如何插入，將新元素添加到char數組中

Question

我推送新元素到char數組前面有問題。我在我的程序中有一個函數，它有兩個參數：一個指向char數組的指針和一個指向int的指針。該函數用一些數據填充數組，並返回此數組中元素的數量。

int function1(char* buffer , int* outSize); 

buffer[1000] 
int size; 
result = function1(buffer , &size); 

// after this a get some data in buffer and count how many data is in buffer. let's say 456 elements 
// now a try push to front two new bytes as size this array 

finallBuffer *char = new char[size+2]; 
memcpy(finallyBuffer, (char*)&size, 2); // here a get size in two bytes and put to finnalBuffer 

// next I try just copy to finnalyBuffer received data from Buffer 
strcat(finallyBuffer , buffer); 
doSomething(finallyBuffer); 
delete []finallyBuffer; 

在此之後在finnalyBuffer我只保存大小兩個字節。爲什麼我看不到來自緩衝區的數據？

在最後我要實現新表在前面的兩個新的字節。這兩個字節是大小舊的表。比方說，接收到的數據HEVE只有5個字符

char table[5] = {'a','b','b','c','t'};

所以尺寸爲5.5兩個字節是char size = {'5','0'};

結果應該是的樣子。

char table[5] = {'5','0','a','b','b','c','t'};

Answer 1

我不知道確切地知道你想要做什麼，但我試圖理解它。在代碼見下面的意見，我希望它會幫助你。

int function1(char* buffer , int* outSize); 

buffer[1000] 
int size; 
result = function1(buffer , &size); 

// after this a get some data in buffer and count how many data is in buffer. let's say 456 elements 
// now a try push to front two new bytes as size this array 

char *finallBuffer = new char[size*sizeof(char)+2]; 
short ssize = (short)size; 
memcpy(finallyBuffer, &ssize, 2); // here a get size in two bytes and put to finnalBuffer 

// next I try just copy to finnalyBuffer received data from Buffer 

/* NOTE: strcat is for null terminated string. If i understand what you want 
    to do you want store int in 4 bytes ? 
    I assume size is the actual size of the buffer 
*/ 
//strcat(finallyBuffer , buffer); 
memcpy(&finallyBuffer[2], buffer, sizeof(char)*size); 
doSomething(finallyBuffer); 
delete []finallyBuffer; 

Answer 2

那些線接錯：

finallBuffer *char = new char[size+2]; 
memcpy(finallyBuffer, (char*)&size, 2); 

他們應該是：

char * finalBuffer = new char[size+2]; 
memcopy(finallyBuffer, buffer, size); 

但我真的理解你正在嘗試做一些事情。

編輯：

現在我看到你在做什麼，奧利弗給了你答案。如果你不想（或不能）爲你的緩衝區使用std :: vector，那麼無論如何你都可以節省重新分配數組的代價。

• 剛開始爲緩衝區2分配更多字節：char buffer[1002];。
• 然後要存儲值，您可以將指針傳遞給第三個元素：char* ptr = buffer + 2;。
• 當你知道這些數據的實際尺寸，只是把字節buffer[0]和buffer[1]。

一個結構應建議。