【原】AMFObject数据格式详解

AMF

　　AMF是Action Message Format(动作消息格式)的简写，它是一种二进制的数据格式。它的设计是为了把actionscript里面的数据(包括Object, Array, Boolean, Number等)序列化成二进制数据，然后把这段数据随意发送给其他接收方程序，比如发给远程的服务器，在远程服务器那边，可以把这段数据给还原出来，以此达到一个数据传输的作用。

为什么要用AMF

　　通常情况下我们使用JSON或者XML来做数据的传输，他们的好处是文本数据易读、容易修改，坏处在于文本数据体积较大，而且数据的组织有其局限性。那么二进制协议是不是只有AMF一个呢？ 答案明显是否定的，你完全可以自定义自己的二进制数据格式，用AMF只是由于它是现成的，拿来即可用，不用重新去发明轮子。

AMFObject详解

AMF分成两种： 1. AMF0，基本的数据转换规则； 2. AMF3，是AMF0的扩展。

　　  // AMF0数据类型;
    typedef enum
    {
        AMF_NUMBER = 0,			// 数字(double);
		AMF_BOOLEAN,			// 布尔;
		AMF_STRING,				// 字符串;
		AMF_OBJECT,				// 对象;
        AMF_MOVIECLIP,			// 保留,未使用;
        AMF_NULL,				// null;
		AMF_UNDEFINED,			// 未定义;
		AMF_REFERENCE,			// 引用;
		AMF_ECMA_ARRAY,			// 数组;
		AMF_OBJECT_END,			// 对象结束;
        AMF_STRICT_ARRAY,		// 严格的数组;
		AMF_DATE,				// 日期;
		AMF_LONG_STRING,		// 长字符串;
		AMF_UNSUPPORTED,		// 未支持;
        AMF_RECORDSET,			// 保留,未使用;
        AMF_XML_DOC,			// xml文档;
		AMF_TYPED_OBJECT,		// 有类型的对象;
        AMF_AVMPLUS,			// 需要扩展到AMF3;
        AMF_INVALID = 0xff		// 无效的;
    }AMFDataType;

　　  // AMF3数据类型;
    typedef enum
    {
        AMF3_UNDEFINED = 0,		// 未定义;
		AMF3_NULL,				// null;
		AMF3_FALSE,				// false;
		AMF3_TRUE,				// true;
        AMF3_INTEGER,			// 数字int;
		AMF3_DOUBLE,			// double;
		AMF3_STRING,			// 字符串;
		AMF3_XML_DOC,			// xml文档;
		AMF3_DATE,				// 日期;
        AMF3_ARRAY,				// 数组;
		AMF3_OBJECT,			// 对象;
		AMF3_XML,				// xml;
		AMF3_BYTE_ARRAY			// 字节数组;
    } AMF3DataType;

AMF定义了自己的字符串类型：

　　// AMF自定义的字符串;
    typedef struct AVal
    {
        char *av_val;
        int av_len;
    } AVal;

// AVal的快速初始化;
#define AVC(str)		{str, sizeof(str)-1}
// 比较AVal字符串;
#define AVMATCH(a1,a2)	((a1)->av_len == (a2)->av_len && !memcmp((a1)->av_val,(a2)->av_val,(a1)->av_len))

AMFObject表示AMF对象，o_num 代表 o_props的个数， 一个对象内部可以包含N个对象属性;

    // AMF对象, 就是由一系列的属性构成的;
    typedef struct AMFObject
    {
        int o_num;							// 属性数目;
        struct AMFObjectProperty *o_props;	// 属性数组;
    } AMFObject;

AMFObject表示AMF对象属性，即key-value键值对。p_name表示key；p_type表示value的类型；p_vu表示value的数值。

    // AMF对象的属性;
    typedef struct AMFObjectProperty
    {
        AVal p_name;			// 属性名称;
        AMFDataType p_type;		// 属性类型;
        union
        {
            double p_number;
            AVal p_aval;
            AMFObject p_object;
        } p_vu;					// 属性数值;
        int16_t p_UTCoffset;	// UTC偏移;
    } AMFObjectProperty;

p_vu设置为联合体的目的：

当p_type为number时, m_vu取值double类型 p_number;

当p_type为string时,    m_vu取值AVal类型 p_aval;

当p_type为object时,   m_vu取值AMFObject类型 p_object。

AMF编码、解码的具体实现

#include "rtmp_sys.h"
#include "amf.h"
#include "log.h"
#include "bytes.h"

static const AMFObjectProperty AMFProp_Invalid = { {0, 0}, AMF_INVALID };
static const AVal AV_empty = { 0, 0 };

/* Data is Big-Endian */
/************************************************************************************************************
*	解码int16(这个整数占用两个字节);
*
*	c[0]左移8位(就是乘以256)+c[1];
************************************************************************************************************/
unsigned short AMF_DecodeInt16(const char* data)
{
    unsigned char* c = (unsigned char* ) data;
    unsigned short val;
    val = (c[0] << 8) | c[1];
    return val;
}

/************************************************************************************************************
*	解码int24(这个整数占用三个字节);
*
*	c[0]左移16位+c[1]左移8位+c[2];
************************************************************************************************************/
unsigned int AMF_DecodeInt24(const char* data)
{
    unsigned char* c = (unsigned char* ) data;
    unsigned int val;
    val = (c[0] << 16) | (c[1] << 8) | c[2];
    return val;
}

/************************************************************************************************************
*	解码int32(这个整数占用四个字节);
*
*	c[0]左移24位+c[1]左移16位+c[2]左移8位+c[3];
************************************************************************************************************/
unsigned int AMF_DecodeInt32(const char* data)
{
    unsigned char* c = (unsigned char* )data;
    unsigned int val;
    val = (c[0] << 24) | (c[1] << 16) | (c[2] << 8) | c[3];
    return val;
}

