Start new assembler

1 files changed, 84 insertions, 0 deletions

diff --git a/newasm/input.s b/newasm/input.s
new file mode 100644
index 0000000..d9c8c73
--- /dev/null
+++ b/newasm/input.s
@@ -0,0 +1,84 @@
+.syntax unified
+.cpu cortex-m0plus
+.thumb
+
+.type getline, %function
+.global getline
+
+getline:
+        PUSH    {R4, R5, LR}    // save registers
+        MOVS    R4, R0          // put strbuf in R4
+next:   BL      uart_recv       // get a char
+        CMP     R0, 0x03        // end of text (^C)
+        BEQ     cancel          // don't submit, start on next line
+        CMP     R0, 0x04        // end of transmission (^D)
+        BEQ     done            // begin of line done, in a line submit the line
+        CMP     R0, 0x7F        // delete (backspace)
+        BEQ     back            // in a line go back a space, begin of line do nothing
+        CMP     R0, 0x0D        // carriage return (Enter)
+        BEQ     submit          // submit the line
+        CMP     R0, 0x15        // NAK (^U)
+        BEQ     retry           // restart the line
+        // CMP     R0, 0x1B        // Escape (ESC)
+        // BEQ     address         // enter a new address to edit at
+        CMP     R0, 0x20        // start of printable range
+        BLO     next
+        CMP     R0, 0x7E        // end of printable range
+        BHI     next
+good:   BL      uart_send       // echo the printable char
+        STRB    R0, [R4, R5]    // write the printable char
+        ADDS    R5, 1           // increment strbuf offset
+        B       next            // get another char
+cancel: MOVS    R5, 0           // reset offset
+        STRB    R5, [R4, R5]    // write empty string
+        LDR     R0, =crlf       // newline
+        BL      putstr
+        MOVS    R0, 1           // error code 1 (line canceled)
+        POP     {R4, R5, PC}    // return
+done:   TST     R5, R5          // check if offset is zero
+        BNE     submit          // if not zero submit line
+        STRB    R5, [R4, R5]    // clear input buffer
+        LDR     R0, =crlf       // newline
+        BL      putstr
+        MOVS    R0, 2           // error code 2 (end of input)
+        POP     {R4, R5, PC}    // return
+back:   TST     R5, R5          // check if offset is zero
+        BEQ     next            // if so get another char
+        SUBS    R5, 1           // push back offset
+        MOVS    R0, 0           // null byte
+        STRB    R0, [R4, R5]    // delete character
+        MOVS    R0, 0x08        // backspace
+        BL      uart_send       // move cursor back
+        MOVS    R0, '           // space
+        BL      uart_send       // overwrite
+        MOVS    R0, 0x08        // backspace
+        BL      uart_send       // move cursor back again
+        B       next            // get another char
+submit: MOVS    R0, 0           // null byte
+        STRB    R0, [R4, R5]    // terminate string
+        MOVS    R0, 0x0D        // carriage return
+        BL      uart_send
+        MOVS    R0, 0x0A        // line feed
+        BL      uart_send
+        MOVS    R0, 0           // return code 0 (success)
+        POP     {R4, R5, PC}
+retry:  MOVS    R0, 0x08        // backspace
+        MOVS    R1, '           // space
+        MOVS    R2, R5          // repeat once per character
+        MOVS    R5, 0           // reset offset
+        TST     R2, R2          // check if already zero
+1:      BEQ     2f              // while not zero
+        STRB    R0, [R4, R5]    // write backspace
+        ADDS    R5, 1
+        STRB    R1, [R4, R5]    // write space
+        ADDS    R5, 1
+        STRB    R0, [R4, R5]    // write backspace
+        ADDS    R5, 1
+        SUBS    R2, 1           // decrement amount
+        B       1b              // repeat
+2:      STRB    R2, [R4, R5]    // terminate string
+        MOVS    R0, R4          // copy strbuf address
+        BL      putstr          // print backspace sequence
+        MOVS    R5, 0           // null byte and reset offset
+        STRB    R5, [R4]        // write empty string
+        B       next            // get new chars