Implement faster base conversion

Author: czurnieden

demo/test.c

@@ -1157,30 +1157,27 @@ static int test_mp_montgomery_reduce(void)
 
 }
 
+#include <time.h>
 static int test_mp_read_radix(void)
 {
    char buf[4096];
-   size_t written;
+   size_t written, maxlen;
 
-   mp_int a;
-   DOR(mp_init_multi(&a, NULL));
+   int bignum, i, j, k;
+   char *buffer, *bcpy, *startb;
+   clock_t start, stop, t_slow, t_fast;
+   double slow = 0.0, fast = 0.0, sum_slow = 0.0, sum_fast = 0.0;
+   double s_bases_slow[65] = {0.0};
+   double s_bases_fast[65] = {0.0};
+
+   mp_int a, b, c;
+   DOR(mp_init_multi(&a, &b, &c, NULL));
 
    DO(mp_read_radix(&a, "123456", 10));
 
    DO(mp_to_radix(&a, buf, sizeof(buf), &written, 10));
    printf(" '123456' a == %s, length = %zu", buf, written);
 
-   /* See comment in mp_to_radix.c */
-   /*
-      if( (err = mp_to_radix(&a, buf, 3u, &written, 10) ) != MP_OKAY)              goto LBL_ERR;
-      printf(" '56' a == %s, length = %zu\n", buf, written);
-
-      if( (err = mp_to_radix(&a, buf, 4u, &written, 10) ) != MP_OKAY)              goto LBL_ERR;
-      printf(" '456' a == %s, length = %zu\n", buf, written);
-      if( (err = mp_to_radix(&a, buf, 30u, &written, 10) ) != MP_OKAY)             goto LBL_ERR;
-      printf(" '123456' a == %s, length = %zu, error = %s\n",
-             buf, written, mp_error_to_string(err));
-   */
    DO(mp_read_radix(&a, "-123456", 10));
    DO(mp_to_radix(&a, buf, sizeof(buf), &written, 10));
    printf("\r '-123456' a == %s, length = %zu", buf, written);
@@ -1198,10 +1195,71 @@ static int test_mp_read_radix(void)
       printf("%s, %lu\n", buf, (unsigned long)a.dp[0] & 3uL);
    }
 
-   mp_clear(&a);
+   /* Test the fast method with a slightly larger number (about a minute on an older machine) */
+   for (k = 100; k < 6000; k += 1000) {
+      bignum = k;
+      buffer = (char *)malloc((size_t)(bignum + 2));
+      if (buffer == NULL) {
+         goto LBL_ERR;
+      }
+      DO(mp_rand(&a, bignum / MP_DIGIT_BIT));
+      /*fprintf(stderr,"\nNumber of limbs in &b = %d, bit_count of &b = %d\n", bignum / MP_DIGIT_BIT, mp_count_bits(&a));*/
+      for (i = 2; i < 65; i++) {
+         start = clock();
+         for (j = 0; j < 100; j++) {
+            DO(mp_to_radix(&a, buffer, (size_t)(bignum + 1), &written, i));
+            mp_zero(&b);
+            DO(mp_read_radix(&b, buffer, i));
+            /* Check roundabout */
+            EXPECT(mp_cmp(&a, &b) == MP_EQ);
+         }
+         stop = clock();
+         t_fast = stop - start;
+
+         start = clock();
+         for (j = 0; j < 100; j++) {
+            maxlen = (size_t)(bignum + 1);
+            bcpy = buffer;
+            /* s_mp_slower_to_radix is very rudimentary and needs some help to work as a stand-alone */
+            startb = bcpy;
+            DO(s_mp_slower_to_radix(&a, &bcpy, &maxlen, &written, i, false));
+            bcpy = startb;
+            mp_zero(&c);
+            DO(s_mp_slower_read_radix(&c, bcpy, 0, strlen(bcpy), i));
+            /* Check roundabout */
+            EXPECT(mp_cmp(&a, &c) == MP_EQ);
+            /* Check against result of fast algorithms above */
+            EXPECT(mp_cmp(&b, &c) == MP_EQ);
+         }
+         stop = clock();
+         t_slow = stop - start;
+
+         slow = (double)t_slow/(double)CLOCKS_PER_SEC;
+         fast = (double)t_fast/(double)CLOCKS_PER_SEC;
+
+         fprintf(stderr,"Bits %d Base %d SLOW: %.10f, FAST: %.10f\n", mp_count_bits(&a), i, slow, fast);
+
+         sum_slow += slow;
+         sum_fast += fast;
+         s_bases_slow[i] += slow;
+         s_bases_fast[i] += fast;
+      }
+      free(buffer);
+   }
+
+   fprintf(stderr,"\nSUM: SLOW: %.10f, FAST: %.10f\n",sum_slow, sum_fast);
+
+   for (i = 2; i < 65; i++) {
+      fprintf(stderr,"Sums for Base %d SLOW: %.10f, FAST: %.10f\n",i, s_bases_slow[i], s_bases_fast[i]);
+   }
+
+   /* Very basic check if the fast algorithms are actually faster. */
+   EXPECT(sum_slow > sum_fast);
+
+   mp_clear_multi(&a, &b, &c, NULL);
    return EXIT_SUCCESS;
 LBL_ERR:
-   mp_clear(&a);
+   mp_clear_multi(&a, &b, &c, NULL);
    return EXIT_FAILURE;
 }
 
