clean up

demo/test.c

@@ -1158,7 +1158,7 @@ static int test_mp_read_radix(void)
    size_t written, maxlen;
    int bignum, i;
 
-   char *buffer, *bcpy;
+   char *buffer, *bcpy, *startb;
 
    clock_t start, stop, t_slow, t_fast;
 
@@ -1191,18 +1191,19 @@ static int test_mp_read_radix(void)
 
    /* Test the fast method with a slightly larger number */
 
-   /* Must be bigger than the cut-off value, of course */
-   bignum = (2 * 20 * MP_RADIX_BARRETT_START_MULTIPLICATOR)  * 10;
+   /* Needs to be big enough to make a sufficiently large timing difference */
+   bignum = 30000;
    buffer = (char *)malloc((size_t)(bignum + 2));
    if (buffer == NULL) {
       goto LBL_ERR;
    }
    DO(mp_rand(&a, bignum / MP_DIGIT_BIT));
-   printf("\nNumber of limbs in &b = %d, bit_count of &b = %d\n", bignum / MP_DIGIT_BIT, mp_count_bits(&a));
+   fprintf(stderr,"\nNumber of limbs in &b = %d, bit_count of &b = %d\n", bignum / MP_DIGIT_BIT, mp_count_bits(&a));
    start = clock();
    for (i = 2; i < 65; i++) {
       /* printf("FAST radix = %d\n",i); */
       DO(mp_to_radix(&a, buffer, (size_t)(bignum + 1), &written, i));
+      mp_zero(&b);
       DO(mp_read_radix(&b, buffer, i));
       EXPECT(mp_cmp(&a, &b) == MP_EQ);
    }
@@ -1215,7 +1216,11 @@ static int test_mp_read_radix(void)
       /* printf("SLOW radix = %d\n",i); */
       maxlen = (size_t)(bignum + 1);
       bcpy = buffer;
+      /* s_mp_slower_to_radix is very rudimentary as a stand-alone */
+      startb = bcpy;
       DO(s_mp_slower_to_radix(&a, &bcpy, &maxlen, &written, i, false));
+      bcpy = startb;
+      mp_zero(&b);
       DO(s_mp_slower_read_radix(&b, bcpy, 0, strlen(bcpy), i));
       EXPECT(mp_cmp(&a, &b) == MP_EQ);
    }
@@ -1226,15 +1231,14 @@ static int test_mp_read_radix(void)
    fprintf(stderr,"SLOW: %.10f, FAST: %.10f\n", (double)t_slow/(double)CLOCKS_PER_SEC,
            (double)t_fast/(double)CLOCKS_PER_SEC);
 
-   /* Check if the branching works.
+   /* Check if the branching works. */
    if (MP_HAS(S_MP_FASTER_READ_RADIX) && MP_HAS(S_MP_FASTER_TO_RADIX)) {
       if (t_fast > t_slow) {
          fprintf(stderr, "Timing suspicious in test_mp_read_radix. No fast multiplication? Cut-off too low?\n");
          DO(mp_fwrite(&a, 16, stderr));
          goto LBL_ERR;
       }
    }
-   */
 
    free(buffer);
 

mp_to_radix.c

@@ -47,7 +47,9 @@ mp_err mp_to_radix(const mp_int *a, char *str, size_t maxlen, size_t *written, i
       if ((err = s_mp_faster_to_radix(&a_bar, str, maxlen, &part_written, radix)) != MP_OKAY)            goto LBL_ERR;
    } else {
       if (MP_HAS(S_MP_SLOWER_TO_RADIX)) {
+         char *start = str;
          if ((err = s_mp_slower_to_radix(&a_bar, &str, &maxlen, &part_written, radix, false)) != MP_OKAY) goto LBL_ERR;
+         str = start;
          /* part_written does not count EOS */
          part_written++;
       }

s_mp_faster_read_radix.c

@@ -3,7 +3,7 @@
 /* LibTomMath, multiple-precision integer library -- Tom St Denis */
 /* SPDX-License-Identifier: Unlicense */
 
