github.com/bhojpur/cache@v0.0.4/pkg/file/core/split.go (about)

     1  package core
     2  
     3  // Copyright (c) 2018 Bhojpur Consulting Private Limited, India. All rights reserved.
     4  
     5  // Permission is hereby granted, free of charge, to any person obtaining a copy
     6  // of this software and associated documentation files (the "Software"), to deal
     7  // in the Software without restriction, including without limitation the rights
     8  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     9  // copies of the Software, and to permit persons to whom the Software is
    10  // furnished to do so, subject to the following conditions:
    11  
    12  // The above copyright notice and this permission notice shall be included in
    13  // all copies or substantial portions of the Software.
    14  
    15  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    16  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    17  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
    18  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    19  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
    20  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
    21  // THE SOFTWARE.
    22  
    23  import "errors"
    24  
    25  // ErrCannotSplitBytes is returned when a byte slice cannot be split evenly
    26  // with the given size array.
    27  var ErrCannotSplitBytes = errors.New(
    28  	"byte array can not be split given size vector",
    29  )
    30  
    31  // calculateSizeSum calculates the sum of all of the uint32s in a []uint32.
    32  func calculateSizeSum(sizes []uint32) uint32 {
    33  	var sum uint32 // Init the sum
    34  
    35  	// Add all of the slice's elements
    36  	for _, size := range sizes {
    37  		sum += size
    38  	}
    39  
    40  	return sum // Return the sum
    41  }
    42  
    43  // SplitBytes splits a []byte n times.
    44  func SplitBytes(bytes []byte, sizes []uint32) ([][]byte, error) {
    45  	// Check that the bytes can be split given the size vector
    46  	if uint32(len(bytes)) != calculateSizeSum(sizes) {
    47  		return nil, ErrCannotSplitBytes
    48  	}
    49  
    50  	var splitBytes [][]byte // Init the master slice
    51  	currentBytePos := 0     // Init the byte position
    52  
    53  	// For each size (shard)
    54  	for _, currentSize := range sizes {
    55  		var tempBytes []byte // Init shard[i]'s byte slice
    56  
    57  		// For each byte that needs to be added
    58  		for i := 0; i < int(currentSize); i++ {
    59  			tempBytes = append(tempBytes, bytes[currentBytePos]) // Add the byte
    60  
    61  			currentBytePos++ // Move the "byte cursor"
    62  		}
    63  
    64  		// Append the shard's bytes to the master slice
    65  		splitBytes = append(splitBytes, tempBytes)
    66  	}
    67  
    68  	return splitBytes, nil
    69  }