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Chapter 11 Accessing a File Using Mapped Access

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E0300 Edition 6 ♥
E0692 Edition 5

Table of Contents
How to Access a File Mapped
Advantages of mapped access
Short-mapped access
Long-mapped access
Large-mapped access
Opening a File Mapped
New Intrinsics
HPFADDTOPOINTER
HPFFILLDATA
HPFMOVEDATA
HPFMOVEDATALTOR
HPFMOVEDATARTOL
A major enhancement to the MPE/iX file system is mapped file access, a method that allows you to access a file directly through memory load and store instructions. Mapped file access is available through three HPFOPEN intrinsic optional parameters:

  • Item #18 short-mapped option returns a 32-bit value of type address.

  • Item #21 long-mapped option returns a 64-bit value of type address.

  • Item #87 large-mapped option returns a 64-bit value of type address. Long-mapped and large-mapped options are identical with the exception that attempts to open a file larger than 4GB - 64KB with the long-mapped option will result in a failure. The large-mapped option may be used to open any file and is therefore considered more reliable.



Chapter 10 Updating a File

How to Access a File Mapped