#include <iostream>
#include <fstream>
#include <string>
using namespace std;
void main()
{
FILE *filePtr;
filePtr = fopen("file.txt", "wb");
string line = "textures/sometexture.tga";
unsigned int length = (unsigned int)line.length();
fwrite(&length, sizeof(unsigned int), 1, filePtr);
fwrite(line.c_str(), length, 1, filePtr);
line = "";
length = 0;
fclose(filePtr);
filePtr = fopen("file.txt", "rb");
fread(&length, sizeof(unsigned int), 1, filePtr);
char *buffer = new char[length];
fread(buffer, sizeof(char), length, filePtr);
line = buffer;
delete [] buffer;
cout<<"Length= "<<length<<endl;
cout<<line<<endl;
fclose(filePtr);
}
ascii in binary files.
Author
I want to write a binary file but I also need to have some text in it that links to outside files. I wrote some test code but when I write a string I always gte gibberish attached to the end of it.
This program takes a string, writes the length of the string as an unsigned int then writes the string itself.
The problem comes from reading the file after.
this is the text file output:
textures/sometexture.tga
but when I read it back I get chinese characters and stuff appended.
this is the frist time I tried to do this...I thought it would be simple.
You forgot the null terminator.
You neither wrote nor read the null terminator.
C strings suck, don't they?
You neither wrote nor read the null terminator.
C strings suck, don't they?
To expand a little on what NotAYakk said:
unsigned int length = (unsigned int)line.length();
Should be:
unsigned int length = (unsigned int)line.length()+1;
unsigned int length = (unsigned int)line.length();
Should be:
unsigned int length = (unsigned int)line.length()+1;
Author
added this and it seemed to work.
char *buffer = new char[length+1];
fread(buffer, sizeof(char), length, filePtr);
buffer[length] = NULL;
line = buffer;
delete [] buffer;
thanks.
char *buffer = new char[length+1];
fread(buffer, sizeof(char), length, filePtr);
buffer[length] = NULL;
line = buffer;
delete [] buffer;
thanks.
You can do it that way, but doing your own memory management kinda sucks. Unfortunately you can't just resize a string's buffer and read in, because it isn't even guaranteed to have contiguous storage (for really long strings, that might actually be a bad idea). And fread() can't take a back_insert_iterator or anything that nice ;\ (On the other hand, why are you still using C file I/O?)
But, you can always make use of the one standard library container that *does* guarantee contiguous storage - std::vector - and also not have to worry about the null terminator:
But, you can always make use of the one standard library container that *does* guarantee contiguous storage - std::vector - and also not have to worry about the null terminator:
vector<char> buffer(length);// with an 'istream myfile(ios::binary);', a binary read looks like:myfile.read(&buffer[0], length);// Note there's no need to distinguish a "block size" from an "element count".// Also, in C++, sizeof(char) == 1 by definition.line.assign(buffer.begin(), buffer.end());This topic is closed to new replies.
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