先复习何谓大小端
小端格式和大端格式(Little-Endian&Big-Endian)
x86系列的CPU都是little-endian的字节序。
C语言和C#语言中,对于浮点类型的数据采用单精度类型(float)和双精度类型(double)来存储,float数据占用32bit,double数据占用64bit,我们在声明一个变量float f= 2.25f的时候,是如何分配内存的呢?如果胡乱分配,那世界岂不是乱套了么,其实不论是float还是double在存储方式上都是遵从IEEE的规范的,float遵从的是IEEE R32.24 ,而double 遵从的是R64.53。
无论是单精度还是双精度在存储中都分为三个部分:
- 符号位(Sign) : 0代表正,1代表为负
- 指数位(Exponent):用于存储科学计数法中的指数数据,并且采用移位存储
- 尾数部分(Mantissa):尾数部分
其中float的存储方式如下图所示:
而双精度的存储方式为:
S | E | M | 表示公式 | 偏移量 | |
单精度浮点数 |
1(第31位) |
8(30到23位) |
23(22到0位) |
(-1)^S*2(E-127)*1.M |
127 |
双精度浮点数 |
1(第63位) |
11(62到52位) |
52(51到0位) |
(-1)^S*2(E-1023)*1.M |
1023 |
M为尾数,其中单精度数为23位长,双精度数为52位长。IEEE标准要求浮点数必须是规范的。这意味着尾数的小数点左侧必须为1,因此在保存尾数的时候,可以省略小数点前面这个1,从而腾出一个二进制位来保存更多的尾数。这样实际上用23位长的尾数域表达了24位的尾数。例如对于单精度数而言,二进制的1001.101(对应于十进制的9.625)可以表达为1.001101 × 23,所以实际保存在尾数域中的值为00110100000000000000000,即去掉小数点左侧的1,并用0在右侧补齐。
根据标准要求,无法精确保存的值必须向最接近的可保存的值进行舍入,即不足一半则舍,一半以上(包括一半)则进。不过对于二进制浮点数而言,还多一条规矩,就是当需要舍入的值刚好是一半时,不是简单地进,而是在前后两个等距接近的可保存的值中,取其中最后一位有效数字为零者。
据以上分析,IEEE 754标准中定义浮点数的表示范围为:
二进制(Binary) |
十进制(Decimal) |
|
单精度浮点数 |
± (2-2^-23) × 2127 |
~ ± 10^38.53 |
双精度浮点数 |
± (2-2^-52) × 21023 |
~ ± 10^308.25 |
1、当P=0,M=0时,表示0。
2、当P=255,M=0时,表示无穷大,用符号位来确定是正无穷大还是负无穷大。
3、当P=255,M≠0时,表示NaN(Not a Number,不是一个数)。
R32.24和R64.53的存储方式都是用科学计数法来存储数据的,比如8.25用十进制的科学计数法表示就为:8.25*,而120.5可以表示为:1.205*,这些小学的知识就不用多说了吧。而我们傻蛋计算机根本不认识十进制的数据,他只认识0,1,所以在计算机存储中,首先要将上面的数更改为二进制的科学计数法表示,8.25用二进制表示可表示为1000.01,我靠,不会连这都不会转换吧?那我估计要没辙了。120.5用二进制表示为:1110110.1用二进制的科学计数法表示1000.01可以表示为1.0001*,1110110.1可以表示为1.1101101*,任何一个数都的科学计数法表示都为1.xxx*,尾数部分就可以表示为xxxx,第一位都是1嘛,干嘛还要表示呀?可以将小数点前面的1省略,所以23bit的尾数部分,可以表示的精度却变成了24bit,道理就是在这里,那24bit能精确到小数点后几位呢,我们知道9的二进制表示为1001,所以4bit能精确十进制中的1位小数点,24bit就能使float能精确到小数点后6位,而对于指数部分,因为指数可正可负,8位的指数位能表示的指数范围就应该为:-127-128了,所以指数部分的存储采用移位存储,存储的数据为元数据+127,下面就看看8.25和120.5在内存中真正的存储方式。
首先看下8.25,用二进制的科学计数法表示为:1.0001*
按照上面的存储方式,符号位为:0,表示为正,指数位为:3+127=130 ,位数部分为,故8.25的存储方式如下图所示:
而单精度浮点数120.5的存储方式如下图所示:
那么如果给出内存中一段数据,并且告诉你是单精度存储的话,你如何知道该数据的十进制数值呢?其实就是对上面的反推过程,比如给出如下内存数据:0100001011101101000000000000,首先我们现将该数据分段,0 10000 0101 110 1101 0000 0000 0000 0000,在内存中的存储就为下图所示:
根据我们的计算方式,可以计算出,这样一组数据表示为:1.1101101*=120.5
而双精度浮点数的存储和单精度的存储大同小异,不同的是指数部分和尾数部分的位数。所以这里不再详细的介绍双精度的存储方式了,只将120.5的最后存储方式图给出,大家可以仔细想想为何是这样子的
下面我就这个基础知识点来解决一个我们的一个疑惑,请看下面一段程序,注意观察输出结果
float f = 2.2f;
double d = (double)f;
