Function sha256_transform

src/foundation/sha256.c:27–65

#define SIG1(x) (ROTR(x, 17) ^ ROTR(x, 19) ^ ((x) >> 10))

static void sha256_transform(cbm_sha256_ctx *c, const uint8_t *data) {
    /* Scratch comes from the context, not this frame: a 256-byte local here
     * is fake-stacked by ASan's use-after-return mode on every 64-byte block
     * (see the note on cbm_sha256_ctx::sched). Identical values, allocated
     * once per hash instead of once per block. */
    uint32_t *m = c->sched;
    for (int i = 0, j = 0; i < 16; i++, j += 4) {
        m[i] = ((uint32_t)data[j] << 24) | ((uint32_t)data[j + 1] << 16) |
               ((uint32_t)data[j + 2] << 8) | (uint32_t)data[j + 3];
    }
    for (int i = 16; i < 64; i++) {
        m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];
    }

    uint32_t a = c->state[0], b = c->state[1], cc = c->state[2], d = c->state[3];
    uint32_t e = c->state[4], f = c->state[5], g = c->state[6], h = c->state[7];

    for (int i = 0; i < 64; i++) {
        uint32_t t1 = h + EP1(e) + CH(e, f, g) + K[i] + m[i];
        uint32_t t2 = EP0(a) + MAJ(a, b, cc);
        h = g;
        g = f;
        f = e;
        e = d + t1;
        d = cc;
        cc = b;
        b = a;
        a = t1 + t2;
    }

    c->state[0] += a;
    c->state[1] += b;
    c->state[2] += cc;
    c->state[3] += d;
    c->state[4] += e;
    c->state[5] += f;
    c->state[6] += g;
    c->state[7] += h;
}

void cbm_sha256_init(cbm_sha256_ctx *c) {
    c->bitlen = 0;