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# The Storage Kit

## B MimeType

Declared in: storage/Mime.h

### GetSnifferRule() , SetSnifferRule() , CheckSnifferRule()

`status_t` `GetSnifferRule(BString *`result`)` `const`
`status_t` `SetSnifferRule(const char *`rule`)`
`static status_t` `CheckSnifferRule(const char *`rule, `BString *`parseError`)`

`GetSnifferRule()` and `SetSnifferRule()` get and set the pattern-matching rule that the file type sniffer uses to detect the MIME type represented by this object. The sniffer rule is a string that follows this format:

       rating [begin:end] ( [begin:end] 'pattern1' | [begin:end] 'pattern2' | ... )

- rating is a mandatory float between 0.0 and 1.0 that describes the priority of the rule, compared to other rules for the same type.

- [begin:end] is the optional "global byte range" declaration. The sniffer will look for a matching pattern that begins within this range of data. The [begin:end] that appears outside the parenthesis (i.e. just after rating) applies to all the patterns for this rule. If a pattern must begin at a particular byte offset, you can exclude the ":end" declaration.

- 'pattern1', 'pattern2', etc. These are the patterns themselves. You can OR patterns with the "|" operator. (You can't AND patterns.) An immediately preceding byte range declaration applies to the following pattern (only), and overrides the global byte range declaration.

If no byte range declaration is provided, [0:0] is assumed—i.e. the pattern(s) must start at the first byte.

For example, the following rule strings says that the content of an examined file must begin with the characters 'ABCD':

       "1.0 ('ABCD')"

This rule says that the content must contain the characters 'ABCD' or 'abcd' starting somewhere in the first three bytes:

       "1.0 [0:3] ('ABCD' | 'abcd')"

Here the content must contain 'ABCD' or 'abcd' starting in the first three bytes, or it must contain 'EFGH' starting at byte 13:

       "1.0 [0:3] ('ABCD' | 'abcd' | [13] 'EFGH')"

The `CheckSnifferRule()` function is a debugging tool that checks your sniffer rule (independent of MIME type) and returns a string that describes the error. If the rule is correct, you get back (in result) a string that says "rule is correct". Otherwise, the result string contains an error message with a pointer to the offending part of the rule. The string is meant to be viewed in a monospace font.

### B_SNIFFER_RULE_CHANGED

`enum` { ... B_SNIFFER_RULE_CHANGED, ... };

`B_SNIFFER_RULE_CHANGED` is a new MIME database-watching bit vector value. If your application has called `BMimeType::StartWatching()` and someone changes a sniffer rule, your target will receive a `B_META_MIME_CHANGED` message that has, as in its "be:which" field, the value `B_SNIFFER_RULE_CHANGED`.

### GuessMimeType()

`static status_t` `GuessMimeType(const entry_ref *`file, `BMimeType *`result`)`
`static status_t` `GuessMimeType(const void *`buffer, `int32` length, `BMimeType *`result`)`
`static status_t` `GuessMimeType(const char *`filename, `BMimeType *`result`)`

These new class functions ask the sniffer to identify the MIME type of a file or data. result must be allocated before it's passed in.

## B Node

Declared in: storage/Node.h

### WriteAttrString() , ReadAttrString()

`status_t` `WriteAttrString(const char *`attr, `const BString *`string`)`
`status_t` `ReadAttrString(const char *`attr, `BString *`result`)` `const`

New functions to more easily work with string-valued file attributes. `WriteAttrString()` writes a `NULL`-terminator at the end of the string.

## B Path

Declared in: storage/Path.h

BPath has new versions of the constructor and the `SetTo()` function that accepts `entry_ref` arguments.

### BPath()

`BPath(const entry_ref *`ref`)`

### SetTo()

`status_t` `SetTo(const entry_ref *`ref`)`

## B Query

Declared in: storage/Query.h

### GetPredicate()

`status_t` `GetPredicate(BString *`result`)`

This new version of `GetPredicate()` returns the query's predicate string as a BString object.

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