Console.WriteLine(d.ToString("0.0000000000000"));
f = 2.25f;
d = (double)f;
Console.WriteLine(d.ToString("0.0000000000000"));
可能输出的结果让大家疑惑不解,单精度的2.2转换为双精度后,精确到小数点后13位后变为了2.2000000476837,而单精度的2.25转换为双精度后,变为了2.2500000000000,为何2.2在转换后的数值更改了而2.25却没有更改呢?很奇怪吧?其实通过上面关于两种存储结果的介绍,我们已经大概能找到答案。首先我们看看2.25的单精度存储方式,很简单 0 1000 0001 001 0000 0000 0000 0000 0000,而2.25的双精度表示为:0 100 0000 0001 0010 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000,这样2.25在进行强制转换的时候,数值是不会变的,而我们再看看2.2呢,2.2用科学计数法表示应该为:将十进制的小数转换为二进制的小数的方法为将小数*2,取整数部分,所以0.282=0.4,所以二进制小数第一位为0.4的整数部分0,0.4×2=0.8,第二位为0,0.8*2=1.6,第三位为1,0.6×2 = 1.2,第四位为1,0.2*2=0.4,第五位为0,这样永远也不可能乘到=1.0,得到的二进制是一个无限循环的排列 00110011001100110011... ,对于单精度数据来说,尾数只能表示24bit的精度,所以2.2的float存储为:
但是这样存储方式,换算成十进制的值,却不会是2.2的,应为十进制在转换为二进制的时候可能会不准确,如2.2,而double类型的数据也存在同样的问题,所以在浮点数表示中会产生些许的误差,在单精度转换为双精度的时候,也会存在误差的问题,对于能够用二进制表示的十进制数据,如2.25,这个误差就会不存在,所以会出现上面比较奇怪的输出结果。
Bytes.h
//自已字节序的一些宏,在win32平台下,系统的字节序默认为小端字节序
#ifndef __BYTES_H__
#define __BYTES_H__
#include <stdint.h>
#ifdef _WIN32
/* Windows is little endian only */
#define __LITTLE_ENDIAN 1234
#define __BIG_ENDIAN 4321
#define __BYTE_ORDER __LITTLE_ENDIAN
#define __FLOAT_WORD_ORDER __BYTE_ORDER
typedef unsigned char uint8_t;
#else /* !_WIN32 */
#include <sys/param.h>
#if defined(BYTE_ORDER) && !defined(__BYTE_ORDER)
#define __BYTE_ORDER BYTE_ORDER
#endif
#if defined(BIG_ENDIAN) && !defined(__BIG_ENDIAN)
#define __BIG_ENDIAN BIG_ENDIAN
#endif
#if defined(LITTLE_ENDIAN) && !defined(__LITTLE_ENDIAN)
#define __LITTLE_ENDIAN LITTLE_ENDIAN
#endif
#endif /* !_WIN32 */
/* define default endianness */
#ifndef __LITTLE_ENDIAN
#define __LITTLE_ENDIAN 1234
#endif
#ifndef __BIG_ENDIAN
#define __BIG_ENDIAN 4321
#endif
#ifndef __BYTE_ORDER
#warning "Byte order not defined on your system, assuming little endian!"
#define __BYTE_ORDER __LITTLE_ENDIAN
#endif
/* ok, we assume to have the same float word order and byte order if float word order is not defined */
#ifndef __FLOAT_WORD_ORDER
#warning "Float word order not defined, assuming the same as byte order!"
#define __FLOAT_WORD_ORDER __BYTE_ORDER
#endif
#if !defined(__BYTE_ORDER) || !defined(__FLOAT_WORD_ORDER)
#error "Undefined byte or float word order!"
#endif
#if __FLOAT_WORD_ORDER != __BIG_ENDIAN && __FLOAT_WORD_ORDER != __LITTLE_ENDIAN
#error "Unknown/unsupported float word order!"
