uiter.h File Reference

C API: Unicode Character Iteration. More...

#include "unicode/utypes.h"

Go to the source code of this file.

Data Structures

struct  UCharIterator
 C API for code unit iteration. More...

Defines

#define UITER_NO_STATE   ((uint32_t)0xffffffff)
 Constant for UCharIterator getState() indicating an error or an unknown state.

Typedefs

typedef struct UCharIterator UCharIterator
 C typedef for struct UCharIterator.
typedef int32_t UCharIteratorGetIndex (UCharIterator *iter, UCharIteratorOrigin origin)
 Function type declaration for UCharIterator.getIndex().
typedef int32_t UCharIteratorMove (UCharIterator *iter, int32_t delta, UCharIteratorOrigin origin)
 Function type declaration for UCharIterator.move().
typedef UBool UCharIteratorHasNext (UCharIterator *iter)
 Function type declaration for UCharIterator.hasNext().
typedef UBool UCharIteratorHasPrevious (UCharIterator *iter)
 Function type declaration for UCharIterator.hasPrevious().
typedef UChar32 UCharIteratorCurrent (UCharIterator *iter)
 Function type declaration for UCharIterator.current().
typedef UChar32 UCharIteratorNext (UCharIterator *iter)
 Function type declaration for UCharIterator.next().
typedef UChar32 UCharIteratorPrevious (UCharIterator *iter)
 Function type declaration for UCharIterator.previous().
typedef int32_t UCharIteratorReserved (UCharIterator *iter, int32_t something)
 Function type declaration for UCharIterator.reservedFn().
typedef uint32_t UCharIteratorGetState (const UCharIterator *iter)
 Function type declaration for UCharIterator.getState().
typedef void UCharIteratorSetState (UCharIterator *iter, uint32_t state, UErrorCode *pErrorCode)
 Function type declaration for UCharIterator.setState().

Enumerations

enum  UCharIteratorOrigin {
  UITER_START, UITER_CURRENT, UITER_LIMIT, UITER_ZERO,
  UITER_LENGTH
}
 

Origin constants for UCharIterator.getIndex() and UCharIterator.move().

More...
enum  { UITER_UNKNOWN_INDEX = -2 }
 

Constants for UCharIterator.

More...

Functions

UChar32 uiter_current32 (UCharIterator *iter)
 Helper function for UCharIterator to get the code point at the current index.
UChar32 uiter_next32 (UCharIterator *iter)
 Helper function for UCharIterator to get the next code point.
UChar32 uiter_previous32 (UCharIterator *iter)
 Helper function for UCharIterator to get the previous code point.
uint32_t uiter_getState (const UCharIterator *iter)
 Get the "state" of the iterator in the form of a single 32-bit word.
void uiter_setState (UCharIterator *iter, uint32_t state, UErrorCode *pErrorCode)
 Restore the "state" of the iterator using a state word from a getState() call.
void uiter_setString (UCharIterator *iter, const UChar *s, int32_t length)
 Set up a UCharIterator to iterate over a string.
void uiter_setUTF16BE (UCharIterator *iter, const char *s, int32_t length)
 Set up a UCharIterator to iterate over a UTF-16BE string (byte vector with a big-endian pair of bytes per UChar).
void uiter_setUTF8 (UCharIterator *iter, const char *s, int32_t length)
 Set up a UCharIterator to iterate over a UTF-8 string.

Detailed Description

C API: Unicode Character Iteration.

See also:
UCharIterator

Definition in file uiter.h.


Define Documentation

#define UITER_NO_STATE   ((uint32_t)0xffffffff)

Constant for UCharIterator getState() indicating an error or an unknown state.

Returned by uiter_getState()/UCharIteratorGetState when an error occurs. Also, some UCharIterator implementations may not be able to return a valid state for each position. This will be clearly documented for each such iterator (none of the public ones here).

Stable:
ICU 2.6

Definition at line 84 of file uiter.h.


Typedef Documentation

typedef struct UCharIterator UCharIterator

C typedef for struct UCharIterator.

Stable:
ICU 2.1

Definition at line 41 of file uiter.h.

