procedure ddfopen: open DDF file procedure ddfread: read DDF record procedure ddfclose: close DDF file
link ddfread
August 2, 2001; Gregg M. Townsend
This file is in the public domain.
These procedures read DDF files ("Data Descriptive Files",
ISO standard 8211) such as those specified by the US Geological
Survey's "Spatial Data Transfer Standard" for digital maps.
ISO8211 files from other sources may contain additional data
encodings not recognized by these procedures.
ddfopen(filename) opens a file and returns a handle.
ddfdda(handle) returns a list of header records.
ddfread(handle) reads the next data record.
ddfclose(handle) closes the file.
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ddfopen(filename) opens a DDF file, decodes the header, and
returns an opaque handle for use with subsequent calls. It
fails if any problems are encountered. Instead of a filename,
an already-open file can be supplied.
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ddfdda(handle) returns a list of records containing data
from the Data Descriptive Area (DDA) of the file header.
Each record contains the following fields:
tag DDR entry tag
control field control data
name field name
labels list of field labels
format data format
The records may also contain other fields used internally.
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ddfread(handle) reads the next data record from the file.
It returns a list of lists, with each sublist containing
a tag name followed by the associated data values, already
decoded according to the specification given in the header.
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ddfclose(handle) closes a DDF file.