.  Used to help detect when UText functions are handed
+     *                        invalid or unitialized UText structs.
+     *                        utext_openXYZ() functions take an initialized,
+     *                        but not necessarily open, UText struct as an
+     *                        optional fill-in parameter.  This magic field
+     *                        is used to check for that initialization.
+     *                        Text provider close functions must NOT clear
+     *                        the magic field because that would prevent
+     *                        reuse of the UText struct.
+     * @internal
+     */
+    uint32_t       magic;
+
+
+    /**
+     *     (private)  Flags for managing the allocation and freeing of
+     *                memory associated with this UText.
+     * @internal
+     */
+    int32_t        flags;
+
+
+    /**
+      *  Text provider properties.  This set of flags is maintainted by the
+      *                             text provider implementation.
+      *  @stable ICU 3.4
+      */
+    int32_t         providerProperties;
+
+    /**
+     * (public) sizeOfStruct=sizeof(UText)
+     * Allows possible backward compatible extension.
+     *
+     * @stable ICU 3.4
+     */
+    int32_t         sizeOfStruct;
+    
+    /* ------ 16 byte alignment boundary -----------  */
+    
+
+    /**
+      *  (protected) Native index of the first character position following
+      *              the current chunk.
+      *  @stable ICU 3.6
+      */
+    int64_t         chunkNativeLimit;
+
+    /**
+     *   (protected)  Size in bytes of the extra space (pExtra).
+     *  @stable ICU 3.4
+     */
+    int32_t        extraSize;
+
+    /**
+      *    (protected) The highest chunk offset where native indexing and
+      *    chunk (UTF-16) indexing correspond.  For UTF-16 sources, value
+      *    will be equal to chunkLength.
+      *
+      *    @stable ICU 3.6
+      */
+    int32_t         nativeIndexingLimit;
+
+    /* ---- 16 byte alignment boundary------ */
+    
+    /**
+     *  (protected) Native index of the first character in the text chunk.
+     *  @stable ICU 3.6
+     */
+    int64_t         chunkNativeStart;
+
+    /**
+     *  (protected) Current iteration position within the text chunk (UTF-16 buffer).
+     *  This is the index to the character that will be returned by utext_next32().
+     *  @stable ICU 3.6
+     */
+    int32_t         chunkOffset;
+
+    /**
+     *  (protected) Length the text chunk (UTF-16 buffer), in UChars.
+     *  @stable ICU 3.6
+     */
+    int32_t         chunkLength;
+
+    /* ---- 16  byte alignment boundary-- */
+    
+
+    /**
+     *  (protected)  pointer to a chunk of text in UTF-16 format.
+     *  May refer either to original storage of the source of the text, or
+     *  if conversion was required, to a buffer owned by the UText.
+     *  @stable ICU 3.6
+     */
+    const UChar    *chunkContents;
+
+     /**
+      * (public)     Pointer to Dispatch table for accessing functions for this UText.
+      * @stable ICU 3.6
+      */
+    const UTextFuncs     *pFuncs;
+
+    /**
+     *  (protected)  Pointer to additional space requested by the
+     *               text provider during the utext_open operation.
+     * @stable ICU 3.4
+     */
+    void          *pExtra;
+
+    /**
+     * (protected) Pointer to string or text-containin object or similar.
+     * This is the source of the text that this UText is wrapping, in a format
+     *  that is known to the text provider functions.
+     * @stable ICU 3.4
+     */
+    const void   *context;
+
+    /* --- 16 byte alignment boundary--- */
+
+    /**
+     * (protected) Pointer fields available for use by the text provider.
+     * Not used by UText common code.
+     * @stable ICU 3.6
+     */
+    const void     *p; 
+    /**
+     * (protected) Pointer fields available for use by the text provider.
+     * Not used by UText common code.
+     * @stable ICU 3.6
+     */
+    const void     *q;
+     /**
+     * (protected) Pointer fields available for use by the text provider.
+     * Not used by UText common code.
