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160
I/O Handling
The following is an example of a typical call to these utilities to read a record from mass
storage -
ISG~2CE
Number"
BSS
.L : :::
~
1.,1
.=
!"':.; ....
r"
:
.....
~.
:
"':
:,...
...
············:!f.:::··········
:1.
:::1 .:::
t ::::
v', .:.;
F'
v', .... :'.
::::j
~::.~) .~
1:···:1ii ..
.:r:.=.,,_i::: .
.: r
o
"
;;;~:::
. L .::::1,):."=1"::
i
: .. -
Writing to Mass Storage
Writing to mass storage is very much like reading from it. The flow of data is buffered. To get
the data from the user space into the device buffer, and then to transfer the data from the buffer
to the mass storage device, the Mm _write_start utility is used. Then a test can be made to
determine when the transfer is complete by using the Mm _write _test utility.
As with the reading utilities, these utilities accomplish their purposes with the help of the same
two locations - MSD and MSTID. They contain the same information as they do in the reading
utilities and are used in a similar fashion.
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