-/* TODO: It is tunable */
+/* TODO: It is tunable. Or is it? */
 #define MP_READ_RADIX_CUTOFF_MULTIPLICATOR 3
 
 /* for(n=2,64,t = ceil(log(2^100)/log(n)); printf(t", "); ) */
@@ -41,8 +41,8 @@ mp_err s_mp_faster_read_radix(mp_int *a, const char *str, size_t start, size_t e
       return err;
    }
 
-   if ((err = s_mp_slower_read_radix(&A, str, start, start + mid + 1, radix)) != MP_OKAY)                goto LTM_ERR;
-   if ((err = s_mp_slower_read_radix(&B, str, start + mid +1, end, radix)) != MP_OKAY)                   goto LTM_ERR;
+   if ((err = s_mp_faster_read_radix(&A, str, start, start + mid + 1, radix)) != MP_OKAY)                goto LTM_ERR;
+   if ((err = s_mp_faster_read_radix(&B, str, start + mid +1, end, radix)) != MP_OKAY)                   goto LTM_ERR;
 
    if (MP_IS_2EXPT(radix_)) {
       if ((err = mp_mul_2d(&A, (int)(((len - mid) - 1u) * s_mp_floor_ilog2(radix_)), &A)) != MP_OKAY)    goto LTM_ERR;

s_mp_slower_to_radix.c

@@ -20,29 +20,30 @@ mp_err s_mp_slower_to_radix(const mp_int *a, char **str,
    mp_int t;
    mp_digit d;
    mp_err err = MP_OKAY;
-
-   /* The number of digits of "radix" to be filled if this chunk is not the most significant one. */
-   int ybar = s_mp_radix_exponent_y[radix] * MP_RADIX_BARRETT_START_MULTIPLICATOR;
+   int ybar = 0;
 
    /* A temporary pointer to the output string to make reversal simpler */
    char *s = *str;
 
-   /* TODO: input a is already a copy of the original and we could use it destructively? */
+   /* The number of digits of "radix" to be filled if this chunk is not the most significant one. */
+   if (pad) {
+      ybar = s_mp_radix_exponent_y[radix] * MP_RADIX_BARRETT_START_MULTIPLICATOR;
+   }
+
    if ((err = mp_init_copy(&t, a)) != MP_OKAY)                                                           goto LTM_ERR;
 
    while (!mp_iszero(&t)) {
-      /* TODO: this method to decrease "maxlen" is not threadsafe! */
       if ((--(*part_maxlen)) < 1u) {
          /* no more room */
          err = MP_BUF;
          goto LTM_ERR;
       }
-      if ((err = mp_div_d(&t, (mp_digit)radix, &t, &d)) != MP_OKAY) {
-         goto LTM_ERR;
-      }
+      if ((err = mp_div_d(&t, (mp_digit)radix, &t, &d)) != MP_OKAY)                                      goto LTM_ERR;
       *s++ = s_mp_radix_map[d];
       ++digs;
-      ybar--;
+      if (pad) {
+         ybar--;
+      }
    }
 
    /* Fill in leading zeros if this chunk does not contain the most significant digits. */
@@ -53,7 +54,6 @@ mp_err s_mp_slower_to_radix(const mp_int *a, char **str,
       }
    }
 
-   /* TODO: I think that can be done more elegantly */
    /* "rewind" */
    s = *str;
    /* reverse */
@@ -63,7 +63,6 @@ mp_err s_mp_slower_to_radix(const mp_int *a, char **str,
    /* Add EOS at the end of every chunk to allow this function to be used stand-alone */
    **str = '\0';
 
-   /* TODO: this method to increase "written" is not threadsafe! */
    if (part_written != NULL) {
       *part_written = *part_written + digs;
    }