@@ -2600,13 +2658,16 @@ static int unit_tests(int argc, char **argv)
       T3(s_mp_div_recursive, ONLY_PUBLIC_API, S_MP_DIV_RECURSIVE, S_MP_DIV_SCHOOL),
       T3(s_mp_div_small, ONLY_PUBLIC_API, S_MP_DIV_SMALL, S_MP_DIV_SCHOOL),
       T2(s_mp_sqr, ONLY_PUBLIC_API, S_MP_SQR),
+
       /* s_mp_mul_comba not (yet) testable because s_mp_mul branches to s_mp_mul_comba automatically */
+
       T2(s_mp_sqr_comba, ONLY_PUBLIC_API, S_MP_SQR_COMBA),
       T2(s_mp_mul_balance, ONLY_PUBLIC_API, S_MP_MUL_BALANCE),
       T2(s_mp_mul_karatsuba, ONLY_PUBLIC_API, S_MP_MUL_KARATSUBA),
       T2(s_mp_sqr_karatsuba, ONLY_PUBLIC_API, S_MP_SQR_KARATSUBA),
       T2(s_mp_mul_toom, ONLY_PUBLIC_API, S_MP_MUL_TOOM),
       T2(s_mp_sqr_toom, ONLY_PUBLIC_API, S_MP_SQR_TOOM)
+
 #undef T3
 #undef T2
 #undef T1

libtommath_VS2008.vcproj

@@ -836,6 +836,14 @@
 			RelativePath="s_mp_exptmod_fast.c"
 			>
 		</File>
+		<File
+			RelativePath="s_mp_faster_read_radix.c"
+			>
+		</File>
+		<File
+			RelativePath="s_mp_faster_to_radix.c"
+			>
+		</File>
 		<File
 			RelativePath="s_mp_fp_log.c"
 			>
@@ -912,6 +920,14 @@
 			RelativePath="s_mp_rand_platform.c"
 			>
 		</File>
+		<File
+			RelativePath="s_mp_slower_read_radix.c"
+			>
+		</File>
+		<File
+			RelativePath="s_mp_slower_to_radix.c"
+			>
+		</File>
 		<File
 			RelativePath="s_mp_sqr.c"
 			>

