udata.h File Reference

C API: Data loading interface. More...

`#include "unicode/utypes.h"`
`#include "unicode/localpointer.h"`

Go to the source code of this file.

## Data Structures

struct | UDataInfo
| UDataInfo contains the properties about the requested data. More...

## Namespaces

namespace | icu
| File coll.h.

## Macros

#define | U_TREE_SEPARATOR '-'
| Character used to separate package names from tree names.
#define | U_TREE_SEPARATOR_STRING "-"
| String used to separate package names from tree names.
#define | U_TREE_ENTRY_SEP_CHAR '/'
| Character used to separate parts of entry names.
#define | U_TREE_ENTRY_SEP_STRING "/"
| String used to separate parts of entry names.
#define | U_ICUDATA_ALIAS "ICUDATA"
| Alias for standard ICU data.

## Typedefs

typedef struct UDataMemory | UDataMemory
| Forward declaration of the data memory type.
typedef UBool | UDataMemoryIsAcceptable(void *context, const char *type, const char *name, const UDataInfo *pInfo)
| Callback function for udata_openChoice().
typedef enum UDataFileAccess | UDataFileAccess
| Possible settings for udata_setFileAccess()

## Enumerations

enum | UDataFileAccess { UDATA_FILES_FIRST , UDATA_DEFAULT_ACCESS = UDATA_FILES_FIRST , UDATA_ONLY_PACKAGES , UDATA_PACKAGES_FIRST , UDATA_NO_FILES , UDATA_FILE_ACCESS_COUNT }
| Possible settings for udata_setFileAccess() More...

## Functions

U_CAPI UDataMemory * | udata_open (const char *path, const char *type, const char *name, UErrorCode *pErrorCode)
| Convenience function.
U_CAPI UDataMemory * | udata_openChoice (const char *path, const char *type, const char *name, UDataMemoryIsAcceptable *isAcceptable, void *context, UErrorCode *pErrorCode)
| Data loading function.
U_CAPI void | udata_close (UDataMemory *pData)
| Close the data memory.
U_CAPI const void * | udata_getMemory (UDataMemory *pData)
| Get the pointer to the actual data inside the data memory.
U_CAPI void | udata_getInfo (UDataMemory *pData, UDataInfo *pInfo)
| Get the information from the data memory header.
U_CAPI void | udata_setCommonData (const void *data, UErrorCode *err)
| This function bypasses the normal ICU data loading process and allows you to force ICU's system data to come out of a user-specified area in memory.
U_CAPI void | udata_setAppData (const char *packageName, const void *data, UErrorCode *err)
| This function bypasses the normal ICU data loading process for application-specific data and allows you to force the it to come out of a user-specified pointer.
U_CAPI void | udata_setFileAccess (UDataFileAccess access, UErrorCode *status)
| This function may be called to control how ICU loads data.

## Detailed Description

C API: Data loading interface.

## Information about data loading interface

This API is used to find and efficiently load data for ICU and applications using ICU. It provides an abstract interface that specifies a data type and name to find and load the data. Normally this API is used by other ICU APIs to load required data out of the ICU data library, but it can be used to load data out of other places.

See the User Guide Data Management chapter.

Definition in file udata.h.

## Macro Definition Documentation

## U_ICUDATA_ALIAS

#define U_ICUDATA_ALIAS "ICUDATA"

Alias for standard ICU data.

Internal:
  Do not use. This API is for internal use only. ICU 3.0

Definition at line 74 of file udata.h.

## U_TREE_ENTRY_SEP_CHAR

#define U_TREE_ENTRY_SEP_CHAR '/'

Character used to separate parts of entry names.

Internal:
  Do not use. This API is for internal use only. ICU 3.0

Definition at line 62 of file udata.h.

## U_TREE_ENTRY_SEP_STRING

#define U_TREE_ENTRY_SEP_STRING "/"

String used to separate parts of entry names.

Internal:
  Do not use. This API is for internal use only. ICU 3.0

Definition at line 68 of file udata.h.

## U_TREE_SEPARATOR

#define U_TREE_SEPARATOR '-'

Character used to separate package names from tree names.

Internal:
  Do not use. This API is for internal use only. ICU 3.0

Definition at line 50 of file udata.h.

## U_TREE_SEPARATOR_STRING

#define U_TREE_SEPARATOR_STRING "-"

String used to separate package names from tree names.

Internal:
  Do not use. This API is for internal use only. ICU 3.0

Definition at line 56 of file udata.h.

## Typedef Documentation

## UDataFileAccess

typedef enum UDataFileAccess UDataFileAccess

Possible settings for udata_setFileAccess()

See also
  udata_setFileAccess

Stable:
  ICU 3.4

## UDataMemory

typedef struct UDataMemory UDataMemory

Forward declaration of the data memory type.