#endif
#if __BYTE_ORDER != __BIG_ENDIAN && __BYTE_ORDER != __LITTLE_ENDIAN
#error "Unknown/unsupported byte order!"
#endif
#endif
amf.h
#include <stdint.h>
#ifndef TRUE
#define TRUE 1
#define FALSE 0
#endif
#ifdef __cplusplus
extern "C"
{
#endif
//AMF0的数据类型
{ AMF_NUMBER = 0, //double,占6个字节
AMF_BOOLEAN, //bool型
AMF_STRING, //字符串
AMF_OBJECT,//AMF对象
AMF_MOVIECLIP, /* reserved, not used */
AMF_NULL,//空类型
AMF_UNDEFINED,//未定义类型
AMF_REFERENCE, AMF_ECMA_ARRAY,
AMF_OBJECT_END,//标识嵌套结束
AMF_STRICT_ARRAY, AMF_DATE, AMF_LONG_STRING, AMF_UNSUPPORTED,AMF_RECORDSET, /* reserved, not used */
AMF_XML_DOC, AMF_TYPED_OBJECT,
AMF_AVMPLUS, /* switch to AMF3 */
AMF_INVALID = 0xff
} AMFDataType;
//AMF3的数据类型
typedef enum
{ AMF3_UNDEFINED = 0, AMF3_NULL, AMF3_FALSE, AMF3_TRUE,
AMF3_INTEGER, AMF3_DOUBLE, AMF3_STRING, AMF3_XML_DOC, AMF3_DATE,
AMF3_ARRAY, AMF3_OBJECT, AMF3_XML, AMF3_BYTE_ARRAY
} AMF3DataType;
//定义一种AVal类型,封装过的字符串
typedef struct AVal
{
char *av_val;
int av_len;
} AVal;
//定义获取Aval类型数据大小的宏
#define AVC(str) {str,sizeof(str)-1}
//比较两个Aval类型数据是否相等
#define AVMATCH(a1,a2) ((a1)->av_len == (a2)->av_len && !memcmp((a1)->av_val,(a2)->av_val,(a1)->av_len))
struct AMFObjectProperty;
//定义AMF对象类型
typedef struct AMFObject
{
int o_num;
struct AMFObjectProperty *o_props;
} AMFObject;
typedef struct AMFObjectProperty
{
AVal p_name;//键名和长度
AMFDataType p_type;//键值数据类型
//键值,有可能是number型,string型,嵌套对象类型
union
{
double p_number;
AVal p_aval;
AMFObject p_object;
} p_vu;
int16_t p_UTCoffset;
} AMFObjectProperty;
char *AMF_EncodeString(char *output, char *outend, const AVal * str);
char *AMF_EncodeNumber(char *output, char *outend, double dVal);
char *AMF_EncodeInt16(char *output, char *outend, short nVal);
char *AMF_EncodeInt24(char *output, char *outend, int nVal);
char *AMF_EncodeInt32(char *output, char *outend, int nVal);
char *AMF_EncodeBoolean(char *output, char *outend, int bVal);
/* Shortcuts for AMFProp_Encode */
char *AMF_EncodeNamedString(char *output, char *outend, const AVal * name, const AVal * value);
char *AMF_EncodeNamedNumber(char *output, char *outend, const AVal * name, double dVal);
char *AMF_EncodeNamedBoolean(char *output, char *outend, const AVal * name, int bVal);
unsigned short AMF_DecodeInt16(const char *data);
unsigned int AMF_DecodeInt24(const char *data);
unsigned int AMF_DecodeInt32(const char *data);
void AMF_DecodeString(const char *data, AVal * str);
void AMF_DecodeLongString(const char *data, AVal * str);
int AMF_DecodeBoolean(const char *data);
double AMF_DecodeNumber(const char *data);
char *AMF_Encode(AMFObject * obj, char *pBuffer, char *pBufEnd);
char *AMF_EncodeEcmaArray(AMFObject *obj, char *pBuffer, char *pBufEnd);
char *AMF_EncodeArray(AMFObject *obj, char *pBuffer, char *pBufEnd);
int AMF_Decode(AMFObject * obj, const char *pBuffer, int nSize,
int bDecodeName);
int AMF_DecodeArray(AMFObject * obj, const char *pBuffer, int nSize,
int nArrayLen, int bDecodeName);
int AMF3_Decode(AMFObject * obj, const char *pBuffer, int nSize,
int bDecodeName);
void AMF_Dump(AMFObject * obj);
void AMF_Reset(AMFObject * obj);
void AMF_AddProp(AMFObject * obj, const AMFObjectProperty * prop);
int AMF_CountProp(AMFObject * obj);
AMFObjectProperty *AMF_GetProp(AMFObject * obj, const AVal * name,
int nIndex);
AMFDataType AMFProp_GetType(AMFObjectProperty * prop);
void AMFProp_SetNumber(AMFObjectProperty * prop, double dval);
void AMFProp_SetBoolean(AMFObjectProperty * prop, int bflag);
void AMFProp_SetString(AMFObjectProperty * prop, AVal * str);
