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// Copyright © 2020 rsiddharth <s@ricketyspace.net>
// SPDX-License-Identifier: ISC
package lib
// Breaks 'cb' into blocks of 'keysize'
func BreakIntoBlocks(cb []byte, keysize int) [][]byte {
if len(cb) < 1 {
return make([][]byte, 0)
}
// Compute the number of blocks.
nb := len(cb) / keysize
if len(cb)%keysize != 0 {
nb += 1
}
blocks := make([][]byte, nb)
for i, j, k := 0, 0, 0; i < len(cb); i++ {
if len(blocks[k]) == 0 {
blocks[k] = make([]byte, keysize)
}
blocks[k][j] = cb[i]
j += 1
if j == keysize {
j = 0
k += 1
}
}
return blocks
}
func TransposeBlocks(blocks [][]byte, keysize int) [][]byte {
if len(blocks) < 1 {
return make([][]byte, 0)
}
tblocks := make([][]byte, keysize)
for i := 0; i < len(blocks); i++ {
for j := 0; j < len(blocks[i]); j++ {
if len(tblocks[j]) == 0 {
tblocks[j] = make([]byte, len(blocks))
}
tblocks[j][i] = blocks[i][j]
}
}
return tblocks
}
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