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[Bug 15434] New: [IndexedDB] Detail steps for assigning a key to a value

From: <bugzilla@jessica.w3.org>
Date: Thu, 05 Jan 2012 21:44:12 +0000
To: public-webapps@w3.org
Message-ID: <bug-15434-2927@http.www.w3.org/Bugs/Public/>

           Summary: [IndexedDB] Detail steps for assigning a key to a
           Product: WebAppsWG
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: minor
          Priority: P2
         Component: Indexed Database API
        AssignedTo: dave.null@w3.org
        ReportedBy: jsbell@chromium.org
         QAContact: member-webapi-cvs@w3.org
                CC: mike@w3.org, public-webapps@w3.org

In section 5.1 "Object Store Storage Operation", step 2: when a key generator
is used with store with in line keys, the spec says: "set the property in value
pointed to by store's key path to the new value for key"

The "steps for extracting a key from a value using a key path" are called out
explicitly under Algorithms in 4.7. Should the steps for assigning a key to a
value using a key path be similarly documented? 

Cribbing from the spec, this could read as:

4.X Steps for assigning a key to a value using a key path

When taking the steps for assigning a key to a value using a key path, the
implementation must run the following algorithm. The algorithm takes a key path
named /keyPath/, a key named /key/, and a value named /value/ which may be
modified by the steps of the algorithm.

1. If /keyPath/ is the empty string, skip the remaining steps and /value/ is
not modified.
2. Let /remainingKeypath/ be /keyPath/ and /object/ be /value/.
3. If /remainingKeypath/ has a period in it, assign /remainingKeypath/ to be
everything after the first period and assign /attribute/ to be everything
before that first period. Otherwise, go to step 7.
4. If /object/ does not have an attribute named /attribute/, then skip the rest
of these steps and /value/ is not modified.
5. Assign /object/ to be the /value/ of the attribute named /attribute/ on
6. Go to step 3.
7. NOTE: The steps leading here ensure that /remainingKeyPath/ is a single
attribute name (i.e. string without periods) by this step.
8. Let /attribute/ be /remainingKeyPath/
9. If /object/ has an attribute named /attribute/ which is not modifiable, then
skip the remaining steps and /value/ is not modified.
10. Set an attribute named /attribute/ on /object/ with the value /key/.


The above talks in terms of a mutable value. It could be amended to have an
initial step which produces a clone of the value, which is later returned, but
given how this algorithm is used the difference is not observable, since the
value stored should already be a clone that doesn't have any other references.

Step 9 is present in case the key path refers to a "special" property, e.g. a
String/Array length, Blob/File properties, etc.

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Received on Thursday, 5 January 2012 21:44:20 UTC

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