/************************************************************************************************************
*	解码String;
*
*	前两个字节是长度,后面是内容;
************************************************************************************************************/
void AMF_DecodeString(const char* data, AVal* bv)
{
    bv->av_len = AMF_DecodeInt16(data);
    bv->av_val = (bv->av_len > 0) ? (char* )data + 2 : NULL;
}

/************************************************************************************************************
*	解码LongString;
*
*	前四个字节是长度,后面是内容;
************************************************************************************************************/
void AMF_DecodeLongString(const char* data, AVal* bv)
{
    bv->av_len = AMF_DecodeInt32(data);
    bv->av_val = (bv->av_len > 0) ? (char* )data + 4 : NULL;
}

/************************************************************************************************************
*	解码数值double;
*
*	float字的存储顺序等于字节顺序;
*		大端字节顺序,直接赋值; 小端字节顺序,反转赋值;
*
*	float字的存储顺序不等字节顺序;
*		大端字节顺序,反转赋值; 小端字节顺序,直接赋值;
************************************************************************************************************/
double AMF_DecodeNumber(const char* data)
{
    double dVal;
#if __FLOAT_WORD_ORDER == __BYTE_ORDER		// 如果float字的存储顺序等于字节顺序;
#if __BYTE_ORDER == __BIG_ENDIAN			// 如果是大端字节顺序;
    memcpy(&dVal, data, 8);					// 直接复制;
#elif __BYTE_ORDER == __LITTLE_ENDIAN		// 如果是小端字节顺序;
    unsigned char* ci, *co;
    ci = (unsigned char* )data;
    co = (unsigned char* )&dVal;
    co[0] = ci[7];
    co[1] = ci[6];
    co[2] = ci[5];
    co[3] = ci[4];
    co[4] = ci[3];
    co[5] = ci[2];
    co[6] = ci[1];
    co[7] = ci[0];
#endif
#else
#if __BYTE_ORDER == __LITTLE_ENDIAN	/* __FLOAT_WORD_ORER == __BIG_ENDIAN */
    unsigned char* ci, *co;
    ci = (unsigned char* )data;
    co = (unsigned char* )&dVal;
    co[0] = ci[3];
    co[1] = ci[2];
    co[2] = ci[1];
    co[3] = ci[0];
    co[4] = ci[7];
    co[5] = ci[6];
    co[6] = ci[5];
    co[7] = ci[4];
#else /* __BYTE_ORDER == __BIG_ENDIAN && __FLOAT_WORD_ORER == __LITTLE_ENDIAN */
    unsigned char* ci, *co;
    ci = (unsigned char* )data;
    co = (unsigned char* )&dVal;
    co[0] = ci[4];
    co[1] = ci[5];
    co[2] = ci[6];
    co[3] = ci[7];
    co[4] = ci[0];
    co[5] = ci[1];
    co[6] = ci[2];
    co[7] = ci[3];
#endif
#endif
    return dVal;
}

/************************************************************************************************************
*	解码布尔;
*
*	判断内容是否为0;
************************************************************************************************************/
int AMF_DecodeBoolean(const char* data)
{
    return *data != 0;
}

/************************************************************************************************************
*	编码int16(这个整数占用两个字节);
*
*	依次截取1个字节进行赋值;
************************************************************************************************************/
char*  AMF_EncodeInt16(char* output, char* outend, short nVal)
{
	if (output + 2 > outend)
	{
        return NULL;
	}

    output[1] = nVal & 0xff;	// output[1] = nVal; 两者等价;
    output[0] = nVal >> 8;
    return output+2;
}

/************************************************************************************************************
*	编码int24(这个整数占用三个字节);
*
*	依次截取1个字节进行赋值;
************************************************************************************************************/
char* AMF_EncodeInt24(char* output, char* outend, int nVal)
{
    if (output+3 > outend)
        return NULL;

    output[2] = nVal & 0xff;
    output[1] = nVal >> 8;
    output[0] = nVal >> 16;
    return output+3;
}

/************************************************************************************************************
*	编码int32(这个整数占用四个字节);
*
*	依次截取1个字节进行赋值;
************************************************************************************************************/
char* AMF_EncodeInt32(char* output, char* outend, int nVal)
{
    if (output+4 > outend)
        return NULL;

    output[3] = nVal & 0xff;
    output[2] = nVal >> 8;
    output[1] = nVal >> 16;
    output[0] = nVal >> 24;
    return output+4;
}

/************************************************************************************************************
*	编码字符串bv;
*
*	第一个字节存字符串类型;
*	若字节小于65536,用两个字节存储长度; 否则用4个字节存储长度;
************************************************************************************************************/
char* AMF_EncodeString(char* output, char* outend, const AVal* bv)
{
	if ((bv->av_len < 65536 && output + 1 + 2 + bv->av_len > outend) || (output + 1 + 4 + bv->av_len > outend))
	{
        return NULL;
	}

	// 第一个字节存字符串类型;
	// 若字节小于65536, 用两个字节存储长度; 否则用4个字节存储长度;
    if (bv->av_len < 65536)
    {
        *output++ = AMF_STRING;
        output = AMF_EncodeInt16(output, outend, bv->av_len);
    }
    else
    {
        *output++ = AMF_LONG_STRING;
        output = AMF_EncodeInt32(output, outend, bv->av_len);
    }

	// 然后将avl内容赋值即可;
    memcpy(output, bv->av_val, bv->av_len);
    output += bv->av_len;

    return output;
}

/************************************************************************************************************
*	编码数值double;
*
*	float字的存储顺序等于字节顺序;
*		大端字节顺序,直接赋值; 小端字节顺序,反转赋值;
*
*	float字的存储顺序不等字节顺序;
*		大端字节顺序,反转赋值; 小端字节顺序,直接赋值;
************************************************************************************************************/
char* AMF_EncodeNumber(char* output, char* outend, double dVal)
{
	if (output + 1 + 8 > outend)
	{
        return NULL;
	}

