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SeqFile

Semantics

The component type SeqFile is intended to capture the abstraction of a sequential file in which lines, characters, or records (the format of the data is specified using the RecordFormat property) are read sequentially from the front and written sequentially at the end.

Player types

Players of the following types can be legally exposed in the interface of a component of type SeqFile:

WriteNext

the next data item to be written

Properties

The following properties can be legally included in the property list of a component of type SeqFile. Properties legal in an <interface> property list have a C in parentheses after the property name; those legal in an <instantiation> property list have an I:

InstFormals (C)

The syntax for an InstFormals property in a component of type
SeqFile is a comma-separated list of <parameter>s enclosed in parentheses. A <parameter> consists of an <identifier>, followed by a `=', followed by a <complex string> or the language keyword NODEFAULT. A <complex string> is a simple "string" or a sequence of "string"s concatenated by the `&' character:

INSTFORMALS (first_parameter = "an initial value",

second_parameter = "a much" &
"longer initial value that " &
"will not fit on one line",
third_parameter = NODEFAULT)

Variant (C, I)

The syntax for a Variant property in a component of type
SeqFile is a single <identifier> or "string" surrounded by parentheses:

VARIANT (a_variant_name)
VARIANT ("a variant name")

Processor (C, I)

The syntax for a Processor property in a component of type
SeqFile is a single <identifier> or "string" surrounded by parentheses:

PROCESSOR (a_processor_name)
PROCESSOR ("a.processor.name")

RecordFormat (C, I)

The syntax for a RecordFormat property in a component of type
SeqFile is a comma-separated list of items, surrounded by parentheses, that are either <identifier>s or "strings":

RECORDFORMAT (a_type_name, "another type name")

If this property is omitted from the property list of the interface in a SeqFile component, the following default property is assumed:

RECORDFORMAT ("line")

OpenMode (C, I)

The syntax for an OpenMode property in a component of type
SeqFile is a comma-separated list containing a subset of the words truncate, append, and create, surrounded by parentheses. These words can be specified as either <identifier>s or "strings":

OPENMODE (create, "append")

Library (C, I)

The Library property has no associated value. The syntax, therefore, is simply:

LIBRARY

Semantic Checks

If the SeqFile component has a primitive implementation, the implementation type of the source file (specified in the ImplType property in the variant's property list) must be of type Data.

Implementation Considerations

The implementation of a SeqFile component in the environment is simply a sequential file containing ASCII data.