C++中的java迭代器等价物?(附代码)
大家好。一个朋友为我编写了一些java代码,我很容易将它转换成C++,但是我非常好奇C++中的java迭代器。这是代码,我很可能希望数据返回到向量中。任何帮助都将不胜感激
public class RLEIterator
extends RegionIterator
{
public int reg = 0;
public int mode = 0;
public int skip = 0;
// mode is the number of IDs that are valid still (count down)
// skip is used after we run out of mode IDs, and move forward
// The goal is, to always have a valid 'hasNext' state, after
// an ID is read via 'next'. Thus, the initial search, and then
// the reading forward if mode == 0, after the ID is found.
public int i;
public RLEIterator()
{
// Need to set up the skip of an initial part, so we can
// correctly handle there not being anything, despite there
// being data encoded.
int comp;
i = 0;
while ((mode == 0) && (i<nearRLE.length))
{
// set up the next code
comp = ((int)nearRLE[i]) & 0xff;
if ((comp > 0) && (comp <= 0x3e))
{
// skip forward by comp;
reg += comp;
i++;
mode = 0; // have to keep on reading
}
else if (comp == 0x3f)
{
// skip forward by the following 16 bit word;
// second byte is hi-byte of the word
reg += ((int)nearRLE[i+1]) & 0xff;
reg += (((int)nearRLE[i+2]) & 0xff) << 8;
i+=3;
}
else if (comp == 0xff)
{
// include the following WORD of regions
mode = ((int)nearRLE[i+1]) & 0xff;
mode += (((int)nearRLE[i+2]) & 0xff) << 8;
i += 3;
}
else if ((comp >= 0xc0) && (comp <= 0xfe))
{
// comp - 0xc0 regions are nearby
mode = comp - 0xc0; // +1 perhaps?
i++;
}
else if ((comp >= 0x40) && (comp <= 0x7f))
{
// skip bits 3-5 IDs and then include bits 0-2
reg += (comp & 0x38) >> 3;
mode = (comp & 0x7);
i++;
}
else if ((comp >= 0x80) && (comp <= 0xbf))
{
// include IDs bits 3-5, then skip bits 0-2
mode = (comp & 0x38) >> 3;
skip = (comp & 0x7);
i++;
}
}
}
public boolean hasNext()
{
// not at the end of the RLE, and not currently processing a
// directive. (mode)
return (mode > 0);
}
public int next()
{
int ret = -1;
int comp;
// sanity check first. Shouldn't truthfully get called if mode
// isn't >0
if (mode <= 0)
return -1;
ret = reg;
reg++;
mode--;
if (mode == 0)
{
// skip forward
reg += skip;
skip = 0;
while ((mode == 0) && (i<nearRLE.length))
{
// set up the next code
comp = ((int)nearRLE[i]) & 0xff;
if ((comp > 0) && (comp <= 0x3e))
{
// skip forward by comp;
reg += comp;
i++;
mode = 0; // have to keep on reading
}
else if (comp == 0x3f)
{
// skip forward by the following 16 bit word;
// second byte is hi-byte of the word
reg += ((int)nearRLE[i+1]) & 0xff;
reg += (((int)nearRLE[i+2]) & 0xff) << 8;
i+=3;
}
else if (comp == 0xff)
{
// include the following WORD of regions
mode = ((int)nearRLE[i+1]) & 0xff;
mode += (((int)nearRLE[i+2]) & 0xff) << 8;
i += 3;
}
else if ((comp >= 0xc0) && (comp <= 0xfe))
{
// comp - 0xc0 regions are nearby
mode = comp - 0xc0; // +1 perhaps?
i++;
}
else if ((comp >= 0x40) && (comp <= 0x7f))
{
// skip bits 3-5 IDs and then include bits 0-2
reg += (comp & 0x38) >> 3;
mode = (comp & 0x7);
i++;
}
else if ((comp >= 0x80) && (comp <= 0xbf))
{
// include IDs bits 3-5, then skip bits 0-2
mode = (comp & 0x38) >> 3;
skip = (comp & 0x7);
i++;
}
}
}
return ret;
}
}
再次,在C++中如何帮助它适应一个单一函数(如果可能的话)的方案将是非常棒的。谢谢
# 1 楼答案
it
:将增加迭代器(跳到下一个元素)
将取消对迭代器的引用(将引用返回到它所指向的元素)
将(如果已定义)递减迭代器(返回到上一个元素)
一般来说,P> C++迭代器对它们所操作的容器一无所知。特别是,检查序列中是否还有更多元素的方法不是调用迭代器上的HasNext
,而是将其与指向序列末尾的迭代器进行比较。(或者,严格地说,将其与指向序列末尾的元素进行比较。)除此之外,迭代器还需要定义一些typedef和其他辅助内容,以帮助编译器分类和理解迭代器的功能
定义迭代器的最简单方法是使用Boost。迭代器库的
iterator_facade
类,它为您实现了几乎所有的管道。该库有优秀的文档,包括一个描述如何定义自己的迭代器类型的教程如果使用Boost是一种选择,那么你肯定应该这么做。否则,标准库有
std::iterator
,这也有点帮助(但值得注意的是,不是强制性的,迭代器可以完全有效地定义,而无需从这个类派生)很抱歉,我没有写出完整的例子,但我现在有点赶时间。(而且,如果您能够使用Boost,那么从头定义一个示例迭代器将是浪费时间)。希望以上内容足以让你开始