Function type declaration for UCharIterator.current().

Return the code unit at the current position, or U_SENTINEL if there is none (index is at the limit).

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
the current code unit
See also:
UCharIterator
Stable:
ICU 2.1

Definition at line 186 of file uiter.h.

Function type declaration for UCharIterator.getIndex().

Gets the current position, or the start or limit of the iteration range.

This function may perform slowly for UITER_CURRENT after setState() was called, or for UITER_LENGTH, because an iterator implementation may have to count UChars if the underlying storage is not UTF-16.

Parameters:
iter the UCharIterator structure ("this pointer")
origin get the 0, start, limit, length, or current index
Returns:
the requested index, or U_SENTINEL in an error condition
See also:
UCharIteratorOrigin
UCharIterator
Stable:
ICU 2.1

Definition at line 105 of file uiter.h.

typedef uint32_t UCharIteratorGetState(const UCharIterator *iter)

Function type declaration for UCharIterator.getState().

Get the "state" of the iterator in the form of a single 32-bit word. It is recommended that the state value be calculated to be as small as is feasible. For strings with limited lengths, fewer than 32 bits may be sufficient.

This is used together with setState()/UCharIteratorSetState to save and restore the iterator position more efficiently than with getIndex()/move().

The iterator state is defined as a uint32_t value because it is designed for use in ucol_nextSortKeyPart() which provides 32 bits to store the state of the character iterator.

With some UCharIterator implementations (e.g., UTF-8), getting and setting the UTF-16 index with existing functions (getIndex(UITER_CURRENT) followed by move(pos, UITER_ZERO)) is possible but relatively slow because the iterator has to "walk" from a known index to the requested one. This takes more time the farther it needs to go.

An opaque state value allows an iterator implementation to provide an internal index (UTF-8: the source byte array index) for fast, constant-time restoration.

After calling setState(), a getIndex(UITER_CURRENT) may be slow because the UTF-16 index may not be restored as well, but the iterator can deliver the correct text contents and move relative to the current position without performance degradation.

Some UCharIterator implementations may not be able to return a valid state for each position, in which case they return UITER_NO_STATE instead. This will be clearly documented for each such iterator (none of the public ones here).

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
the state word
See also:
UCharIterator
UCharIteratorSetState
UITER_NO_STATE
Stable:
ICU 2.6

Definition at line 279 of file uiter.h.

Function type declaration for UCharIterator.hasNext().

Check if current() and next() can still return another code unit.

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
boolean value for whether current() and next() can still return another code unit
See also:
UCharIterator
Stable:
ICU 2.1

Definition at line 157 of file uiter.h.

Function type declaration for UCharIterator.hasPrevious().

Check if previous() can still return another code unit.

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
boolean value for whether previous() can still return another code unit
See also:
UCharIterator
Stable:
ICU 2.1

Definition at line 171 of file uiter.h.

typedef int32_t UCharIteratorMove(UCharIterator *iter, int32_t delta, UCharIteratorOrigin origin)

Function type declaration for UCharIterator.move().

Use iter->move(iter, index, UITER_ZERO) like CharacterIterator::setIndex(index).

Moves the current position relative to the start or limit of the iteration range, or relative to the current position itself. The movement is expressed in numbers of code units forward or backward by specifying a positive or negative delta. Out of bounds movement will be pinned to the start or limit.

This function may perform slowly for moving relative to UITER_LENGTH because an iterator implementation may have to count the rest of the UChars if the native storage is not UTF-16.

When moving relative to the limit or length, or relative to the current position after setState() was called, move() may return UITER_UNKNOWN_INDEX (-2) to avoid an inefficient determination of the actual UTF-16 index. The actual index can be determined with getIndex(UITER_CURRENT) which will count the UChars if necessary. See UITER_UNKNOWN_INDEX for details.

Parameters:
iter the UCharIterator structure ("this pointer")
delta can be positive, zero, or negative
origin move relative to the 0, start, limit, length, or current index
Returns:
the new index, or U_SENTINEL on an error condition, or UITER_UNKNOWN_INDEX when the index is not known.
See also:
UCharIteratorOrigin
UCharIterator
UITER_UNKNOWN_INDEX
Stable:
ICU 2.1

Definition at line 142 of file uiter.h.

