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BMimeType

Derived from: none
Declared in:  be/storage/Mime.h
Library: libbe.so
Summary:  more...


The BMimeType class provides three services:

All three services operate on MIME strings. In other words, they answer questions such as "Does this string have a supertype?", "Is this string installed in the database?", and so on. You can get the MIME strings from anywhere: from a file's file type attribute, from and application's signature, from the header of an e-mail message, you can even make them up.

Valid MIME Strings

A valid MIME string takes the form...

...where supertype is one of the seven "media" strings:

...and (the optional) subtype can be just about anything...Except it can't include spaces or any of these forbidden characters:

When you initialize a BMimeType object (through the constructor or SetTo() function), you have to tell it what MIME string you want it to represent:

You can check the validity of a MIME string without constructing a BMimeType object by calling the static IsValid() function:

BMimeType::IsValid("text/qwerty");

Constructor and Destructor

BMimeType()

BMimeType(void)
BMimeType(const char *MIME_string)

Constructs a new BMimeType object and initializes its MIME type to a copy of MIME_string (if the argument is given). The rules of validity apply (see "Valid MIME Strings", above). To see if the initialization was successful, call InitCheck() after you construct a new BMimeType object.

You can also set the MIME type through the SetTo() function.

~BMimeType()

virtual ~BMimeType()

Frees the object's MIME string and destroys the object.

Member Functions

Contains()

bool Contains(const BMimeType *other) const

Compares the MIME string with other, returning true if they are identical. If the object is a supertype and it's the supertype of other, then the method returns true. Otherwise, it returns false.

Delete()  see Install()

GetAppHint() , SetAppHint()

status_t GetAppHint(entry_ref *app_ref) const
status_t SetAppHint(const entry_ref *app_ref)

These functions get and set the "app hint" for the object's application signature. The app hint is a path that identifies the executable that should be used when launching an application that has this signature. For example, when the Tracker needs to launch an app of type "application/YourAppHere", it asks the database for the application hint. This hint is converted to an entry_ref before it is passed to the caller. Of course, the path may not point to an application, or it might point to an application with the wrong signature (and so on)—that's why this is merely a hint.

GetAppHint() function initializes the entry_ref to the hint recorded in the database; the argument must be allocated before it's passed in.

SetAppHint() copies the path corresponding to the entry_ref into the database. app_ref should point to an executable file that has the same signature as this object's MIME type.

RETURN CODES

See also: BNodeInfo::GetAppHint()

GetAttrInfo() , SetAttrInfo()

status_t GetAttrInfo(BMessage *info) const
status_t SetAttrInfo(BMessage *info)

These functions use a BMessage to get and set the list of attributes that are typically associated with files of the MIME type. The BMessage must have the following fields:

Field Name Type element[0..n]
"attr:name" B_STRING_TYPE Each element is the name of one attribute.
"attr:public_name" B_STRING_TYPE Each element is the human-readable name of one attribute.
"attr:type" B_INT32_TYPE Each element is the type code for the corresponding attribute.
"attr:public" B_BOOL_TYPE true if the attribute is public, false if it's private.
"attr:editable" B_BOOL_TYPE true if the attribute should be user-editable, false if not.

You can actually have any fields you want; it's up to applications to determine which attributes they recognize and which they don't.

Each element in each field describes the next attribute. If a file has three attributes, there should be three elements in each field, one per attribute.

RETURN CODES

GetFileExtensions() , SetFileExtensions()

status_t GetFileExtensions(BMessage *msg) const
status_t SetFileExtensions(const BMessage *msg)

The database associates a list of file extensions (".xxx..." filename appendages) with each file type. If a file is otherwise untyped, clients of the database can figure out its type by matching the file's extension to the lists in the database.

These functions get and set the file extensions that are associated with the object's MIME type.

For example, to retrieve all the extensions that correspond to this object's MIME type, you would do the following:

BMessage msg();
uint32 i=0;
char *ptr;

if (mime.GetFileExtensions(&msg) != B_OK)
   /* Handle the error. */

while (true) {
   if (msg.FindString("extensions", i++, &ptr) != B_OK)
      break;
   printf("> Extension: %sn", ptr);
}

A given extension can be associated with more than one MIME type.

A NULL msg to SetFileExtensions() clears the type's extension list.

SetFileExtensions() clobbers the existing set of extensions. If you want to augment a type's extensions, you should retrieve the existing set, add the new ones, and then call SetFileExtensions().

Also, there's no way to ask the database to give you a set of file types that map to a given extension. To find a type for an extension, you have to get all the installed types with GetInstalledTypes() and ask each one for its set of extensions.

RETURN CODES

GetIcon() , SetIcon()

status_t GetIcon(BBitmap *icon, icon_size which) const
status_t SetIcon(const BBitmap *icon, icon_size which)

GetIcon() and SetIcon() get and set the icons that are associated (in the database) with this object's MIME type. You specify which icon you want (large or small) by passing B_LARGE_ICON or B_MINI_ICON as the which argument. The icon is passed in or returned through the icon argument. The icon data is copied out of or into the BBitmap object.

