我正在学习操作数组。我将从文件读取的逐个元素数据存储到 main() 外部名为 readInput() 的函数中的 char 和 int 数组中。数据读取:
D E D D E E E D E E E D E
21 32 35 59 58 16 11 29
我尝试调整两个数组的大小以使用 realloc 排除数组中的垃圾:我的问题:
在 main() 中打印 char 数组时，它包含正确的元素，但在数组末尾打印垃圾。我注意到它在 readInput() 中正确打印。我做错了什么？
realloc 前后的readInput() 和main() 中，int 数组从文件中读取的元素是正确的，只是后面跟着垃圾。我做错了什么？
输出:
从 readInput() 打印 - 重新分配之前的字符数组:D E D D E E E D E E E D E
从 readInput() 打印 - 重新分配之前的 Int 数组:21 32 35 59 58 16 11 29 -8421 50451 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -8421504 51 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451
从 readInput() 打印 - 重新分配后的字符数组:D E D D E E E D E E E D E
从 readInput() 打印 - Int After after realloc:21 32 35 59 58 16 11 29 -336860 19 -842150451 739749649 37763 4849560 4849264 -842150451 -842150451 -842150451 - 842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -842
从 main() 打印 - 字符数组(重新分配后): D E D D E E E D E E E D E ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ═ ² ² ² ` ² w ³ É·yÉVt══════════════════════════════════════════════²
Print from main() - Int Array (after realloc): 21 32 35 59 58 16 11 29 -33686019 -842150451 874388096 31426 6946712 6946416 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 -842150451 继续
项目背景: 读取的数据存储在 main() 外部名为 readInput() 的函数中，char by char/int by int 分别存储在 char 和 int 数组中，这些数组通过 main() 中的 malloc 声明和初始大小。
在数组中存储数据后，我需要将数组的大小调整为文件中读取的数据的大小。
最后，为了验证 main 也可以访问该数组，在 main() 和 readInput() 中分别写入 char 和 int 数组。
感谢您的帮助。 编辑更正的工作代码，谢谢!
#include <stdio.h>
#include <ctype.h>
#include <string.h>
//prototypes
void openFile(char *fileNames, FILE **inputFilePointer);
void closeFile(FILE **inputFilePointer);
void readInput(char *choiceArray, int *valueArray, int *charArraySize, int *intArraySize, FILE **inputFilePointer);
void memCharReallocation(char **choiceArray, int requiredArraySize);//resize char array to what's actually required after reading the file
void memIntReallocation(int **valueArray, int intSize);//resize int array to what's actually required after reading the file
void main()
{
char *charArray =NULL;
int *valueArray;
int inputSize;
int charInputSize = 0;//size of elements read from file
int intInputSize = 0;//size of elements read from file
//file read/write variables
FILE *iFilePointer;//file pointer
char *filename = "inputFileTest.txt";
//open and read Files
openFile(filename, &iFilePointer);
//initial mem allocation to size char and int array
valueArray = (int*)malloc(sizeof(int) * 100);
if (valueArray == NULL)
{
printf("\nCould not allocate memory, exiting.\n");
exit(1);
}
charArray = (char*)malloc(sizeof(char) * 100);
if (charArray == NULL)
{
printf("\nCould not allocate memory, exiting.\n");
exit(1);
}
//read file and allocate to array
readInput(charArray, valueArray, &charInputSize, &intInputSize, &iFilePointer);
//print char array: Test I can read it here too
printf("\nPrint from main() - Char Array: ");
for (int j = 0; j<charInputSize; j++)
{
printf("%c ", charArray[j]);
}
//Print int array
printf("\nPrint from main() - Int Array: ");
for (int j = 0; j<intInputSize; j++)
{
printf("%d ", valueArray[j]);
}
}
//read data from file
void readInput(char *readCharArray, int *readValueArray, int *charArraySize, int *intArraySize, FILE **inputFilePointer)
{
int i, j = 0;//loop variables
char *pbuffer = NULL;//buffer to read input file
int bufferSize = 200;//max initial size for buffer
char *token = NULL;////tonize
char ch = NULL;//convert string char to char
int readingChar = 0;//flag we are reading char from file
//alloc memory to pbuffer
pbuffer = (char*)malloc(sizeof(char)*bufferSize);
if (pbuffer == NULL)
{
