fopen - can't write more than 16K?

I'm currently using fopen to write/read binary files. With small files all is fines. But in some cases, when "exactly" the content is > 16K the remainder of the file is invalid !!!

The code is simple, fopen ... fread/fwrite ... fflush ... fclose !

I have try with C++. But now I got a problem during the "read"

in BinaryDefaultRead it return -1 !!! But really don't know why ! I only write 4 bytes at a time !!!

It is under Win7 64 bits with MSVC 2008 compiler.

#include <fstream>

using namespace std;

size_t BinaryDefaultRead(ifstream& stream, void* buffer, unsigned int bufferSize)
{
    //return fread(buffer, 1, (size_t) bufferSize, file);
    stream.read((char*)buffer, bufferSize);
    if (!stream)
        return -1;

    return bufferSize;
}

size_t BinaryDefaultWrite(ofstream& stream, const void* buffer, unsigned int bufferSize)
{
    //return fwrite(buffer, 1, (size_t) bufferSize, file);
    stream.write((char*)buffer, bufferSize);
    if (!stream)
        return -1;

    return bufferSize;
}

// Read an unsigned integer from a stream in a machine endian independent manner (for portability).
size_t BinaryReadUINT(ifstream& stream, unsigned int* value)
{
    unsigned char buf[4];
    size_t result = BinaryDefaultRead(stream, (void *)buf, 4);

    if (result < 0)
        return result;

    *value = ((unsigned int) buf[0]) |
    (((unsigned int) buf[1]) << 8) |
    (((unsigned int) buf[2]) << 16) |
    (((unsigned int) buf[3]) << 24);

    return result;
}

// Write an unsigned integer to a stream in a machine endian independent manner (for portability).
size_t BinaryWriteUINT(ofstream& stream, unsigned int aValue)
{
    unsigned char buf[4];
    buf[0] = aValue & 0x000000ff;
    buf[1] = (aValue >> 8) & 0x000000ff;
    buf[2] = (aValue >> 16) & 0x000000ff;
    buf[3] = (aValue >> 24) & 0x000000ff;

    return BinaryDefaultWrite(stream, (void*)buf, 4);
}

// Read a floating point value from a stream in a machine endian independent manner (for portability).
size_t BinaryReadFLOAT(ifstream& stream, float* value)
{
    union {
        float f;
        unsigned int  i;
    } u;
    size_t result = BinaryReadUINT(stream, &u.i);

    if (result < 0)
        return result;

    *value = u.f;

    return result;
}

// Write a floating point value to a stream in a machine endian independent manner (for portability).
size_t BinaryWriteFLOAT(ofstream& stream, float aValue)
{
    union {
        float f;
        unsigned int  i;
    } u;
    u.f = aValue;
    return BinaryWriteUINT(stream, u.i);
}

size_t BinaryReadUINTArray(ifstream& stream, unsigned int* buffer, unsigned int count)
{
    size_t result;
    for(unsigned int i = 0; i < count; i++)
    {
        result = BinaryReadUINT(stream, buffer + i);
        if (result < 0)
            return result;
    }

    return result;
}

size_t BinaryWriteUINTArray(ofstream& stream, unsigned int* buffer, unsigned int count)
{
    size_t res开发者_运维技巧ult;
    for(unsigned int i = 0; i < count; i++)
    {
        result = BinaryWriteUINT(stream, buffer[i]);
        if (result < 0)
            return result;
    }

    return result;
}

size_t BinaryReadFLOATArray(ifstream& stream, float* buffer, unsigned int count)
{
    size_t result;
    for(unsigned int i = 0; i < count; i++)
    {
        result = BinaryReadFLOAT(stream, buffer + i);
        if (result < 0)
            return result;
    }

    return result;
}

size_t BinaryWriteFLOATArray(ofstream& stream, float* buffer, unsigned int count)
{
    size_t result;
    for(unsigned int i = 0; i < count; i++)
    {
        result = BinaryWriteFLOAT(stream, buffer[i]);
        if (result < 0)
            return result;
    }

    return result;
}

---

fopen is only used to open a file stream, not to read or write. fread and fwrite are used to do that.

fwrite and fread don't ensure you to write all the elements you pass them: they return the number of elements written, which can be lesser than the number of elements you passed it.

Just check the returned value, and keep fwrite-ing until you write out all of your elements or until there's an error with the stream: use ferror to check for an error.

---

From fwrite manual:

fread() and fwrite() return the number of items successfully read or written (i.e., not the number of characters). If an error occurs, or the end-of-file is reached, the return value is a short item count (or zero).

fread() does not distinguish between end-of-file and error, and callers must use feof(3) and ferror(3) to determine which occurred.