c - 我无法理解原因，但应用崩溃了

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7年前关闭。




输入文件是in.wav。我必须读取块(成功)并读取样本以规范音频文件...

问题在于，尝试获取.wav文件样本的max和min值时，它崩溃了。
它只会在数组中找到最小值和最大值，但是会崩溃...
请告诉我有什么问题。

这是代码:

#include <stdio.h>
#include <stdlib.h>
#include "main.h"
#define hdr_SIZE 64

typedef struct FMT
{
    char        SubChunk1ID[4];
    int         SubChunk1Size;
    short int   AudioFormat;
    short int   NumChannels;
    int         SampleRate;
    int         ByteRate;
    short int   BlockAlign;
    short int   BitsPerSample;

} fmt;

typedef struct DATA
{
    char        Subchunk2ID[4];
    int         Subchunk2Size;
    int         Data[441000];
} data;

typedef struct HEADER
{
    char        ChunkID[4];
    int         ChunkSize;
    char        Format[4];
    fmt         S1;
    data        S2;
} header;



int main()
{
    FILE *input = fopen( "in.wav", "rb");   /// nameIn

    if(input == NULL)
    {
        printf("Unable to open wave file (input)\n");
        exit(EXIT_FAILURE);
    }

    FILE *output = fopen( "out.wav", "wb"); /// nameOut
    header hdr;


    fread(&hdr, sizeof(char), hdr_SIZE, input);
    /* NOTE: Chunks has been copied successfully. */


    /*###############################*/
    /*##### UPDATE (char *ptr;) #####*/
    /*###############################*/
    char *ptr;  // 'int' was written here instead of 'char'. That's was a stupid mistake...
    long n = hdr.S2.Subchunk2Size;


    /// COPYING SAMPLES...
    ptr = malloc(sizeof(hdr.S2.Subchunk2Size));
    while ( n-- != 0 )
    {
        fread(&ptr, 1, 1, input);  // Continues reading after the least 'stop' place.
    }                              // I was being told here (on "stack") that it is so...


    n = hdr.S2.Subchunk2Size; // Resetting 'n'.
    int min = ptr[0], max = ptr[0], i;

    /* THE PROBLEM IS HERE: */
    for ( i = 0; i < n; i++ )
        {
            if ( ptr[i] < min )     // If the next elements is less than previous, swap them.
                min = ptr[i];
            if ( ptr[i] > max ) // If the next elements is bigger than previous, swap them.
                max = ptr[i];
    }

    printf("> > >%d__%d\n", min, max);    // Displaying of 'min' and 'max'.

    fclose(input);
    fclose(output);

    return 0;
}

更新:

EUREKA!这是因为每个样本有8位!我必须像使用char类型一样对它们进行操作(使用示例)。 (请参见代码中的“### UPDATE ###”注释)

最佳答案

这段代码:

    /// COPYING SAMPLES...
    ptr = malloc(sizeof(hdr.S2.Subchunk2Size));
    while ( n-- != 0 )
    {
        fread(&ptr, 1, 1, input);  // Continues reading after the least 'stop' place.
    }                              // I was being told here (on "stack") that it is so...

覆盖ptr变量n次的第一个字节。这会破坏ptr的值。即使您将其固定为读入分配的缓冲区(通过删除&)，您也只会重写分配的内存的第一个字节。

您可能想要的是:

    fread(ptr, 1, n, input);

注意，不需要while循环。但是，那将是我对您的真实意图的猜测。

关于c - 我无法理解原因，但应用崩溃了，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/16468793/