Zig 0.17.0-dev (Split by item)

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hmacExpandLabel

tls.hmacExpandLabel

pub fn hmacExpandLabel(
    comptime Hmac: type,
    secret: []const u8,
    label_then_seed: []const []const u8,
    comptime len: usize,
) [len]u8

File

lib/std/crypto/tls.zig:535

Code

pub fn hmacExpandLabel(
    comptime Hmac: type,
    secret: []const u8,
    label_then_seed: []const []const u8,
    comptime len: usize,
) [len]u8 {
    const initial_hmac: Hmac = .init(secret);
    var a: [Hmac.mac_length]u8 = undefined;
    var result: [std.mem.alignForwardAnyAlign(usize, len, Hmac.mac_length)]u8 = undefined;
    var index: usize = 0;
    while (index < result.len) : (index += Hmac.mac_length) {
        var a_hmac = initial_hmac;
        if (index > 0) a_hmac.update(&a) else for (label_then_seed) |part| a_hmac.update(part);
        a_hmac.final(&a);

        var result_hmac = initial_hmac;
        result_hmac.update(&a);
        for (label_then_seed) |part| result_hmac.update(part);
        result_hmac.final(result[index..][0..Hmac.mac_length]);
    }
    return result[0..len].*;
}