Alchemy安装记录6：实战Alchemy，Huffman的Alchemy实现

 

huffman编码是常见的压缩算法之一，

例如我们平常看到的jpeg图片就是用huffman进行熵编码压缩。

 

我实现了huffman的alchemy版和AS3版两个版本。

纯AS3实现是把C算法完整地移植过去的（使用uint的Array数组模拟char[]）

因为huffman算法在网上比较容易找到，我就不详细介绍。

下面只着重记录如何用Alchemy技术把huffman的API暴露到AS3，

然后与纯AS3实现的结果进行比较。

（这里说的huffman算法压缩后头四个字节为解压长度，压缩使用位流）

 

一、安装Alchemy。

Alchemy的安装方法以前已经说过，不过我是按照官方的做法再做了一次

（稍有不同的是我的alchemy不需要alc-on）：

以下以windows xp+cygwin为开发环境（假设已经安装flex sdk和jdk）

1. 在adobe官方网站下载alchemy的cygwin二进制包。

 

2. 本地或在线安装cygwin，Select packages时选中make，perl、zip（不需要安装gcc，也不需要安装源代码）。

本地安装是cygwin把在线安装的文件缓存在硬盘中，最开始一般都是在线安装。

选择zip时要小心，不要选其它名字带zip的压缩工具。zip程序用于后面生成swc文件。

 

3. 启动cygwin的批处理文件Cygwin.bat，完成cygwin的全部安装。

 

4. 把alchemy的二进制文件解压到cygwin安装目录下

 

5. 在/etc/profile最后加入

export PATH=/cygdrive/D/java/flex_sdk_4.1.0.16076/bin:$PATH

export PATH=/cygdrive/D/java/jdk1.6.0_20/bin:$PATH

export PATH=/alchemy-cygwin-v0.5a/achacks:/alchemy-cygwin-v0.5a/bin:$PATH

export ALCHEMY_HOME=/alchemy-cygwin-v0.5a

export FLEX_HOME=D:/java/flex_sdk_4.1.0.16076

export ASC=C:/cygwin3/alchemy-cygwin-v0.5a/bin/asc.jar

注意：这里jdk、flex sdk的位置和alchemy的目录位置可变；

cygdrive用于转换windows的绝对路径；

冒号用于分割；

另外FLEX_HOME和ASC最好不要用cygdrive转换，因为它用于flex的jar文件定位，

windows下的java可能无法识别路径名而报错；

因为cygwin没有装gcc，所以我直接把achacks目录加入PATH（与官网的安装方法不一样，所以后面不需要alc-on那么麻烦）

把/etc/profile保存为Unix换行（注意：需要用特殊的编辑器编辑，我是使用Notepad2 MOD菜单中的“行末符号->Unix换行”保存）

重新启动cygwin控制台以使环境变量生效。

 

6. 执行以下命令

$ cd /alchemy-cygwin-v0.5a/

$ ./config

Generating alchemy-setup...

Turning execution bit on for Alchemy binaries...

cygwin warning:

  MS-DOS style path detected: C:/cygwin3/alchemy-cygwin-v0.5a/alchemy-setup

  Preferred POSIX equivalent is: /alchemy-cygwin-v0.5a/alchemy-setup

  CYGWIN environment variable option "nodosfilewarning" turns off this warning.

  Consult the user's guide for more details about POSIX paths:

    http://cygwin.com/cygwin-ug-net/using.html#using-pathnames

 

Add "source /alchemy-cygwin-v0.5a/alchemy-setup" to your login script.

  "alc-home" takes you to the Alchemy install folder.

  "alc-on" puts Alchemy gcc toolchain replacements at the front of your path.

  "alc-off" restores original path.

  "alc-util" shows you various Alchemy-related environment vars

You need Flash 10 or AIR 1.5 and the Flex 3.2 SDK installed for testing.

 

7. 测试一下以下命令：

$ explorer .

$ mxmlc -help （如果无法运行，请确保jar的路径是windows的绝对路径，设置FLEX_HOME环境变量）

$ java -help

$ perl --help

$ zip --help

 

8. 测试gcc是否正常：（不需要alc-on，是因为我已经把alchemy的gcc加入了PATH，而且cygwin中并没有装真正的gcc）

$ which gcc

/alchemy-cygwin-v0.5a/achacks/gcc

$ gcc -v

Using built-in specs.

