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How to create an AsciiReader
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The
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input
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for
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model
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systems
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is
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often
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contained
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in
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simple
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ASCII
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files.
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Wrapping
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these
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files
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allows
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you
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to
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make
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the
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data
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available
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to
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OpenMI-compliant
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systems.
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For
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example,
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you
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can
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wrap
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the
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output
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file
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from
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one
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component
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so
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that
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it
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serves
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as
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the
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input
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for
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another
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component.
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When
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such
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a
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file
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is
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wrapped,
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it
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can
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be
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accessed
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in
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the
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same
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way
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as
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any
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other
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OpenMI
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component.
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The
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wrapped
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output
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file
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makes
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it
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easy
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to
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test
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the
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OpenMI
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component
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that
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uses
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the
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file
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as
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input.
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It
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will
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also
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be
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possible
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to
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run
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the
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component
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using
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the
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data
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without
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having
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to
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run
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the
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delivering
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component.
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To
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be
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OpenMI-compliant,
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a
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component
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needs
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to
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implement
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two
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interfaces:
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the
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IPublisher
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and
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ILinkableComponent
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interfaces.
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Therefore
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the
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ASCII
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reader
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needs
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to
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implement
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these
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interfaces.
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As
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with
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model
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systems,
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this
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can
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be
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done
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by
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inheriting
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from
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Oatc.OpenMI.
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Sdk.Wrapper.LinkableEngine
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and
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implementing
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specific
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methods.
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The
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difference
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between
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the
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wrapping
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of
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ASCII
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files
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and
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the
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approach
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used
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for
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model
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components
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lies
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in
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the
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implementation
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of
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the
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ExchangeItems
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(GetOutputExchangeItem)
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and
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the
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GetValues
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call.
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In
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the
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case
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of
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a
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model
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component,
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the
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ExchangeItems
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will
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usually
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be
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provided
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by
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a
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populated
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model
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kernel.
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When
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wrapping
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an
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ASCII
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file,
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the
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information
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about
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possible
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ExchangeItems
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must
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be
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contained
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in
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the
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ASCII
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file itself.
Figure 1 is an example of an ASCII file (get file; there are four lines of comments, followed by a line specifying the quantity and another containing the three locations.
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itself. // Lines starting with // are comment // The first uncommented line defines the quantity // The second uncommented line defines the locations // All next lines consist of a timestamp and values of the quantity for each location "Flow" "Loc1";"Loc2";"Loc3" "2005-01-01 00:00";"15.4";"18.2";"22.4" "2005-01-01 03:00";"15.3";"18.5";"22.5" "2005-01-01 06:00";"15.4";"18.9";"22.4" "2005-01-01 09:00";"15.2";"19.0";"22.6" "2005-01-01 12:00";"15.1";"18.8";"22.7" "2005-01-01 15:00";"14.8";"18.6";"22.9" "2005-01-01 18:00";"14.7";"18.4";"23.4" "2005-01-01 21:00";"14.7";"18.2";"23.8" "2005-01-02 00:00";"14.6";"18.2";"23.9" "2005-01-02 03:00";"14.1";"18.1";"24.0" "2005-01-02 06:00";"13.8";"18.2";"23.5" "2005-01-02 09:00";"13.9";"18.0";"23.6" "2005-01-02 12:00";"13.6";"17.8";"23.5" "2005-01-02 15:00";"13.2";"17.3";"23.3" "2005-01-02 18:00";"12.8";"17.4";"23.2" "2005-01-02 21:00";"12.7";"17.2";"23.1" "2005-01-03 00:00";"12.6";"17.2";"22.9" "2005-01-03 03:00";"12.1";"16.8";"22.7" "2005-01-03 06:00";"12.2";"16.6";"22.5" "2005-01-03 09:00";"11.4";"16.5";"22.4" "2005-01-03 12:00";"11.6";"16.4";"22.2" "2005-01-03 15:00";"11.7";"16.3";"21.8" "2005-01-03 18:00";"11.6";"16.0";"21.5" "2005-01-03 21:00";"11.2";"15.8";"21.4" "2005-01-04 00:00";"11.0";"15.6";"21.3" |
Figure
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1
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An
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example
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ASCII file
This information defines the possible OutputExchangeItems.
