2023年11月29日发(作者：)
[C++]c++中⼆进制⽂件的创建与使⽤
⼆进制⽂件和⽂本⽂件是不同的⽂件类型，因此在创建等⽅式也是不⼀样的
使⽤⽂件⽅式见下表：
"r"（只读） 为输⼊打开⼀个⽂本⽂件
"w"（只写） 为输出打开⼀个⽂本⽂件
"a"（追加） 为追加打开⼀个⽂本⽂件
"rb"（只读） 为输⼊打开⼀个⼆进制⽂件
"wb"（只写） 为输出打开⼀个⼆进制⽂件
"ab"（追加） 为追加打开⼀个⼆进制⽂件
"r+"（读写） 为读／写打开⼀个⽂本⽂件
"w+"（读写） 为读／写创建⼀个⽂本⽂件
"a+"（读写） 为读／写打开⼀个⽂本⽂件
"rb+"（读写） 为读／写打开⼀个⼆进制⽂件
"wb+"（读写） 为读／写创建⼀个⼆进制⽂件
"ab+"（读写） 为读／写打开⼀个⼆进制⽂件
void generateBin(string filename, int npattern ,int ninput, int noutput){
FILE* file;
file = fopen(filename.c_str(), "w");
if (file == NULL)
{
throw runtime_error("network: could not open " + string(filename) + " for writing");
}
fwrite(&npattern, sizeof(int), 1, file);
fwrite(&ninput, sizeof(int), 1, file);
fwrite(&noutput, sizeof(int), 1, file);
float * input = new float[ninput];
float * output = new float[noutput];
float range = 1;
for (int n = 0; n < npattern;n++){
for (int i = 0; i < ninput; i++){
input[i] = range * ((float)rand() / RAND_MAX - 0.5);
}
fwrite(input,sizeof(float),ninput,file);
for (int o = 0; o < noutput; o++){
if (file == NULL)
throw runtime_error("Cannot open file " + filename + " for reading");
int ok =
fread(&npatterns, sizeof(int), 1, file) &&
fread(&ninput, sizeof(int), 1, file) &&
fread(&noutput, sizeof(int), 1, file);
cout << npatterns << " " << ninput << " " << noutput << endl;
cout << "ninput is:" << ninput << endl;
cout << "noutput is:" << noutput << endl;
cout << "npatterns is:" << npatterns << endl;
for (int i = 0; i < npatterns; i++) {
cout << "load_patterns i:" << i << endl;
data_read = fread(inputs, sizeof(float), ninput, file);
cout << "need: " << ninput << " get: " << data_read << endl;
if (data_read != ((size_t)ninput)) {
cout << "Wrong file format " << endl;
fclose(file);
throw runtime_error("Wrong file format");
}
data_read = fread(targets, sizeof(float), noutput, file);
if (data_read != ((size_t)noutput)) {
cout << "Wrong file format " << endl;
fclose(file);
throw runtime_error("Wrong file format");
}
cout << "load_patterns i:" << i << endl;
}
delete inputs;
delete targets;
fclose(file);
}
上⾯两段程序，试图创建⼀个⼆进制⽂件，并且向其中写⼊data，并且再在其中读出⼆进制数据。
但是运⾏的结果是错误的，
data_read 的数量⼩于ninput，原因是因为使⽤了⽂本⽂件的创建⽅式，但是确使⽤了⼆进制⽂件的操作。应该改为如下的代码
void generateBin(string filename, int npattern ,int ninput, int noutput){
FILE* file;
file = fopen(filename.c_str(), "wb");
if (file == NULL)
{
throw runtime_error("network: could not open " + string(filename) + " for writing");
}
fwrite(&npattern, sizeof(int), 1, file);
fwrite(&ninput, sizeof(int), 1, file);
fwrite(&noutput, sizeof(int), 1, file);
float * input = new float[ninput];
float * output = new float[noutput];
float range = 1;
for (int n = 0; n < npattern;n++){
for (int i = 0; i < ninput; i++){
input[i] = range * ((float)rand() / RAND_MAX - 0.5);
}
fwrite(input,sizeof(float),ninput,file);
for (int o = 0; o < noutput; o++){
output[o] = range * ((float)rand() / RAND_MAX - 0.5);
}
fwrite(output, sizeof(float), noutput, file);
}
if (fclose(file) != 0) {
throw runtime_error("network: error on saving to " + string(filename));
}
delete input;
delete output;
}
void readdata(){
int ninput =0;
int noutput = 0;
int npatterns = 0;
size_t data_read = 0;
float* inputs = new float[ninput];
float* targets = new float[noutput];
string filename = "";
FILE *file = fopen(filename.c_str(), "rb");
if (file == NULL)
throw runtime_error("Cannot open file " + filename + " for reading");
int ok =
fread(&npatterns, sizeof(int), 1, file) &&
fread(&ninput, sizeof(int), 1, file) &&
fread(&noutput, sizeof(int), 1, file);
cout << npatterns << " " << ninput << " " << noutput << endl;
cout << "ninput is:" << ninput << endl;
cout << "noutput is:" << noutput << endl;
cout << "npatterns is:" << npatterns << endl;
for (int i = 0; i < npatterns; i++) {
cout << "load_patterns i:" << i << endl;
data_read = fread(inputs, sizeof(float), ninput, file);
cout << "need: " << ninput << " get: " << data_read << endl;
if (data_read != ((size_t)ninput)) {
cout << "Wrong file format " << endl;
fclose(file);
throw runtime_error("Wrong file format");
}
data_read = fread(targets, sizeof(float), noutput, file);
if (data_read != ((size_t)noutput)) {
cout << "Wrong file format " << endl;
fclose(file);
throw runtime_error("Wrong file format");
}
cout << "load_patterns i:" << i << endl;
}
delete inputs;
delete targets;
fclose(file);
}
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