diff options
Diffstat (limited to 'newasm/input.s')
| -rw-r--r-- | newasm/input.s | 84 |
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 |