From 6a804a9c64a30752535e8d3dc05b09de48b27fbf Mon Sep 17 00:00:00 2001
From: Virgil Dupras <hsoft@hardcoded.net>
Date: Fri, 10 May 2019 19:55:01 -0400
Subject: [PATCH] zasm: buffer stdin in emulator

Also, add a port for rewinding stdin.
---
 tools/emul/zasm.c | 32 ++++++++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/tools/emul/zasm.c b/tools/emul/zasm.c
index b7772e2..adaca66 100644
--- a/tools/emul/zasm.c
+++ b/tools/emul/zasm.c
@@ -18,24 +18,32 @@
  * I/O Ports:
  *
  * 0 - stdin / stdout
+ * 1 - When written to, rewind stdin buffer to the beginning.
  */
 
 // in sync with zasm_glue.asm
 #define USER_CODE 0x4800
 #define STDIO_PORT 0x00
+#define STDIN_REWIND 0x01
 
+// Other consts
+#define STDIN_BUFSIZE 0x8000
 static Z80Context cpu;
-static uint8_t mem[0xffff];
+static uint8_t mem[0x10000];
+// STDIN buffer, allows us to seek and tell
+static uint8_t inpt[STDIN_BUFSIZE];
+static int inpt_size;
+static int inpt_ptr;
 
 static uint8_t io_read(int unused, uint16_t addr)
 {
     addr &= 0xff;
     if (addr == STDIO_PORT) {
-        int c = getchar();
-        if (c == EOF) {
+        if (inpt_ptr < inpt_size) {
+            return inpt[inpt_ptr++];
+        } else {
             return 0;
         }
-        return c;
     } else {
         fprintf(stderr, "Out of bounds I/O read: %d\n", addr);
         return 0;
@@ -47,6 +55,8 @@ static void io_write(int unused, uint16_t addr, uint8_t val)
     addr &= 0xff;
     if (addr == STDIO_PORT) {
         putchar(val);
+    } else if (addr == STDIN_REWIND) {
+        inpt_ptr = 0;
     } else {
         fprintf(stderr, "Out of bounds I/O write: %d / %d\n", addr, val);
     }
@@ -71,6 +81,20 @@ int main()
     for (int i=0; i<sizeof(USERSPACE); i++) {
         mem[i+USER_CODE] = USERSPACE[i];
     }
+    // read stdin in buffer
+    inpt_size = 0;
+    inpt_ptr = 0;
+    int c = getchar();
+    while (c != EOF) {
+        inpt[inpt_ptr] = c & 0xff;
+        inpt_ptr++;
+        if (inpt_ptr == STDIN_BUFSIZE) {
+            break;
+        }
+        c = getchar();
+    }
+    inpt_size = inpt_ptr;
+    inpt_ptr = 0;
     Z80RESET(&cpu);
     cpu.ioRead = io_read;
     cpu.ioWrite = io_write;