makefile

@@ -44,13 +44,14 @@ mp_reduce_setup.o mp_root_n.o mp_rshd.o mp_sbin_size.o mp_set.o mp_set_double.o
 mp_set_l.o mp_set_u32.o mp_set_u64.o mp_set_ul.o mp_shrink.o mp_signed_rsh.o mp_sqrmod.o mp_sqrt.o \
 mp_sqrtmod_prime.o mp_sub.o mp_sub_d.o mp_submod.o mp_to_radix.o mp_to_sbin.o mp_to_ubin.o mp_ubin_size.o \
 mp_unpack.o mp_warray_free.o mp_xor.o mp_zero.o s_mp_add.o s_mp_copy_digs.o s_mp_div_3.o \
-s_mp_div_recursive.o s_mp_div_school.o s_mp_div_small.o s_mp_exptmod.o s_mp_exptmod_fast.o s_mp_fp_log.o \
-s_mp_fp_log_d.o s_mp_get_bit.o s_mp_invmod.o s_mp_invmod_odd.o s_mp_log_2expt.o \
-s_mp_montgomery_reduce_comba.o s_mp_mul.o s_mp_mul_balance.o s_mp_mul_comba.o s_mp_mul_high.o \
-s_mp_mul_high_comba.o s_mp_mul_karatsuba.o s_mp_mul_toom.o s_mp_prime_is_divisible.o s_mp_prime_tab.o \
-s_mp_radix_map.o s_mp_radix_size_overestimate.o s_mp_rand_platform.o s_mp_sqr.o s_mp_sqr_comba.o \
-s_mp_sqr_karatsuba.o s_mp_sqr_toom.o s_mp_sub.o s_mp_warray.o s_mp_warray_get.o s_mp_warray_put.o \
-s_mp_zero_buf.o s_mp_zero_digs.o
+s_mp_div_recursive.o s_mp_div_school.o s_mp_div_small.o s_mp_exptmod.o s_mp_exptmod_fast.o \
+s_mp_faster_read_radix.o s_mp_faster_to_radix.o s_mp_fp_log.o s_mp_fp_log_d.o s_mp_get_bit.o \
+s_mp_invmod.o s_mp_invmod_odd.o s_mp_log_2expt.o s_mp_montgomery_reduce_comba.o s_mp_mul.o \
+s_mp_mul_balance.o s_mp_mul_comba.o s_mp_mul_high.o s_mp_mul_high_comba.o s_mp_mul_karatsuba.o \
+s_mp_mul_toom.o s_mp_prime_is_divisible.o s_mp_prime_tab.o s_mp_radix_map.o \
+s_mp_radix_size_overestimate.o s_mp_rand_platform.o s_mp_slower_read_radix.o s_mp_slower_to_radix.o \
+s_mp_sqr.o s_mp_sqr_comba.o s_mp_sqr_karatsuba.o s_mp_sqr_toom.o s_mp_sub.o s_mp_warray.o \
+s_mp_warray_get.o s_mp_warray_put.o s_mp_zero_buf.o s_mp_zero_digs.o
 
 #END_INS
 

makefile.mingw

@@ -46,13 +46,14 @@ mp_reduce_setup.o mp_root_n.o mp_rshd.o mp_sbin_size.o mp_set.o mp_set_double.o
 mp_set_l.o mp_set_u32.o mp_set_u64.o mp_set_ul.o mp_shrink.o mp_signed_rsh.o mp_sqrmod.o mp_sqrt.o \
 mp_sqrtmod_prime.o mp_sub.o mp_sub_d.o mp_submod.o mp_to_radix.o mp_to_sbin.o mp_to_ubin.o mp_ubin_size.o \
 mp_unpack.o mp_warray_free.o mp_xor.o mp_zero.o s_mp_add.o s_mp_copy_digs.o s_mp_div_3.o \
-s_mp_div_recursive.o s_mp_div_school.o s_mp_div_small.o s_mp_exptmod.o s_mp_exptmod_fast.o s_mp_fp_log.o \
-s_mp_fp_log_d.o s_mp_get_bit.o s_mp_invmod.o s_mp_invmod_odd.o s_mp_log_2expt.o \
-s_mp_montgomery_reduce_comba.o s_mp_mul.o s_mp_mul_balance.o s_mp_mul_comba.o s_mp_mul_high.o \
-s_mp_mul_high_comba.o s_mp_mul_karatsuba.o s_mp_mul_toom.o s_mp_prime_is_divisible.o s_mp_prime_tab.o \
-s_mp_radix_map.o s_mp_radix_size_overestimate.o s_mp_rand_platform.o s_mp_sqr.o s_mp_sqr_comba.o \
-s_mp_sqr_karatsuba.o s_mp_sqr_toom.o s_mp_sub.o s_mp_warray.o s_mp_warray_get.o s_mp_warray_put.o \
-s_mp_zero_buf.o s_mp_zero_digs.o
+s_mp_div_recursive.o s_mp_div_school.o s_mp_div_small.o s_mp_exptmod.o s_mp_exptmod_fast.o \
+s_mp_faster_read_radix.o s_mp_faster_to_radix.o s_mp_fp_log.o s_mp_fp_log_d.o s_mp_get_bit.o \
+s_mp_invmod.o s_mp_invmod_odd.o s_mp_log_2expt.o s_mp_montgomery_reduce_comba.o s_mp_mul.o \
+s_mp_mul_balance.o s_mp_mul_comba.o s_mp_mul_high.o s_mp_mul_high_comba.o s_mp_mul_karatsuba.o \
+s_mp_mul_toom.o s_mp_prime_is_divisible.o s_mp_prime_tab.o s_mp_radix_map.o \
+s_mp_radix_size_overestimate.o s_mp_rand_platform.o s_mp_slower_read_radix.o s_mp_slower_to_radix.o \
+s_mp_sqr.o s_mp_sqr_comba.o s_mp_sqr_karatsuba.o s_mp_sqr_toom.o s_mp_sub.o s_mp_warray.o \
+s_mp_warray_get.o s_mp_warray_put.o s_mp_zero_buf.o s_mp_zero_digs.o
 
