Apple Newton Utilities User's Guide download pdf (Page 491)

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CHAPTER 11

Data Storage and Retrieval

Using Newton Data Storage Objects 11-59

No more than 32 KB of text (total of all strings, keeping in mind that one character

is 2 bytes) can reside in any soup entry. Another practical limitation is that there

must be space in the NewtonScript heap to hold the entire soup entry. You should

also be aware that Newton Backup Utility and Newton Connection Kit do not

support entries larger than 32K.

Keeping these limitations in mind, you can put any slots you need into your soup

entries. Entries within the same soup need not have the same set of slots. The only

slots to which you must pay special attention are those that are indexed. When you

create a soup, you specify which of its entries’ slots to index. Indexed slots must

contain data of the type speciﬁed by the index. For example, if you specify that an

index is to be built on slot

foo and that foo contains a text string, it’s important

that every

foo slot in every entry in the indexed soup contains a text string or nil.

Entries that do not have a

foo slot will not be found in queries on the foo index.

Entries having a

foo slot that contains data of some type other than text cause

various exceptions. For example, if you should try to add this kind of frame to an

indexed soup, the method that attempts to add the frame throws an exception; if

you try to add a new index on a slot that varies in data type from entry to entry, the

AddIndex method throws an exception, and so on. Soup entries can contain nil-

value slots, but querying for such slots is not supported; that is, you can query only

for slots that hold non-

nil values.

Removing Entries From Soups 11

To remove an entry, pass it to the EntryRemoveFromSoupXmit function, as

shown in the following code fragment. If you try to remove an invalid entry, this

function throws an exception. An entry can become invalid when, for example, the

user ejects the storage card on which it resides.

local myCursor := Query(nil);

local theEntry := myCursor:Entry();

if theEntry then

EntryRemoveFromSoup(theEntry, '|MyApp:MySig|);

Modifying Entries 11

Only one instance of a particular entry exists at any time, regardless of how the

entry was obtained. That is, if two cursors from two different queries on a

particular soup happen to be pointing at identical entries, they are actually both

pointing at the same entry.

When ﬁrst retrieved from a soup, an entry is just an identiﬁer. When the entry is

accessed as a frame (by getting or setting one of its slots), the complete entry frame

is constructed in the NewtonScript heap. The frame is marked to identify it as a

member of the soup from which it came.

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Apple Newton Utilities User's Guide Page 491

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