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Add a memory insertion routine to swap the end block into middle of a block
author William Astle <lost@l-w.ca>
date Tue, 09 Jul 2024 22:18:30 -0600
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children e49bd0493baf
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3a4cb89a419c Add a memory insertion routine to swap the end block into middle of a block
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1 *pragmapush list
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2 *pragma list
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3 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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4 ; Insert the sequence of bytes at U, of length D, at X. The memory from X to (U+D-1) is assumed to be a continguous
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5 ; block and that D bytes of free memory are not available at U+D. That is, this is an in-place insertion of D bytes at
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6 ; the end of a memory block into said memory block.
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7 ;
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8 ; This works in two stages. As long as there are more than D bytes between X and U, a full copy that swaps the data
3a4cb89a419c Add a memory insertion routine to swap the end block into middle of a block
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9 ; at U with the data at X is done and then X is advanced by D bytes. Once there are less than D bytes between X and U,
3a4cb89a419c Add a memory insertion routine to swap the end block into middle of a block
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10 ; a byte by byte insertion process is run.
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11 ;
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12 ; Without the first phase, U-X bytes must by copied D times making the process O((U-X)*D). However, the first phase
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13 ; will run FLOOR((U-X)/D) times, each time swapping exactly D bytes, but at basically twice the cost per byte and then
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14 ; only the remainder needs to be copied on the byte by byte sequence meaning each byte sequence will have to shift
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15 ; (U-X)%D bytes. This will show the biggest gain for larger insertion sizes inserted a fairly large number of bytes
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16 ; before the end of the memory block.
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17 ;
3a4cb89a419c Add a memory insertion routine to swap the end block into middle of a block
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18 ; Entry:
3a4cb89a419c Add a memory insertion routine to swap the end block into middle of a block
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19 ; X Insertion point
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20 ; U Source data
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21 ; D Length of source data (must not be zero)
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22 ;
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23 ; Exit:
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24 ;
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25 ; DO NOT ENTER WITH D SET TO 0
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26 mem_insert pshs d,u ; save the length and insertion point
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27 mem_insert0 leay d,x ; point to the end of this copy iteration
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28 cmpy 2,s ; is there room for a full iteration?
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29 bhi mem_insert2 ; brif not
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30 tfr d,y ; get copy length somewhere usfule
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31 mem_insert1 ldb ,x ; swap a byte
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32 lda ,u
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33 sta ,x+
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34 stb ,u+
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35 leay -1,y ; done this iteration?
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36 bne mem_insert1 ; brif not
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37 ldd ,s ; get back length
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38 ldu 2,s ; get back source pointer
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39 cmpx 2,s ; did we actually finish?
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40 bne mem_insert0 ; brif not
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41 puls d,x,pc ; we're done - clean up stack and return
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42 mem_insert2 ldy ,s ; get number bytes to insert one by one
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43 mem_insert3 pshs x,u ; save the pointers
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44 lda ,u ; get byte at top of move range
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45 mem_insert4 ldb ,-u
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46 stb 1,u
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47 cmpu ,s
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48 bne mem_insert4
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49 puls x,u ; get back original pointers
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50 sta ,x+ ; save new byte in insert location
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51 leau 1,u ; move to next source byte
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52 leay -1,y ; done all source bytes?
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53 bne mem_insert3 ; brif not
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54 puls d,x,pc ; clean up stack and return
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55 *pragmapop list