 HEADERS_PUB=tommath.h
 HEADERS=tommath_private.h tommath_class.h tommath_superclass.h tommath_cutoffs.h $(HEADERS_PUB)

makefile.msvc

@@ -42,13 +42,14 @@ mp_reduce_setup.obj mp_root_n.obj mp_rshd.obj mp_sbin_size.obj mp_set.obj mp_set
 mp_set_l.obj mp_set_u32.obj mp_set_u64.obj mp_set_ul.obj mp_shrink.obj mp_signed_rsh.obj mp_sqrmod.obj mp_sqrt.obj \
 mp_sqrtmod_prime.obj mp_sub.obj mp_sub_d.obj mp_submod.obj mp_to_radix.obj mp_to_sbin.obj mp_to_ubin.obj mp_ubin_size.obj \
 mp_unpack.obj mp_warray_free.obj mp_xor.obj mp_zero.obj s_mp_add.obj s_mp_copy_digs.obj s_mp_div_3.obj \
-s_mp_div_recursive.obj s_mp_div_school.obj s_mp_div_small.obj s_mp_exptmod.obj s_mp_exptmod_fast.obj s_mp_fp_log.obj \
-s_mp_fp_log_d.obj s_mp_get_bit.obj s_mp_invmod.obj s_mp_invmod_odd.obj s_mp_log_2expt.obj \
-s_mp_montgomery_reduce_comba.obj s_mp_mul.obj s_mp_mul_balance.obj s_mp_mul_comba.obj s_mp_mul_high.obj \
-s_mp_mul_high_comba.obj s_mp_mul_karatsuba.obj s_mp_mul_toom.obj s_mp_prime_is_divisible.obj s_mp_prime_tab.obj \
-s_mp_radix_map.obj s_mp_radix_size_overestimate.obj s_mp_rand_platform.obj s_mp_sqr.obj s_mp_sqr_comba.obj \
-s_mp_sqr_karatsuba.obj s_mp_sqr_toom.obj s_mp_sub.obj s_mp_warray.obj s_mp_warray_get.obj s_mp_warray_put.obj \
-s_mp_zero_buf.obj s_mp_zero_digs.obj
+s_mp_div_recursive.obj s_mp_div_school.obj s_mp_div_small.obj s_mp_exptmod.obj s_mp_exptmod_fast.obj \
+s_mp_faster_read_radix.obj s_mp_faster_to_radix.obj s_mp_fp_log.obj s_mp_fp_log_d.obj s_mp_get_bit.obj \
+s_mp_invmod.obj s_mp_invmod_odd.obj s_mp_log_2expt.obj s_mp_montgomery_reduce_comba.obj s_mp_mul.obj \
+s_mp_mul_balance.obj s_mp_mul_comba.obj s_mp_mul_high.obj s_mp_mul_high_comba.obj s_mp_mul_karatsuba.obj \
+s_mp_mul_toom.obj s_mp_prime_is_divisible.obj s_mp_prime_tab.obj s_mp_radix_map.obj \
+s_mp_radix_size_overestimate.obj s_mp_rand_platform.obj s_mp_slower_read_radix.obj s_mp_slower_to_radix.obj \
+s_mp_sqr.obj s_mp_sqr_comba.obj s_mp_sqr_karatsuba.obj s_mp_sqr_toom.obj s_mp_sub.obj s_mp_warray.obj \
+s_mp_warray_get.obj s_mp_warray_put.obj s_mp_zero_buf.obj s_mp_zero_digs.obj
 
