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add cmd line args
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@barrettotte
barrettotte committed Sep 6, 2021
1 parent 148decb commit 1567971
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7 changes: 6 additions & 1 deletion Makefile
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Expand Up @@ -2,6 +2,8 @@

OUT = bin
BIN = qrcode
BINARGS = "https://github.com/barrettotte" 3

SRC := $(patsubst %.s,%.o,$(wildcard *.s))

AS = arm-none-eabi-as
Expand Down Expand Up @@ -36,7 +38,10 @@ clean:
rm -f qrcode.pbm

qemu: .FORCE
qemu-arm -singlestep -g 1234 $(OUT)/$(BIN)
qemu-arm -singlestep -g 1234 $(OUT)/$(BIN) $(BINARGS)

debug: .FORCE
$(GDB) $(DBGARGS)

test:
./$(OUT)/$(BIN) $(BINARGS)
9 changes: 7 additions & 2 deletions README.md
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Expand Up @@ -24,9 +24,14 @@ I constrained the QR code generation a lot. I just wanted to encode a url, not b
- QR version 4 and below (up to 80 characters with v4-L)
- Mask evaluation not implemented, hardcoded to mask 0 (I think masks only effect scan efficiency)

## Running Locally
## Usage

`Usage: qrcode msg err_lvl`

My primary test - `./bin/qrcode "https://github.com/barrettotte" 3`

error levels: `L=1, M=0, Q=3, H=2`

Requires ARM cross compiler - `apt-get install gcc-arm-linux-gnueabihf`

### Debugging with GDB

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90 changes: 60 additions & 30 deletions main.s
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Expand Up @@ -26,10 +26,14 @@
.data

// error Messages
err_01: .asciz "Invalid error correction level.\n"
err_01: .string "Invalid error correction level.\n"
.equ err_01_len, (.-err_01)
err_02: .asciz "Only QR versions 1-4 are supported.\n"
err_02: .string "Only QR versions 1-4 are supported.\n"
.equ err_02_len, (.-err_02)
err_03: .string "Usage: qrcode msg err_lvl\n"
.equ err_03_len, (.-err_03)
err_04: .string "Message size too large.\n"
.equ err_04_len, (.-err_04)

// lookup tables
tbl_eclvl: // error correction level lookup
Expand Down Expand Up @@ -67,9 +71,8 @@ tbl_ecprops: // error correction config lookup
tbl_rem: .byte 0, 7, 7, 7 // remainder lookup (v1-4)

// variables
msg: .asciz "https://github.com/barrettotte"
.equ msg_len, (.-msg) // (30 bytes) TODO: from cmd line args

msg: .space MAX_DATA_CAP // message (from stdin)
msg_len: .space 1 // message length
out_file: .asciz "qrcode.pbm" // (10 bytes)

version: .space 1 // QR code version (zero indexed)
Expand Down Expand Up @@ -98,24 +101,42 @@ data_bin: .space MAX_PAYLOAD*8 // payload converted to binary ASCII
.text

_start: // ***** program entry point *****
mov r0, #0 // i = 0
mov r1, #msg_len // length; TODO: get from command line args
ldr r2, =msg // pointer; TODO: get from command line args
ldr r0, [sp] // get argv[0] = argc
cmp r0, #3 // check argc
blt bad_argc // if (argc < 3)

save_args: // ***** save command line arguments to memory *****
mov r0, #2 // TODO: get from command line args offset 2=Q
ldr r1, =eclvl_idx // pointer to error correction index
strb r0, [r1] // store error correction index
ldr r1, [sp, #8] // get argv[1]; message
ldr r2, =msg // pointer to message
mov r3, #0 // i = 0
_msg_loop:
ldrb r4, [r1, r3] // c = argv[i]
cmp r4, #0x00 // check loop condition
beq _msg_done // done copy
strb r4, [r2, r3] // msg[i] = c
add r3, r3, #1 // i++
b _msg_loop // while (1)
_msg_done:
cmp r3, #MAX_DATA_CAP // check if message too large
bgt bad_msglen // if (msg_len > MAX)

ldr r4, =msg_len // pointer to message length
strb r3, [r4] // save message length

set_eclvl: // ***** set error correction level *****
ldr r5, [sp, #12] // get argv[2]
ldrb r5, [r5] // error level ASCII
cmp r5, #51 // check '3'
bgt bad_eclvl // if (argv[2] > 51)
cmp r5, #48 // check '0'
blt bad_eclvl // if (argv[2] < 48)

ldr r1, =eclvl_idx // pointer to error correction index
ldrb r0, [r1] // load error correction index
mov r1, #4 // size of error correction table
cmp r0, r1 // check error correction
bhi bad_eclvl // branch if error correction invalid
sub r5, r5, #48 // convert ASCII number to decimal
sub r5, r5, #1 // zero index error correction level
strb r5, [r1] // save error correction index

ldr r1, =tbl_eclvl // pointer to error correction table
ldrb r0, [r1, r0] // lookup error correction value
ldrb r0, [r1, r5] // lookup error correction value
ldr r1, =eclvl // pointer to error correction level
strb r0, [r1] // save error correction level

