273 lines
4.5 KiB
NASM
273 lines
4.5 KiB
NASM
//==============================================================================
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// http://en.wikipedia.org/wiki/Double_dabble
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// int bin_to_bcd(int binary)
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// In:
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// r0: binary number
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// Out:
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// r0: BCD-coded number
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// r1: amount of digits used
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//==============================================================================
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bin_to_bcd:
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push {r2-r7,lr}
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mov r2,r8
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mov r3,r9
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push {r2-r3}
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lsl r0,r0,5
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mov r1,0
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mov r3,27
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mov r4,3
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lsl r4,r4,8
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lsl r5,r4,4
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lsl r6,r5,4
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lsl r7,r6,12
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mov r9,r7
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lsl r7,r6,8
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mov r8,r7
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lsl r7,r6,4
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//--------------------------------
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@@prev:
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// Ones
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lsl r2,r1,28
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lsr r2,r2,28
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cmp r2,5
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bcc @@next
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add r1,r1,3
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@@next:
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// Tens
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lsl r2,r1,24
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lsr r2,r2,28
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cmp r2,5
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bcc @@next2
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add r1,0x30
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@@next2:
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// Hundreds
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lsl r2,r1,20
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lsr r2,r2,28
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cmp r2,5
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bcc @@next3
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add r1,r1,r4
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@@next3:
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// Thousands
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lsl r2,r1,16
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lsr r2,r2,28
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cmp r2,5
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bcc @@next4
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add r1,r1,r5
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@@next4:
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// Ten-thousands
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lsl r2,r1,12
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lsr r2,r2,28
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cmp r2,5
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bcc @@next5
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add r1,r1,r6
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@@next5:
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// Hundred-thousands
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lsl r2,r1,8
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lsr r2,r2,28
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cmp r2,5
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bcc @@next6
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add r1,r1,r7
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@@next6:
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// Millions
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lsl r2,r1,4
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lsr r2,r2,28
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cmp r2,5
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bcc @@next7
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add r1,r8
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@@next7:
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// Ten-millions
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lsr r2,r2,28
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cmp r2,5
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bcc @@next8
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add r1,r9
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@@next8:
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// Shift
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lsl r1,r1,1
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tst r0,r0
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bpl @@next9
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add r1,r1,1
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@@next9:
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lsl r0,r0,1
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sub r3,r3,1
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bne @@prev
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mov r0,r1
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//--------------------------------
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// Check how many digits are used
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mov r3,1
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@@prev2:
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lsr r1,r1,4
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beq @@next10
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add r3,r3,1
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b @@prev2
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@@next10:
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//--------------------------------
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mov r1,r3
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pop {r2-r3}
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mov r8,r2
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mov r9,r3
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pop {r2-r7,pc}
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//==============================================================================
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// int bcd_to_bin(int bcd)
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// In:
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// r0: BCD-coded number
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// Out:
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// r0: binary number
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//==============================================================================
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bcd_to_bin:
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push {r1-r4,lr}
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mov r1,0
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mov r2,10
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mov r3,1
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//--------------------------------
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// Ones
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lsl r4,r0,28
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lsr r4,r4,28
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mul r4,r3
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add r1,r1,r4
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mul r3,r2
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// Tens
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lsl r4,r0,24
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lsr r4,r4,28
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mul r4,r3
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add r1,r1,r4
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mul r3,r2
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// Hundreds
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lsl r4,r0,20
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lsr r4,r4,28
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mul r4,r3
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add r1,r1,r4
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mul r3,r2
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// Thousands
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lsl r4,r0,16
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lsr r4,r4,28
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mul r4,r3
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add r1,r1,r4
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mul r3,r2
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// Ten-thousands
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lsl r4,r0,12
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lsr r4,r4,28
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mul r4,r3
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add r1,r1,r4
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mul r3,r2
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// Hundred-thousands
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lsl r4,r0,8
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lsr r4,r4,28
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mul r4,r3
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add r1,r1,r4
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mul r3,r2
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// Millions
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lsl r4,r0,4
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lsr r4,r4,28
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mul r4,r3
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add r1,r1,r4
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mul r3,r2
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// Ten-millions
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lsr r4,r0,28
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mul r4,r3
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add r1,r1,r4
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//--------------------------------
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mov r0,r1
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pop {r1-r4,pc}
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//==============================================================================
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// ushort format_cash(int amount, char* output, int digits)
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// In:
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// r0: amount
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// r1: output string
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// r2: digits
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// Out:
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// r0: = digits - (digits rendered) - 1
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//==============================================================================
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format_cash:
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push {r1-r7,lr}
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mov r4,r1
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mov r6,r2
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//--------------------------------
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// Figure out how many digits we need
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bl bin_to_bcd
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mov r5,r1
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mov r7,r1
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// The window is 56 pixels wide:
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// each digit uses 6 pixels, the 0x sign uses 6, and the
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// double-zero uses 8
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mov r2,42 // = 56 - 6 - 8
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lsl r3,r1,2
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add r3,r3,r1
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add r1,r1,r3 // r1 *= 6
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sub r1,r2,r1 // r1 = 42 - r1
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// Store the control code to the output
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mov r2,0x5F
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strb r2,[r4,0]
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mov r2,0xFF
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strb r2,[r4,1]
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strb r1,[r4,2]
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// Store the dollar sign
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mov r2,0x54
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strb r2,[r4,3]
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add r4,r4,4
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// Store the digits to the output
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mov r2,8
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sub r2,r2,r5
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lsl r2,r2,2
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lsl r0,r2 // Now the number is pushed to the left of the register
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@@prev:
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lsr r1,r0,28 // Get the left-most digit
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add r1,0x60 // Integer-to-char
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strb r1,[r4,0]
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add r4,r4,1
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lsl r0,r0,4
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sub r5,r5,1
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bne @@prev
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// Store the double-zero sign
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mov r1,0x56
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strb r1,[r4,0]
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// Store the end code
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mov r1,0
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strb r1,[r4,1]
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mov r1,0xFF
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strb r1,[r4,2]
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//--------------------------------
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sub r5,r6,r7
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sub r0,r5,1
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pop {r1-r7,pc}
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