mask.c

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#include "ccsds124.h"
 
void ccsds124_update_build(
    bitvector_t *build,
    const bitvector_t *input,
    const bitvector_t *prev_input,
    int new_mask_flag,
    size_t t
) {
    /* Case 1: t=0 or new_mask_flag set → reset build to 0 */
    if ((t == 0U) || (new_mask_flag != 0)) {
        bitvector_zero(build);
    } else {
        /* Case 2: Normal operation (t > 0 and new_mask_flag = 0)
         * Bₜ = (Iₜ XOR Iₜ₋₁) OR Bₜ₋₁
         */
 
        /* Create temporary vector for changes */
        bitvector_t changes;
        (void)bitvector_init(&changes, build->length);
 
        /* Calculate changes: Iₜ XOR Iₜ₋₁ */
        bitvector_xor(&changes, input, prev_input);
 
        /* Update build: Bₜ = changes OR Bₜ₋₁ */
        bitvector_or(build, &changes, build);
    }
}
 
 
void ccsds124_update_mask(
    bitvector_t *mask,
    const bitvector_t *input,
    const bitvector_t *prev_input,
    const bitvector_t *build_prev,
    int new_mask_flag
) {
    /* Create temporary vector for changes */
    bitvector_t changes;
    (void)bitvector_init(&changes, mask->length);
 
    /* Calculate changes: Iₜ XOR Iₜ₋₁ */
    bitvector_xor(&changes, input, prev_input);
 
    if (new_mask_flag != 0) {
        /* Case 1: new_mask_flag set → Mₜ = (Iₜ XOR Iₜ₋₁) OR Bₜ₋₁ */
        bitvector_or(mask, &changes, build_prev);
    } else {
        /* Case 2: Normal operation → Mₜ = (Iₜ XOR Iₜ₋₁) OR Mₜ₋₁ */
        bitvector_or(mask, &changes, mask);
    }
}
 
 
void ccsds124_compute_change(
    bitvector_t *change,
    const bitvector_t *mask,
    const bitvector_t *prev_mask,
    size_t t
) {
    (void)t;  /* Always use XOR — caller sets prev_mask appropriately */
    /* Dₜ = Mₜ XOR Mₜ₋₁ */
    bitvector_xor(change, mask, prev_mask);
}