79 lines
2.2 KiB
Tal
79 lines
2.2 KiB
Tal
( alloc.tal )
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( )
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( simple arena allocator )
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( )
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( the idea here is to pre-allocate a large arena of memory )
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( and then keep a pointer to the first unallocated byte. )
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( memory is released in reverse order of when it was allocated. )
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( )
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( in this example we're preallocating 16,384 bytes (#4000) )
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( located at mem-arena. we're using mem-cursor to point to )
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( the next unallocated byte. )
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( )
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( if mem-cursor ever contains the address of mem-cursor it )
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( means we've reached the limit of what we can allocate. )
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( we raise divide-by-zero errors if we cannot allocate )
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( or release memory as requested. )
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( )
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( memory can be freed by size (number of bytes) or cleared )
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( all at once. )
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( macro to allocate one byte of memory )
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%mem-alloc-byte { #0001 ;mem-alloc JMP2r } ( -> addr* )
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( macro to allocate two bytes of memory )
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%mem-alloc-short { #0002 ;mem-alloc JMP2r } ( -> addr* )
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( macro to allocate an 8-bit count of memory (n) )
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%mem-alloc8 { #00 SWP ;mem-alloc JMP2r } ( n^ -> addr* )
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( macro to allocate a 16-bit count of memory (n) )
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%mem-alloc16 { ;mem-alloc JMP2r } ( n* -> addr* )
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|10 @Console [ &vector $2 &read $1 &pad $5 &write $1 ]
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|0100
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;mem-init JSR2
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;on-input .Console/vector DEO2
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;mem-cursor LDA2 ;start STA2
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BRK
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@start $2
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@on-input
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.Console/read DEI DUP ,&continue JCN
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( ;on-complete JSR2 ) POP BRK
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&continue ( mem-alloc-byte STA ) BRK
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@on-complete
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;mem-cursor LDA2 STH2
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;start LDA2
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&loop
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DUP2 STH2kr LTH2 ,&continue JCN
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;mem-init JSR2 POP2 POP2r JMP2r
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&continue
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LDA2k .Console/write DEO
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INC2 ,&loop JMP
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( allocate n bytes of memory )
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@mem-alloc ( n* -> addr* )
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;mem-cursor LDA2 ADD2 DUP2 ( new-addr new-addr )
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;mem-cursor LTH2 ,&ok JCN DIV2 #0000 ( fail if we reach mem-cursor's own address )
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&ok DUP2 ;mem-cursor STA2 JMP2r
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( initialize memory, release all allocated memory )
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@mem-init ( -> )
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;mem-arena ;mem-cursor STA2 JMP2r
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( release n bytes of allocated memory )
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@mem-release ( n* -> )
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;mem-cursor LDA2 SUB2 DUP2 ( new-addr new-addr )
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;mem-arena LTH2 ,&fail JCN ;mem-cursor STA2 JMP2r
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&fail DIV2 #0000 ( fail if we reach beyond mem-arena's own address )
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( location of the memory to be allocated )
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@mem-arena $4000
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( pointer to the next free byte, if any )
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@mem-cursor $2
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