    *output++ = AMF_NUMBER;	/* type: Number */

#if __FLOAT_WORD_ORDER == __BYTE_ORDER
#if __BYTE_ORDER == __BIG_ENDIAN
    memcpy(output, &dVal, 8);
#elif __BYTE_ORDER == __LITTLE_ENDIAN
    {
        unsigned char* ci, *co;
        ci = (unsigned char* )&dVal;
        co = (unsigned char* )output;
        co[0] = ci[7];
        co[1] = ci[6];
        co[2] = ci[5];
        co[3] = ci[4];
        co[4] = ci[3];
        co[5] = ci[2];
        co[6] = ci[1];
        co[7] = ci[0];
    }
#endif
#else
#if __BYTE_ORDER == __LITTLE_ENDIAN	/* __FLOAT_WORD_ORER == __BIG_ENDIAN */
    {
        unsigned char* ci, *co;
        ci = (unsigned char* )&dVal;
        co = (unsigned char* )output;
        co[0] = ci[3];
        co[1] = ci[2];
        co[2] = ci[1];
        co[3] = ci[0];
        co[4] = ci[7];
        co[5] = ci[6];
        co[6] = ci[5];
        co[7] = ci[4];
    }
#else /* __BYTE_ORDER == __BIG_ENDIAN && __FLOAT_WORD_ORER == __LITTLE_ENDIAN */
    {
        unsigned char* ci, *co;
        ci = (unsigned char* )&dVal;
        co = (unsigned char* )output;
        co[0] = ci[4];
        co[1] = ci[5];
        co[2] = ci[6];
        co[3] = ci[7];
        co[4] = ci[0];
        co[5] = ci[1];
        co[6] = ci[2];
        co[7] = ci[3];
    }
#endif
#endif

    return output+8;
}

/************************************************************************************************************
*	编码布尔;
*
*	第一个字节存字符串类型;
*	若二个字节： bVal若为真存1 为假存0;
************************************************************************************************************/
char* AMF_EncodeBoolean(char* output, char* outend, int bVal)
{
	if (output + 2 > outend)
	{
        return NULL;
	}

    *output++ = AMF_BOOLEAN;

    *output++ = bVal ? 0x01 : 0x00;

    return output;
}

/************************************************************************************************************
*	编码strName+strValue;
*
*	name : 长度+内容;
:	value: string编码;
************************************************************************************************************/
char* AMF_EncodeNamedString(char* output, char* outend, const AVal* strName, const AVal* strValue)
{
	if (output + 2 + strName->av_len > outend)
	{
        return NULL;
	}
    output = AMF_EncodeInt16(output, outend, strName->av_len);

    memcpy(output, strName->av_val, strName->av_len);
    output += strName->av_len;

    return AMF_EncodeString(output, outend, strValue);
}

/************************************************************************************************************
*	编码strName+dVal;
*
*	name : 长度+内容;
:	value: double编码;
************************************************************************************************************/
char* AMF_EncodeNamedNumber(char* output, char* outend, const AVal* strName, double dVal)
{
	if (output + 2 + strName->av_len > outend)
	{
        return NULL;
	}
    output = AMF_EncodeInt16(output, outend, strName->av_len);

    memcpy(output, strName->av_val, strName->av_len);
    output += strName->av_len;

    return AMF_EncodeNumber(output, outend, dVal);
}

/************************************************************************************************************
*	编码strName+dVal;
*
*	name : 长度+内容;
:	value: bool编码;
************************************************************************************************************/
char* AMF_EncodeNamedBoolean(char* output, char* outend, const AVal* strName, int bVal)
{
	if (output + 2 + strName->av_len > outend)
	{
        return NULL;
	}
    output = AMF_EncodeInt16(output, outend, strName->av_len);

    memcpy(output, strName->av_val, strName->av_len);
    output += strName->av_len;

    return AMF_EncodeBoolean(output, outend, bVal);
}

/************************************************************************************************************
*	获取对象属性的name;
*
************************************************************************************************************/
void AMFProp_GetName(AMFObjectProperty* prop, AVal* name)
{
    *name = prop->p_name;
}

/************************************************************************************************************
*	设置对象属性的name;
*
************************************************************************************************************/
void AMFProp_SetName(AMFObjectProperty* prop, AVal* name)
{
    prop->p_name = *name;
}

/************************************************************************************************************
*	获取对象属性的type;
*
************************************************************************************************************/
AMFDataType AMFProp_GetType(AMFObjectProperty* prop)
{
    return prop->p_type;
}

/************************************************************************************************************
*	设置对象属性的数值(double);
*
************************************************************************************************************/
double AMFProp_GetNumber(AMFObjectProperty* prop)
{
    return prop->p_vu.p_number;
}

/************************************************************************************************************
*	获取对象属性的数值(bool);
*
************************************************************************************************************/
int AMFProp_GetBoolean(AMFObjectProperty* prop)
{
    return prop->p_vu.p_number != 0;
}

/************************************************************************************************************
*	获取对象属性的数值(string);
*
************************************************************************************************************/
void AMFProp_GetString(AMFObjectProperty* prop, AVal* str)
{
    *str = prop->p_vu.p_aval;
}

/************************************************************************************************************
*	获取对象属性的数值(object);
*
************************************************************************************************************/
void AMFProp_GetObject(AMFObjectProperty* prop, AMFObject* obj)
{
    *obj = prop->p_vu.p_object;
}

/************************************************************************************************************
*	判断对象属性的类型是否有效;
*
************************************************************************************************************/
int AMFProp_IsValid(AMFObjectProperty* prop)
{
    return prop->p_type != AMF_INVALID;
}

/************************************************************************************************************
*	编码： 对象的属性prop;
*
************************************************************************************************************/
char* AMFProp_Encode(AMFObjectProperty* prop, char* pBuffer, char* pBufEnd)
{
	if (prop->p_type == AMF_INVALID)
	{
        return NULL;
	}

	if (prop->p_type != AMF_NULL && pBuffer + prop->p_name.av_len + 2 + 1 >= pBufEnd)
	{
        return NULL;
	}

