Implement negative number parsing

strint.asm

@@ -1,3 +1,9 @@
+; Internal convention:
+; r1 - Partially parsed output integer
+; r2 - Parsing position
+; r3 - Character being parsed
+; r4 - Flag set if negative
+
 ; Convert string to integer
 ; Arguments:
 ; r1 - Pointer to string
@@ -9,30 +15,37 @@
 ; r3 - last character read
 ; Note: Unless the input is "0", tail-calls into a base-specific specialization.
 pub atoi:
-load_8 r3, [r1]
-cmp r3, 0x30 ; '0'
-jne atoi_dec ; No prefix, parse decimal
-add r1, r1, 1
-load_8 r3, [r1] ; From "boxBOX", or an octal digit
-cmp r3, 0x30 ; '0'
-jl atoi_badprefix
-cmp r3, 0x37 ; '7'
-jle atoi_oct
-add r1, r1, 1 ; Not octal; 2-byte prefix 
-and r3, r3, 0x5f ; to uppercase
-cmp r3, 0x42 ; 'B'
-je atoi_bin
-cmp r3, 0x4F ; 'O'
-je atoi_oct
-cmp r3, 0x58 ; 'X'
-je atoi_hex
-
-; not a valid prefix, but we did see a zero
-atoi_badprefix:
 mov r2, r1
 mov r1, 0
-; Only exists because conditional register jumps are not allowed
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne atoi_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+load_8 r3, [r2]
+atoi_positive:
+cmp r3, 0x30 ; '0'
+jne atoi_dec_loop       ; No prefix, parse decimal
+add r2, r2, 1
+load_8 r3, [r2]         ; From "boxBOX", or an octal digit
+cmp r3, 0x30 ; '0'
+jl atoi_done
+cmp r3, 0x37 ; '7'
+jle atoi_oct_loop       ; Octal with just '0' prefix
+add r2, r2, 1           ; 2-byte prefix 
+and r3, r3, 0x5F        ; to uppercase
+cmp r3, 0x42 ; 'B'
+je atoi_bin_loop
+cmp r3, 0x4F ; 'O'
+je atoi_oct_loop
+cmp r3, 0x58 ; 'X'
+je atoi_hex_loop
+
+; FALLTHROUGH: not a valid prefix, but we did see a zero
 atoi_done:
+add r1, r1, r4
+xor r1, r1, r4
 jmp r13
 
 ; Convert decimal string to integer
@@ -73,6 +86,11 @@ jmp atoi_dec_loop
 pub atoi_bin:
 mov r2, r1
 mov r1, 0
+load_16 r3, [r2]        ; check for prefix
+and r3, r3, 0xFF5F      ; to uppercase
+cmp r3, 0x3042 ; "0B"
+jne atoi_bin_loop
+add r2, r2, 2
 atoi_bin_loop:
 load_8 r3, [r2]
 cmp r3, 0x30 ; '0'
@@ -97,6 +115,11 @@ jmp atoi_bin_loop
 pub atoi_oct:
 mov r2, r1
 mov r1, 0
+load_16 r3, [r2]        ; check for prefix
+and r3, r3, 0xFF5F      ; to uppercase
+cmp r3, 0x304F ; "0O"
+jne atoi_oct_loop
+add r2, r2, 2
 atoi_oct_loop:
 load_8 r3, [r2]
 cmp r3, 0x30 ; '0'
@@ -121,6 +144,11 @@ jmp atoi_oct_loop
 pub atoi_hex:
 mov r2, r1
 mov r1, 0
+load_16 r3, [r2]        ; check for prefix
+and r3, r3, 0xFF5F      ; to uppercase
+cmp r3, 0x3058 ; "0X"
+jne atoi_oct_loop
+add r2, r2, 2
 atoi_hex_loop:
 load_8 r3, [r2]
 cmp r3, 0x30 ; '0'
@@ -134,7 +162,7 @@ add r1, r1, r3
 jmp atoi_hex_loop
 
 atoi_hex_letter:
-and r3, r3, 0x5f ; to uppercase
+and r3, r3, 0x5F ; to uppercase
 cmp r3, 0x41 ; 'A'
 jl atoi_done
 cmp r3, 0x46 ; 'F'