WIP bsr

Signed-off-by: Davide Bettio <davide@uninstall.it>

Author: bettio

src/libAtomVM/bif.c

@@ -1628,9 +1628,7 @@ term bif_erlang_bsr_2(Context *ctx, uint32_t fail_label, int live, term arg1, te
         args_to_bigint(arg1, arg2, tmp_buf1, tmp_buf2, &m, &m_len, &m_sign, &n, &n_len, &n_sign);
 
         intn_digit_t bigres[INTN_MAX_RES_LEN];
-        size_t bigres_len;
-        //intn_bsl(m, m_len, b, bigres, &bigres_len); //FIXME TODO CHANGE ME
-        abort();
+        size_t bigres_len = intn_bsr(m, m_len, b, bigres);
 
         return make_bigint(ctx, fail_label, live, bigres, bigres_len, m_sign);
     } else {

src/libAtomVM/intn.c

@@ -604,6 +604,55 @@ size_t intn_bsl(const uint32_t num[], size_t len, size_t n, uint32_t *out)
     return initial_zeros + i;
 }
 
+size_t intn_bsr(const uint32_t num[], size_t len, size_t n, uint32_t *out)
+{
+    size_t digit_bit_size = sizeof(uint32_t) * 8;
+
+    size_t digit_right_bit_shift = n % 32;
+    size_t left_shift_n = (32 - digit_right_bit_shift);
+
+    size_t counted_digits = intn_count_digits(num, len);
+    size_t ms_digit_bits = 32 - uint32_nlz(num[counted_digits - 1]);
+    size_t effective_bits_len = (counted_digits - 1) * digit_bit_size + ms_digit_bits;
+    size_t new_bits_len = size_round_to(effective_bits_len - n, digit_bit_size);
+
+    size_t new_digits_count = new_bits_len / digit_bit_size;
+
+    if (new_digits_count > INTN_BSL_MAX_OUT_LEN) {
+        return new_digits_count;
+    }
+
+    size_t discarded = MIN(n / digit_bit_size, len);
+
+    if (left_shift_n == 32) {
+        memcpy(out, num + discarded, (len - discarded) * sizeof(uint32_t));
+        return len - discarded;
+    }
+
+    size_t i;
+    for (i = discarded; i < counted_digits - 1; i++) {
+        uint32_t next_digit = num[i + 1];
+        uint32_t digit = num[i];
+        out[i - discarded] = (digit >> digit_right_bit_shift) | (next_digit << left_shift_n);
+    }
+    uint32_t maybe_last_out = (num[i] >> digit_right_bit_shift);
+
+/*
+    if (initial_zeros + i > new_digits_count) {
+        abort();
+    }
+*/
+
+    if (maybe_last_out) {
+        out[i - discarded] = maybe_last_out;
+        return i - discarded + 1;
+    }
+
+    return i - discarded;
+}
+
+
+
 /*
     uint32_t last_digit = 0;
     for (size_t i = initial_zeros; i < out_len - 1; i++) {

src/libAtomVM/intn.h

@@ -86,6 +86,7 @@ size_t intn_bxormn(const intn_digit_t m[], size_t m_len, intn_integer_sign_t m_s
     intn_integer_sign_t *out_sign);
 
 size_t intn_bsl(const uint32_t num[], size_t len, size_t n, uint32_t *out);
+size_t intn_bsr(const uint32_t num[], size_t len, size_t n, uint32_t *out);
 
 size_t intn_count_digits(const intn_digit_t *num, size_t num_len);
 

tests/erlang_tests/bigint.erl

@@ -55,7 +55,8 @@ start() ->
         big_literals() +
         to_external_term() +
         test_bor() +
-        test_bsl().
+        test_bsl() +
+        test_bsr().
 
 test_mul() ->
     Expected_INT64_MIN = ?MODULE:pow(-2, 63),
@@ -890,6 +891,23 @@ test_bsl() ->
 
     0.
 
+test_bsr() ->
+    erlang:display('bsr'),
+    %% versione negativa
+    Pattern1 = erlang:binary_to_integer(?MODULE:id(<<"CAFE1234AABBCCDD98765432987654321">>), 16),
+    <<"CAFE1234AABBCCDD98765432987">> = erlang:integer_to_binary(Pattern1 bsr ?MODULE:id(24), 16),
+    <<"657F091A555DE66ECC3B2A194C">> = erlang:integer_to_binary(Pattern1 bsr ?MODULE:id(29), 16),
+    <<"CAFE1234AABBCCDD987654329">> = erlang:integer_to_binary(Pattern1 bsr ?MODULE:id(32), 16),
+    <<"195FC2469557799BB30ECA865">> = erlang:integer_to_binary(Pattern1 bsr ?MODULE:id(35), 16),
+    <<"CAFE1234AABBCCDD98765">> = erlang:integer_to_binary(Pattern1 bsr ?MODULE:id(48), 16),
+    <<"195FC2469557799BB30EC">> = erlang:integer_to_binary(Pattern1 bsr ?MODULE:id(51), 16),
+    <<"CAFE1234AABBCCDD9">> = erlang:integer_to_binary(Pattern1 bsr ?MODULE:id(64), 16),
+    <<"C">> = erlang:integer_to_binary(Pattern1 bsr ?MODULE:id(128), 16),
+
+    0.
+
+
+
 
 id(X) ->
     X.