在C中通过引用将值从一个函数传递到另一个函数
我需要一个从文件中读取数据块的程序。块有一个在C中通过引用将值从一个函数传递到另一个函数,c,pass-by-reference,C,Pass By Reference,我需要一个从文件中读取数据块的程序。块有一个dwData和dwLength字段。dwLength字段是dwData的sizeof,就像strlen用于字符串一样 此程序中的问题是readChunk 0无法从readChunk获取初始化的dwLength值。dwLength值在readChunkascvar中正常。mbsz消息正确显示该值(消息框用于字符串) 为什么我不能在测试函数中读取dwLength?为什么dwData可以正常传递,而不是dwLength ///////////////////
dwData
和dwLength
字段。dwLength
字段是dwData的sizeof
,就像strlen
用于字符串一样
此程序中的问题是readChunk 0
无法从readChunk
获取初始化的dwLength
值。dwLength
值在readChunk
ascvar中正常。mbsz
消息正确显示该值(消息框用于字符串)
为什么我不能在测试函数中读取dwLength
?为什么dwData
可以正常传递,而不是dwLength
//////////////////////////////////////////////////////////////
// read contents of a chunk in dwData
// and dwLength value in a hex file
//
//////////////////////////////////////////////////////////////
DWORD readChunk(DWORD dwData, DWORD dwLength, TCHAR ccSymbol[6]){
HWND hWnd=cvar.get_hwnd();
STRCK strform;//readChunk
strform.cksize=sizeof(STRCK);
// strform.ccSymbol=
// strform.ckmaxsize=200;
// strform.nextck=0x4;
//open file in HMMIO mode
//filename is a common one
cchmmio=mmioOpen("vocer.hex", NULL, MMIO_READ|MMIO_DENYNONE);
if (cchmmio==NULL){
MessageBox(hWnd, "eroare 1 mmioOpen", "titlu", 0);
return 1;
};
MMCKINFO lpckParent={0,0,mmioFOURCC('W','A','V','E'),0,0};
lpckParent.fccType=mmioFOURCC('W','A','V','E');
lpckParent.cksize=sizeof(MMCKINFO)+sizeof(STRCK);
HRESULT hr=mmioDescend(cchmmio, (LPMMCKINFO)&lpckParent, NULL, MMIO_FINDCHUNK);
if ((hr!=MMSYSERR_NOERROR)&(hr!=MMIOERR_CHUNKNOTFOUND)){//&(hr!=MMIOERR_CHUNKNOTFOUND)){
MessageBox(hWnd, "eroare 2", "titlu", 0);
return 2;
};
if (hr==MMIOERR_CHUNKNOTFOUND){
MessageBox(hWnd, "eroare 3 WAVE CHUNKNOTFOUND", "titlu", 0);
return 3;
};
MMCKINFO mmckinfo;
mmckinfo.ckid=mmioStringToFOURCC(ccSymbol, 0);
//if you find the symbol, read dwData chunk;
hr=mmioDescend(cchmmio, &mmckinfo, &lpckParent, MMIO_FINDCHUNK);
if (hr==MMIOERR_CHUNKNOTFOUND){
MessageBox(hWnd, "4) eroare fatala. ccSymbol not found", "titlu", 0);
return 4;
};
if ((hr!=MMSYSERR_NOERROR)&(hr!=MMIOERR_CHUNKNOTFOUND)){
MessageBox(hWnd, "eroare 5", "titlu", 0);
return 5;
}
dwLength=(DWORD*)mmckinfo.cksize;
// memcpy(&dwLength, &mmckinfo.cksize, 2);
hr=mmioRead(cchmmio, (LPSTR)&dwData, (LONG)dwLength);
if (hr!=(LONG)dwLength){
MessageBox(hWnd, "eroare 6 mmioRead ccSymbol", "titlu", 0);
return 6;
};
hr=mmioClose(cchmmio, 0);
if (hr!=MMSYSERR_NOERROR){
MessageBox(hWnd, "eroare 9 mmioClose", "titlu", 0);
return 9;
};
//ok
// cvar.mbsz((LPSTR)dwData, "titlu", 0);//display dwData contents
