当从字节序列中读取可变长度数据时,不应将所有内容都放入单个结构或变量中。 指针也用于存储这个可变长度。
以下建议,没有进行测试:
// data is stored in memory,
// in a different way,
// NOT as sequence of bytes,
// as provided
struct data {
short sh1;
short sh2;
int abclength;
// a pointer, maybe variable in memory !!!
char* abc;
bool bool1;
bool bool2;
};
// reads a single byte
bool readByte(byte* MyByteBuffer)
{
// your reading code goes here,
// character by character, from stream,
// file, pipe, whatever.
// The result should be true if not error,
// false if cannot rea anymore
}
// used for reading several variables,
// with different sizes in bytes
int readBuffer(byte* Buffer, int BufferSize)
{
int RealCount = 0;
byte* p = Buffer;
while (readByte(p) && RealCount <= BufferSize)
{
RealCount++
p++;
}
return RealCount;
}
void read()
{
// real data here:
data Mydata;
byte MyByte = 0;
// long enough, used to read temporally, the variable string
char temp[64000];
// fill buffer for string with null values
memset(temp, '\0', 64000);
int RealCount = 0;
// try read "sh1" field
RealCount = (readBuffer(&(MyData.sh1), sizeof(short)));
if (RealCount == sizeof(short))
{
// try read "sh2" field
RealCount = readBuffer(&(MyData.sh2), sizeof(short));
if (RealCount == sizeof(short))
{
RealCount = readBuffer(temp, 64000);
if (RealCount > 0)
{
// store real bytes count
MyData.abclength = RealCount;
// allocate dynamic memory block for variable length data
MyData.abc = malloc(RealCount);
// copy data from temporal buffer into data structure plus pointer
// arrays in "plain c" or "c++" doesn't require the "&" operator for address:
memcpy(MyData.abc, temp, RealCount);
// comented should be read as:
//memcpy(&MyData.abc, &temp, RealCount);
// continue with rest of data
RealCount = readBuffer(&(MyData.bool1), sizeof(bool));
if (RealCount > 0)
{
// continue with rest of data
RealCount = readBuffer(&(MyData.bool2), sizeof(bool));
}
}
}
}
} // void read()
干杯。
Yuk,二进制序列化。补偿排序。 –
而'char *'从不具有可变长度。它始终是'char *'的大小。 –
@Tom van der Woerdt,你的意思是由“abc”引用的数据是一个“空终止的字符串”,可能会改变它的大小。听起来像一个愚蠢的问题,但是,它更好清楚;-) – umlcat