From 12fdea5b21b1292214852c148dd2585e5381e1d3 Mon Sep 17 00:00:00 2001
From: Olaf Seibert <rhialto@falu.nl>
Date: Tue, 19 May 2015 00:56:40 +0200
Subject: [PATCH] Adapt the generating and dumping of object files to what is
 observed

in RSX-11M+ files. Use conditional compilation so the RT-11 version can
be restored.
---
 dumpobj.c | 19 ++++++++++++++++++-
 object.c  | 16 ++++++++++++++++
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/dumpobj.c b/dumpobj.c
index 8399d6e..8b61551 100644
--- a/dumpobj.c
+++ b/dumpobj.c
@@ -64,6 +64,7 @@ char           *readrec(
 
     chksum = 0;
 
+#if RT11
     while (c = fgetc(fp), c != EOF && c == 0) ;
 
     if (c == EOF)
@@ -83,6 +84,7 @@ char           *readrec(
     }
 
     chksum -= c;                       // even though for 0 the checksum isn't changed...
+#endif /* RT11 */
 
     c = fgetc(fp);
     if (c == EOF) {
@@ -103,7 +105,9 @@ char           *readrec(
 
     chksum -= c;
 
+#if RT11
     *len -= 4;                         // Subtract header and length bytes from length
+#endif
     if (*len < 0) {
         fprintf(stderr, "Improperly formatted OBJ file (5)\n");
         return NULL;
@@ -125,15 +129,28 @@ char           *readrec(
     for (i = 0; i < *len; i++)
         chksum -= (buf[i] & 0xff);
 
+#if RT11
     c = fgetc(fp);
     c &= 0xff;
     chksum &= 0xff;
 
     if (c != chksum) {
         free(buf);
-        fprintf(stderr, "Bad record checksum, " "calculated=%d, recorded=%d\n", chksum, c);
+        fprintf(stderr, "Bad record checksum, " "calculated=$%04x, recorded=$%04x\n", chksum, c);
         return NULL;
     }
+#else
+    if (*len & 1) {
+        /* skip 1 byte of padding */
+        c = fgetc(fp);
+        if (c == EOF) {
+            free(buf);
+            fprintf(stderr, "EOF where padding byte should be");
+            return NULL;
+        }
+
+    }
+#endif /* RT11 */
 
     return buf;
 }
diff --git a/object.c b/object.c
index b64dc26..4a29bb2 100644
--- a/object.c
+++ b/object.c
@@ -55,6 +55,10 @@ DAMAGE.
   Each is preceeded by any number of 0 bytes, begins with a 1,0 pair,
   followed by 2 byte length, followed by data, followed by 1 byte
   negative checksum.
+
+  The RSX version is similar but subtly different:
+  There are no "any number of 0 bytes", nor the "1,0 pair" following it.
+  There is no checksum byte, but odd lengths are padded with a 0-byte.
 */
 
 static int writerec(
@@ -65,18 +69,24 @@ static int writerec(
     int             chksum;     /* Checksum is negative sum of all
                                    bytes including header and length */
     int             i;
+#if RT11
     unsigned        hdrlen = len + 4;
+#else
+    unsigned        hdrlen = len;
+#endif
 
     if (fp == NULL)
         return 1;                      /* Silently ignore this attempt to write. */
 
     chksum = 0;
+#if RT11
     if (fputc(FBR_LEAD1, fp) == EOF)   /* All recs begin with 1,0 */
         return 0;
     chksum -= FBR_LEAD1;
     if (fputc(FBR_LEAD2, fp) == EOF)
         return 0;
     chksum -= FBR_LEAD2;
+#endif /* RT11 */
 
     i = hdrlen & 0xff;                 /* length, lsb */
     chksum -= i;
@@ -99,7 +109,13 @@ static int writerec(
 
     chksum &= 0xff;
 
+#if RT11
     fputc(chksum, fp);                 /* Followed by the checksum byte */
+#else /* RT11 */
+    if (hdrlen & 1) {
+        fputc(0, fp);                  /* Padding to even boundary */
+    }
+#endif /* RT11 */
 
     return 1;                          /* Worked okay. */
 }