	// 编码对象的name,两个字节存长度;
	// 之所以不直接调用AMF_EncodeString 是因为会多存一个字节(表示数据类型);
    if (prop->p_type != AMF_NULL && prop->p_name.av_len)
    {
        *pBuffer++ = prop->p_name.av_len >> 8;
        *pBuffer++ = prop->p_name.av_len & 0xff;
        memcpy(pBuffer, prop->p_name.av_val, prop->p_name.av_len);
        pBuffer += prop->p_name.av_len;
    }

	// 编码对象的value, 不同类型不同处理;
    switch (prop->p_type)
    {
	case AMF_NUMBER:
		{
			pBuffer = AMF_EncodeNumber(pBuffer, pBufEnd, prop->p_vu.p_number);
		}
        break;
	case AMF_BOOLEAN:
		{
			pBuffer = AMF_EncodeBoolean(pBuffer, pBufEnd, prop->p_vu.p_number != 0);
		}
        break;
	case AMF_STRING:
		{
			pBuffer = AMF_EncodeString(pBuffer, pBufEnd, &prop->p_vu.p_aval);
		}
        break;
	case AMF_NULL:
		{
			if (pBuffer+1 >= pBufEnd)
			{
				return NULL;
			}
			*pBuffer++ = AMF_NULL;
		}
        break;
	case AMF_OBJECT:
		{
			pBuffer = AMF_Encode(&prop->p_vu.p_object, pBuffer, pBufEnd);
		}
        break;
	case AMF_ECMA_ARRAY:
		{
			pBuffer = AMF_EncodeEcmaArray(&prop->p_vu.p_object, pBuffer, pBufEnd);
		}
        break;
	case AMF_STRICT_ARRAY:
		{
			pBuffer = AMF_EncodeArray(&prop->p_vu.p_object, pBuffer, pBufEnd);
		}
        break;
	default:
		{
			RTMP_Log(RTMP_LOGERROR, "%s, invalid type. %d", __FUNCTION__, prop->p_type);
			pBuffer = NULL;
		}
		break;
    };

    return pBuffer;
}

#define AMF3_INTEGER_MAX	268435455
#define AMF3_INTEGER_MIN	-268435456

/************************************************************************************************************
*	AMF读取数值;
*
************************************************************************************************************/
int AMF3ReadInteger(const char* data, int32_t* valp)
{
    int i = 0;
    int32_t val = 0;

    while (i <= 2)
    {
        /* handle first 3 bytes */
        if (data[i] & 0x80)
        {
            /* byte used */
            val <<= 7;					/* shift up */
            val |= (data[i] & 0x7f);	/* add bits */
            i++;
        }
        else
        {
            break;
        }
    }

    if (i > 2)
    {
        /* use 4th byte, all 8bits */
        val <<= 8;
        val |= data[3];

        /* range check */
		if (val > AMF3_INTEGER_MAX)
		{
            val -= (1 << 29);
		}
    }
    else
    {
        /* use 7bits of last unparsed byte (0xxxxxxx) */
        val <<= 7;
        val |= data[i];
    }

    *valp = val;

    return i > 2 ? 4 : i + 1;
}

int AMF3ReadString(const char* data, AVal* str)
{
    int32_t ref = 0;
    int len;
    assert(str != 0);

    len = AMF3ReadInteger(data, &ref);
    data += len;

    if ((ref & 0x1) == 0)
    {
        /* reference: 0xxx */
        uint32_t refIndex = (ref >> 1);
        RTMP_Log(RTMP_LOGDEBUG, "%s, string reference, index: %d, not supported, ignoring!", __FUNCTION__, refIndex);
        return len;
    }
    else
    {
        uint32_t nSize = (ref >> 1);

        str->av_val = (char* )data;
        str->av_len = nSize;

        return len + nSize;
    }
    return len;
}

int AMF3Prop_Decode(AMFObjectProperty* prop, const char* pBuffer, int nSize,
                int bDecodeName)
{
    int nOriginalSize = nSize;
    AMF3DataType type;

    prop->p_name.av_len = 0;
    prop->p_name.av_val = NULL;

    if (nSize == 0 || !pBuffer)
    {
        RTMP_Log(RTMP_LOGDEBUG, "empty buffer/no buffer pointer!");
        return -1;
    }

    /* decode name */
    if (bDecodeName)
    {
        AVal name = AV_empty;
        int nRes = AMF3ReadString(pBuffer, &name);

        if (name.av_len <= 0)
            return nRes;

        prop->p_name = name;
        pBuffer += nRes;
        nSize -= nRes;
    }

    /* decode */
    type = *pBuffer++;
    nSize--;

    switch (type)
    {
    case AMF3_UNDEFINED:
    case AMF3_NULL:
        prop->p_type = AMF_NULL;
        break;
    case AMF3_FALSE:
        prop->p_type = AMF_BOOLEAN;
        prop->p_vu.p_number = 0.0;
        break;
    case AMF3_TRUE:
        prop->p_type = AMF_BOOLEAN;
        prop->p_vu.p_number = 1.0;
        break;
    case AMF3_INTEGER:
    {
        int32_t res = 0;
        int len = AMF3ReadInteger(pBuffer, &res);
        prop->p_vu.p_number = (double)res;
        prop->p_type = AMF_NUMBER;
        nSize -= len;
        break;
    }
    case AMF3_DOUBLE:
        if (nSize < 8)
            return -1;
        prop->p_vu.p_number = AMF_DecodeNumber(pBuffer);
        prop->p_type = AMF_NUMBER;
        nSize -= 8;
        break;
    case AMF3_STRING:
    case AMF3_XML_DOC:
    case AMF3_XML:
    {
        int len = AMF3ReadString(pBuffer, &prop->p_vu.p_aval);
        prop->p_type = AMF_STRING;
        nSize -= len;
        break;
    }
    case AMF3_DATE:
    {
        int32_t res = 0;
        int len = AMF3ReadInteger(pBuffer, &res);