// cvar.mbsz("strlen(szData):", "titlu", strlen((LPSTR)dwData));//display szData value
cvar.mbsz("(DWORD)dwLength:", "titlu", (DWORD)dwLength);//display length read
return 0;
}
// Test Function///////////////////////////////////////
// open vocer.hex file
// read a ccSymbol chunk and return the
// dwData and dwLength values
//
void readChunk0(void){
HWND hWnd=cvar.get_hwnd();
DWORD dwData=(DWORD)calloc(200, sizeof(DWORD));
DWORD dwLength=2;
TCHAR cc[6]="x002";
HRESULT hr=readChunk((DWORD*)&dwData, (DWORD*)&dwLength, cc);
if (hr){
cvar.mbsz("eroare la revenirea din readChunk:", "titlu", hr);
return;
};
//result is read in dwData
//and has dwLength length
//display the length of the message: dwLength (2 methods)
//and contents of the dwData buffer
TCHAR sztemp[256];
sprintf(sztemp, "%d", dwLength);
MessageBox(hWnd, sztemp, "titlu", 0);
cvar.mbsz("(DWORD)dwlength:", "titlu", (DWORD)dwLength);
MessageBox(hWnd, (LPSTR)dwData, "titlu:", 0);
}
编辑
谢谢你们,迪戈斯,你们的建议既快又好。我把它放在一起让你知道
让我把我目前所了解的写下来
//////////////////////////////////////////////////////////////
// read contents of a iData chunk and iLength value
// in vocer.hex RIFF file
//
//////////////////////////////////////////////////////////////
DWORD readChunk(int* iData, int* iLength, LPSTR ccSymbol){
HWND hWnd=cvar.get_hwnd();
if (!PathFileExists(szName0))
strcpy(szName0, "vocer.hex");
cchmmio=mmioOpen(szName0, NULL, MMIO_READ|MMIO_DENYNONE);
MMCKINFO lpckParent={0};
lpckParent.fccType=mmioFOURCC('W','A','V','E');
HRESULT hr=mmioDescend(cchmmio, (LPMMCKINFO)&lpckParent, NULL, MMIO_FINDCHUNK);
if ((hr!=MMSYSERR_NOERROR)&(hr!=MMIOERR_CHUNKNOTFOUND)){
MessageBox(hWnd, "eroare 2", "titlu", 0);
return 2;
};
if (hr==MMIOERR_CHUNKNOTFOUND){
MessageBox(hWnd, "eroare 3 WAVE CHUNKNOTFOUND", "titlu", 0);
return 3;
};
MMCKINFO mmckinfo={0};
mmckinfo.ckid=mmioStringToFOURCC(ccSymbol, 0);
//daca ai gasit symbolul, citeste chunkul dwData;
hr=mmioDescend(cchmmio, &mmckinfo, &lpckParent, MMIO_FINDCHUNK);
if (hr==MMIOERR_CHUNKNOTFOUND){
MessageBox(hWnd, "eroare 4. ccSymbol not found", "titlu", 0);
return 4;
};
if ((hr!=MMSYSERR_NOERROR)&(hr!=MMIOERR_CHUNKNOTFOUND)){
MessageBox(hWnd, "eroare 5", "titlu", 0);
return 5;
};
// memcpy((int*)iLength, (long*)mmckinfo.cksize, 2);
iLength[0]=mmckinfo.cksize;
TCHAR sztemp2[256];
TCHAR* sztemp=(TCHAR*)calloc(iLength[0]+1, sizeof(TCHAR));
hr=mmioRead(cchmmio, (LPSTR)sztemp, (long)iLength[0]);
sprintf(sztemp2, "iData:%s\nmmioRead:%d", (LPSTR)sztemp, hr);
