progress on serial and added editor

dsa_resources/serial.dsa

@@ -1,63 +1,116 @@
-// lib:
-// serial.dsa
-//
-// usage:
-//   include serial "<relative path>"
-//
-//   push (register containing address of string)
-//   call serial::print
-//
-//   push (register containing byte)
-//   call serial::print_byte
-
 dw uart: 0x40000
-
 // ------------------------------------------
-// transmit a single byte via sentinel protocol
-// expects: byte in rg0, trashes rg2, rg3, rg4, rg5
+// reads up to rg1 bytes into buffer at rg2
+// args: buf_size @ bpr+8, buf_addr @ bpr+12
+// returns: 0 in bpr+8 on success, 1 on nullptr error
+buf_read: func
+    push rg0
+    push rg1
+    push rg2
+    push rg3
+    ldw bpr, rg1, 8         // buf size
+    ldw bpr, rg2, 12        // buf addr
+    jez rg2, _buf_read_err  // return err if nullptr
+_buf_read_loop:
+    jez rg1, _buf_read_end
+    call read_byte
+    ldw bpr, rg3, 8         // read return value from frame
+    stb rg3, rg2            // store into buffer
+    addi rg2, 1, rg2
+    subi rg1, 1, rg1
+    jmp _buf_read_loop
+_buf_read_end:
+    stw zero, bpr, 8        // return 0 (success)
+    pop rg3
+    pop rg2
+    pop rg1
+    pop rg0
+    return
+_buf_read_err:
+    lli 1, rg0
+    stw rg0, bpr, 8         // return 1 (error)
+    pop rg3
+    pop rg2
+    pop rg1
+    pop rg0
+    return
+
+// read_byte: emulator → kernel
+// reads data from base+0x00, valid flag at base+0x01
+read_byte: func
+    push rg0
+    push rg1
+    push rg2
+    ldw uart, rg1
+_serial_read_wait:
+    ldb rg1, rg0, 1         // base+0x01 = read valid flag
+    lli 0x01, rg2
+    ieq rg0, rg2, rg2
+    jnz rg2, _serial_read_ready
+    hlt
+    jmp _serial_read_wait
+_serial_read_ready:
+    ldb rg1, rg0, 0         // base+0x00 = data byte
+    stb zero, rg1, 1        // clear read valid flag
+    stb rg0, bpr, 8         // return byte
+    pop rg2
+    pop rg1
+    pop rg0
+    return
+
+// _serial_send: kernel → emulator
+// writes data to base+0x02, valid flag to base+0x03
 _serial_send:
-    shl rg0, 16, rg2        // shift byte to bits [23:16]
-    lli 0x01, rg0
-    shl rg0, 24, rg0        // valid flag in bits [31:24]
-    or rg0, rg2, rg2        // rg2 = 0x01_XX_0000
-
-    ldw uart, rg5           // rg5 = 0x40000 (uart address, held for store)
-
+    push rg0
+    push rg2
+    push rg3
+    push rg4
+    push rg5
+    ldw uart, rg5
 _serial_wait:
-    ldw rg5, rg0            // poll mem[0x40000]
-    shr rg0, 24, rg0
+    ldb rg5, rg2, 3         // base+0x03 = write valid flag
     lli 0x01, rg3
-    ieq rg0, rg3, rg4
-    jnz rg4, _serial_wait   // loop while valid == 1
-
-    stw rg2, rg5            // mem[0x40000] = sentinel word
+    ieq rg2, rg3, rg4
+    jnz rg4, _serial_wait   // wait while emulator hasn't consumed yet
+    stb rg0, rg5, 2         // base+0x02 = data byte
+    lli 0x01, rg2
+    stb rg2, rg5, 3         // base+0x03 = set valid flag
+    pop rg5
+    pop rg4
+    pop rg3
+    pop rg2
+    pop rg0
     ret
-
 // ------------------------------------------
 // prints the null-terminated string at addr(arg[0])
 print: func
+    push rg0
+    push rg1
+    push rg2
     ldw bpr, rg0, 8         // load string address from arg
-
 _serial_print_loop:
-    ldb rg0, rg2            // load byte
-    ieq rg2, zero, rg4      // null terminator?
-    jnz rg4, _serial_end
-
+    ldb rg0, rg1            // load byte
+    ieq rg1, zero, rg2      // null terminator?
+    jnz rg2, _serial_print_end
     push rg0                // save string pointer
-    mov rg2, rg0
+    mov rg1, rg0
     call _serial_send
     pop rg0
-
-    addi rg0, 1
+    addi rg0, 1, rg0
     jmp _serial_print_loop
-
+_serial_print_end:
+    pop rg2
+    pop rg1
+    pop rg0
+    jmp _serial_end
 // ------------------------------------------
 // prints the last byte of arg[0]
 print_byte: func
+    push rg0
     ldw bpr, rg0, 8
     call _serial_send
+    pop rg0
     jmp _serial_end
-
 // ------------------------------------------
 _serial_end:
     return