how to use memblock ? - GameCreators Forum

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dman

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Posted: 19th Feb 2011 19:41

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trying to use memblock in darkbasic pro, trying to skip every fourth bytes of data. how can I implement in code?

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IanM

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Posted: 19th Feb 2011 20:27

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Quote: "trying to skip every fourth bytes of data"

Where's the data coming from, and what will you be doing with the data? Did you mean 'bytes', or 'byte' (I'm guessing you meant use the first three bytes and skip the fourth)?

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dman

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Posted: 19th Feb 2011 20:34 Edited at: 19th Feb 2011 21:25

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yes I meant skip the fourth byte. can you help?

I'm trying to read audio from the memblock.

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enderleit

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Posted: 19th Feb 2011 21:25

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+ Code Snippet

make memblock 1, SizeInBytes
offset = 0

repeat
    write memblock byte 1, offset, bData1
    write memblock byte 1, offset+1, bData2
    write memblock byte 1, offset+2, bData3
    inc offset, 4
until NoMoreData

WRITE MEMBLOCK BYTE MemblockNo, offset(in bytes), ByteToWrite
offset is set to 0, which is the start of the memblock, then after each 3-bytes have been written, you increase the offset by 4. This will move the writing position forward by 4 bytes... Repeat until you have written the data you wanted to write...

- Martin Enderleit
http://sites.google.com/site/menderleit

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dman

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Posted: 19th Feb 2011 21:35 Edited at: 19th Feb 2011 21:41

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I already wrote to the memblock, I'm using get memblock ptr(1) and I'm trying to read the data, for every three bytes and skip the fourth.

ex.

245 <-
100 <-
32 <-
51 <- skip
128 <-
45 <-
80 <-
51 <- skip

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enderleit

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Posted: 19th Feb 2011 21:47 Edited at: 19th Feb 2011 21:50

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+ Code Snippet

pointer as dword
ptr as dword
pointer = get memblock ptr(1)
offset = 0

repeat
    ptr = pointer + offset
        bData1 = (0x000000ff and *ptr)
        bData2 = (0x0000ff00 and *ptr) >> 8
        bData3 = (0x00ff0000 and *ptr) >> 16
    inc offset, 4
until NoMoreData

You might have to change the order of the bData1-3, can't remember if the highest byte comes first or the lowest...

It would probably be easier to read the memblock using the regular memblock commands instead...

bData1 = memblock byte(1, offset)

- Martin Enderleit
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dman

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Posted: 19th Feb 2011 22:12 Edited at: 19th Feb 2011 22:14

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that is what I'm doing, using memblock byte(1,offset)
I tried using this.

if n > offset
inc offset,3
else
memblock byte(1,n)
inc n,1
endif

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enderleit

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Posted: 19th Feb 2011 22:20

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+ Code Snippet

offset = 0

repeat
    for i=0 to 2
        bData(i) = memblock byte(1, offset+i)
    next i
    inc offset, 4
until NoMoreData

Ofcourse you have to change the bData variable to fill in your own variables, and make sure you don't read beyond the size of the memblock... That goes for previous examples aswell...

- Martin Enderleit
http://sites.google.com/site/menderleit

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IanM

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Posted: 19th Feb 2011 23:06

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Why not read a whole dword (or integer) and then mask off the byte you don't want? Wouldn't that be easier?

+ Code Snippet

Top = (memblock size(1) && 0xfffffffc) - 1   ` <- needs testing, but should stop the loop running off the end of the memblock
for i = 0 to Top step 4
    value = memblock dword(1, i) && 0xffffff  ` Mask out high byte
next

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dman

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Posted: 20th Feb 2011 01:16

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thanks for the help everyone I appreciate the help.
It was most helpful.