Implement atoi

Parse strings to integer (binary, octal, decimal, or hexadecimal)

src/stdlib.asm

@@ -3,6 +3,7 @@ pub include imath
 pub include array
 pub include console
 pub include mem
+pub include strint
 
 ; Needs to be last!
 pub include LUTs

src/strint.asm

@@ -0,0 +1,188 @@
+; Internal register assignments:
+; r1 - Partially parsed output integer
+; r2 - Parsing position
+; r3 - Character being parsed
+; r4 - Set to -1 if the input is negative
+
+; Convert string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+; Note: Unless the input is "0", tail-calls into a base-specific specialization.
+pub atoi:
+mov r2, r1
+mov r1, 0
+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
+atoi_positive:
+load_16 r3, [r2]        ; 2-byte prefix "0b", "0o", "0x", etc.
+or r3, r3, 0x20         ; 2nd char to lower case
+add r2, r2, 2
+cmp r3, 0x3062 ; "0b"
+je atoi_bin_loop
+cmp r3, 0x306F ; "0o"
+je atoi_oct_loop
+cmp r3, 0x3078 ; "0x"
+je atoi_hex_loop
+sub r2, r2, 2           ; no matching prefix, move pointer back
+jmp atoi_dec_loop
+
+; Epilogue
+atoi_done:
+add r1, r1, r4          ; If r4 is -1, negate r1. Else it's 0 and no effect.
+xor r1, r1, r4
+mov flags, 0            ; No error
+jmp r13
+
+; Convert decimal string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub atoi_dec:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne atoi_dec_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+atoi_dec_loop:
+load_8 r3, [r2]
+atoi_dec_positive:
+sub r3, r3, 0x30 ; '0'
+cmp r3, 9
+ja atoi_done
+add r2, r2, 1
+lsl flags, r1, 2        ; Use flags to help multiply by 10
+add r1, r1, flags
+lsl r1, r1, 1
+add r1, r1, r3
+jmp atoi_dec_loop
+
+; Convert binary string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub atoi_bin:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne atoi_bin_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+atoi_bin_positive:
+load_16 r3, [r2]        ; check for prefix
+or r3, r3, 0x20         ; 2nd char to lower case
+cmp r3, 0x3062 ; "0b"
+jne atoi_bin_loop
+add r2, r2, 2
+atoi_bin_loop:
+load_8 r3, [r2]
+sub r3, r3, 0x30 ; '0'
+cmp r3, 1
+ja atoi_done
+add r2, r2, 1
+lsl r1, r1, 1
+add r1, r1, r3
+jmp atoi_bin_loop
+
+; Convert octal string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub atoi_oct:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne atoi_oct_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+atoi_oct_positive:
+load_16 r3, [r2]        ; check for prefix
+or r3, r3, 0x20         ; 2nd char to lower case
+cmp r3, 0x306F ; "0o"
+jne atoi_oct_loop
+add r2, r2, 2
+atoi_oct_loop:
+load_8 r3, [r2]
+sub r3, r3, 0x30 ; '0'
+cmp r3, 7
+ja atoi_done
+add r2, r2, 1
+lsl r1, r1, 3
+add r1, r1, r3
+jmp atoi_oct_loop
+
+; Convert hexadecimal string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub atoi_hex:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne atoi_hex_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+atoi_hex_positive:
+load_16 r3, [r2]        ; check for prefix
+or r3, r3, 0x20         ; 2nd char to lower case
+cmp r3, 0x3078 ; "0x"
+jne atoi_hex_loop
+add r2, r2, 2
+atoi_hex_loop:
+load_8 r3, [r2]
+sub r3, r3, 0x30 ; '0'
+cmp r3, 10
+jb atoi_hex_add
+sub r3, r3, 0x11 ; 'A' - '0'
+and r3, r3, 0xdf        ; to lower case
+cmp r3, 5               ; 0-5: 6 letters
+ja atoi_done
+add r3, r3, 10          ; Adjust for digits below
+atoi_hex_add:
+add r2, r2, 1
+lsl r1, r1, 4
+add r1, r1, r3
+jmp atoi_hex_loop