Question

我目前正在使用fopen来编写/读取二进制文件。小文件都是罚款。但在某些情况下，当“确切”内容是＆gt; 16K文件的其余部分无效!!!

代码很简单，fopen ... fread / fwrite ... fflush ... fclose！

我尝试过使用C ++。但是现在我在“阅读”期间遇到了一个问题

在BinaryDefaultRead中

它返回-1 !!!但真的不知道为什么！我一次只写4个字节!!!

使用MSVC 2008编译器在Win7 64位下。

#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 result;
    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;
}

Answer 1

fopen仅用于打开文件流，而不是用于读取或写入。 fread和fwrite用于执行此操作。

fwrite和fread不能确保您编写传递给它们的所有元素：它们返回写入的元素数，这可能小于您传递的元素数。< / p>

只需检查返回的值，并保留fwrite - 直到您写出所有元素或直到流出错：使用ferror检查错误。

来自fwrite手册：

fread（）和fwrite（）返回成功读取或写入的项目数（即不是字符数）。如果发生错误或达到文件结尾，则返回值为短项目计数（或零）。

fread（）不区分文件结束和错误，并且调用者必须使用feof（3）和ferror（3）来确定发生了什么。

fopen - 不能写超过16K？

1 个答案: