Difference between revisions of "Get Combined Bit Value From Stored Pointer"
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(Created page with " # ROUTINE : GET COMBINED BIT VALUE FROM STORED POINTER # Gets the combined bit value based on a previously stored pointer. The combined value can span several bytes...") |
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| − | # ROUTINE : GET COMBINED BIT VALUE FROM STORED POINTER | + | # ROUTINE: GET COMBINED BIT VALUE FROM STORED POINTER |
# Gets the combined bit value based on a previously stored pointer. The combined value can span several bytes. | # Gets the combined bit value based on a previously stored pointer. The combined value can span several bytes. | ||
# The bits can also be read sequentially with repeated calls to this function. | # The bits can also be read sequentially with repeated calls to this function. | ||
Latest revision as of 19:12, 7 December 2024
# ROUTINE: GET COMBINED BIT VALUE FROM STORED POINTER # Gets the combined bit value based on a previously stored pointer. The combined value can span several bytes. # The bits can also be read sequentially with repeated calls to this function. # Parameters: # r4 = (numBits) Number of bits to combine into the final value # Pseudo-Parameters: Set by Store Combined Bit Value Pointer # *0x8018e47c = (shouldResetReadBitIndex) Whether or not to reset the bit index to read from # *0x801ca650 = (storedPtr) The stored pointer to read bits from # Returns: # r2 = Combined bit value 8012b1ec: 10800028 beq r4,r0,0x8012b290 # if (numBits == 0) 8012b1f0: 00001021 addu r2,r0,r0 # return 0; 8012b1f4: 3c028019 lui r2,0x8019 8012b1f8: 9042e47c lbu r2,-0x1b84(r2) # value = *0x8018e47c 8012b1fc: 00000000 nop 8012b200: 10400006 beq r2,r0,0x8012b21c 8012b204: 00003821 addu r7,r0,r0 # combinedValue = 0 # if (shouldResetReadBitIndex) { 8012b208: 34020007 ori r2,r0,0x0007 8012b20c: 3c018019 lui r1,0x8019 8012b210: ac22e480 sw r2,-0x1b80(r1) # invertedReadBitIndex = 7 8012b214: 3c018019 lui r1,0x8019 8012b218: a020e47c sb r0,-0x1b84(r1) # shouldResetReadBitIndex = false # } 8012b21c: 2484ffff addiu r4,r4,-0x0001 # bitIndex = numBits - 1 8012b220: 2402ffff addiu r2,r0,-0x0001 # -1 8012b224: 1082001a beq r4,r2,0x8012b290 # if (bitIndex == -1) 8012b228: 00e01021 addu r2,r7,r0 # return combinedValue; 8012b22c: 340a0001 ori r10,r0,0x0001 # 1 8012b230: 34090007 ori r9,r0,0x0007 # 7 8012b234: 2408ffff addiu r8,r0,-0x0001 # -1 # do { 8012b238: 3c06801d lui r6,0x801d 8012b23c: 8cc6a6f0 lw r6,-0x5910(r6) # storedPtr 8012b240: 3c038019 lui r3,0x8019 8012b244: 8c63e480 lw r3,-0x1b80(r3) # invertedReadBitIndex 8012b248: 90c20000 lbu r2,0x0000(r6) # storedValue = *storedPtr 8012b24c: 2465ffff addiu r5,r3,-0x0001 # invertedReadBitIndex - 1 8012b250: 3c018019 lui r1,0x8019 8012b254: ac25e480 sw r5,-0x1b80(r1) # invertedReadBitIndex = invertedReadBitIndex - 1 8012b258: 00621007 srav r2,r2,r3 # storedValue >> invertedReadBitIndex 8012b25c: 30420001 andi r2,r2,0x0001 # bitValue = (storedValue >> invertedReadBitIndex) & 0x01 8012b260: 10400002 beq r2,r0,0x8012b26c # if (bitValue != 0) { 8012b264: 008a1004 sllv r2,r10,r4 # 1 << bitIndex 8012b268: 00e23825 or r7,r7,r2 # combinedValue = combinedValue | (1 << bitIndex) # } 8012b26c: 04a10006 bgez r5,0x8012b288 8012b270: 2484ffff addiu r4,r4,-0x0001 # bitIndex = bitIndex - 1 # if (invertedReadBitIndex < 0) { 8012b274: 24c20001 addiu r2,r6,0x0001 # storedPtr + 1 8012b278: 3c018019 lui r1,0x8019 8012b27c: ac29e480 sw r9,-0x1b80(r1) # invertedReadBitIndex = 7 8012b280: 3c01801d lui r1,0x801d 8012b284: ac22a6f0 sw r2,-0x5910(r1) # storedPtr = storedPtr + 1 # } 8012b288: 1488ffeb bne r4,r8,0x8012b238 # } while (bitIndex != -1); 8012b28c: 00e01021 addu r2,r7,r0 # return combinedValue; 8012b290: 03e00008 jr r31 8012b294: 00000000 nop
