zasm: implement stdin/stdout in emulator

apps/zasm/emul/wrapper.asm

@@ -4,10 +4,12 @@ ld	sp, hl
 ; zasm input
 ld	hl, 0x9000
 ; zasm output
-ld	hl, 0xc000
+ld	de, 0xc000
 call	zasm
 ; signal the emulator we're done
-out	(0), a
+; BC contains the number of written bytes
+ld	a, b
+out	(c), a
 halt
 zasm:
 ; beginning of the code

apps/zasm/emul/zasm.c

@@ -1,4 +1,5 @@
 #include <stdint.h>
+#include <stdio.h>
 #include "libz80/z80.h"
 #include "wrapper.h"
 #include "zasm.h"
@@ -10,9 +11,17 @@
  * zasm in a special wrapper, wait until we receive the stop signal, then
  * spit the contents of the dest memory to stdout.
  */
+
+// in sync with wrapper.asm
+#define READFROM 0x9000
+#define WRITETO 0xc000
+
 static Z80Context cpu;
 static uint8_t mem[0xffff];
 static int running;
+// Number of bytes written to WRITETO
+// We receive that result from an OUT (C), A call. C contains LSB, A is MSB.
+static uint16_t written;
 
 
 static uint8_t io_read(int unused, uint16_t addr)
@@ -22,8 +31,7 @@ static uint8_t io_read(int unused, uint16_t addr)
 
 static void io_write(int unused, uint16_t addr, uint8_t val)
 {
-    // zasm doesn't do any IO. If we receive any IO, it means that we're done
-    // because the wrapper told us through an "out"
+    written = (val << 8) + (addr & 0xff);
     running = 0;
 }
 
@@ -48,6 +56,13 @@ int main()
     for (int i=0; i<zasm; i++) {
         mem[i+wrapperlen] = ZASM[i];
     }
+    int ptr = READFROM;
+    int c = getchar();
+    while (c != EOF) {
+        mem[ptr] = c;
+        ptr++;
+        c = getchar();
+    }
     // Run!
     running = 1;
     Z80RESET(&cpu);
@@ -59,6 +74,9 @@ int main()
     while (running) {
         Z80Execute(&cpu);
     }
-    printf("and... %d!\n", mem[0x100]);
+
+    for (int i=0; i<written; i++) {
+        putchar(mem[WRITETO+i]);
+    }
     return 0;
 }

apps/zasm/zasm.asm

@@ -1,4 +1,6 @@
 ; dummy code, to test emulator
-ld	a, 0x42
-ld	(0x100), a
+ld	a, (hl)
+inc	a
+ld	(de), a
+ld	bc, 1
 ret