 HEADERS_PUB=tommath.h
 HEADERS=tommath_private.h tommath_class.h tommath_superclass.h tommath_cutoffs.h $(HEADERS_PUB)

makefile.shared

@@ -41,13 +41,14 @@ mp_reduce_setup.o mp_root_n.o mp_rshd.o mp_sbin_size.o mp_set.o mp_set_double.o
 mp_set_l.o mp_set_u32.o mp_set_u64.o mp_set_ul.o mp_shrink.o mp_signed_rsh.o mp_sqrmod.o mp_sqrt.o \
 mp_sqrtmod_prime.o mp_sub.o mp_sub_d.o mp_submod.o mp_to_radix.o mp_to_sbin.o mp_to_ubin.o mp_ubin_size.o \
 mp_unpack.o mp_warray_free.o mp_xor.o mp_zero.o s_mp_add.o s_mp_copy_digs.o s_mp_div_3.o \
-s_mp_div_recursive.o s_mp_div_school.o s_mp_div_small.o s_mp_exptmod.o s_mp_exptmod_fast.o s_mp_fp_log.o \
-s_mp_fp_log_d.o s_mp_get_bit.o s_mp_invmod.o s_mp_invmod_odd.o s_mp_log_2expt.o \
-s_mp_montgomery_reduce_comba.o s_mp_mul.o s_mp_mul_balance.o s_mp_mul_comba.o s_mp_mul_high.o \
-s_mp_mul_high_comba.o s_mp_mul_karatsuba.o s_mp_mul_toom.o s_mp_prime_is_divisible.o s_mp_prime_tab.o \
-s_mp_radix_map.o s_mp_radix_size_overestimate.o s_mp_rand_platform.o s_mp_sqr.o s_mp_sqr_comba.o \
-s_mp_sqr_karatsuba.o s_mp_sqr_toom.o s_mp_sub.o s_mp_warray.o s_mp_warray_get.o s_mp_warray_put.o \
-s_mp_zero_buf.o s_mp_zero_digs.o
+s_mp_div_recursive.o s_mp_div_school.o s_mp_div_small.o s_mp_exptmod.o s_mp_exptmod_fast.o \
+s_mp_faster_read_radix.o s_mp_faster_to_radix.o s_mp_fp_log.o s_mp_fp_log_d.o s_mp_get_bit.o \
+s_mp_invmod.o s_mp_invmod_odd.o s_mp_log_2expt.o s_mp_montgomery_reduce_comba.o s_mp_mul.o \
+s_mp_mul_balance.o s_mp_mul_comba.o s_mp_mul_high.o s_mp_mul_high_comba.o s_mp_mul_karatsuba.o \
+s_mp_mul_toom.o s_mp_prime_is_divisible.o s_mp_prime_tab.o s_mp_radix_map.o \
+s_mp_radix_size_overestimate.o s_mp_rand_platform.o s_mp_slower_read_radix.o s_mp_slower_to_radix.o \
+s_mp_sqr.o s_mp_sqr_comba.o s_mp_sqr_karatsuba.o s_mp_sqr_toom.o s_mp_sub.o s_mp_warray.o \
+s_mp_warray_get.o s_mp_warray_put.o s_mp_zero_buf.o s_mp_zero_digs.o
 
