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52 lines
1.0 KiB
ArmAsm
52 lines
1.0 KiB
ArmAsm
.cpu arm946e-s
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.section "romoffsettosdsector", "ax"
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.syntax unified
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.thumb
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// r0 = rom offset
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// returns sd sector in r0
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// returns cluster shift in r1
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// returns remaining sectors in cluster in lr
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.global rom_offset_to_sd_sector_asm
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.type rom_offset_to_sd_sector_asm, %function
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rom_offset_to_sd_sector_asm:
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push {r4,r5,lr}
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retry:
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ldr r5, romoffsettosdsector_fatDataPtr
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ldmia r5!, {r1,r2,r3,r4} // clusterShift, database, clusterMask, clusterMap[0]
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lsrs r0, r0, #9
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2:
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adds r4, r3, #1
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ands r3, r0
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subs r4, r3
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mov lr, r4 // remaining sectors in cluster
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adds r3, r2
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lsrs r0, r1 // cl
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1:
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ldmia r5!, {r2,r4} // ncl, startSector
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cmp r2, #0
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beq out_of_bounds
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subs r0, r2 // cl -= ncl
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bcs 1b
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adds r0, r2
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adds r0, r4 // + startSector
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subs r0, #2 // - 2
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lsls r0, r1
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adds r0, r3 // r0 = src sector
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pop {r4,r5,pc}
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out_of_bounds:
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movs r0, #0x40
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lsls r0, r0, #9
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b retry
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.balign 4
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.global romoffsettosdsector_fatDataPtr
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romoffsettosdsector_fatDataPtr:
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.word 0x027FF800
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.pool
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.end |