MessageBox(hWnd, (LPSTR)sztemp2, "titlu", 0);
if (hr!=iLength[0]){
cvar.mbsz("valoare dwLength:", "titlu", (long)iLength[0]);
MessageBox(hWnd, "eroare 6 mmioRead ccSymbol", "titlu", 0);
return 6;
};
for(int i=0; i<iLength[0]; i++)
iData[i]=sztemp[i];
// memcpy(&iData[i], &sztemp[i], 1);
hr=mmioClose(cchmmio, 0);
return 0;
}
//Functie Test//////////////////////////////////////////
// open vocer.hex file
// read ccSymbol chunk and return
// dwData of dwLength
//
//////////////////////////////////////////////////////////////
void readChunk00(void){
HWND hWnd=cvar.get_hwnd();
int* iLength=(int*)calloc(1, sizeof(int));
int* iData=(int*)calloc(200, sizeof(int));
TCHAR ccSymbol[6]="0x02";
TCHAR sztemp[200];//=(TCHAR*)calloc(iLength[0]+2, sizeof(TCHAR));
HRESULT hr=readChunk((int*)iData, (int*)iLength, ccSymbol);
wsprintf(sztemp, "dwLength:%d\niData:%s", iLength[0], (LPSTR)&iData[0]);
MessageBox(hWnd, (LPSTR)sztemp, "titlu", 0);
strcpy(sztemp, "");
MessageBox(hWnd, "inainte de for", "titlu", 0);
for(int i=0; i<iLength[0]; i++){
// strcat(sztemp,(LPSTR)&iData[i]);
sztemp[i]=(TCHAR)&iData[i];
};
TCHAR* sztemp2=(TCHAR*)calloc(iLength[0]+2, sizeof(TCHAR));
sprintf(sztemp2, "dwLength:%d\niData:%s", iLength[0], (LPSTR)sztemp);
// sprintf(sztemp, "dwLength:%d\niData[1]:%d", iLength[0], iData[1]);
MessageBox(hWnd, (LPSTR)sztemp2, "titlu", 0);
}
//Functie Test///////////////////////////////////////
// deschide fisierul voce.hex
// citeste un chunk ccSymbol si returneaza
// dwData de dimensiune dwLength
// metoda cu pointer
void readChunk0(void){
HWND hWnd=cvar.get_hwnd();
LPSTR ccSymbol="0x02";
int* dwLength=(int*)calloc(1, sizeof(int));
HGLOBAL hData=GlobalAlloc(GHND, (int)dwLength);
if (hData==0){
cvar.mbsz("eroare la GlobalAlloc:", "titlu", GetLastError());
return;
};
int* iData=(int*)GlobalLock(hData);
if (iData==0){
cvar.mbsz("eroare la GlobalLock:", "titlu", GetLastError());
return;
};
HRESULT hr=readChunk((int*)iData, (int*)dwLength, ccSymbol);
if (hr){
cvar.mbsz("eroare la revenirea din readChunk:", "titlu", hr);
return;
};
hr=GlobalUnlock(hData);
if (hr!=0){
cvar.mbsz("eroare la GlobalUnlock:", "titlu", GetLastError());
return;
};
TCHAR* sztemp=(TCHAR*)calloc(dwLength[0]+2, sizeof(TCHAR));
for(int i=0; i<dwLength[0]; i++)
sztemp[i]=iData[i];
strcat(sztemp, "\0");
MessageBox(hWnd, (LPSTR)sztemp, "titlu", 0);
cvar.mbsz("(DWORD)dwLength:", "titlu", dwLength[0]);
}
//////////////////////////////////////////////////////////////
