在Nim中寫入/讀取二進制文件

Question

在Nim中編寫和讀取二進制文件的最佳方式是什麼？我想寫一個二進制文件交替浮動和整數，然後能夠讀取文件。爲了寫這個二進制文件在Python我會做類似

import struct 

# list of alternating floats and ints 
arr = [0.5, 1, 1.5, 2, 2.5, 3] 

# here 'f' is for float and 'i' is for int  
binStruct = struct.Struct('fi' * (len(arr)/2)) 
# put it into string format 
packed = binStruct.pack(*tuple(arr)) 

# open file for writing in binary mode 
with open('/path/to/my/file', 'wb') as fh: 
    fh.write(packed) 

讀書，我會做類似

arr = [] 
    with open('/path/to/my/file', 'rb') as fh: 
    data = fh.read() 
    for i in range(0, len(data), 8): 
     tup = binStruct.unpack('fi', data[i: i + 8]) 
     arr.append(tup) 

在這個例子中，讀取文件後，編曲將

[(0.5, 1), (1.5, 2), (2.5, 3)] 

在Nim中尋找類似的功能。

Answer 1

我想你應該在streams模塊中找到你需要的一切。這裏是一個小例子：

import streams 

type 
    Alternating = seq[(float, int)] 

proc store(fn: string, data: Alternating) = 
    var s = newFileStream(fn, fmWrite) 
    s.write(data.len) 
    for x in data: 
    s.write(x[0]) 
    s.write(x[1]) 
    s.close() 

proc load(fn: string): Alternating = 
    var s = newFileStream(fn, fmRead) 
    let size = s.readInt64() # actually, let's not use it to demonstrate s.atEnd 
    result = newSeq[(float, int)]() 
    while not s.atEnd: 
    let element = (s.readFloat64.float, s.readInt64.int) 
    result.add(element) 
    s.close() 


let data = @[(1.0, 1), (2.0, 2)] 

store("tmp.dat", data) 
let dataLoaded = load("tmp.dat") 

echo dataLoaded