void AMFProp_SetObject(AMFObjectProperty * prop, AMFObject * obj);
void AMFProp_GetName(AMFObjectProperty * prop, AVal * name);
void AMFProp_SetName(AMFObjectProperty * prop, AVal * name);
double AMFProp_GetNumber(AMFObjectProperty * prop);
int AMFProp_GetBoolean(AMFObjectProperty * prop);
void AMFProp_GetString(AMFObjectProperty * prop, AVal * str);
void AMFProp_GetObject(AMFObjectProperty * prop, AMFObject * obj);
int AMFProp_IsValid(AMFObjectProperty * prop);
char *AMFProp_Encode(AMFObjectProperty * prop, char *pBuffer, char *pBufEnd);
int AMF3Prop_Decode(AMFObjectProperty * prop, const char *pBuffer,
int nSize, int bDecodeName);
int AMFProp_Decode(AMFObjectProperty * prop, const char *pBuffer,
int nSize, int bDecodeName);
void AMFProp_Dump(AMFObjectProperty * prop);
void AMFProp_Reset(AMFObjectProperty * prop);
typedef struct AMF3ClassDef
{
AVal cd_name;
char cd_externalizable;
char cd_dynamic;
int cd_num;
AVal *cd_props;
} AMF3ClassDef;
void AMF3CD_AddProp(AMF3ClassDef * cd, AVal * prop);
AVal *AMF3CD_GetProp(AMF3ClassDef * cd, int idx);
#ifdef __cplusplus
}
#endif
#endif /* __AMF_H__ */
amf.c
#include <string.h>
#include <assert.h>
#include <stdlib.h>
#include "rtmp_sys.h"
#include "amf.h"
#include "log.h"
#include "bytes.h"
static const AMFObjectProperty AMFProp_Invalid = { {0, 0}, AMF_INVALID };
static const AMFObject AMFObj_Invalid = { 0, 0 };
static const AVal AV_empty = { 0, 0 };
/* Data is Big-Endian,把两个大端的1字节数据合成一个小端short型 */
unsigned short
AMF_DecodeInt16(const char *data)
{
unsigned char *c = (unsigned char *) data;
unsigned short val;
val = (c[0] << 8) | c[1];
return val;
}
//把三个1字节数据合成1个int型小端数据
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;
}
//把四个1字节数据合成1个int型小段数据
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;
}
//data中前两个字节为字符串长度,提取出字符串长度,再加两字节偏移即为数据部分
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;
}
//同上,只不过data中前4个字节为字符串长度
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;
}
//解析number型数据,这里的转换我还不清楚
double
AMF_DecodeNumber(const char *data)
{
double dVal;
#if __FLOAT_WORD_ORDER == __BYTE_ORDER
#if __BYTE_ORDER == __BIG_ENDIAN
memcpy(&dVal, data, 8);
//如果是小端
#elif __BYTE_ORDER == __LITTLE_ENDIAN
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;
}
//解析bool型数据,0x00表示false 0x01表示true
int
AMF_DecodeBoolean(const char *data)
{
return *data != 0;
}
//
char *
AMF_EncodeInt16(char *output, char *outend, short nVal)
{
if (output+2 > outend)
return NULL;
output[1] = nVal & 0xff;
output[0] = nVal >> 8;
return output+2;
}
//
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;
}
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;
}
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;
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);
}
memcpy(output, bv->av_val, bv->av_len);
output += bv->av_len;
return output;
}
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;
}
char *
AMF_EncodeBoolean(char *output, char *outend, int bVal)
{
if (output+2 > outend)
return NULL;
*output++ = AMF_BOOLEAN;
*output++ = bVal ? 0x01 : 0x00;
return output;
}
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);
}
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);
}
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);
}
void
AMFProp_GetName(AMFObjectProperty *prop, AVal *name)
{
*name = prop->p_name;
}
void
AMFProp_SetName(AMFObjectProperty *prop, AVal *name)
{
prop->p_name = *name;
}
AMFDataType
AMFProp_GetType(AMFObjectProperty *prop)
{
return prop->p_type;
}
double
AMFProp_GetNumber(AMFObjectProperty *prop)
{
return prop->p_vu.p_number;
}
int