+     * @stable ICU 3.6
+      */
+    const void     *r;
+
+    /**
+      *  Private field reserved for future use by the UText framework
+      *     itself.  This is not to be touched by the text providers.
+      * @internal ICU 3.4
+      */
+    void           *privP;
+
+
+    /* --- 16 byte alignment boundary--- */
+    
+
+    /**
+      * (protected) Integer field reserved for use by the text provider.
+      * Not used by the UText framework, or by the client (user) of the UText.
+      * @stable ICU 3.4
+      */
+    int64_t         a;
+
+    /**
+      * (protected) Integer field reserved for use by the text provider.
+      * Not used by the UText framework, or by the client (user) of the UText.
+      * @stable ICU 3.4
+      */
+    int32_t         b;
+
+    /**
+      * (protected) Integer field reserved for use by the text provider.
+      * Not used by the UText framework, or by the client (user) of the UText.
+      * @stable ICU 3.4
+      */
+    int32_t         c;
+
+    /*  ---- 16 byte alignment boundary---- */
+
+
+    /**
+      *  Private field reserved for future use by the UText framework
+      *     itself.  This is not to be touched by the text providers.
+      * @internal ICU 3.4
+      */
+    int64_t         privA;
+    /**
+      *  Private field reserved for future use by the UText framework
+      *     itself.  This is not to be touched by the text providers.
+      * @internal ICU 3.4
+      */
+    int32_t         privB;
+    /**
+      *  Private field reserved for future use by the UText framework
+      *     itself.  This is not to be touched by the text providers.
+      * @internal ICU 3.4
+      */
+    int32_t         privC;
+};
+
+
+/**
+ *  Common function for use by Text Provider implementations to allocate and/or initialize
+ *  a new UText struct.  To be called in the implementation of utext_open() functions.
+ *  If the supplied UText parameter is null, a new UText struct will be allocated on the heap.
+ *  If the supplied UText is already open, the provider's close function will be called
+ *  so that the struct can be reused by the open that is in progress.
+ *
+ * @param ut   pointer to a UText struct to be re-used, or null if a new UText
+ *             should be allocated.
+ * @param extraSpace The amount of additional space to be allocated as part
+ *             of this UText, for use by types of providers that require
+ *             additional storage.
+ * @param status Errors are returned here.
+ * @return pointer to the UText, allocated if necessary, with extra space set up if requested.
+ * @stable ICU 3.4
+ */
+U_STABLE UText * U_EXPORT2
+utext_setup(UText *ut, int32_t extraSpace, UErrorCode *status);
+
+/**
+  * @internal
+  *  Value used to help identify correctly initialized UText structs.
+  *  Note:  must be publicly visible so that UTEXT_INITIALIZER can access it.
+  */
+enum {
+    UTEXT_MAGIC = 0x345ad82c
+};
+
+/**
+ * initializer to be used with local (stack) instances of a UText
+ *  struct.  UText structs must be initialized before passing
+ *  them to one of the utext_open functions.
+ *
+ * @stable ICU 3.6
+ */
+#define UTEXT_INITIALIZER {                                        \
+                  UTEXT_MAGIC,          /* magic                */ \
+                  0,                    /* flags                */ \
+                  0,                    /* providerProps        */ \
+                  sizeof(UText),        /* sizeOfStruct         */ \
+                  0,                    /* chunkNativeLimit     */ \
+                  0,                    /* extraSize            */ \
+                  0,                    /* nativeIndexingLimit  */ \
+                  0,                    /* chunkNativeStart     */ \
+                  0,                    /* chunkOffset          */ \
+                  0,                    /* chunkLength          */ \
+                  NULL,                 /* chunkContents        */ \
+                  NULL,                 /* pFuncs               */ \
+                  NULL,                 /* pExtra               */ \
+                  NULL,                 /* context              */ \
+                  NULL, NULL, NULL,     /* p, q, r              */ \
+                  NULL,                 /* privP                */ \
+                  0, 0, 0,              /* a, b, c              */ \
+                  0, 0, 0               /* privA,B,C,           */ \
+                  }
+
+
+U_CDECL_END
+
+
+
+#endif