xex.c: add xex_get_run_addr() and xex_get_init_addr().

3 files changed, 32 insertions, 1 deletions

diff --git a/TODO b/TODO
index bb1f1a6..d656b9a 100644
--- a/TODO
+++ b/TODO
@@ -2,7 +2,8 @@ for now:
 These may need library (xex.c) changes:
 xexcat: handle run/init addresses embedded in a segment longer than
   2 bytes.
-xexcat: handle or at least detect DOS 1.0 executables.
+xexcat: handle or at least detect DOS 1.0 executables. currently
+  xex_fread_seg_header() will warn about them, but that's all.
 xexcat: warn if an an init address occurs before the code it
   references. or at least if it occurs before *any* code!
 
diff --git a/xex.c b/xex.c
index e4b66ce..8584286 100644
--- a/xex.c
+++ b/xex.c
@@ -114,6 +114,10 @@ int xex_fread_seg_header(xex_segment *seg, FILE *file) {
 	if(d == EOF) return 0;
 
 	addr = XEX_ADDR(c, d);
+	if(addr == 0x0984) {
+		fprintf(stderr, "xex_fread_seg_header(): warning: this might be a DOS 1.0 file (not supported)\n");
+	}
+
 	if(addr == 0xffff) {
 		seg->has_ff_header = 1;
 		c = read_char(file);
@@ -289,6 +293,24 @@ int xex_check_seg(xex_segment *seg) {
 	return ret;
 }
 
+static int xex_get_addr_from(xex_segment *seg, int location) {
+	int i;
+
+	if(seg->start_addr > location) return -1;
+	if(seg->end_addr  <= location) return -1;
+
+	i = location - seg->start_addr;
+	return XEX_ADDR(seg->object[i], seg->object[i + 1]);
+}
+
+int xex_get_run_addr(xex_segment *seg) {
+	return xex_get_addr_from(seg, XEX_RUNAD);
+}
+
+int xex_get_init_addr(xex_segment *seg) {
+	return xex_get_addr_from(seg, XEX_INITAD);
+}
+
 char *xex_strerror(int err) {
 	if(err < 0 || err >= XERR_MAXERR)
 		err = XERR_MAXERR;
diff --git a/xex.h b/xex.h
index 2300481..2b113fc 100644
--- a/xex.h
+++ b/xex.h
@@ -104,6 +104,14 @@ int xex_get_object(xex_segment *seg, unsigned char *data);
 	Returns true if segment is OK. */
 int xex_check_seg(xex_segment *seg);
 
+/* Get run address from a segment, if there is one. This can handle the case
+	where the address is embedded in a larger segment (that doesn't just consist
+	of 2 bytes loaded at RUNAD). Returns -1 if there is no run address. */
+int xex_get_run_addr(xex_segment *seg);
+
+/* Same as above, for init address. */
+int xex_get_init_addr(xex_segment *seg);
+
 /* Get human-readable error message. If xex_errno is XSYSCALL, the system's
 	strerror() is called. */
 char *xex_strerror(int err);