//读取iData块的内容和iLength值
//在vocer.hex-RIFF文件中
//
//////////////////////////////////////////////////////////////
DWORD读块(int*iData、int*iLength、LPSTR ccSymbol){
HWND HWND=cvar.get_HWND();
如果(!PathFileExists(szName0))
strcpy(szName0,“vocer.hex”);
cchmmio=mmiopen(szName0,NULL,MMIO_READ | MMIO_DENYNONE);
MMCKINFO lpckParent={0};
fccType=mmiosource('W','A','V','E');
HRESULT hr=mmioDescend(cchmmio,(LPMMCKINFO)和lpckParent,NULL,MMIO_FINDCHUNK);
如果((hr!=MMSYSERR\u NOERROR)和(hr!=MMIOERR\u CHUNKNOTFOUND)){
消息框(hWnd,“eroare 2”,“titlu”,0);
返回2;
};
如果(hr==MMIOERR\u CHUNKNOTFOUND){
消息框(hWnd,“未找到eroare 3波块”,“标题”,0);
返回3;
};
MMCKINFO MMCKINFO={0};
mmckinfo.ckid=mmiostringtosource(ccSymbol,0);
//daca ai gasit symbolul,citeste chunkul dwData;
hr=mmioDescend(cchmmio、mmckinfo和lpckParent、MMIO\U FINDCHUNK);
如果(hr==MMIOERR\u CHUNKNOTFOUND){
MessageBox(hWnd,“eroare 4.未找到ccSymbol”,“titlu”,0);
返回4;
};
如果((hr!=MMSYSERR\u NOERROR)和(hr!=MMIOERR\u CHUNKNOTFOUND)){
消息框(hWnd,“eroare 5”,“titlu”,0);
返回5;
};
//memcpy((int*)长度,(long*)mmckinfo.cksize,2);
iLength[0]=mmckinfo.cksize;
TCHAR sztemp2[256];
TCHAR*sztemp=(TCHAR*)calloc(iLength[0]+1,sizeof(TCHAR));
hr=mIOREAD(cchmmio,(LPSTR)sztemp,(长)iLength[0]);
sprintf(sztemp2,“iData:%s\nmmiored:%d”,(LPSTR)sztemp,hr);
消息框(hWnd,(LPSTR)sztemp2,“titlu”,0);
if(hr!=iLength[0]){
cvar.mbsz(“valoare dwLength:,”titlu“,(long)iLength[0]);
消息框(hWnd,“eroare 6 mmioRead ccSymbol”,“titlu”,0);
返回6;
};
对于(int i=0;i您需要将指向dwLength
的指针传递到readChunk
并在函数内部取消引用它,如果您希望修改调用者看到的值
另外,给定dwData
的初始化,它的数据类型应该是DWORD*
编辑以跟上新信息
您的新aproach仍然存在一些问题。下面是一些代码片段,我希望您可以将它们组合在一起
以下是您应该如何声明readChunk
函数:
DWORD readChunk(DWORD* dwData, DWORD* dwLength, TCHAR ccSymbol[6])
在函数内部,这是设置dwLength
所指向的值的方式:
*dwLength = mmckinfo.cksize;
DWORD dwLength;
在测试函数中,以下是如何声明dwData
:
DWORD* dwData = calloc(200, sizeof(DWORD));
这就是您如何声明dwLength
:
*dwLength = mmckinfo.cksize;
DWORD dwLength;
最后,这是如何将所有数据传递给readChunk
:
HRESULT hr = readChunk(dwData, &dwLength, cc);
你真的需要熟悉指针是如何工作的,以及参数是如何通过值传递的,或者是通过C中指针的间接方式传递的。你的标题、问题、代码和标记似乎彼此不相关。请编辑你的问题(?)并清理。要读取数据块,请使用std::istream::read()
。请将问题标记为[c]
或[c++]
,但不能同时标记两者。它们不是一回事。标记[voice recording]
与读取文件有什么关系?无需在此处强制转换:(长*)&dwLength
&dwLength
就可以了,因为dwLength
被定义为一个long
。很抱歉,它对dwData很有效;您尝试过DWORD*但效果相同。int*等于int是真的吗?它对dwData
有效,因为强制转换(LPSTR)dwData
使值成为指针。在DWORD大小与指针大小相同的体系结构中,它可以工作,但通常情况并非如此。(即64位)@paul80抱歉,恕我冒昧,但如果它有效,那只是因为你在编译32位代码,而不是因为它应该有效。你违反了严格的别名。这个答案是正确的。通过引用传递dwLength
,或者通过地址传递,这取决于你在实际语言中使用的轮盘赌,因为这个问题被标记为botH.C和C++。@迭戈涅托CID \DWDATA的NPASS值非常清楚,C不支持通过引用。所有的都是按值。