First shot at terminal read

sw/kernel/devices/terminal.s

@@ -2,6 +2,9 @@
 
 .autoimport
 
+.importzp tmp1, ptr1
+
+.import _serial_getc
 .export _terminal_read, _terminal_write, _terminal_open, _terminal_close
 
 .data
@@ -10,10 +13,89 @@ terminal_buf: .res 128
 
 .code
 
+; int8_t terminal_read(uint8_t fd, void* buf, uint8_t nbytes);
+; Read up to size-1 (127 max) before the enter key is pressed.
+; A newline character is automatically added.
+; Inputs: int8_t* buf - where input characters are stored
+;         uint8_t n - number of characters to read (max buf size minux 1)
+; Return Value: number of characters read on success, -1 on failure
+; Function: Reads keyboard input
 .proc _terminal_read
+        cmp #$00            ; Check that nbytes is > 0 and < 128
+        beq FAIL
+        cmp #$80
+        bge FAIL
+        sta tmp1            ; Store nbytes in tmp1
+        
+        jsr pushax          ; Check that buf != NULL
+        cmp #$00
+        bne L1
+        cpx #$00
+        bne L1
+        bra FAIL
 
+
+        ; while i < nbytes, store getc into terminal_buf y
+L1:     sta ptr1    
+        stx ptr1+1
+        ldy #$00
+LOOP:   cpy tmp1
+        bge END
+        jsr _serial_getc
+        sta terminal_buf,y
+
+        cmp #$0a            ; If newline, do something
+        bne L2
+        jsr _serial_putc
+        bra END
+
+L2:     cmp #$08            ; Handle backspace
+        bne L3
+        lda tmp1
+        beq LOOP
+        lda #$08
+        jsr _serial_putc
+        dey
+        lda #$00
+        sta terminal_buf,y
+        bra LOOP
+
+L3:     lda terminal_buf,y  ; Normal character
+        sta (tmp1),y
+        jsr _serial_putc
+        iny
+        bra LOOP
+
+END:    phy                 ; Zero out terminal buffer
+        ldy #$00
+        lda #$00
+L4:     sta terminal_buf,y
+        iny
+        cpy #$80
+        blt L4
+
+L5:     ply                 ; End string with NULL
+        lda #$0a
+        sta (ptr1),y
+        iny
+        cpy #$80            ; But not if we are at max
+        bge L6
+        lda #$00
+        sta (ptr1),y
+
+L6:     lda #$00            ; Return - on success
+        rts
+
+FAIL:   lda #$ff            ; return -1 on fail
+        rts
 .endproc
 
+; terminal_write
+; write characters to the terminal
+; Inputs: int8_t* buf - buffer of characters to write
+;         uint8_t n - number of characters to write
+; Return Value: 0 on success, -1 on failure
+; Writes to screen. Only stops after n chars written.
 .proc _terminal_write
 
 .endproc