The OutputExchangeItems could look like the following:
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file
Figure 5 1 is an example of an ASCII file; there are four lines of comments, followed by a line specifying the quantity and another containing the three locations. This information defines the possible OutputExchangeItems.
The OutputExchangeItems could look like the following:
OutputExchangeItem[0] = { "Flow", "Loc1"}
OutputExchangeItem[1] = { "Flow", "Loc2"}
OutputExchangeItem[2] = { "Flow", "Loc3"}
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Implementing
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an
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OpenMI-compatible
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linkable
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component
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that
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uses
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this
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ASCII
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file
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as
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input
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and
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makes
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the
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contents
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of
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the
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file
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available
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through
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OutputExchangeItems
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requires
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the
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following
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steps:
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- Start
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- developing
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- the
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- component
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- by
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- implementing
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- org.OpenMI.Utilities.Wrapper.LinkableEngine.
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- Write
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- code
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- for
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- methods
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- such
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- as
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- Initialize,
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- Finalize,
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- GetModelID
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- and
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- GetModelDescription.
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- Write
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- code
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- for
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- the
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- SetValues,
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- GetInputExchangeItem
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- and
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- GetInputExchangeItemCount
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- methods; these methods are empty because the ASCII reader does not accept data.
- Write code for the GetOutputExchangeItem method; make sure the ASCII file is read, the ExchangeItems are extracted from the file and the OutputExchangeItems are defined.
- Write code for the GetValues method; this should extract the correct data for the requested timestamp/ExchangeItem combination from the ASCII file.
Prototype code for GetOutputExchangeItem is given in Figure 2.
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public IOutputExchangeItem GetOutputExchangeItem(int outputExchangeItemIndex)
{
return _output;
}
private void ReadFile()
{
StreamReader reader = new StreamReader(_inputFile);
bool quantityRead = false;
bool elementsRead = false;
_timeStamps.Clear();
_elementValues.Clear();
string line;
while ((line = reader.ReadLine()) != null)
{
if (line.StartsWith("//"))
{
// ignore
}
else if (!quantityRead)
{
_quantity = new Quantity(line.Trim(' ', '"'));
_output = new OutputExchangeItem();
_output.Quantity = _quantity;
quantityRead = true;
}
else if (!elementsRead)
{
string[] elements = line.Split(';');
_elementSet = new ElementSet();
_elementSet.ID = "File Contents";
_output.ElementSet = _elementSet;
for (int i = 0; i < elements.Length; i++)
{
_elementSet.AddElement (new Element(elements[i].Trim('"')));
}
elementsRead = true;
}
else
{
string[] values = line.Split(';');
DateTime timestamp = Convert.ToDateTime (values[0].Trim('"'), _culture);
double modifiedJulianDateTime = CalendarConverter.Gregorian2ModifiedJulian(timestamp);
double[] locationValues = new double[values.Length - 1];
for (int i = 1; i < values.Length; i++)
{
locationValues[i - 1] = Convert.ToDouble (values[i].Trim('"'), _culture);
}
_timeStamps.Add (modifiedJulianDateTime);
_elementValues.Add (locationValues);
}
}
}
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Figure 2 Code for GetOutputExchangeItem
A prototype of the GetValues method is shown in Figure 3.
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public IValueSet GetValues(ITime time, string linkID)
{
ILink outgoingLink = (Link) _links[linkID];
if (outgoingLink == null)
{
throw new Exception ("Unknown link or quantity");
}
if (time is TimeStamp)
{
TimeStamp timestamp = (TimeStamp) time;
double[] results;
for (int i = 0; i < _timeStamps.Count; i++)
{
if ( (double)_timeStamps[i] + _delta > timestamp.ModifiedJulianDay)
{
results = (double[]) _elementValues[i];
return new ScalarSet(results);
}
}
throw new Exception ("No appropriate values found");
}
throw new Exception ("Time should be of type TimeStamp");
}
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Figure 3 Example GetValues method