英文:
Write an array of uint32 to a slice of bytes and obtain it back
问题
我正在尝试创建一个os.File的模拟对象，或者更具体地说是io.Reader。我想要模拟读取128位具体数据的操作，而不进行实际读取。
对于单个的uint32，没有问题。
模拟代码：
func (f *FileMock) Read(buf []byte) (n int, err error) {
binary.BigEndian.PutUint32(buf, uint32(2052))
return len(buf), nil
}
被测试的方法（简化版）：
b := make([]byte, 128)
meta_data := make([]uint32, 4)
_, err = s.Read(b)
if err != nil {
// 处理错误
}
binary.Read(bytes.NewBuffer(b), binary.BigEndian, &meta_data)
log.Print(meta_data) // 输出 [2052 0 0 0]
但是，当我需要模拟读取一个uint32切片时，PutUint32方法就不再适用，因为它会从切片的开头开始写入（覆盖之前写入的数据）。我尝试了许多bytes和binary工具的组合，但每次都无法从字节中获取数据。以下是我最后一次尝试（不是唯一的尝试）：
func (f *FileMock) Read(b []byte) (n int, err error) {
buf := bytes.NewBuffer(make([]byte, len(b)))
err = binary.Write(buf, binary.BigEndian, [4]uint32{2051, 123, 28, 28})
buf.Read(b)
return len(b), nil
}
使用上述相同的被测试方法，我得到了一个空的切片[0, 0, 0, 0]。请注意，这是os.File.Read方法的模拟，所以我不能创建一个新的字节切片，而是需要将数据写入现有的切片。
首先，我想知道如何解决这个问题。另外，我想知道为什么结果只是[0, 0, 0, 0]。
感谢您的回答！
英文:
I'm trying to create a mock for a os.File or to be more specific io.Reader. I want to emulate reading of 128 bits of concrete data without actual reading.
With a single uint32 there is no problems.
Mock:
func (f *FileMock) Read(buf []byte) (n int, err error) {
binary.BigEndian.PutUint32(buf, uint32(2052))
return len(buf), nil
}
Tested method (simplified):
b := make([]byte, 128)
meta_data := make([]uint32, 4)
_, err = s.Read(b)
if err != nil {
// Handle error
}
binary.Read(bytes.NewBuffer(b), binary.BigEndian, &meta_data)
log.Print(meta_data) // Output [2052 0 0 0]
But when I need to mock reading of a uint32 slice PutUint32 is not helpful because it writes to a slice from beginning (overrites previously wrtten data). I tried a bunch of combinations of bytesand binary tools but had no luck every time I can't get the data back from bytes. There is my last attempt (it is not the only):
func (f *FileMock) Read(b []byte) (n int, err error) {
buf := bytes.NewBuffer(make([]byte, len(b)))
err = binary.Write(buf, binary.BigEndian, [4]uint32{2051, 123, 28, 28})
buf.Read(b)
return len(b), nil
}
With the same tested method as described above I'm obtaining an empty slice [0, 0, 0, 0]. Please note, this is a mock for os.File.Read method so I can't create a new slice of bytes instead of it I need to write my data to an existing slice.
At first I'm wondering how to solve the issue. Also I want to know why there is just [0, 0, 0, 0]?
Grateful for answers!
答案1
得分: 0
切片共享一个底层数组，你可以将 (PutUint32) 写入 buf[4:]、buf[8:] 等位置。
英文:
Slices share an underlying array, you can write (PutUint32) to buf[4:], buf[8:] etc.
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论