 #END_INS
 

makefile.unix

@@ -47,13 +47,14 @@ mp_reduce_setup.o mp_root_n.o mp_rshd.o mp_sbin_size.o mp_set.o mp_set_double.o
 mp_set_l.o mp_set_u32.o mp_set_u64.o mp_set_ul.o mp_shrink.o mp_signed_rsh.o mp_sqrmod.o mp_sqrt.o \
 mp_sqrtmod_prime.o mp_sub.o mp_sub_d.o mp_submod.o mp_to_radix.o mp_to_sbin.o mp_to_ubin.o mp_ubin_size.o \
 mp_unpack.o mp_warray_free.o mp_xor.o mp_zero.o s_mp_add.o s_mp_copy_digs.o s_mp_div_3.o \
-s_mp_div_recursive.o s_mp_div_school.o s_mp_div_small.o s_mp_exptmod.o s_mp_exptmod_fast.o s_mp_fp_log.o \
-s_mp_fp_log_d.o s_mp_get_bit.o s_mp_invmod.o s_mp_invmod_odd.o s_mp_log_2expt.o \
-s_mp_montgomery_reduce_comba.o s_mp_mul.o s_mp_mul_balance.o s_mp_mul_comba.o s_mp_mul_high.o \
-s_mp_mul_high_comba.o s_mp_mul_karatsuba.o s_mp_mul_toom.o s_mp_prime_is_divisible.o s_mp_prime_tab.o \
-s_mp_radix_map.o s_mp_radix_size_overestimate.o s_mp_rand_platform.o s_mp_sqr.o s_mp_sqr_comba.o \
-s_mp_sqr_karatsuba.o s_mp_sqr_toom.o s_mp_sub.o s_mp_warray.o s_mp_warray_get.o s_mp_warray_put.o \
-s_mp_zero_buf.o s_mp_zero_digs.o
+s_mp_div_recursive.o s_mp_div_school.o s_mp_div_small.o s_mp_exptmod.o s_mp_exptmod_fast.o \
+s_mp_faster_read_radix.o s_mp_faster_to_radix.o s_mp_fp_log.o s_mp_fp_log_d.o s_mp_get_bit.o \
+s_mp_invmod.o s_mp_invmod_odd.o s_mp_log_2expt.o s_mp_montgomery_reduce_comba.o s_mp_mul.o \
+s_mp_mul_balance.o s_mp_mul_comba.o s_mp_mul_high.o s_mp_mul_high_comba.o s_mp_mul_karatsuba.o \
+s_mp_mul_toom.o s_mp_prime_is_divisible.o s_mp_prime_tab.o s_mp_radix_map.o \
+s_mp_radix_size_overestimate.o s_mp_rand_platform.o s_mp_slower_read_radix.o s_mp_slower_to_radix.o \
+s_mp_sqr.o s_mp_sqr_comba.o s_mp_sqr_karatsuba.o s_mp_sqr_toom.o s_mp_sub.o s_mp_warray.o \
+s_mp_warray_get.o s_mp_warray_put.o s_mp_zero_buf.o s_mp_zero_digs.o
 
 
 HEADERS_PUB=tommath.h

mp_fread.c

@@ -4,12 +4,23 @@
 /* SPDX-License-Identifier: Unlicense */
 
 #ifndef MP_NO_FILE
+
+/* TODO: It would be some effort involved to connect mp_fwrite (mp_fread) to s_faster_read_radix.
+
+         It is rather simple, on the other side, to just read the whole string into
+         memory and send it to s_faster_read_radix but it would need heap that may or
+         may not be available. So: check if there is something in the middle (e.g.: read
+         in chunks (LSD to MSD) and send those strings to s_faster_read_radix).
+
+         NOTE: reading from a stream is quite fast already, especially bases of the form 2^n. */
+
 /* read a bigint from a file stream in ASCII */
 mp_err mp_fread(mp_int *a, int radix, FILE *stream)
 {
    mp_err err;
    mp_sign sign = MP_ZPOS;
    int ch;
+   mp_digit binary_radix = 0u;
 
    /* make sure the radix is ok */
    if ((radix < 2) || (radix > 64)) {
@@ -31,6 +42,10 @@ mp_err mp_fread(mp_int *a, int radix, FILE *stream)
    /* clear a */
    mp_zero(a);
 
+   if (MP_IS_2EXPT(radix)) {
+      binary_radix = (mp_digit)s_mp_log2_radix[radix];
+   }
+
    do {
       uint8_t y;
       unsigned pos;
@@ -47,19 +62,21 @@ mp_err mp_fread(mp_int *a, int radix, FILE *stream)
       }
 
       /* shift up and add */
-      if ((err = mp_mul_d(a, (mp_digit)radix, a)) != MP_OKAY) {
-         return err;
-      }
-      if ((err = mp_add_d(a, y, a)) != MP_OKAY) {
-         return err;
+      if (binary_radix != 0u) {
+         if ((err = mp_mul_2d(a, binary_radix, a)) != MP_OKAY)                                            goto LBL_ERR;
+      } else {
+         if ((err = mp_mul_d(a, (mp_digit)radix, a)) != MP_OKAY)                                          goto LBL_ERR;
       }
+      if ((err = mp_add_d(a, y, a)) != MP_OKAY)                                                           goto LBL_ERR;
+
    } while ((ch = fgetc(stream)) != EOF);
 
    if (!mp_iszero(a)) {
       a->sign = sign;
    }
 
-   return MP_OKAY;
+LBL_ERR:
+   return err;
 }
 #endif