        nSize -= len;
        pBuffer += len;

        if ((res & 0x1) == 0)
        {
            /* reference */
            uint32_t nIndex = (res >> 1);
            RTMP_Log(RTMP_LOGDEBUG, "AMF3_DATE reference: %d, not supported!", nIndex);
        }
        else
        {
            if (nSize < 8)
                return -1;

            prop->p_vu.p_number = AMF_DecodeNumber(pBuffer);
            nSize -= 8;
            prop->p_type = AMF_NUMBER;
        }
        break;
    }
    case AMF3_OBJECT:
    {
        int nRes = AMF3_Decode(&prop->p_vu.p_object, pBuffer, nSize, TRUE);
        if (nRes == -1)
            return -1;
        nSize -= nRes;
        prop->p_type = AMF_OBJECT;
        break;
    }
    case AMF3_ARRAY:
    case AMF3_BYTE_ARRAY:
    default:
        RTMP_Log(RTMP_LOGDEBUG, "%s - AMF3 unknown/unsupported datatype 0x%02x, @%p",
                 __FUNCTION__, (unsigned char)(*pBuffer), pBuffer);
        return -1;
    }

    return nOriginalSize - nSize;
}

/************************************************************************************************************
*	解码： pBuffer->prop;
*
************************************************************************************************************/
int AMFProp_Decode(AMFObjectProperty* prop, const char* pBuffer, int nSize,
               int bDecodeName)
{
    int nOriginalSize = nSize;
    int nRes;

    prop->p_name.av_len = 0;
    prop->p_name.av_val = NULL;

    if (nSize == 0 || !pBuffer)
    {
        RTMP_Log(RTMP_LOGDEBUG, "%s: Empty buffer/no buffer pointer!", __FUNCTION__);
        return -1;
    }

    if (bDecodeName && nSize < 4)
    {
        /* at least name (length + at least 1 byte) and 1 byte of data */
        RTMP_Log(RTMP_LOGDEBUG, "%s: Not enough data for decoding with name, less than 4 bytes!", __FUNCTION__);
        return -1;
    }

    if (bDecodeName)
    {
		// 解码对象属性的name;
        unsigned short nNameSize = AMF_DecodeInt16(pBuffer);
        if (nNameSize > nSize - 2)
        {
            RTMP_Log(RTMP_LOGDEBUG, "%s: Name size out of range: namesize (%d) > len (%d) - 2", __FUNCTION__, nNameSize, nSize);
            return -1;
        }

        AMF_DecodeString(pBuffer, &prop->p_name);
        nSize -= 2 + nNameSize;
        pBuffer += 2 + nNameSize;
    }

    if (nSize == 0)
    {
        return -1;
    }

	// 获取属性类型;
    nSize--;
    prop->p_type = *pBuffer++;
    switch (prop->p_type)
    {
	case AMF_NUMBER:
		{
			if (nSize < 8)
			{
				return -1;
			}

			prop->p_vu.p_number = AMF_DecodeNumber(pBuffer);
			nSize -= 8;
		}
        break;
	case AMF_BOOLEAN:
		{
			if (nSize < 1)
			{
				return -1;
			}

			prop->p_vu.p_number = (double)AMF_DecodeBoolean(pBuffer);
			nSize--;
		}
		break;
    case AMF_STRING:
		{
			unsigned short nStringSize = AMF_DecodeInt16(pBuffer);
			if (nSize < (long)nStringSize + 2)
			{
				return -1;
			}
			AMF_DecodeString(pBuffer, &prop->p_vu.p_aval);
			nSize -= (2 + nStringSize);
		}
		break;
    case AMF_OBJECT:
		{
			int nRes = AMF_Decode(&prop->p_vu.p_object, pBuffer, nSize, TRUE);
			if (nRes == -1)
			{
				return -1;
			}
			nSize -= nRes;
		}
		break;
    case AMF_MOVIECLIP:
		{
			RTMP_Log(RTMP_LOGERROR, "AMF_MOVIECLIP reserved!");
			return -1;
		}
		break;
    case AMF_NULL:
    case AMF_UNDEFINED:
	case AMF_UNSUPPORTED:
		{
			prop->p_type = AMF_NULL;
		}
        break;
    case AMF_REFERENCE:
		{
			RTMP_Log(RTMP_LOGERROR, "AMF_REFERENCE not supported!");
			return -1;
		}
		break;
    case AMF_ECMA_ARRAY:
		{
			nSize -= 4;
			/* next comes the rest, mixed array has a final 0x000009 mark and names, so its an object */
			nRes = AMF_Decode(&prop->p_vu.p_object, pBuffer + 4, nSize, TRUE);
			if (nRes == -1)
			{
				return -1;
			}
			nSize -= nRes;
		}
		break;
    case AMF_OBJECT_END:
		{
			return -1;
		}
		break;
    case AMF_STRICT_ARRAY:
		{
			unsigned int nArrayLen = AMF_DecodeInt32(pBuffer);
			nSize -= 4;
			nRes = AMF_DecodeArray(&prop->p_vu.p_object, pBuffer + 4, nSize, nArrayLen, FALSE);
			if (nRes == -1)
			{
				return -1;
			}
			nSize -= nRes;
		}
		break;
    case AMF_DATE:
		{
			RTMP_Log(RTMP_LOGDEBUG, "AMF_DATE");
			if (nSize < 10)
			{
				return -1;
			}
			prop->p_vu.p_number = AMF_DecodeNumber(pBuffer);
			prop->p_UTCoffset = AMF_DecodeInt16(pBuffer + 8);