Function type declaration for UCharIterator.next().

Return the code unit at the current index and increment the index (post-increment, like s[i++]), or return U_SENTINEL if there is none (index is at the limit).

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
the current code unit (and post-increment the current index)
See also:
UCharIterator
Stable:
ICU 2.1

Definition at line 202 of file uiter.h.

Function type declaration for UCharIterator.previous().

Decrement the index and return the code unit from there (pre-decrement, like s[--i]), or return U_SENTINEL if there is none (index is at the start).

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
the previous code unit (after pre-decrementing the current index)
See also:
UCharIterator
Stable:
ICU 2.1

Definition at line 218 of file uiter.h.

typedef int32_t UCharIteratorReserved(UCharIterator *iter, int32_t something)

Function type declaration for UCharIterator.reservedFn().

Reserved for future use.

Parameters:
iter the UCharIterator structure ("this pointer")
something some integer argument
Returns:
some integer
See also:
UCharIterator
Stable:
ICU 2.1

Definition at line 232 of file uiter.h.

typedef void UCharIteratorSetState(UCharIterator *iter, uint32_t state, UErrorCode *pErrorCode)

Function type declaration for UCharIterator.setState().

Restore the "state" of the iterator using a state word from a getState() call. The iterator object need not be the same one as for which getState() was called, but it must be of the same type (set up using the same uiter_setXYZ function) and it must iterate over the same string (binary identical regardless of memory address). For more about the state word see UCharIteratorGetState.

After calling setState(), a getIndex(UITER_CURRENT) may be slow because the UTF-16 index may not be restored as well, but the iterator can deliver the correct text contents and move relative to the current position without performance degradation.

Parameters:
iter the UCharIterator structure ("this pointer")
state the state word from a getState() call on a same-type, same-string iterator
pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.
See also:
UCharIterator
UCharIteratorGetState
Stable:
ICU 2.6

Definition at line 307 of file uiter.h.


Enumeration Type Documentation

anonymous enum

Constants for UCharIterator.

Stable:
ICU 2.6
Enumerator:
UITER_UNKNOWN_INDEX 

Constant value that may be returned by UCharIteratorMove indicating that the final UTF-16 index is not known, but that the move succeeded.

This can occur when moving relative to limit or length, or when moving relative to the current index after a setState() when the current UTF-16 index is not known.

It would be very inefficient to have to count from the beginning of the text just to get the current/limit/length index after moving relative to it. The actual index can be determined with getIndex(UITER_CURRENT) which will count the UChars if necessary.

Stable:
ICU 2.6

Definition at line 54 of file uiter.h.

Origin constants for UCharIterator.getIndex() and UCharIterator.move().

See also:
UCharIteratorMove
UCharIterator
Stable:
ICU 2.1

Definition at line 49 of file uiter.h.


Function Documentation

UChar32 uiter_current32 ( UCharIterator iter  ) 

Helper function for UCharIterator to get the code point at the current index.

Return the code point that includes the code unit at the current position, or U_SENTINEL if there is none (index is at the limit). If the current code unit is a lead or trail surrogate, then the following or preceding surrogate is used to form the code point value.

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
the current code point
See also:
UCharIterator
U16_GET
UnicodeString::char32At()
Stable:
ICU 2.1
uint32_t uiter_getState ( const UCharIterator iter  ) 

Get the "state" of the iterator in the form of a single 32-bit word.

This is a convenience function that calls iter->getState(iter) if iter->getState is not NULL; if it is NULL or any other error occurs, then UITER_NO_STATE is returned.

Some UCharIterator implementations may not be able to return a valid state for each position, in which case they return UITER_NO_STATE instead. This will be clearly documented for each such iterator (none of the public ones here).

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
the state word
See also:
UCharIterator
UCharIteratorGetState
UITER_NO_STATE
Stable:
ICU 2.6
UChar32 uiter_next32 ( UCharIterator iter  ) 

Helper function for UCharIterator to get the next code point.