Stable:
  ICU 2.0

Definition at line 161 of file udata.h.

## UDataMemoryIsAcceptable

typedef UBool UDataMemoryIsAcceptable(void *context, const char *type, const char *name, const UDataInfo *pInfo)

Callback function for udata_openChoice().

Parameters

  context | parameter passed into `udata_openChoice()`.
  type | The type of the data as passed into `udata_openChoice()`. It may be `NULL`.
  name | The name of the data as passed into `udata_openChoice()`.
  pInfo | A pointer to the `UDataInfo` structure of data that has been loaded and will be returned by `udata_openChoice()` if this function returns `true`.

Returns
  true if the current data memory is acceptable

Stable:
  ICU 2.0

Definition at line 177 of file udata.h.

## Enumeration Type Documentation

## UDataFileAccess

enum UDataFileAccess

Possible settings for udata_setFileAccess()

See also
  udata_setFileAccess

Stable:
  ICU 3.4

Enumerator

UDATA_FILES_FIRST

ICU looks for data in single files first, then in packages.

(default)

Stable:
  ICU 3.4

UDATA_DEFAULT_ACCESS

An alias for the default access mode.

Stable:
  ICU 3.4

UDATA_ONLY_PACKAGES

ICU only loads data from packages, not from single files.

Stable:
  ICU 3.4

UDATA_PACKAGES_FIRST

ICU loads data from packages first, and only from single files if the data cannot be found in a package.

Stable:
  ICU 3.4

UDATA_NO_FILES

ICU does not access the file system for data loading.

Stable:
  ICU 3.4

UDATA_FILE_ACCESS_COUNT

Number of real UDataFileAccess values.

Deprecated:
  ICU 58 The numeric value may change over time, see ICU ticket #12420.

Definition at line 385 of file udata.h.

## Function Documentation

## udata_close()

U_CAPI void udata_close | ( | UDataMemory * | pData | ) |

Close the data memory.

This function must be called to allow the system to release resources associated with this data memory.

Parameters

  pData | The pointer to data memory object

Stable:
  ICU 2.0

## udata_getInfo()

U_CAPI void udata_getInfo | ( | UDataMemory * | pData,
|  | UDataInfo * | pInfo
| ) |  |

Get the information from the data memory header.

This allows to get access to the header containing platform data properties etc. which is not part of the data itself and can therefore not be accessed via the pointer that `udata_getMemory()` returns.

Parameters

  pData | pointer to the data memory object
  pInfo | pointer to a UDataInfo object; its `size` field must be set correctly, typically to `sizeof(UDataInfo)`.

`*pInfo` will be filled with the UDataInfo structure in the data memory object. If this structure is smaller than `pInfo->size`, then the `size` will be adjusted and only part of the structure will be filled.

Stable:
  ICU 2.0

## udata_getMemory()

U_CAPI const void * udata_getMemory | ( | UDataMemory * | pData | ) |

Get the pointer to the actual data inside the data memory.

The data is read-only.

ICU data must be at least 8-aligned, and should be 16-aligned.

Parameters

  pData | The pointer to data memory object

Stable:
  ICU 2.0

## udata_open()

U_CAPI UDataMemory * udata_open | ( | const char * | path,
|  | const char * | type,
|  | const char * | name,
|  | UErrorCode * | pErrorCode
| ) |  |

Convenience function.

This function works the same as `udata_openChoice` except that any data that matches the type and name is assumed to be acceptable.

Parameters

  path | Specifies an absolute path and/or a basename for the finding of the data in the file system. `NULL` for ICU data.
  type | A string that specifies the type of data to be loaded. For example, resource bundles are loaded with type "res", conversion tables with type "cnv". This may be `NULL` or empty.
  name | A string that specifies the name of the data.
  pErrorCode | An ICU UErrorCode parameter. It must not be `NULL`.

Returns
  A pointer (handle) to a data memory object, or `NULL` if an error occurs. Call `udata_getMemory()` to get a pointer to the actual data.

See also
  udata_openChoice

Stable:
  ICU 2.0

## udata_openChoice()

U_CAPI UDataMemory * udata_openChoice | ( | const char * | path,
|  | const char * | type,
|  | const char * | name,
|  | UDataMemoryIsAcceptable * | isAcceptable,
|  | void * | context,
|  | UErrorCode * | pErrorCode
| ) |  |

Data loading function.

This function is used to find and load efficiently data for ICU and applications using ICU. It provides an abstract interface that allows to specify a data type and name to find and load the data.

The implementation depends on platform properties and user preferences and may involve loading shared libraries (DLLs), mapping files into memory, or fopen()/fread() files. It may also involve using static memory or database queries etc. Several or all data items may be combined into one entity (DLL, memory-mappable file).

