From a34c1bf593b1cca9561cfbcb9b3576509edc0528 Mon Sep 17 00:00:00 2001
From: Andreas Enge <andreas.enge@inria.fr>
Date: Mon, 20 Feb 2023 18:06:08 +0100
Subject: [PATCH] Add function to read a factor from a checkpoint file.
* lib/cm-impl.h (cm_file_read_factor): Declare function.
* lib/file.c (cm_file_read_factor): New function.
---
lib/cm-impl.h | 2 ++
lib/file.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 54 insertions(+)
diff --git a/lib/cm-impl.h b/lib/cm-impl.h
index 934fbbb..9dee7c3 100644
--- a/lib/cm-impl.h
+++ b/lib/cm-impl.h
@@ -261,6 +261,8 @@ extern bool cm_file_read_primorial (const char *tmpdir, mpz_ptr prim,
const int i);
extern bool cm_file_write_factor (const char *tmpdir, mpzx_srcptr factor,
mpzx_srcptr F, mpz_srcptr p);
+extern bool cm_file_read_factor (const char *tmpdir, mpzx_ptr factor,
+ mpzx_srcptr F, mpz_srcptr p);
extern bool cm_write_ecpp_cert1_line (FILE *f, mpz_t *line, cm_stat_t stat);
extern bool cm_write_ecpp_cert2_line (FILE *f, mpz_t *line, int no,
cm_stat_t stat);
diff --git a/lib/file.c b/lib/file.c
index 872accc..13ae283 100644
--- a/lib/file.c
+++ b/lib/file.c
@@ -444,6 +444,58 @@ bool cm_file_write_factor (const char *tmpdir, mpzx_srcptr factor,
/*****************************************************************************/
+bool cm_file_read_factor (const char *tmpdir, mpzx_ptr factor,
+ mpzx_srcptr F, mpz_srcptr p)
+ /* If a corresponding file can be opened, try to read a factor of the
+ monic polynomial F modulo p and return it in factor, or leave factor
+ unchanged. The return value reflects the success of the operation. */
+{
+ char *filename;
+ uint64_t hash;
+ FILE *f;
+ unsigned int len;
+ bool res;
+ mpz_t ploc;
+ mpzx_t Floc;
+
+ len = strlen (tmpdir) + 29;
+ filename = (char *) malloc (len * sizeof (char));
+ hash = mpzx_mod_hash (F, p);
+ snprintf (filename, len, "%s/factor_%016"PRIx64".dat", tmpdir, hash);
+
+ f = fopen (filename, "r");
+ res = (f != NULL);
+
+ if (res) {
+ /* Read p and F and check whether they are the same; otherwise
+ there has been a hash collision. */
+ mpz_init (ploc);
+ mpzx_init (Floc, -1);
+ res &= (mpz_inp_str (ploc, f, 10) != 0);
+ res &= mpzx_inp_str (Floc, f, 10);
+ if (mpz_cmp (p, ploc) != 0 || mpzx_cmp (F, Floc) != 0) {
+ printf ("***** Warning: Hash collision in reading a factor\n");
+ printf ("p ");
+ mpz_out_str (stdout, 10, ploc);
+ printf ("\nF ");
+ mpzx_out_str (stdout, 10, Floc);
+ printf ("\n");
+ res = false;
+ }
+ else
+ res &= mpzx_inp_str (Floc, f, 10);
+ res &= (fclose (f) == 0);
+ if (res)
+ mpzx_set (factor, Floc);
+ mpz_clear (ploc);
+ mpzx_clear (Floc);
+ }
+
+ return res;
+}
+
+/*****************************************************************************/
+
static bool write_stat (FILE *f, cm_stat_t stat)
/* Write the content of stat to the file f. */
{
--
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