Return the code point at the current index and increment the index (post-increment, like s[i++]), or return U_SENTINEL if there is none (index is at the limit).

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
the current code point (and post-increment the current index)
See also:
UCharIterator
U16_NEXT
Stable:
ICU 2.1
UChar32 uiter_previous32 ( UCharIterator iter  ) 

Helper function for UCharIterator to get the previous code point.

Decrement the index and return the code point from there (pre-decrement, like s[--i]), or return U_SENTINEL if there is none (index is at the start).

Parameters:
iter the UCharIterator structure ("this pointer")
Returns:
the previous code point (after pre-decrementing the current index)
See also:
UCharIterator
U16_PREV
Stable:
ICU 2.1
void uiter_setState ( UCharIterator iter,
uint32_t  state,
UErrorCode pErrorCode 
)

Restore the "state" of the iterator using a state word from a getState() call.

This is a convenience function that calls iter->setState(iter, state, pErrorCode) if iter->setState is not NULL; if it is NULL, then U_UNSUPPORTED_ERROR is set.

Parameters:
iter the UCharIterator structure ("this pointer")
state the state word from a getState() call on a same-type, same-string iterator
pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.
See also:
UCharIterator
UCharIteratorSetState
Stable:
ICU 2.6
void uiter_setString ( UCharIterator iter,
const UChar s,
int32_t  length 
)

Set up a UCharIterator to iterate over a string.

Sets the UCharIterator function pointers for iteration over the string s with iteration boundaries start=index=0 and length=limit=string length. The "provider" may set the start, index, and limit values at any time within the range 0..length. The length field will be ignored.

The string pointer s is set into UCharIterator.context without copying or reallocating the string contents.

getState() simply returns the current index. move() will always return the final index.

Parameters:
iter UCharIterator structure to be set for iteration
s String to iterate over
length Length of s, or -1 if NUL-terminated
See also:
UCharIterator
Stable:
ICU 2.1
void uiter_setUTF16BE ( UCharIterator iter,
const char *  s,
int32_t  length 
)

Set up a UCharIterator to iterate over a UTF-16BE string (byte vector with a big-endian pair of bytes per UChar).

Everything works just like with a normal UChar iterator (uiter_setString), except that UChars are assembled from byte pairs, and that the length argument here indicates an even number of bytes.

getState() simply returns the current index. move() will always return the final index.

Parameters:
iter UCharIterator structure to be set for iteration
s UTF-16BE string to iterate over
length Length of s as an even number of bytes, or -1 if NUL-terminated (NUL means pair of 0 bytes at even index from s)
See also:
UCharIterator
uiter_setString
Stable:
ICU 2.6
void uiter_setUTF8 ( UCharIterator iter,
const char *  s,
int32_t  length 
)

Set up a UCharIterator to iterate over a UTF-8 string.

Sets the UCharIterator function pointers for iteration over the UTF-8 string s with UTF-8 iteration boundaries 0 and length. The implementation counts the UTF-16 index on the fly and lazily evaluates the UTF-16 length of the text.

The start field is used as the UTF-8 offset, the limit field as the UTF-8 length. When the reservedField is not 0, then it contains a supplementary code point and the UTF-16 index is between the two corresponding surrogates. At that point, the UTF-8 index is behind that code point.

The UTF-8 string pointer s is set into UCharIterator.context without copying or reallocating the string contents.

getState() returns a state value consisting of

  • the current UTF-8 source byte index (bits 31..1)
  • a flag (bit 0) that indicates whether the UChar position is in the middle of a surrogate pair (from a 4-byte UTF-8 sequence for the corresponding supplementary code point)

getState() cannot also encode the UTF-16 index in the state value. move(relative to limit or length), or move(relative to current) after setState(), may return UITER_UNKNOWN_INDEX.

Parameters:
iter UCharIterator structure to be set for iteration
s UTF-8 string to iterate over
length Length of s in bytes, or -1 if NUL-terminated
See also:
UCharIterator
Stable:
ICU 2.6
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