Expand All @@ -124,10 +145,10 @@ find_version: // ***** find QR version *****
ldr r1, =eclvl_idx // pointer to error correction index
ldrb r1, [r1] // i = eclvl
ldr r2, =tbl_version // pointer to version table
mov r3, #msg_len // load message length
sub r3, r3, #1 // msg_len --; null terminator (TODO: remove ?)
ldr r3, =msg_len // pointer to message length
ldrb r3, [r3] // load message length
ldr r4, =count_ind // pointer to char count indicator
strb r3, [r4] // save msg_len-1 as char count indicator byte
strb r3, [r4] // save msg_len as char count indicator byte
mov r4, #MAX_VERSION // load max QR version supported

version_loop: // ***** search version lookup table *****
Expand Down Expand Up @@ -188,8 +209,8 @@ init_dw: // ***** init data words *****
add r6, r6, #1 // dw_idx++

ldr r2, =msg // pointer to message
mov r5, #msg_len // load msg_len for loop exit
sub r5, r5, #1 // msg_len --; null terminator (TODO: remove ?)
ldr r5, =msg_len // pointer to message length
ldrb r5, [r5] // load msg_len for loop exit
mov r8, #0 // msg_idx = 0
msg_loop: // ***** load message into data words array *****
eor r0, r0, r0 // reset scratch register for low nibble
Expand Down Expand Up @@ -330,6 +351,7 @@ _pay_ecw_next:

ldr r9, =pyld_size // pointer to payload size
strb r4, [r9] // store size of payload

qr_init: // ***** QR matrix init *****
ldr r5, =version // pointer to version
ldrb r5, [r5] // load version
Expand Down Expand Up @@ -364,7 +386,7 @@ qr_bin_loop:
cmp r7, r4 // check loop condition
blt qr_data_loop // while (i < payload_bytes)

qr_remainder:
qr_remainder: // ***** Calculate remainder bits *****
lsl r4, r4, #3 // convert size to bits; 2^3 = 8
ldr r7, =tbl_rem // pointer to remainder table
ldr r6, =version // pointer to version
Expand All @@ -385,7 +407,7 @@ qr_rem_loop:
ldr r7, =pyld_bits // pointer to payload size in bits
strh r4, [r7] // store calculated payload size

qr_fill:
qr_fill: // ****** Populate QR matrix *****
ldr r0, =qr_mat // pointer to QR matrix
mov r2, r11 // pass qr_width
ldr r3, =version // pointer to version
Expand All @@ -406,24 +428,32 @@ qr_fill:
bl qr_quiet // add quiet zone to QR matrix
add r2, r2, #8 // add quiet zone width

qr_pbm: // ***** Output QR matrix to PBM file *****
bl qr_normalize // normalize QR matrix to ['0','1']
ldr r1, =out_file // pointer to PBM file name
mov r3, r2 // use width for PBM width + length (square)
bl pbm_write // create new PBM file from QR matrix

nop // ****************************************************************
nop // END OF PROGRAM !!!! TODO: remove when finished developing
nop // ****************************************************************
b _end // end of main program flow

b _end
bad_eclvl: // ***** invalid error correction level *****
ldr r1, =err_01 // pointer to buffer address
mov r2, #err_01_len // length
mov r2, #err_01_len // string length
b error_exit // exit program with error

bad_version: // ***** invalid version *****
ldr r1, =err_02 // pointer to buffer address
mov r2, #err_02_len // length
mov r2, #err_02_len // string length
b error_exit // exit program with error

bad_argc: // ***** invalid arguments *****
ldr r1, =err_03 // pointer to buffer address
mov r2, #err_03_len // string length
b error_exit // exit program with error

bad_msglen: // ***** invalid message length *****
ldr r1, =err_04 // pointer to buffer address
mov r2, #err_04_len // string length
b error_exit // exit program with error

error_exit: // ***** exit with error *****
Expand Down

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