			nSize -= 10;
		}
		break;
    case AMF_LONG_STRING:
    case AMF_XML_DOC:
		{
			unsigned int nStringSize = AMF_DecodeInt32(pBuffer);
			if (nSize < (long)nStringSize + 4)
			{
				return -1;
			}
			AMF_DecodeLongString(pBuffer, &prop->p_vu.p_aval);
			nSize -= (4 + nStringSize);
			if (prop->p_type == AMF_LONG_STRING)
			{
				prop->p_type = AMF_STRING;
			}
		}
		break;
    case AMF_RECORDSET:
		{
			RTMP_Log(RTMP_LOGERROR, "AMF_RECORDSET reserved!");
			return -1;
		}
		break;
    case AMF_TYPED_OBJECT:
		{
			RTMP_Log(RTMP_LOGERROR, "AMF_TYPED_OBJECT not supported!");
			return -1;
		}
		break;
    case AMF_AVMPLUS:
		{
			int nRes = AMF3_Decode(&prop->p_vu.p_object, pBuffer, nSize, TRUE);
			if (nRes == -1)
			{
				return -1;
			}
			nSize -= nRes;
			prop->p_type = AMF_OBJECT;
		}
		break;
	default:
		{
			RTMP_Log(RTMP_LOGDEBUG, "%s - unknown datatype 0x%02x, @%p", __FUNCTION__, prop->p_type, pBuffer - 1);
			return -1;
		}
		break;
    }

    return nOriginalSize - nSize;
}

/************************************************************************************************************
*	对属性prop进行输出显示,用于调试;
*
************************************************************************************************************/
void AMFProp_Dump(AMFObjectProperty* prop)
{
    char strRes[256];
    char str[256];
    AVal name;

    if (prop->p_type == AMF_INVALID)
    {
        RTMP_Log(RTMP_LOGDEBUG, "Property: INVALID");
        return;
    }

    if (prop->p_type == AMF_NULL)
    {
        RTMP_Log(RTMP_LOGDEBUG, "Property: NULL");
        return;
    }

    if (prop->p_name.av_len)
    {
        name = prop->p_name;
    }
    else
    {
        name.av_val = "no-name.";
        name.av_len = sizeof("no-name.") - 1;
    }
	if (name.av_len > 18)
	{
        name.av_len = 18;
	}
    snprintf(strRes, 255, "Name: %18.*s, ", name.av_len, name.av_val);

    switch (prop->p_type)
    {
	case AMF_OBJECT:
		{
			RTMP_Log(RTMP_LOGDEBUG, "Property: <%sOBJECT>", strRes);
			AMF_Dump(&prop->p_vu.p_object);
			return;
		}
		break;
	case AMF_ECMA_ARRAY:
		{
			RTMP_Log(RTMP_LOGDEBUG, "Property: <%sECMA_ARRAY>", strRes);
			AMF_Dump(&prop->p_vu.p_object);
			return;
		}
		break;
	case AMF_STRICT_ARRAY:
		{
			RTMP_Log(RTMP_LOGDEBUG, "Property: <%sSTRICT_ARRAY>", strRes);
			AMF_Dump(&prop->p_vu.p_object);
			return;
		}
		break;
    case AMF_NUMBER:
        snprintf(str, 255, "NUMBER:\t%.2f", prop->p_vu.p_number);
        break;
    case AMF_BOOLEAN:
        snprintf(str, 255, "BOOLEAN:\t%s", prop->p_vu.p_number != 0.0 ? "TRUE" : "FALSE");
        break;
    case AMF_STRING:
        snprintf(str, 255, "STRING:\t%.*s", prop->p_vu.p_aval.av_len, prop->p_vu.p_aval.av_val);
        break;
    case AMF_DATE:
        snprintf(str, 255, "DATE:\ttimestamp: %.2f, UTC offset: %d", prop->p_vu.p_number, prop->p_UTCoffset);
        break;
    default:
        snprintf(str, 255, "INVALID TYPE 0x%02x", (unsigned char)prop->p_type);
		break;
    }

    RTMP_Log(RTMP_LOGDEBUG, "Property: <%s%s>", strRes, str);
}

/************************************************************************************************************
*	属性prop的重置;
*
************************************************************************************************************/
void AMFProp_Reset(AMFObjectProperty* prop)
{
	if (prop->p_type == AMF_OBJECT || prop->p_type == AMF_ECMA_ARRAY || prop->p_type == AMF_STRICT_ARRAY)
	{
        AMF_Reset(&prop->p_vu.p_object);
	}
    else
    {
        prop->p_vu.p_aval.av_len = 0;
        prop->p_vu.p_aval.av_val = NULL;
    }
    prop->p_type = AMF_INVALID;
}

/************************************************************************************************************
*	编码: obj->pBuffer;
*
************************************************************************************************************/
char*  AMF_Encode(AMFObject* obj, char* pBuffer, char* pBufEnd)
{
    int i;
	if (pBuffer + 4 >= pBufEnd)
	{
		return NULL;
	}
    *pBuffer++ = AMF_OBJECT;

    for (i = 0; i < obj->o_num; i++)
    {
		// 各个属性依次编码;
        char* res = AMFProp_Encode(&obj->o_props[i], pBuffer, pBufEnd);
        if (res == NULL)
        {
            RTMP_Log(RTMP_LOGERROR, "AMF_Encode - failed to encode property in index %d", i);
            break;
        }
        else
        {
            pBuffer = res;
        }
    }

	if (pBuffer + 3 >= pBufEnd)
	{
        return NULL;			/* no room for the end marker */
	}

	// oject的对象需要以009结尾标识;
    pBuffer = AMF_EncodeInt24(pBuffer, pBufEnd, AMF_OBJECT_END);

    return pBuffer;
}

/************************************************************************************************************
*	编码: obj->pBuffer;
*
************************************************************************************************************/
char* AMF_EncodeEcmaArray(AMFObject* obj, char* pBuffer, char* pBufEnd)
{
    int i;
	if (pBuffer + 4 >= pBufEnd)
	{
        return NULL;
	}
    *pBuffer++ = AMF_ECMA_ARRAY;