The bitmap (if you're calling SetIcon()) or icon (if you're calling GetIcon()) must be the proper size: 32x32 for the large icon, 16x16 for the small one. Additionally, the bitmap must be in the B_CMAP8 color space (8-bit color), or the application will crash.

If you want to erase the node's icon, pass NULL as the icon argument to SetIcon().

RETURN CODES

GetIconForType() , SetIconForType()

status_t GetIconForType(const char *file_type, BBitmap *icon,
      icon_size which) const
status_t SetIconForType(const char *file_type, const BBitmap *icon, icon_size which)

These functions get and set the icons that an application that has this object's MIME type as a signature uses to display the given file type. file_type must be a valid MIME string.

The icon is passed in or returned through the icon argument:

RETURN CODES

GetInstalledTypes() , GetInstalledSupertypes()

static status_t GetInstalledTypes(BMessage *types)
static status_t GetInstalledTypes(const char *supertype, BMessage *subtypes)
static status_t GetInstalledSupertypes(BMessage *supertypes)

These static functions retrieve all the file types that are currently installed in the database, all the installed subtypes for a given supertype, and all the installed supertypes. The types are copied into the "types" field of the passed-in BMessage (which must be allocated).

RETURN CODES

GetLongDescription() , SetLongDescription() , GetShortDescription() , SetShortDescription()

status_t GetLongDescription(char *description) const
status_t SetLongDescription(const char *description)
status_t GetShortDescription(char *description) const
status_t SetShortDescription(const char *description)

Each file type has a couple of human-readable description strings associated with it. Neither description string may be longer than B_MIME_TYPE_LENGTH characters.

These functions get and set the long and short description strings. The Get functions copy the string into the argument (which must be allocated). The Set functions copy the string that the argument points to.

RETURN CODES

GetPreferredApp() , SetPreferredApp()

status_t GetPreferredApp(char *signature, app_verb verb = B_OPEN) const
status_t SetPreferredApp(const char *signature, app_verb verb = B_OPEN)

These functions get and set the "preferred app" for this object's MIME type. The preferred app is the application that's used to access a file when, for example, the user double-clicks the file in a Tracker window: Unless the file identifies (in its attributes) a "custom" preferred app, the Tracker will ask the File Type database for the preferred app that's associated with the file's type.

RETURN CODES

GetShortDescription()  see GetLongDescription()
GetSupertype()  see Type()

GetSupportingApps() , GetWildcardApps()

status_t GetSupportingApps(BMessage *msg) const
static status_t GetWildcardApps(BMessage *msg)

These functions retrieve a list of applications (identified by signature) that know how to handle the object's MIME type (for GetSupportingApps()) or all MIME types (GetWildCardApps()). The information is returned in msg, which must be allocated by the caller. The msg format is:

Field name Type Meaning
"applications" B_STRING_TYPE
(array)		 The signatures of the application that know how to handle the MIME type. The first n applications (where n is defined by "be:sub", below) can handle the full type (supertype and subtype). The rest of the applications in the array handle the supertype only.
"be:sub" B_INT32_TYPE The number of applications in the "applications" array that can handle the object's full MIME type. These applications are listed first in the array. This field is omitted if the object represents a supertype only.
"be:super" B_INT32_TYPE The number of applications in the "applications" array that can handle the object's supertype (not counting those that can handle the full type). These applications are listed after the full-MIME type supporters. By definition, the GetWildcardApps() function never returns supertype-only apps.

For example, here we print the signatures of the apps that can handle "text/plain" and "text" (without checking for errors):

BMessage msg();
BMimeType mime("text/plain");
int32 subs=0, supers=0, n, hold;
char *ptr;

mime.GetSupportingApps(&msg);
msg.FindInt32("be:subs", &subs);
msg.FindInt32("be:supers", &supers);

for (n = 0; n < subs; n++) {
   msg.FindString("applications", n, &ptr);
   printf("Full support: %sn", ptr);
}
hold = n;
for (n = 0; n < supers; n++) {
   msg.FindString("applications", n+hold, &ptr);
   printf("Supertype support: %sn", ptr);
}

If an application supports both the full type and the supertype, it will be listed only once in the "applications" array (as a full supporter).

To set the types that an application supports, use BAppFileInfo::SetSupportedTypes(). To tell an app to support all types, add "application/octet-stream" to its supported-types list.

See also:

RETURN CODES

GetWildcardApps()  see GetSupportingApps()

InitCheck()

status_t InitCheck(void) const

Returns the status of the most recent construction or SetTo() call.

RETURN CODES

Install() , Delete() , IsInstalled()

status_t Install(void)
status_t Delete(void)
bool IsInstalled(void) const

Install() adds the object's MIME type to the File Type database. Delete() removes the type from the database. IsInstalled() tells you if the type is currently installed.

None of these functions affect the object's copy of the MIME type; for instance, deleting a MIME type from the database doesn't uninitialize the object.