Target: i686-pc-cygwin

Configured with: /home/anon/llvm-gcc4.0-2.1.source/configure  : (reconfigured) /

home/anon/llvm-gcc4.0-2.1.source/configure  : (reconfigured) /home/anon/llvm-gcc

4.0-2.1.source/configure --disable-libgcj --disable-libjava : (reconfigured) ../

../src/llvm-gcc4/configure --prefix=/home/anon/llvm-gcc4 --disable-threads --dis

able-nls --disable-shared --enable-languages=c,c++ --disable-c-mbchar --program-

prefix=llvm- --enable-llvm=/home/anon/src/llvm : (reconfigured) /home/anon/src/l

lvm-gcc4/configure --prefix=/home/anon/llvm-gcc4 --disable-threads --disable-nls

 --disable-shared --enable-languages=c,c++ --disable-c-mbchar --program-prefix=l

lvm- --enable-llvm=/home/anon/src/llvm

Thread model: single

gcc version 4.0.1 (Apple Computer, Inc. build 5449)

可以看到alchemy官方版附带的gcc版本是4，用苹果机编译。

 

 

 

 

二、编写代码编译运行，比较Alchemy和AS3实现的结果。

为了简单起见忽略huffman压缩和解压算法的实现代码。

 

 

Alchemy的API导出文件（.gg文件）

---------------------------

 

 

{
/* 
   注意用大括号包含C代码，
   一些通常用到的C函数定义，方便C和AS3的类型转换
*/
#include <stdlib.h>
#include <string.h>
#include <malloc.h>

/*
	需要用到的头文件
*/
#include "Huffman.h"

/* AS3.h is included automatically by gluegen */

void sztrace(char*);

AS3_Val no_params = NULL;
AS3_Val zero_param = NULL;
AS3_Val ByteArray_class = NULL;
AS3_Val getTimer_method = NULL;

// 保存压缩大小
static int compress_size = 0;

/* This function will be called at the top of the generated main(). The GGINIT_DEFINED macro is required. */
/* 必须预定义GGINIT_DEFINED */
#define GGINIT_DEFINED true
static void ggInit()
{
	//sztrace("setting up as3_crypto_wrapper library");

	/* setup some useful constants */
	no_params = AS3_Array("");
	zero_param = AS3_Int(0);
	AS3_Val flash_utils_namespace = AS3_String("flash.utils");
	ByteArray_class = AS3_NSGetS(flash_utils_namespace, "ByteArray");
	getTimer_method = AS3_NSGetS(flash_utils_namespace, "getTimer");
	AS3_Release(flash_utils_namespace);

	/* initialize */
	/* 这里插入全局初始化代码*/
}

/* Copy the byteArray data into a malloc'd buffer */
/* ByteArray转void* */
static void* newMallocFromByteArray(AS3_Val byteArray, unsigned int* size)
{
	AS3_Val byteArraySize = AS3_GetS(byteArray, "length");
	*size = AS3_IntValue(byteArraySize);
	AS3_Release(byteArraySize);
	void* bytes = malloc(*size);
	AS3_SetS(byteArray, "position", zero_param);
	AS3_ByteArray_readBytes((char*)bytes, byteArray, (int)*size);
	return bytes;
}

/* Make a new ByteArray containing the data passed */
/* void*转ByteArray  */
static AS3_Val newByteArrayFromMalloc(void *data, unsigned int size)
{
	AS3_Val byteArray = AS3_New(ByteArray_class, no_params);
	AS3_ByteArray_writeBytes(byteArray, data, size);
	return byteArray;
}

#if 0 // use for profiling
/* get a timestamp from Flash */
static int getTimestamp()
{
	AS3_Val ts = AS3_Call(getTimer_method, NULL, no_params);
	int result = AS3_IntValue(ts);
	AS3_Release(ts);
	return result;
}
#endif

/* C代码结束 */
/* 下面就可以加入要在swc中暴露的API声明 */
}

public function huff_uncompress(indata:ByteArray, insize:uint, outsize:uint):ByteArray
{
	unsigned int size = 0;
	unsigned char* inbuf = newMallocFromByteArray(indata, &size);
	unsigned char* outbuf = malloc(outsize);
	
	//测试用
	//memset(outbuf, outsize, 10);
	
	Huffman_Uncompress(inbuf, outbuf, insize, outsize);
	
	AS3_Val ba = newByteArrayFromMalloc(outbuf, outsize);
	free(inbuf);
	free(outbuf);
	return ba;
}

public function huff_compress(indata:ByteArray, insize:uint):ByteArray
{
	unsigned int size = 0;
	unsigned char* inbuf = newMallocFromByteArray(indata, &size);
	//足够容纳压缩内容的大小
	unsigned int outsize = (insize*104+50)/100 + 384;
	unsigned char* outbuf = malloc(outsize);
	