printf("\nCould not allocate memory, exiting.\n");
exit(1);
}
printf("Read Input From File: \n");
//store each element from file in struct variable
while (fgets(pbuffer, bufferSize, *inputFilePointer) != NULL)//read each line from file
{
j = 0;//reset array to subscript zero on each pass
//tokenize file data
for (token = strtok(pbuffer, " "); token != NULL; token = strtok(NULL, " "))
{
//char token
if (isalpha(token[0]))
{
ch = token[0];
readCharArray[j++] = ch;
readingChar = 1;//flag we are reading char from file to get length of array excl array garbage
}
//int token
else if (isdigit(token[0]))
{
readValueArray[j++] = atoi(token);
(*intArraySize)++;
}
else
{
printf("\nCan't read file\n");
exit(1);
}
}
if (readingChar)
{
readCharArray[j] = '\0';//remove excess cells on array
*charArraySize = strlen(readCharArray);//size of array
readingChar = 0;//end of reading char from file
}
}
//print char array: Test 1
printf("\nPrint from readInput() - Char Array before realloc: ");
for (int j = 0; j < *charArraySize; j++)
{
printf("%c ", readCharArray[j]);
}
//Print int array
printf("\nPrint from readInput() - Int Array before realloc: ");
for (int j = 0; j < *intArraySize; j++)
{
printf("%d ", readValueArray[j]);
}
memCharReallocation(&readCharArray, charArraySize);
memIntReallocation(&readValueArray, intArraySize);
printf("\nPrint from readInput() - Char Array after realloc: ");
for (int j = 0; j < *charArraySize; j++)
{
printf("%c ", readCharArray[j]);
}
printf("\nPrint from readInput() - Int After after realloc:");
for (int j = 0; j < *intArraySize; j++)
{
printf("%d ", readValueArray[j]);
}
}
void memCharReallocation(char **charArray, int requiredArraySize)//resize int array to what's actually required after reading the file
{
char *ptempArray = NULL;
ptempArray = (char*)realloc(*charArray, requiredArraySize * sizeof(char*));
if (ptempArray == NULL)
{
printf("Could not allocate memory, exiting");
exit(1);
}
else
*charArray = ptempArray;
if (ptempArray != *charArray)
free(ptempArray);
}
void memIntReallocation(int **valueArray, int intSize)//resize int array to what's actually required after reading the file
{
int *ptempArray = NULL;
ptempArray = (int*)realloc(*valueArray, intSize* sizeof(int*));
if (ptempArray == NULL)
{
printf("Could not allocate memory, exiting");
exit(1);
}
else
*valueArray = ptempArray;
if (ptempArray != *valueArray)
free(ptempArray);
}
void openFile(char *fileNames, FILE **inputFilePointer)
{
printf("\n\n");
//open files and error mssg
if ((*inputFilePointer = fopen(fileNames, "r")) == NULL) {
printf("Can't open input file %s\n", fileNames[1]);
exit(1);
}
}
void closeFile(FILE **inputFilePointer)
{
//close files
fclose(*inputFilePointer);
}
最佳答案
首先，警告是不容忽视的。
void main(char *argv) { ... argv = ...;
应该提出一个(CLang 甚至给出错误!)因为它不符合 C。它应该是:
int main() {
...
char *filename = ...;
不使用argv就不要声明，避免使用argv除了命令行参数之外的任何其他内容。
下一个:for (int j = 0; j < charArray!=NULL; j++)还应该提出大量警告。你先比较j和 charArray (已经是未定义的行为)。看到结果后，j < charArray恰好为真(C 中的值为 1)，您将其与 NULL 进行比较，后者是 void * ! 1 != 0始终为真，您将得到一个永无止境的循环。
for (int j = 0; j < charSize || readValueArray[j] != NULL; j++)还应该发出警告:readValueArray[j]是一个 int和 NULL是 void * .另外就是没用测试readValueArray[j]至 0因为您从未初始化分配的内存。
最终调整大小不会从数组中移除垃圾，它会在内存中某处重新分配具有要求大小的数组，如果您访问分配的内存，您只需调用未定义的行为。在 C 中无法知道数组的大小，程序员的工作就是关心它。
所以这里有 2 种可能的方法:
将数组的实际大小作为
readInput的(输出)参数传递:void readInput(char *choiceArray, int *valueArray, FILE **inputFilePointer, int *choiceArraySize, int *valueArraySize)或使用特殊值(例如 0)作为结束标记。
请注意警告!
关于c - 从文件中读取 int 和 char 数组，然后调整数组大小，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/47787453/