正确的iconv使用方法

网上典型的代码是这一段：

char* ConvertEnc( char *encFrom, char *encTo, const char * in)
{
	static char bufin[1024], bufout[1024], *sin, *sout;
	int lenin, lenout, ret;
	iconv_t c_pt;

	if ((c_pt = iconv_open(encTo, encFrom)) == (iconv_t)-1)
	{
		printf("iconv_open false: %s ==> %s", encFrom, encTo);
		return NULL;
	}
	iconv(c_pt, NULL, NULL, NULL, NULL);

	lenin  = strlen(in) + 1;
	lenout = 1024;
	sin    = (char *)in;
	sout   = bufout;
	ret = iconv(c_pt, (const char**)&sin, (size_t *)&lenin, &sout, (size_t *)&lenout);

	if (ret == -1)
	{
		return NULL;
	}
	iconv_close(c_pt);

	return bufout;
}

这段代码里面有3个问题：
1.没有重复使用初始化后的iconv_t。
2.lenin  = strlen(in) + 1这行代码在某些情况下有问题。
3.转换缓冲区是一个固定值。

我根据iconv官网上的文档重写了相关代码，官网地址如下：

http://www.gnu.org/savannah-checkouts/gnu/libiconv

代码如下

#ifndef _ICONV_PAIR_HXX_
#define _ICONV_PAIR_HXX_

#include <string>
#include <iconv/include/iconv.h>

class IconvPair
{
	enum 
	{
		INIT_BUFFER = 4096
	};

public:
	IconvPair(const std::string &toCode, const std::string &fromCode);
	~IconvPair();

private:
	IconvPair(const IconvPair&);
	IconvPair& operator=(const IconvPair&);

public:
	friend bool operator<(const IconvPair &lhs, const IconvPair &rhs)
	{
		if (lhs.mToCode < rhs.mToCode)
		{
			return true;
		}
		else if (lhs.mToCode > rhs.mToCode)
		{
			return false;
		}

		return lhs.mFromCode <=rhs.mFromCode ? true : false;
	}

	const char* buffer() const {return mBuffer;}
	size_t bufferLen() const {return mBufferLen;}
	size_t contentLen() const {return mContentLen;}

	size_t convert(const char **inBuffer, size_t *inBytesLeft);

private:
	void incBuffer();

private:
	std::string mToCode;
	std::string mFromCode;
	iconv_t mIconv;
	char *mBuffer;
	size_t mBufferLen;
	size_t mContentLen;
};

#endif

#include "statistics/IconvPair.hxx"#include <cstdlib>#include <cerrno>#include <cassert>#include <climits>#include <exception>IconvPair::IconvPair(const std::string &toCode, const std::string &fromCode)	: mToCode(toCode)	, mFromCode(fromCode)	, mIconv(reinterpret_cast<iconv_t>(-1))	, mBuffer(NULL)	, mBufferLen(0)	, mContentLen(0){	if (mToCode.empty() || mFromCode.empty())	{		throw std::exception();	}	mBufferLen = INIT_BUFFER;	mBuffer = reinterpret_cast<char*>(malloc(mBufferLen));	if (NULL == mBuffer)	{		throw std::bad_alloc();	}	mIconv = iconv_open(toCode.c_str(), fromCode.c_str());	if (reinterpret_cast<iconv_t>(-1) == mIconv)	{		throw std::exception();	}}IconvPair::~IconvPair(){	if (reinterpret_cast<iconv_t>(-1) != mIconv)	{		iconv_close(mIconv);	}	free(mBuffer);}size_t IconvPair::convert(const char **inBuffer, size_t *inBytesLeft){	assert((NULL != mBuffer) && (reinterpret_cast<iconv_t>(-1) != mIconv));	assert((NULL != inBuffer) && (NULL != *inBuffer) && (NULL != inBytesLeft));	iconv(mIconv, NULL, NULL, NULL, NULL);	char *outBuffer = mBuffer;	size_t outBytesLeft = mBufferLen;	size_t ret = iconv(mIconv, inBuffer, inBytesLeft, &outBuffer,		&outBytesLeft);	while ((UINT_MAX == ret) && (0 == outBytesLeft)/*(E2BIG == errno)*/)	{		size_t oldBufferLen = mBufferLen;		incBuffer();		outBuffer = mBuffer + oldBufferLen;		outBytesLeft = mBufferLen - oldBufferLen;		ret = iconv(mIconv, inBuffer, inBytesLeft, &outBuffer,			&outBytesLeft);	}	mContentLen = mBufferLen - outBytesLeft;	if (0 == outBytesLeft)	{		incBuffer();	}	mBuffer[mContentLen] = 0;	return ret;}void IconvPair::incBuffer(){	mBufferLen *= 2;	mBuffer = reinterpret_cast<char*>(realloc(mBuffer, mBufferLen));	if (NULL == mBuffer)	{		throw std::bad_alloc();	}}

测试代码块如下：

void UnitTest::testIconv()
{
	const size_t pageSize = 4096;
	IconvPair g2u("utf-8", "gb2312");

	char array[pageSize] = {'a'};
	const char *inArray = array;
	size_t inArrayLen = pageSize;
	size_t ret = g2u.convert(&inArray, &inArrayLen);
	CPPUNIT_ASSERT((0 == ret) && ((pageSize * 2) == g2u.bufferLen()));

	char *buffer = reinterpret_cast<char*>(malloc(1024 * 1024 * sizeof(char)));
	CPPUNIT_ASSERT(NULL != buffer);

	FILE *f = fopen("league2012b.htm", "r");
	CPPUNIT_ASSERT(NULL != f);
	size_t fileLen = 0;
	while (!feof(f))
	{
		fileLen += fread(buffer + fileLen, 1, pageSize, f);
	}
	fclose(f);

	const char *bufferIn = buffer;
	ret = g2u.convert(&bufferIn, &fileLen);
	CPPUNIT_ASSERT(0 == ret);

	f = fopen("league2012b.txt", "w");
	CPPUNIT_ASSERT(NULL != f);
	fwrite(g2u.buffer(), 1, g2u.contentLen(), f);
	fclose(f);

	free(buffer);
}

由于直接将测试代码块中的league2012b.htm复制到CSDN的代码块中会有问题，所以只好请大家直接用快盘共享出来的链接自己下载了。链接地址如下

http://www.kuaipan.cn/file/id_19631556775674797.htm