	//测试用
	//memset(outbuf, outsize, 10);
	
	//调试用
	/*
	char strTrace[1000] = "";
	sprintf(strTrace, "size: %d, outsize:%d, insize:%d", size, outsize, insize);
	sztrace(strTrace);
	sztrace(inbuf);
	*/
	
	compress_size = Huffman_Compress(inbuf, outbuf, insize);
	
	AS3_Val ba = newByteArrayFromMalloc(outbuf, compress_size);
	free(inbuf);
	free(outbuf);
	return ba;
}

public function huff_compress_size():uint
{
	// 取出最近压缩的大小
	return compress_size;
}

 

 

 

 

----------------------------------------------

Alchemy实现的主入口代码如下：

 

 

package 
{
	import flash.display.Sprite;
	import flash.events.Event;
	import flash.utils.ByteArray;
	import flash.utils.Endian;
			
	/**
	 * ...
	 * @author 
	 */
	public class Main extends Sprite 
	{
		import cmodule.huff.CLibInit;
		private static const clibinit:CLibInit = new CLibInit();
		private static const hufflib:Object = clibinit.init();
		
		public function Main():void 
		{
			if (stage) init();
			else addEventListener(Event.ADDED_TO_STAGE, init);
		}
		
		private function init(e:Event = null):void 
		{
			removeEventListener(Event.ADDED_TO_STAGE, init);
			// entry point
			
			//--------------------------------------------------
			[Embed(source='../lib/output.dat', mimeType='application/octet-stream')]
			var output_dat:Class;
			
			//注意，是强制转换，不是new
			var data:ByteArray = ByteArray(new output_dat());
			trace("ByteArray.length = ", data.length);
			
			data.position = 0;
			//不知为何，与网络传输时正好相反
			//0xFF000000 --readUnsignedInt--> 0xFF 
			data.endian = Endian.LITTLE_ENDIAN;  
			if (data.bytesAvailable > 0)
			{
				// 第一个32位数是解压长度
				var uncompress_length:uint = data.readUnsignedInt();
				var inputdata:ByteArray = new ByteArray();
				data.readBytes(inputdata);
				trace("inputdata.bytesAvailable", inputdata.bytesAvailable);
				trace("uncompress_length:", uncompress_length);
				inputdata.position = 0;
				//解码
				var uncompress_bytes:ByteArray = huff_uncompress(inputdata, inputdata.bytesAvailable, uncompress_length);
				
				uncompress_bytes.position = 0;
				trace("uncompress:", uncompress_bytes.bytesAvailable, "bytes");
				var str:String = uncompress_bytes.readMultiByte(uncompress_bytes.bytesAvailable, "gbk");
				trace(str);
			}
			
			//--------------------------------------------------
			//压缩测试
			/*
			var compress_length:uint = huff_compress_size();
			trace("compress_length", compress_length);
			*/
			/**/
			uncompress_bytes.position = 0;
			trace("uncompress_bytes.bytesAvailable:", uncompress_bytes.bytesAvailable);
			var compress_bytes:ByteArray = huff_compress(uncompress_bytes, uncompress_bytes.bytesAvailable);
			var compress_length:uint = huff_compress_size();
			
			compress_bytes.position = 0;
			trace("compress_length:", compress_length);
			trace("compress:", compress_bytes.bytesAvailable, "bytes");
			
			compress_bytes.position = 0;
			while (compress_bytes.bytesAvailable > 0)
			{
				var byte:uint = compress_bytes.readByte() & 0xff;
				trace(byte.toString(16));
			}
			/**/
		}
		
		//对应huff.gg中的三个导出API
		//方便参数类型检查
		public function huff_uncompress(bytes:ByteArray, insize:int, outsize:int):ByteArray
		{
			return hufflib.huff_uncompress(bytes, insize, outsize);
		}
		
		public function huff_compress(bytes:ByteArray, insize:int):ByteArray
		{
			//trace("insize:", insize);
			return hufflib.huff_compress(bytes, insize);
		}
		
		public function huff_compress_size():int
		{
			return hufflib.huff_compress_size();
		}
	}
}

 

 

 

 

-------------------------------------------------

纯AS3实现的主入口代码如下：

 

 

