From 9250cfdf7c6b846b94a2d9790c1b3935035d53c0 Mon Sep 17 00:00:00 2001
From: Jon Feldman <chaos.kagami@gmail.com>
Date: Sun, 22 Jan 2017 11:37:56 -0500
Subject: [PATCH] Move common sources to a dedicated directory

---
 boot/Makefile.am           |  2 +-
 {include => common}/lzss.c | 26 ++++++++++++++++----------
 include/lzss.h             |  6 ++++++
 loader/Makefile            |  2 +-
 loader/source/loader.c     |  2 +-
 5 files changed, 25 insertions(+), 13 deletions(-)
 rename {include => common}/lzss.c (70%)
 create mode 100644 include/lzss.h

diff --git a/boot/Makefile.am b/boot/Makefile.am
index b8e1e77..6e7ae4e 100644
--- a/boot/Makefile.am
+++ b/boot/Makefile.am
@@ -25,4 +25,4 @@ corbenik_SOURCES = \
 	patch/reboot.c patch/svc.c patch/module.c patch/emunand.c \
 	std/fs.c std/draw.c std/memory.c std/abort.c \
 	firm/util.c firm/keys.c firm/firmlaunch.c firm/version.c firm/firm.c firm/decryptor.c \
-	configback/file-dat.c
+	configback/file-dat.c ../common/lzss.c
diff --git a/include/lzss.c b/common/lzss.c
similarity index 70%
rename from include/lzss.c
rename to common/lzss.c
index c2f02de..b0418fa 100644
--- a/include/lzss.c
+++ b/common/lzss.c
@@ -1,13 +1,21 @@
-#ifndef __LZSS_H
-#define __LZSS_H
+#include <stdint.h>
 
-static int
-lzss_decompress(u8 *buffer)
+
+int
+lzss_decompress(uint8_t *buffer)
 {
     // This WAS originally a decompilation in @yifan_lu's repo; it was rewritten
     // for readability following ctrtool's namings.
+
+    // This implementation is particularly interesting in that it's an in-place
+    // decompressor.
+
+    // LZSS is performed in the reverse direction,
+    // and the last four bytes are the decompressed size.
+    // Presumably, Nintendo did as such so decompression can occur in-place without need for temporary buffers.
+
     unsigned int decompSize, v15;
-    u8 *compressEndOff, *index, *stopIndex;
+    uint8_t *compressEndOff, *index, *stopIndex;
     char control;
     int v9, v13, v14, v16;
     int ret = 0;
@@ -16,8 +24,8 @@ lzss_decompress(u8 *buffer)
         return 0;
 
     // v1=decompressedSize, v2=compressedSize, v3=index, v4=stopIndex
-    decompSize = *((u32 *)buffer - 2);
-    compressEndOff = &buffer[*((u32 *)buffer - 1)];
+    decompSize = *((uint32_t *)buffer - 2);
+    compressEndOff = &buffer[*((uint32_t *)buffer - 1)];
     index = &buffer[-(decompSize >> 24)]; // FIXME - The integer negation is due
                                           // to a compiler optimization. It's
                                           // probably okay, but...
@@ -32,7 +40,7 @@ lzss_decompress(u8 *buffer)
                 v13 = *(index - 1);
                 v14 = *(index - 2);
                 index -= 2;
-                v15 = ((v14 | (v13 << 8)) & 0xFFFF0FFF) + 2;
+                v15 = (((unsigned int)v14 | ((unsigned int)v13 << 8)) & 0xFFFF0FFF) + 2;
                 v16 = v13 + 32;
                 do {
                     ret = compressEndOff[v15];
@@ -52,5 +60,3 @@ lzss_decompress(u8 *buffer)
 
     return ret;
 }
-
-#endif
diff --git a/include/lzss.h b/include/lzss.h
new file mode 100644
index 0000000..ab3cbde
--- /dev/null
+++ b/include/lzss.h
@@ -0,0 +1,6 @@
+#ifndef __LZSS_H
+#define __LZSS_H
+
+int lzss_decompress(uint8_t *buffer);
+
+#endif
diff --git a/loader/Makefile b/loader/Makefile
index e3dbd85..5db3812 100644
--- a/loader/Makefile
+++ b/loader/Makefile
@@ -33,7 +33,7 @@ endif
 #---------------------------------------------------------------------------------
 TARGET		:=	loader
 BUILD		:=	build
-SOURCES		:=	source source/patch
+SOURCES		:=	source ../common
 DATA		:=	data
 INCLUDES	:=	include
 
diff --git a/loader/source/loader.c b/loader/source/loader.c
index 1573084..f0fdf34 100644
--- a/loader/source/loader.c
+++ b/loader/source/loader.c
@@ -1,6 +1,6 @@
 #include <3ds.h>
 #include "patcher.h"
-#include <lzss.c>
+#include <lzss.h>
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
-- 
2.39.5