C语言二进制文件读写以及大小端转换

来源：互联网发布：java常用集合类编辑：程序博客网时间：2024/05/13 05:27

因为工作需要所以需要将文件用二进制方式读取。网上资料比较少，所以我再次把自己的实践过程mark一下。
并且由于代码可能需要在不同的机器上运行，所以还需要考虑一下大小端转换问题。
先看下面的代码，然后我在简短的解释一下。

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <string>#define nmemb 7/****************************************************  Date types(Compiler specific) 数据类型（和编译器相关）*****************************************************/typedef unsigned char uint8;      /* Unsigned 8 bit quantity  */typedef signed char int8;         /* Signed 8 bit quantity    */typedef unsigned short uint16;    /* Unsigned 16 bit quantity */typedef signed short int16;       /* Signed 16 bit quantity   */typedef unsigned int uint32;      /* Unsigned 32 bit quantity */typedef signed int int32;         /* Signed 32 bit quantity   */typedef float fp32;               /* Single precision         */                                  /* floating point           */typedef double fp64;              /* Double precision         */                                  /* floating point           *///int32#define BigtoLittle32(A)   ((( (uint32)(A) & 0xff000000 ) >> 24) | \                                               (( (uint32)(A) & 0x00ff0000 ) >> 8)   | \                                               (( (uint32)(A) & 0x0000ff00 ) << 8)   | \                                               (( (uint32)(A) & 0x000000ff ) << 24))//int16#define BigtoLittle16(A)   (( ((uint16)(A) & 0xff00) >> 8 )    | \                            (( (uint16)(A) & 0x00ff ) << 8))/*************************************************************     Conversion little endian float data to big endian*     *************************************************************/float ReverseFloat(const float inFloat){    float retVal;    char *floatToConvert = (char*) & inFloat;    char *returnFloat = (char*) & retVal;    // swap the bytes into a temporary buffer    returnFloat[0] = floatToConvert[3];    returnFloat[1] = floatToConvert[2];    returnFloat[2] = floatToConvert[1];    returnFloat[3] = floatToConvert[0];    return retVal;}struct matrix{    int row;    int column;}s[nmemb];void set_s(int j, int x, int y){    s[j].row = x;    s[j].column = y;}bool is_bigendian(){    int a = 0x1234;    char b =  *(char *)&a;  //b == the Low address part of a    //printf("%c\n", b);    if (b == 0x34) {        return false;    }    return true;}int main(){    if (is_bigendian()) {        printf("BigEndian\n");    } else {        printf("LittleEndian\n");    }    FILE *fp;    set_s(0, 1, 50);    set_s(1, 1, 80);    set_s(2, 4, 20);    set_s(3, 50, 1);    set_s(4, 80, 2);    set_s(5, 100, 3);    set_s(6, 100, 4);    int ans = sizeof(struct matrix);    printf("size: %d\n", ans);    printf("size: %d\n", sizeof(s));    if ((fp = fopen("test", "wb")) == NULL) {        printf("EROOR\n");        return 1;    }    for (int j = 0; j < nmemb; ++j) {        printf("row: %d   column: %d\n", s[j].row, s[j].column);    }    fwrite(s, sizeof(struct matrix), nmemb, fp);    for (int i = 0; i < nmemb; ++i) {        float *m = (float*) malloc(sizeof(float) * s[i].row * s[i].column);        bzero(m, sizeof(float) * s[i].row * s[i].column);        for (int j = 0; j < s[i].row; ++j) {            for (int k = 0; k < s[i].column; ++k) {                m[k + j*s[i].column] = k;            }        }        fwrite(m, sizeof(float), s[i].row * s[i].column, fp);        free(m);    }    fclose(fp);    printf("11\n");    /*    printf("%d\n", sizeof(float));    FILE *fp;    if ((fp = fopen("test", "rb")) == NULL) {        printf("EROOR\n");        return 1;    }    fread(s, sizeof(struct matrix), nmemb, fp);    for (int i = 0; i < nmemb; ++i) {        printf("row: %d   column: %d\n", s[i].row, s[i].column);    }    for (int i = 0; i < nmemb; ++i) {        float *m = (float*) malloc(sizeof(float) * s[i].row * s[i].column);        bzero(m, sizeof(float) * s[i].row * s[i].column);        fread(m, sizeof(float), s[i].row * s[i].column, fp);        for (int j = 0; j < s[i].row; ++j) {            for (int k = 0; k < s[i].column; ++k) {                printf("%lf ", m[k + j*s[i].column]);            }            printf("\n");        }        printf("\n\n");        free(m);    }    fclose(fp);    */    return 0;}

fopen和fclose是很常见的，在这里就不做解释了。我们来看看fwrite和fread，本来以为这个很麻烦，但是用过之后发现这个二进制文件读写才是最简单的。

size_t fwrite(const void * ptr,size_t size,size_t nmemb,FILE * stream);
fwrite()用来将数据写入文件流中。
stream为已打开的文件指针
ptr 指向欲写入的数据地址
写入的字符数以参数size*nmemb来决定。
size表示写入一个nmemb的内存大小。
fwrite()会返回实际写入的nmemb数目。

size_t fread(void * ptr,size_t size,size_t nmemb,FILE * stream);
fread()用来从文件流中读取数据。
stream为已打开的文件指针
ptr 指向欲存放读取进来的数据空间
读取的字符数以参数size*nmemb来决定
size表示读取一个nmemb的内存大小。
fread()会返回实际读取到的nmemb数目，如果此值比参数nmemb 小，则代表可能读到了文件尾或有错误发生，这时必须用feof()或ferror()来决定发生什么情况。
返回实际读取到的nmemb数目。