The data is always preceded by a header that includes a `UDataInfo` structure. The caller's `isAcceptable()` function is called to make sure that the data is useful. It may be called several times if it rejects the data and there is more than one location with data matching the type and name.

If `path==NULL`, then ICU data is loaded. Otherwise, it is separated into a basename and a basename-less directory string. The basename is used as the data package name, and the directory is logically prepended to the ICU data directory string.

For details about ICU data loading see the User Guide Data Management chapter. (https://unicode-org.github.io/icu/userguide/icu_data/)

Parameters

  path | Specifies an absolute path and/or a basename for the finding of the data in the file system. `NULL` for ICU data.
  type | A string that specifies the type of data to be loaded. For example, resource bundles are loaded with type "res", conversion tables with type "cnv". This may be `NULL` or empty.
  name | A string that specifies the name of the data.
  isAcceptable | This function is called to verify that loaded data is useful for the client code. If it returns false for all data items, then `udata_openChoice()` will return with an error.
  context | Arbitrary parameter to be passed into isAcceptable.
  pErrorCode | An ICU UErrorCode parameter. It must not be `NULL`.

Returns
  A pointer (handle) to a data memory object, or `NULL` if an error occurs. Call `udata_getMemory()` to get a pointer to the actual data.

Stable:
  ICU 2.0

## udata_setAppData()

U_CAPI void udata_setAppData | ( | const char * | packageName,
|  | const void * | data,
|  | UErrorCode * | err
| ) |  |

This function bypasses the normal ICU data loading process for application-specific data and allows you to force the it to come out of a user-specified pointer.

ICU data must be at least 8-aligned, and should be 16-aligned. See https://unicode-org.github.io/icu/userguide/icu_data

The format of this data is that of the icu common data file, like 'icudt26l.dat' or the corresponding shared library (DLL) file. The application must read in or otherwise construct an image of the data and then pass the address of it to this function.

Warning: setAppData will set a U_USING_DEFAULT_WARNING code if data with the specified path that has already been opened, or if setAppData with the same path has already been called. Any such calls to setAppData will have no effect.

Parameters

  packageName | the package name by which the application will refer to (open) this data
  data | pointer to the data
  err | outgoing error status `U_USING_DEFAULT_WARNING, U_UNSUPPORTED_ERROR`

See also
  udata_setCommonData

Stable:
  ICU 2.0

## udata_setCommonData()

U_CAPI void udata_setCommonData | ( | const void * | data,
|  | UErrorCode * | err
| ) |  |

This function bypasses the normal ICU data loading process and allows you to force ICU's system data to come out of a user-specified area in memory.

ICU data must be at least 8-aligned, and should be 16-aligned. See https://unicode-org.github.io/icu/userguide/icu_data

The format of this data is that of the icu common data file, as is generated by the pkgdata tool with mode=common or mode=dll. You can read in a whole common mode file and pass the address to the start of the data, or (with the appropriate link options) pass in the pointer to the data that has been loaded from a dll by the operating system, as shown in this code:

      extern const char U_IMPORT U_ICUDATA_ENTRY_POINT [];
       // U_ICUDATA_ENTRY_POINT is same as entry point specified to pkgdata tool
      UErrorCode  status = U_ZERO_ERROR;

      udata_setCommonData(&U_ICUDATA_ENTRY_POINT, &status);

It is important that the declaration be as above. The entry point must not be declared as an extern void*.

Starting with ICU 4.4, it is possible to set several data packages, one per call to this function. udata_open() will look for data in the multiple data packages in the order in which they were set. The position of the linked-in or default-name ICU .data package in the search list depends on when the first data item is loaded that is not contained in the already explicitly set packages. If data was loaded implicitly before the first call to this function (for example, via opening a converter, constructing a UnicodeString from default-codepage data, using formatting or collation APIs, etc.), then the default data will be first in the list.

This function has no effect on application (non ICU) data. See udata_setAppData() for similar functionality for application data.

Parameters

  data | pointer to ICU common data
  err | outgoing error status `U_USING_DEFAULT_WARNING, U_UNSUPPORTED_ERROR`

Stable:
  ICU 2.0

## udata_setFileAccess()

U_CAPI void udata_setFileAccess | ( | UDataFileAccess | access,
|  | UErrorCode * | status
| ) |  |

This function may be called to control how ICU loads data.

It must be called before any ICU data is loaded, including application data loaded with ures/ResourceBundle or udata APIs. This function is not multithread safe.
The results of calling it while other threads are loading data are undefined.

Parameters

  access | The type of file access to be used
  status | Error code.

See also
  UDataFileAccess

Stable:
  ICU 3.4