z80dis: allow disassembly at an offset other than zero

Take an optional argument which is the base address of the file being
disassembled.

1 files changed, 17 insertions, 5 deletions

diff --git a/tools/z80dis.c b/tools/z80dis.c
index fb26c89..774b61f 100644
--- a/tools/z80dis.c
+++ b/tools/z80dis.c
@@ -1,8 +1,9 @@
 #include <stdio.h>
 #include <string.h>
 #include <ctype.h>
+#include <stdlib.h>
 
-int Counter;
+unsigned int Counter;
 
 char *Mnemonics[256] =
 {
@@ -350,9 +351,20 @@ int main(argc,argv)
 {
   FILE *F;  
     
-  if(argc!=2) return(1);
-  if(!(F=fopen(argv[1],"rb"))) return(2);
+  if(argc < 2) {
+    fprintf(stderr, "Usage: %s filename [offset]\n", argv[0]);
+    return 1;
+  }
+
+  if(!(F=fopen(argv[1],"rb"))) {
+    perror(argv[1]);
+    return 2;
+  }
   
-  Counter=0;
-  while(DAsm(F));fclose(F);return(0);
+  Counter = (argc > 2) ? strtoul(argv[2], NULL, 0) : 0;
+  while(DAsm(F))
+    ;
+  fclose(F);
+
+  return 0;
 }