From 622d18a9370842dfd375e58d6f37dc2c192fffb8 Mon Sep 17 00:00:00 2001
From: Kalle Olavi Niemitalo <kon@iki.fi>
Date: Sat, 20 Oct 2007 18:42:04 +0300
Subject: [PATCH] Simplify prepareCommand:withData:.

Also make sure that the result won't exceed 0xFFFF bytes.
---
 TFUSBController.h |  2 +-
 TFUSBController.m | 45 +++++++++++++++++++--------------------------
 2 files changed, 20 insertions(+), 27 deletions(-)

diff --git a/TFUSBController.h b/TFUSBController.h
index f414bee..849b44b 100644
--- a/TFUSBController.h
+++ b/TFUSBController.h
@@ -143,7 +143,7 @@ void hexDump(UInt8 *buf, int len);
 - (USBDeviceContext*) initializeUSB;
 - (id) getFileListForPath:(NSString*) path;
 - (UInt16) findCRC:(const UInt8*)p length:(size_t) n;
-- (NSData*) prepareCommand:(unsigned int)cmd withData:(NSData*) inData ;
+- (NSData*) prepareCommand:(UInt32)cmd withData:(NSData*) inData ;
 - (int) getFile:(NSDictionary*)fileInfo forPath:(NSString*)currentPath toSaveTo:(NSString*)savePath beginAtOffset:(unsigned long long) offset withLooping:(BOOL)looping existingTime:(NSTimeInterval)existingTime;	
 - (NSData*) sendCommand:(NSData*) fullyPackagedCommand toDevice:(USBDeviceContext*)device expectResponse:(BOOL) getResponse careForReturn:(BOOL) careFactor;
 - (NSMutableData*) swap: (NSData*) inData;
diff --git a/TFUSBController.m b/TFUSBController.m
index 55e1f4a..0942e68 100644
--- a/TFUSBController.m
+++ b/TFUSBController.m
@@ -501,32 +501,25 @@ int initDevice(USBDeviceContext *device){
 	return ret; 
 }
 
-- (NSData*) prepareCommand:(unsigned int)cmd withData:(NSData*) inData {	
-		// work out length
-		unsigned short int length = 0;
-		if (inData == nil)
-			length = 8;
-		else {
-			unsigned short int l = [inData length];
-			length = l + 8;
-		}
-		const UInt16 length_bigendian = EndianU16_NtoB(length);
-		NSMutableData* toSend = [NSMutableData dataWithBytes:&length_bigendian length:2];
-		const UInt32 cmd_bigendian = EndianU32_NtoB(cmd);
-		NSMutableData* build = [NSMutableData dataWithBytes:&cmd_bigendian length:4];
-		if (inData != nil)
-			[build appendData:inData];
-		// work out crc
-		UInt8 test[length];
-		memset(test, 0, length);
-		[build getBytes:test length:[build length]];
-		unsigned short int crc = [self findCRC:test length:[build length]];
-		const UInt16 crc_bigendian = EndianU16_NtoB(crc);
-		[toSend appendData:[NSMutableData dataWithBytes:&crc_bigendian length:2]];
-		[toSend appendData:build];
-		// reverse and send
-		toSend = [self swap:toSend];
-		return toSend;
+- (NSData*) prepareCommand:(UInt32)cmd withData:(NSData*) inData {
+	NSMutableData* block = [NSMutableData dataWithLength:8];
+	if (inData != nil)
+		[block appendData:inData];
+	size_t blockLength = [block length];
+	if (blockLength > 0xFFFF)
+		return nil; // wouldn't fit in UInt16
+
+	UInt32 cmd_bigendian = EndianU32_NtoB(cmd);
+	[block replaceBytesInRange:(NSRange){4,4} withBytes:&cmd_bigendian];
+
+	UInt16 crc = [self findCRC:(const UInt8*)[block bytes]+4 length:blockLength-4];
+	UInt16 crc_bigendian = EndianU16_NtoB(crc);
+	[block replaceBytesInRange:(NSRange){2,2} withBytes:&crc_bigendian];
+
+	UInt16 blockLength_bigendian = EndianU16_NtoB(blockLength);
+	[block replaceBytesInRange:(NSRange){0,2} withBytes:&blockLength_bigendian];
+
+	return [self swap:block];
 }
 
 // Check the size and CRC of a received communication block.
-- 
2.11.4.GIT