	// 数组需要把个数编码进去;
    pBuffer = AMF_EncodeInt32(pBuffer, pBufEnd, obj->o_num);
    for (i = 0; i < obj->o_num; i++)
    {
        char* res = AMFProp_Encode(&obj->o_props[i], pBuffer, pBufEnd);
        if (res == NULL)
        {
            RTMP_Log(RTMP_LOGERROR, "AMF_Encode - failed to encode property in index %d", i);
            break;
        }
        else
        {
            pBuffer = res;
        }
    }

	if (pBuffer + 3 >= pBufEnd)
	{
        return NULL;			/* no room for the end marker */
	}

	// oject的对象需要以009结尾标识;
    pBuffer = AMF_EncodeInt24(pBuffer, pBufEnd, AMF_OBJECT_END);

    return pBuffer;
}

/************************************************************************************************************
*	编码: obj->pBuffer;
*
************************************************************************************************************/
char* AMF_EncodeArray(AMFObject* obj, char* pBuffer, char* pBufEnd)
{
    int i;
	if (pBuffer + 4 >= pBufEnd)
	{
        return NULL;
	}
    *pBuffer++ = AMF_STRICT_ARRAY;

	// 数组需要把个数编码进去;
    pBuffer = AMF_EncodeInt32(pBuffer, pBufEnd, obj->o_num);
    for (i = 0; i < obj->o_num; i++)
    {
        char* res = AMFProp_Encode(&obj->o_props[i], pBuffer, pBufEnd);
        if (res == NULL)
        {
            RTMP_Log(RTMP_LOGERROR, "AMF_Encode - failed to encode property in index %d",
                     i);
            break;
        }
        else
        {
            pBuffer = res;
        }
    }

	// 此处oject的对象不需要以009结尾标识;
    //if (pBuffer + 3 >= pBufEnd)
    //  return NULL;			/* no room for the end marker */

    //pBuffer = AMF_EncodeInt24(pBuffer, pBufEnd, AMF_OBJECT_END);

    return pBuffer;
}

/************************************************************************************************************
*	解码: pBuffer->obj;
*
************************************************************************************************************/
int AMF_DecodeArray(AMFObject* obj, const char* pBuffer, int nSize,
                int nArrayLen, int bDecodeName)
{
    int nOriginalSize = nSize;
    int bError = FALSE;

    obj->o_num = 0;
    obj->o_props = NULL;
    while (nArrayLen > 0)
    {
        AMFObjectProperty prop;
        int nRes;
        nArrayLen--;

        nRes = AMFProp_Decode(&prop, pBuffer, nSize, bDecodeName);
		if (nRes == -1)
		{
            bError = TRUE;
		}
        else
        {
			// 解码出来的属性追加到obj上;
            nSize -= nRes;
            pBuffer += nRes;
            AMF_AddProp(obj, &prop);
        }
    }
	if (bError)
	{
        return -1;
	}

    return nOriginalSize - nSize;
}

int AMF3_Decode(AMFObject* obj, const char* pBuffer, int nSize, int bAMFData)
{
    int nOriginalSize = nSize;
    int32_t ref;
    int len;

    obj->o_num = 0;
    obj->o_props = NULL;
    if (bAMFData)
    {
		if (*pBuffer != AMF3_OBJECT)
		{
			RTMP_Log(RTMP_LOGERROR, "AMF3 Object encapsulated in AMF stream does not start with AMF3_OBJECT!");
		}

        pBuffer++;
        nSize--;
    }

    ref = 0;
    len = AMF3ReadInteger(pBuffer, &ref);
    pBuffer += len;
    nSize -= len;

    if ((ref & 1) == 0)
    {
        /* object reference, 0xxx */
        uint32_t objectIndex = (ref >> 1);

        RTMP_Log(RTMP_LOGDEBUG, "Object reference, index: %d", objectIndex);
    }
    else				/* object instance */
    {
        int32_t classRef = (ref >> 1);

        AMF3ClassDef cd = { {0, 0} };
        AMFObjectProperty prop;

        if ((classRef & 0x1) == 0)
        {
            /* class reference */
            uint32_t classIndex = (classRef >> 1);
            RTMP_Log(RTMP_LOGDEBUG, "Class reference: %d", classIndex);
        }
        else
        {
            int32_t classExtRef = (classRef >> 1);
            int i;

            cd.cd_externalizable = (classExtRef & 0x1) == 1;
            cd.cd_dynamic = ((classExtRef >> 1) & 0x1) == 1;

            cd.cd_num = classExtRef >> 2;

            /* class name */

            len = AMF3ReadString(pBuffer, &cd.cd_name);
            nSize -= len;
            pBuffer += len;

            /*std::string str = className; */

            RTMP_Log(RTMP_LOGDEBUG,
                     "Class name: %s, externalizable: %d, dynamic: %d, classMembers: %d",
                     cd.cd_name.av_val, cd.cd_externalizable, cd.cd_dynamic,
                     cd.cd_num);

            for (i = 0; i < cd.cd_num; i++)
            {
                AVal memberName = AV_empty;
                len = AMF3ReadString(pBuffer, &memberName);
                RTMP_Log(RTMP_LOGDEBUG, "Member: %s", memberName.av_val);
                AMF3CD_AddProp(&cd, &memberName);
                nSize -= len;
                pBuffer += len;
            }
        }

        /* add as referencable object */

        if (cd.cd_externalizable)
        {
            int nRes;
            AVal name = AVC("DEFAULT_ATTRIBUTE");

            RTMP_Log(RTMP_LOGDEBUG, "Externalizable, TODO check");

            nRes = AMF3Prop_Decode(&prop, pBuffer, nSize, FALSE);
            if (nRes == -1)
                RTMP_Log(RTMP_LOGDEBUG, "%s, failed to decode AMF3 property!",
                         __FUNCTION__);
            else
            {
                nSize -= nRes;
                pBuffer += nRes;
            }

