CFD Utilities Files

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!
      program extract_blocks
!
!     Description:
!
!        EXTRACT_BLOCKS extracts a list of blocks from a multiblock grid and an
!     optional "q" file (or rather a PLOT3D-type function file).
!
!        This version can handle "iblanked" files at the cost of another prompt.
!
!     Control file ('extract_blocks.inp'):
!
!        This should contain a list of block numbers, any order/one per line.
!     E.g.:
!
!        1        or perhaps to reorder the blocks:       3
!        3                                                1
!        7                                                9
!        :                                                :
!        15                                              12
!
!        [Originally, ascending order was expected, as this enabled efficient
!         I/O.  But it is better to allow extraction of blocks in any order, at
!         the expense of having to read and store all input blocks before the
!         output blocks are written in any indicated order.]
!
!     Procedures:
!
!        XYZQ_IO package  I/O utilities for PLOT3D grid and function files
!
!     History:
!
!        04/06/04  D.A.Saunders  Initial adaptation of GRID_FACES.
!        07/02/10    "      "    Extended to handle OVERFLOW solutions.
!        06/16/25    "      "    Introduced plot3d_order = T to speed up
!                                scanning of function files.
!        08/11/25    "      "    It took 21 years before an attempt to use this
!                                utility to reorder all blocks revealed the
!                                flaw in requiring that the input block numbers
!                                should be in ascending order (for efficient I/O
!                                reasons).  Memory is cheap, so simply store all
!                                input blocks before writing them in the desired
!                                order.
!
!     Author:  David Saunders, ELORET Corporation/NASA Ames Research Center, CA
!                              Later with AMA, Inc. at NASA ARC.
!
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