详情参见上面的代码。

另外就是大小端的问题了。关于大小端的具体解释网上有很多，在此不作解释。参考上面写的代码，我判断了自己机器是大端还是小端，并且实现了int16，int32已经float数据类型的大小端转换，大端转小端，在使用相同的代码一次小端又变成了大端。

PS：float的大小端转化我之前一直以为写的是错的，因为好多数据转化之后输出都是0。后来发现可能是与float类型在内存中的存放有关，我们的程序是对的。

下面是写的比较详细的二进制读和写的函数。包括数值类型，struct，char*等的读写。

bool save_binary(char* file_path){    FILE *fp;    if ((fp = fopen(file_path, "wb")) == NULL) {        printf("EROOR\n");        return false;    }    fwrite(&vocab_total_size, sizeof(int), 1, fp);    FILE *fp1;    if ((fp1 = fopen("../out/vocab", "r")) == NULL) {        printf("No vocab file!\n");        return false;    }    char str[100];    int coun = 0;    while ((fscanf(fp1, "%s", str)) != EOF) {        int len = strlen(str);    coun++;    printf("%d %d %s\n", coun, len, str);    fwrite(&len, sizeof(int), 1, fp);    fwrite(str, sizeof(char), len, fp);    }    fclose(fp1);    //binary head, save the row and column of the matrixs    struct matrix    {        int row;        int column;    }s[NMEMB];    s[0].row = vocab_total_size; s[0].column = projection_size;    s[1].row = projection_size; s[1].column = hidden_size*4;    s[2].row = 1; s[2].column = hidden_size;    s[3].row = 1; s[3].column = hidden_size;    s[4].row = 1; s[4].column = hidden_size;    s[5].row = hidden_size; s[5].column = hidden_size*4;    s[6].row = hidden_size; s[6].column = punc_total_size;    s[7].row = vocab_total_size; s[7].column = projection_size;    s[8].row = projection_size; s[8].column = hidden_size*4;    s[9].row = 1; s[9].column = hidden_size;    s[10].row = 1; s[10].column = hidden_size;    s[11].row = 1; s[11].column = hidden_size;    s[12].row = hidden_size; s[12].column = hidden_size*4;    s[13].row = hidden_size; s[13].column = punc_total_size;    fwrite(s, sizeof(struct matrix), NMEMB, fp);    fwrite(final_We, sizeof(float), s[0].row * s[0].column, fp);    fwrite(final_W, sizeof(float), s[1].row * s[1].column, fp);    fwrite(final_Wip, sizeof(float), s[2].row * s[2].column, fp);    fwrite(final_Wfp, sizeof(float), s[3].row * s[3].column, fp);    fwrite(final_Wop, sizeof(float), s[4].row * s[4].column, fp);    fwrite(final_Wr, sizeof(float), s[5].row * s[5].column, fp);    fwrite(final_Wy, sizeof(float), s[6].row * s[6].column, fp);    fwrite(final_We_hg, sizeof(float), s[7].row * s[7].column, fp);    fwrite(final_W_hg, sizeof(float), s[8].row * s[8].column, fp);    fwrite(final_Wip_hg, sizeof(float), s[9].row * s[9].column, fp);    fwrite(final_Wfp_hg, sizeof(float), s[10].row * s[10].column, fp);    fwrite(final_Wop_hg, sizeof(float), s[11].row * s[11].column, fp);    fwrite(final_Wr_hg, sizeof(float), s[12].row * s[12].column, fp);    fwrite(final_Wy_hg, sizeof(float), s[13].row * s[13].column, fp);    fclose(fp);    return true;}

bool load_binary(char *file_path){    FILE *fp;    if ((fp = fopen(file_path, "rb")) == NULL) {        printf("EROOR\n");        return false;    }    int vocab_size;    fread(&vocab_size, sizeof(int), 1, fp);    printf("%d\n", vocab_size);    int coun = 0;    for (int j = 0; j < vocab_size; ++j) {        int len;        coun++;        fread(&len, sizeof(int), 1, fp);        char str[100];        fread(str, sizeof(char), len, fp);        str[len] = '\0';    //一定要加，不加出错    }    printf("%d\n", coun);    struct matrix    {        int row;        int column;    }s[NMEMB];    fread(s, sizeof(struct matrix), NMEMB, fp);    for (int i = 0; i < NMEMB; ++i) {        printf("row: %d   column: %d\n", s[i].row, s[i].column);    }    fread(We, sizeof(float), s[0].row * s[0].column, fp);    fread(W, sizeof(float), s[1].row * s[1].column, fp);    fread(Wip, sizeof(float), s[2].row * s[2].column, fp);    fread(Wfp, sizeof(float), s[3].row * s[3].column, fp);    fread(Wop, sizeof(float), s[4].row * s[4].column, fp);    fread(Wr, sizeof(float), s[5].row * s[5].column, fp);    fread(Wy, sizeof(float), s[6].row * s[6].column, fp);    fread(We_hg, sizeof(float), s[7].row * s[7].column, fp);    fread(W_hg, sizeof(float), s[8].row * s[8].column, fp);    fread(Wip_hg, sizeof(float), s[9].row * s[9].column, fp);    fread(Wfp_hg, sizeof(float), s[10].row * s[10].column, fp);    fread(Wop_hg, sizeof(float), s[11].row * s[11].column, fp);    fread(Wr_hg, sizeof(float), s[12].row * s[12].column, fp);    fread(Wy_hg, sizeof(float), s[13].row * s[13].column, fp);    fclose(fp);    for (int j = 0; j < s[3].row; ++j) {        for (int k = 0; k < s[3].column; ++k) {            printf("%f ",Wfp[k + j*s[3].column]);        }    printf("\n");    }    return true;}

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