 

package huff 
{
	import flash.display.Sprite;
	import flash.utils.ByteArray;
	import flash.utils.Endian;
	
	public class CodecTest extends Sprite
	{	
		public function CodecTest() 
		{
			/*
			trace("hello, world");
			
			var bytes:ByteArray = new ByteArray();
			bytes.writeByte(0xF8);
			bytes.writeByte(0xF8);
			bytes.position = 0;
			var stream:Bitstream = new Bitstream(bytes);
			try 
			{
				//testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testRead8Bits(stream);
				testRead8Bits(stream);
				testRead8Bits(stream);
			}catch (e:Error) {
				trace(e.getStackTrace());
			}
			//----------------------------------------------------
			stream = new Bitstream();
			stream.writeBits(0xF8, 8);
			stream.writeBits(0xF8, 8);
			stream.rewind();
			try 
			{
				//testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testReadBit(stream);
				testRead8Bits(stream);
				testRead8Bits(stream);
				testRead8Bits(stream);
			}catch (e:Error) {
				trace(e.getStackTrace());
			}
			*/
			var stream:Bitstream = new Bitstream();
			
			//--------------------------------------------------
			[Embed(source='../../lib/output.dat', mimeType='application/octet-stream')]
			var output_dat:Class;
			
			//注意，是强制转换，不是new
			var data:ByteArray = ByteArray(new output_dat());
			trace("ByteArray.length = ", data.length);
			
			data.position = 0;
			//不知为何，与网络传输时正好相反
			//0xFF000000 --readUnsignedInt--> 0xFF 
			data.endian = Endian.LITTLE_ENDIAN;  
			if (data.bytesAvailable > 0)
			{
				// 第一个32位数是解压长度
				var uncompress_length:uint = data.readUnsignedInt();
				trace("uncompress_length:", uncompress_length);
				stream = new Bitstream(data);
				
				var uncompress_bytes:ByteArray = new ByteArray();
				stream.uncompress(uncompress_bytes, uncompress_length);
				uncompress_bytes.position = 0;
				trace("uncompress:", uncompress_bytes.bytesAvailable, "bytes");
				var str:String = uncompress_bytes.readMultiByte(uncompress_bytes.bytesAvailable, "gbk");
				trace(str);
			}
			
			//--------------------------------------------------
			//压缩测试
			
			uncompress_bytes.position = 0;
			var compress_bytes:ByteArray = new ByteArray();
			var stream2:Bitstream = new Bitstream();
			var compress_length:uint = stream2.compress(uncompress_bytes, 
				compress_bytes, 
				uncompress_bytes.bytesAvailable);
			compress_bytes.position = 0;
			trace("compress_length:", compress_length);
			trace("compress:", compress_bytes.bytesAvailable, "bytes");
			
			compress_bytes.position = 0;
			while (compress_bytes.bytesAvailable > 0)
			{
				var byte:uint = compress_bytes.readByte() & 0xff;
				trace(byte.toString(16));
			}
		}
		
		public function testRead8Bits(stream:Bitstream):void
		{
			var i:uint = stream.read8Bits();
			trace(i.toString(16));
		}
		
		public function testReadBit(stream:Bitstream):void
		{
			var i:uint = stream.readBit();
			trace(i);
		}
	}
}

 

 

 

--------------------------

 

 

两种实现的输出如下所示，

* 解压出"Hello World!"，

* 压缩除了alchemy没有加入开头4字节的长度外，其余和AS3版相同。

 

---------------------

alchemy实现的输出：

 

 

ByteArray.length = 20
inputdata.bytesAvailable 16
uncompress_length: 12
uncompress: 12 bytes
Hello World!
uncompress_bytes.bytesAvailable: 12
compress_length: 16
compress: 16 bytes
cd
f1
4
90
21
9b
33
21
5e
72
32
b7
d0
b4
eb
1c

 

 

 

 

------------------------

纯AS3实现的输出

 

 

ByteArray.length = 20
uncompress_length: 12
uncompress: 12 bytes
Hello World!
compress_length: 16
compress: 20 bytes
c
0
0
0
cd
f1
4
90
21
9b
33
21
5e
72
32
b7
d0
b4
eb
1c

 

 

 

------------------------

 

 

结论：

Alchemy和纯AS3都可以处理ByteArray数据，进行类似数据压缩和解压的复杂工作。

从上面的实践可以发现Alchemy开发的一些注意事项：

* 开发环境比较难搭建，需要耐心寻找原因。

* 难于调试。需要使用全局函数sztrace跟踪代码的去向。

* 如果遗漏了.o文件仍可以编译swc成功，但会导致运行期错误，所以写Makefile时必须十分小心。

* .gg文件必须把公共的C代码放在开头的大括号内。导出API放在大括号外。

 

 

代码在svn中：

svn://www.svnhost.cn/weimingtom_reversi/alchemy