            AMFProp_SetName(&prop, &name);
            AMF_AddProp(obj, &prop);
        }
        else
        {
            int nRes, i;
            for (i = 0; i < cd.cd_num; i++)	/* non-dynamic */
            {
                nRes = AMF3Prop_Decode(&prop, pBuffer, nSize, FALSE);
                if (nRes == -1)
                    RTMP_Log(RTMP_LOGDEBUG, "%s, failed to decode AMF3 property!",
                             __FUNCTION__);

                AMFProp_SetName(&prop, AMF3CD_GetProp(&cd, i));
                AMF_AddProp(obj, &prop);

                pBuffer += nRes;
                nSize -= nRes;
            }
            if (cd.cd_dynamic)
            {
                int len = 0;

                do
                {
                    nRes = AMF3Prop_Decode(&prop, pBuffer, nSize, TRUE);
                    AMF_AddProp(obj, &prop);

                    pBuffer += nRes;
                    nSize -= nRes;

                    len = prop.p_name.av_len;
                }
                while (len > 0);
            }
        }
        RTMP_Log(RTMP_LOGDEBUG, "class object!");
    }
    return nOriginalSize - nSize;
}

/************************************************************************************************************
*	解码: pBuffer->obj;
*
************************************************************************************************************/
int AMF_Decode(AMFObject* obj, const char* pBuffer, int nSize, int bDecodeName)
{
    int nOriginalSize = nSize;

    int bError = FALSE;
	/* if there is an error while decoding - try to at least find the end mark AMF_OBJECT_END */
	// 如果解码出错,会尝试查找009结束标识符;

    obj->o_num = 0;
    obj->o_props = NULL;
    while (nSize > 0)
    {
        AMFObjectProperty prop;
        int nRes;

        if (nSize >=3 && AMF_DecodeInt24(pBuffer) == AMF_OBJECT_END)
        {
            nSize -= 3;
            bError = FALSE;
            break;
        }

        if (bError)
        {
            RTMP_Log(RTMP_LOGERROR, "DECODING ERROR, IGNORING BYTES UNTIL NEXT KNOWN PATTERN!");
            nSize--;
            pBuffer++;
            continue;
        }

        nRes = AMFProp_Decode(&prop, pBuffer, nSize, bDecodeName);
		if (nRes == -1)
		{
            bError = TRUE;
		}
        else
        {
			// 解码出来的属性追加到obj上;
            nSize -= nRes;
            pBuffer += nRes;
            AMF_AddProp(obj, &prop);
        }
    }

	if (bError)
	{
        return -1;
	}

    return nOriginalSize - nSize;
}

/************************************************************************************************************
*	将属性prop追加到obj上(深拷贝实现);
*
************************************************************************************************************/
void AMF_AddProp(AMFObject* obj, const AMFObjectProperty* prop)
{
	if (!(obj->o_num & 0x0f))
	{
		// 此处的意思每次一次性申请16块内存, 若第17个属性追加时还会触发再申请16块内存;
		obj->o_props = realloc(obj->o_props, (obj->o_num + 16) * sizeof(AMFObjectProperty));
	}

    memcpy(&obj->o_props[obj->o_num++], prop, sizeof(AMFObjectProperty));
}

/************************************************************************************************************
*	获取obj内的属性数量;
*
************************************************************************************************************/
int AMF_CountProp(AMFObject* obj)
{
    return obj->o_num;
}

/************************************************************************************************************
*	获取obj内的某个属性;
*
*	优先以nIndex进行返回, 若nIndex<0 会根据name进行筛选;
************************************************************************************************************/
AMFObjectProperty* AMF_GetProp(AMFObject* obj, const AVal* name, int nIndex)
{
    if (nIndex >= 0)
    {
		if (nIndex < obj->o_num)
		{
            return &obj->o_props[nIndex];
		}
    }
    else
    {
        int n;
        for (n = 0; n < obj->o_num; n++)
        {
			if (AVMATCH(&obj->o_props[n].p_name, name))
			{
               return &obj->o_props[n];
			}
        }
    }

    return (AMFObjectProperty* )&AMFProp_Invalid;
}

/************************************************************************************************************
*	对obj内的所有属性进行输出显示,用于调试;
*
************************************************************************************************************/
void AMF_Dump(AMFObject* obj)
{
    int n;
    RTMP_Log(RTMP_LOGDEBUG, "(object begin)");
    for (n = 0; n < obj->o_num; n++)
    {
        AMFProp_Dump(&obj->o_props[n]);
    }
    RTMP_Log(RTMP_LOGDEBUG, "(object end)");
}

/************************************************************************************************************
*	对obj内的所有属性进行重置,最后并释放属性数组;
*
************************************************************************************************************/
void AMF_Reset(AMFObject* obj)
{
    int n;
    for (n = 0; n < obj->o_num; n++)
    {
        AMFProp_Reset(&obj->o_props[n]);
    }
    free(obj->o_props);
    obj->o_props = NULL;
    obj->o_num = 0;
}

/* AMF3ClassDefinition */
/************************************************************************************************************
*	将字符串prop追加到cd内的字符串数组中(深拷贝);
*
************************************************************************************************************/
void AMF3CD_AddProp(AMF3ClassDef* cd, AVal* prop)
{
	if (!(cd->cd_num & 0x0f))
	{
        cd->cd_props = realloc(cd->cd_props, (cd->cd_num + 16) * sizeof(AVal));
	}
    cd->cd_props[cd->cd_num++] = *prop;
}

/************************************************************************************************************
*	获取cd对象内的字符串数组内的第nIndex个字符串;
*
************************************************************************************************************/
AVal* AMF3CD_GetProp(AMF3ClassDef* cd, int nIndex)
{
	if (nIndex >= cd->cd_num)
	{
        return (AVal* )&AV_empty;
	}
    return &cd->cd_props[nIndex];
}