RETURN CODES

Currently, Install() may return a random value if the object is already installed. To avoid confusion, you should call IsInstalled() first:

if (!mime.IsInstalled())
   mime.Install();

IsInstalled()  see Install()

IsValid() , IsSupertypeOnly()

static bool IsValid(const char *MIME_string)
bool IsValid(void) const
bool IsSupertypeOnly(void) const

The static IsValid() tests its argument for MIME validity. See "Valid MIME Strings" for the rules. The non-static version checks the validity of the object's MIME string.

IsSupertypeOnly() returns true if the object's MIME string doesn't include a subtype.

SetAppHint()  see GetAppHint()
SetAttrInfo()  see GetAttrInfo()
GetFileExtensions()
GetIcon()
GetIconForType()
GetLongDescription()
GetPreferredApp()
GetLongDescription()

SetTo() , Unset()

status_t SetTo(const char *MIME_string)
void Unset(void)

SetTo() initializes this BMimeType object to represent MIME_string. The object's previous MIME string is freed; the argument is then copied. The argument can be a full supertype/subtype string, or simply a supertype. In any case, it must pass the validity test described in "Valid MIME Strings".

Unset() frees the object's current MIME string, and sets the object's status to B_NO_INITGetLongDescription() .

RETURN CODES

These return codes are also returned by the InitCheck() function.

See also: InitCheck()

StartWatching() , StopWatching()

static status_t StartWatching(BMessenger target)
static status_t StopWatching(BMessenger target)

StartWatching() initiates the MIME monitor, which is used for keeping track of changes to the File Types database. Change notifications will be sent via the BMessenger target in a BMessage with the what field set to B_META_MIME_CHANGED.

Notification messages have the following fields:

Name Type Description
be:which int32 Change bitmap (see below for a list)
be:type string MIME type whose database information was changed
be:extra_type string Extra MIME field used for some notifications
be:large_icon bool For notifications involving icon changes, true if the large icon was changed; false otherwise

"be:which" is a bitmask describing the changes made to the database for MIME type "be:type". The following masks are defined along with the BMimeType methods used to effect the changes they signal:

B_ICON_CHANGED SetIcon()
B_PREFERRED_APP_CHANGED SetPreferredApp()
B_ATTR_INFO_CHANGED SetAttrInfo()
B_FILE_EXTENSIONS_CHANGED SetFileExtensions()
B_SHORT_DESCRIPTION_CHANGED SetShortDescription()
B_LONG_DESCRIPTION_CHANGED SetLongDescription()
B_ICON_FOR_TYPE_CHANGED SetIconForType()
B_APP_HINT_CHANGED SetAppHint()

The BMimeType methods are given for illustrative purposes only –– anything that alters the database for a MIME type will also trigger a notification message. The "be:extra_type" field is used only in the B_ICON_FOR_TYPE_CHANGED message and indicates the application signature for which the change is valid.

StopWatching() terminates the MIME monitor previously initiated for the given BMessenger.

StartWatching()

Type() , GetSupertype()

const char *Type(void) const
status_t GetSupertype(BMimeType *super) const

Type() returns a pointer to the object's MIME string. If the object isn't initialized, this returns a pointer to NULL.

GetSupertype()StartWatching() initializes the argument with this object's supertype. (You can then call GetType() on the argument to see the supertype.) super must be allocated before it's passed in. If this object isn't initialized, super is uninitialized.

RETURN CODES

The errors apply to GetSupertype() only.

SetTo()

Operators

== (comparison)

bool operator==(const BMimeType &type) const
bool operator==(const char *type) const

Two MIME types are equal if they are both initialized to the same string (without regard to case).

C Functions

create_app_meta_mime

status_t create_app_meta_mime(const char *path, int recursive, int synchronous,
      int force)

Creates an entry in the File Types database for a specific application, or for all applications:

The recursive flag is currently unused.

If synchronous is true, the function doesn't return until the operation is complete. If it's false, the function returns immediately while the operation continues in the background.

If force is true, entries are created even if they already exist.

RETURN CODES

get_device_icon

status_t get_device_icon(const char *device, void *icon, int32 size)

Returns the icons that are associated with the given device. You specify which icon you want (large or small) by passing 32 or 16 as the size argument. The icon is then returned through the icon argument.

See also: BVolume::GetIcon()

update_mime_info

int update_mime_info(const char *path, int recursive, int synchronous,
      int force)

Updates the MIME information for one or more files, specified by path. If path is NULL, all files are scanned recursively, and the value of recursive is ignored.

If recursive is true and path indicates a directory, the directory tree contained by path is scanned, with every file in the tree being updated; otherwise, just the file indicated by path is updated.

If synchronous is true, update_mime_info() doesn't return until the update operation is complete. If it's false, update_mime_info() runs asynchronously, and returns immediately while updating continues in the background.

If force is true, files are updated even if they've been updated already.

If an error occurs, update_mime_info() returns a negative error code; otherwise, it returns B_OK.

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