From 152bab24521ea7cefd9e5d8cd1460c5871bff34c Mon Sep 17 00:00:00 2001
From: Nick Bowler <nbowler@draconx.ca>
Date: Mon, 1 Feb 2010 18:30:04 -0500
Subject: [PATCH] music: Add simple file type detection to the dummy module.

The dummy module can be a bit smarter so that the file extension of
exported data is correct.  Add support for xm, it and s3m.
---
 src/engine/music-dummymod.c | 55 +++++++++++++++++++++++++++++++++++--
 1 file changed, 52 insertions(+), 3 deletions(-)

diff --git a/src/engine/music-dummymod.c b/src/engine/music-dummymod.c
index db18fa4..a4c8666 100644
--- a/src/engine/music-dummymod.c
+++ b/src/engine/music-dummymod.c
@@ -18,12 +18,16 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 
 #include "music-module.h"
 #include "upkg.h"
 
 struct music_mod {
 	struct upkg_file *f;
+
+	unsigned char header[64];
+	unsigned long hdrlen;
 };
 
 int music_mod_init(void)
@@ -37,12 +41,15 @@ void music_mod_exit(void)
 
 struct music_mod *music_mod_open(struct upkg_file *f)
 {
-	struct music_mod *m = malloc(sizeof *m);
+	struct music_mod *m;
 
-	if (m) {
-		m->f = f;
+	m = malloc(sizeof *m);
+	if (!m) {
+		return NULL;
 	}
+	m->f = f;
 
+	m->hdrlen = upkg_export_read(f, m->header, sizeof m->header);
 	return m;
 }
 
@@ -85,7 +92,49 @@ int music_mod_dump(struct music_mod *m, FILE *of)
 	}
 }
 
+int is_xm(unsigned char *buf, unsigned long len)
+{
+	static const char head[15] =
+		/* ASCII encoding of "Extended Module" */
+		"\x45\x78\x74\x65\x6e\x64\x65\x64\x20\x4d\x6f\x64\x75\x6c\x65";
+
+	if (len >= sizeof head && memcmp(head, buf, sizeof head) == 0)
+		return 1;
+	return 0;
+}
+
+int is_it(unsigned char *buf, unsigned long len)
+{
+	static const char head[4] =
+		/* ASCII encoding of "IMPM" */
+		"\x49\x4d\x50\x4d";
+
+	if (len >= sizeof head && memcmp(head, buf, sizeof head) == 0)
+		return 1;
+	return 0;
+}
+
+int is_s3m(unsigned char *buf, unsigned long len)
+{
+	static const char head[4] =
+		/* ASCII encoding of "SCRM" */
+		"\x53\x43\x52\x4d";
+
+	if (len < 0x2c + sizeof head)
+		return 0;
+	if (memcmp(head, buf+0x2c, sizeof head) == 0)
+		return 1;
+	return 0;
+}
+
 const char *music_mod_type(struct music_mod *mod)
 {
+	if (is_xm(mod->header, mod->hdrlen))
+		return "xm";
+	if (is_it(mod->header, mod->hdrlen))
+		return "it";
+	if (is_s3m(mod->header, mod->hdrlen))
+		return "s3m";
+
 	return "unknown";
 }
-- 
2.43.0