const std = @import("../std.zig");
const mem = std.mem;
const debug = std.debug;
pub fn ctr(comptime BlockCipher: anytype, block_cipher: BlockCipher, dst: []u8, src: []const u8, iv: [BlockCipher.block_length]u8, endian: std.builtin.Endian) void {
debug.assert(dst.len >= src.len);
const block_length = BlockCipher.block_length;
var counter: [BlockCipher.block_length]u8 = undefined;
var counterInt = mem.readInt(u128, &iv, endian);
var i: usize = 0;
const parallel_count = BlockCipher.block.parallel.optimal_parallel_blocks;
const wide_block_length = parallel_count * 16;
if (src.len >= wide_block_length) {
var counters: [parallel_count * 16]u8 = undefined;
while (i + wide_block_length <= src.len) : (i += wide_block_length) {
comptime var j = 0;
inline while (j < parallel_count) : (j += 1) {
mem.writeInt(u128, counters[j * 16 .. j * 16 + 16], counterInt, endian);
counterInt +%= 1;
}
block_cipher.xorWide(parallel_count, dst[i .. i + wide_block_length][0..wide_block_length], src[i .. i + wide_block_length][0..wide_block_length], counters);
}
}
while (i + block_length <= src.len) : (i += block_length) {
mem.writeInt(u128, &counter, counterInt, endian);
counterInt +%= 1;
block_cipher.xor(dst[i .. i + block_length][0..block_length], src[i .. i + block_length][0..block_length], counter);
}
if (i < src.len) {
mem.writeInt(u128, &counter, counterInt, endian);
var pad = [_]u8{0} ** block_length;
mem.copy(u8, &pad, src[i..]);
block_cipher.xor(&pad, &pad, counter);
mem.copy(u8, dst[i..], pad[0 .. src.len - i]);
}
}