wingo pushed a commit to branch wip-inline-digits
in repository guile.
commit 46cba3725aa18f4ea20f79908d2033d49d6ee088
Author: Andy Wingo <[email protected]>
AuthorDate: Tue Jan 4 10:51:20 2022 +0100
Implement scm_integer_length with new integer library
* libguile/integers.c (scm_integer_length_i)
(scm_integer_length_z): New internal functions.
* libguile/integers.h: Declare the new internal functions.
* libguile/numbers.c (scm_integer_length): Use new internal functions.
---
libguile/integers.c | 36 ++++++++++++++++++++++++++++++++++++
libguile/integers.h | 5 ++++-
libguile/numbers.c | 34 ++--------------------------------
3 files changed, 42 insertions(+), 33 deletions(-)
diff --git a/libguile/integers.c b/libguile/integers.c
index db806b35f..fafef184f 100644
--- a/libguile/integers.c
+++ b/libguile/integers.c
@@ -2291,3 +2291,39 @@ scm_integer_logcount_z (struct scm_bignum *n)
scm_remember_upto_here_1 (n);
return scm_from_ulong (count);
}
+
+static const char scm_ilentab[] = {
+ 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4
+};
+
+SCM
+scm_integer_length_i (scm_t_inum n)
+{
+ unsigned long c = 0;
+ unsigned int l = 4;
+ if (n < 0)
+ n = -1 - n;
+ while (n)
+ {
+ c += 4;
+ l = scm_ilentab [15 & n];
+ n >>= 4;
+ }
+ return SCM_I_MAKINUM (c - 4 + l);
+}
+
+SCM
+scm_integer_length_z (struct scm_bignum *n)
+{
+ /* mpz_sizeinbase looks at the absolute value of negatives, whereas we
+ want a ones-complement. If n is ...111100..00 then mpz_sizeinbase is
+ 1 too big, so check for that and adjust. */
+ mpz_t zn;
+ alias_bignum_to_mpz (n, zn);
+ size_t size = mpz_sizeinbase (zn, 2);
+ /* If negative and no 0 bits above the lowest 1, adjust result. */
+ if (mpz_sgn (zn) < 0 && mpz_scan0 (zn, mpz_scan1 (zn, 0)) == ULONG_MAX)
+ size--;
+ scm_remember_upto_here_1 (n);
+ return scm_from_size_t (size);
+}
diff --git a/libguile/integers.h b/libguile/integers.h
index 0ffe713a1..5bc2c7650 100644
--- a/libguile/integers.h
+++ b/libguile/integers.h
@@ -1,7 +1,7 @@
#ifndef SCM_INTEGERS_H
#define SCM_INTEGERS_H
-/* Copyright 2021 Free Software Foundation, Inc.
+/* Copyright 2021, 2022 Free Software Foundation, Inc.
This file is part of Guile.
@@ -141,6 +141,9 @@ SCM_INTERNAL SCM scm_integer_bit_extract_z (struct
scm_bignum *n,
SCM_INTERNAL SCM scm_integer_logcount_i (scm_t_inum n);
SCM_INTERNAL SCM scm_integer_logcount_z (struct scm_bignum *n);
+SCM_INTERNAL SCM scm_integer_length_i (scm_t_inum n);
+SCM_INTERNAL SCM scm_integer_length_z (struct scm_bignum *n);
+
#endif /* SCM_INTEGERS_H */
diff --git a/libguile/numbers.c b/libguile/numbers.c
index 1a840e424..efc9ed06c 100644
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -3409,12 +3409,6 @@ SCM_DEFINE (scm_logcount, "logcount", 1, 0, 0,
}
#undef FUNC_NAME
-
-static const char scm_ilentab[] = {
- 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4
-};
-
-
SCM_DEFINE (scm_integer_length, "integer-length", 1, 0, 0,
(SCM n),
"Return the number of bits necessary to represent @var{n}.\n"
@@ -3430,33 +3424,9 @@ SCM_DEFINE (scm_integer_length, "integer-length", 1, 0,
0,
#define FUNC_NAME s_scm_integer_length
{
if (SCM_I_INUMP (n))
- {
- unsigned long c = 0;
- unsigned int l = 4;
- scm_t_inum nn = SCM_I_INUM (n);
- if (nn < 0)
- nn = -1 - nn;
- while (nn)
- {
- c += 4;
- l = scm_ilentab [15 & nn];
- nn >>= 4;
- }
- return SCM_I_MAKINUM (c - 4 + l);
- }
+ return scm_integer_length_i (SCM_I_INUM (n));
else if (SCM_BIGP (n))
- {
- /* mpz_sizeinbase looks at the absolute value of negatives, whereas we
- want a ones-complement. If n is ...111100..00 then mpz_sizeinbase is
- 1 too big, so check for that and adjust. */
- size_t size = mpz_sizeinbase (SCM_I_BIG_MPZ (n), 2);
- if (mpz_sgn (SCM_I_BIG_MPZ (n)) < 0
- && mpz_scan0 (SCM_I_BIG_MPZ (n), /* no 0 bits above the lowest 1 */
- mpz_scan1 (SCM_I_BIG_MPZ (n), 0)) == ULONG_MAX)
- size--;
- scm_remember_upto_here_1 (n);
- return SCM_I_MAKINUM (size);
- }
+ return scm_integer_length_z (scm_bignum (n));
else
SCM_WRONG_TYPE_ARG (SCM_ARG1, n);
}
