Int to string conversion

Initially only binary output

src/errno.asm

@@ -21,6 +21,9 @@ pub const SCREEN_INVALID_WIDTH = 0x0003
 pub const SCREEN_FB_TOO_SMALL  = 0x0005
 pub const SCREEN_OUTSIDE_FB    = 0x0007
 
+pub const INTTOSTR_BAD_BASE    = 0x0101
+pub const INTTOSTR_BAD_BUFFER  = 0x0103
+
 pub const MAGIC_BAD            = 0x8001
 
 ; Extended error codes, these would require loading a 32 bit value.

src/int_to_string.asm

@@ -0,0 +1,66 @@
+include errno
+
+; Convert integer to string
+; Arguments:
+; r1 - Integer
+; r2 - Start of buffer
+; r3 - Buffer length
+; r4 - Base (2, 8, 10, or 16)
+; Result:
+; none
+; Clobbers:
+; Based on specialization
+pub auto:
+cmp r4, 2
+je bin
+mov flags, errno.INTTOSTR_BAD_BASE
+jmp r13
+
+; Convert integer to binary string
+; Arguments:
+; r1 - Integer
+; r2 - Start of buffer (assumed 'big enough')
+; r3 - Buffer length (ignored)
+; Result:
+; none
+; Clobbers:
+; flags
+; r4 - counter
+; r5 - result character
+pub bin:
+mov r4, 31
+cmp r2, 2
+jl badbuffer
+
+bin_find_one:
+lsr r5, r1, r4          ; Select bit and advance counter
+and r5, r5, 1
+sub r4, r4, 1
+
+cmp r4, 0               ; Start printing if last bit ...
+jl bin_print
+cmp r5, zr              ; .. or if nonzero
+je bin_find_one
+
+add flags, r4, 3        ; Check buffer size
+cmp flags, r3
+ja badbuffer
+
+bin_print:
+add r5, r5, 0x30 ; '0'  ; Add digit to buffer
+store_8 [r2], r5
+add r2, r2, 1
+cmp r4, 0               ; Done if last bit
+jl done
+lsr r5, r1, r4          ; Select bit and advance counter
+and r5, r5, 1
+sub r4, r4, 1
+jmp bin_print
+
+badbuffer:
+mov flags, errno.INTTOSTR_BAD_BUFFER
+jmp r13
+
+done:
+store_8 [r2], zr
+jmp r13

src/stdlib.asm

@@ -3,7 +3,9 @@ pub include imath
 pub include array
 pub include console
 pub include mem
+pub include string
 pub include string_to_int
+pub include int_to_string
 
 ; Needs to be last!
 pub include LUTs

src/string.asm

@@ -0,0 +1,33 @@
+; Compare two strings
+; Arguments:
+; r1 - Pointer to string 1
+; r2 - Pointer to string 2
+; Result:
+; r1:
+;   -  `0` if both segments are equal.
+;   - `<0` if the first segment is less than the second segment.
+;   - `>0` if the first segment is greater than the second segment.
+; flags - Compare result
+; Clobbers:
+; r3 - last byte of r1 tested
+; r4 - last byte of r2 tested
+pub compare:
+load_8 r3, [r1]
+add r1, r1, 1
+load_8 r4, [r2]
+add r2, r2, 1
+cmp zr, r3              ; End of string 1
+je done
+cmp zr, r4              ; End of string 2
+je done
+cmp r3, r4
+je compare              ; Loop, tail recursion, what's the difference
+done:
+cmp r3, r4
+; `flags` is the comparison result in the format of `cmp`. Convert it to the desired format.
+; 00 => 0x40000000 > 0
+; 01 => 0x00000000 = 0
+; 10 => 0xC0000000 < 0
+xor r1, flags, 1
+lsl r1, r1, 30
+jmp r13

tests/int_to_string_test.asm

@@ -0,0 +1,49 @@
+; test harness for int_to_string
+; Registers:
+; r8 - test address
+; r9 - test method
+; r12 - end of tests address
+li r8, tests
+li r12, end_of_tests
+next_test:
+; Set up arguments and run test
+load_32 r1, [r8]        ; Input value
+li r2, scratch          ; Output buffer
+mov r3, 64              ; Output buffer size
+add r4, r8, 4           ; Base
+load_8 r4, [r4]
+mov r13, itoa_test_ret  ; return address
+jmp stdlib.int_to_string.auto
+itoa_test_ret:
+
+; Strcmp to check results
+add r1, r8, 5           ; expected output
+li r2, scratch          ; actual output
+mov r13, itoa_strcmp_ret
+jmp stdlib.string.compare
+itoa_strcmp_ret:
+
+; Verify results
+halt.ne
+
+; Next test
+add r8, r8, 0x40
+cmp r8, r12
+jl next_test
+
+; Done
+halt
+
+include ../src/stdlib
+
+@0x20000
+tests:
+; inlen is the number of input bytes the function is expected to consume
+; addr   int            base  result
+@0x20000 U32 0b0        U8 2  "0\0"
+@0x20040 U32 0xFFFFFFFF U8 2  "11111111111111111111111111111111\0"
+@0x20080 U32 0b101010   U8 2  "101010\0"
+@0x200c0
+end_of_tests:
+scratch: U1024 0
+