AMFProp_GetBoolean(AMFObjectProperty *prop)
{
return prop->p_vu.p_number != 0;
}
void
AMFProp_GetString(AMFObjectProperty *prop, AVal *str)
{
if (prop->p_type == AMF_STRING)
*str = prop->p_vu.p_aval;
else
*str = AV_empty;
}
void
AMFProp_GetObject(AMFObjectProperty *prop, AMFObject *obj)
{
if (prop->p_type == AMF_OBJECT)
*obj = prop->p_vu.p_object;
else
*obj = AMFObj_Invalid;
}
int
AMFProp_IsValid(AMFObjectProperty *prop)
{
return prop->p_type != AMF_INVALID;
}
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;
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;
}
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;
};
return pBuffer;
}
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)
{
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;
}
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;
}
return nOriginalSize - nSize;
}
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);
if (prop->p_type == AMF_OBJECT)
{
RTMP_Log(RTMP_LOGDEBUG, "Property: <%sOBJECT>", strRes);
AMF_Dump(&prop->p_vu.p_object);
return;
}
else if (prop->p_type == AMF_ECMA_ARRAY)
{
RTMP_Log(RTMP_LOGDEBUG, "Property: <%sECMA_ARRAY>", strRes);
AMF_Dump(&prop->p_vu.p_object);
return;
}
else if (prop->p_type == AMF_STRICT_ARRAY)
{
RTMP_Log(RTMP_LOGDEBUG, "Property: <%sSTRICT_ARRAY>", strRes);
AMF_Dump(&prop->p_vu.p_object);
return;
}
switch (prop->p_type)
{
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);
}
RTMP_Log(RTMP_LOGDEBUG, "Property: <%s%s>", strRes, str);
}
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;
}
/* AMFObject */
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++)
{
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 */
pBuffer = AMF_EncodeInt24(pBuffer, pBufEnd, AMF_OBJECT_END);
return pBuffer;
}
char *
AMF_EncodeEcmaArray(AMFObject *obj, char *pBuffer, char *pBufEnd)
{
int i;
if (pBuffer+4 >= pBufEnd)
return NULL;
*pBuffer++ = AMF_ECMA_ARRAY;
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 */
pBuffer = AMF_EncodeInt24(pBuffer, pBufEnd, AMF_OBJECT_END);
return pBuffer;
}
char *
AMF_EncodeArray(AMFObject *obj, char *pBuffer, char *pBufEnd)
{
int i;
if (pBuffer+4 >= pBufEnd)
return NULL;
*pBuffer++ = AMF_STRICT_ARRAY;
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 */
//pBuffer = AMF_EncodeInt24(pBuffer, pBufEnd, AMF_OBJECT_END);
return pBuffer;
}
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--;
if (nSize <= 0)
{
bError = TRUE;
break;
}
nRes = AMFProp_Decode(&prop, pBuffer, nSize, bDecodeName);
if (nRes == -1)
{
bError = TRUE;
break;
}
else
{
nSize -= nRes;
pBuffer += nRes;
AMF_AddProp(obj, &prop);
}
}
if (bError)
return -1;
return nOriginalSize - nSize;
}
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 */
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;
break;
}
else
{
nSize -= nRes;
if (nSize < 0)
{
bError = TRUE;
break;
}
pBuffer += nRes;
AMF_AddProp(obj, &prop);
}
}
if (bError)
return -1;
return nOriginalSize - nSize;
}
//添加属性,这里做了优化,每满15个再添加时,一次性分配16个属性空间
void
AMF_AddProp(AMFObject *obj, const AMFObjectProperty *prop)
{
if (!(obj->o_num & 0x0f))
obj->o_props =
realloc(obj->o_props, (obj->o_num + 16) * sizeof(AMFObjectProperty));
memcpy(&obj->o_props[obj->o_num++], prop, sizeof(AMFObjectProperty));
}
//计算AMF对象属性个数
int
AMF_CountProp(AMFObject *obj)
{
return obj->o_num;
}
//获取AMF对象第nIndex个属性,如果nIndex非法,则返回含有name键的所有属性
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;
}
//打印AMF对象
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)");
}
//复位对象
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;
}