Preserve input line endings in output file

Makefile.am

@@ -43,6 +43,7 @@ checkdiff               = test/diff/diff_bug-2nd-prime-bad.sh \
 			  test/diff/diff_kat6-31.sh \
 			  test/diff/diff_kat7-qq.sh \
 			  test/diff/diff_kat8-qq-truncate.sh \
+			  test/diff/diff_line-endings.sh \
 			  test/diff/diff_linear0-qq.sh \
 			  test/diff/diff_linear1-qq.sh \
 			  test/diff/diff_linear2-qq.sh \

configure.ac

@@ -108,6 +108,7 @@ AC_CONFIG_LINKS([
  input_files/line_endings/in2_unix.ms:input_files/line_endings/in2_unix.ms
  input_files/line_endings/in3_unix.ms:input_files/line_endings/in3_unix.ms
  input_files/line_endings/in4_unix.ms:input_files/line_endings/in4_unix.ms
+ test/diff/diff_line-endings.sh:test/diff/diff_line-endings.sh
  test/diff/diff_source.sh:test/diff/diff_source.sh
  test/diff/diff_source-gb-lm.sh:test/diff/diff_source-gb-lm.sh
  test/diff/diff_source-gb-red.sh:test/diff/diff_source-gb-red.sh

src/msolve/main.c

@@ -435,6 +435,64 @@ static void getoptions(
   files->bin_out_file = bin_out_fname;
 }
 
+/**
+ * Checks whether the first line of file fn ends with "\r\n" (DOS line ending)
+ *
+ * \return 1 if it does, 0 otherwise (including if fn cannot be read)
+ */
+static int has_crlf_line_ending(const char *fn) {
+  FILE *fh = fopen(fn, "rb");
+  if (fh == NULL) {
+    return 0;
+  }
+  int c, prev = EOF;
+  while ((c = fgetc(fh)) != EOF && c != '\n') {
+    prev = c;
+  }
+  fclose(fh);
+  return c == '\n' && prev == '\r';
+}
+
+/**
+ * Rewrites file fn in place, replacing each "\n" which is not already
+ * preceded by "\r" with "\r\n"
+ *
+ * \return 0 on success, 1 on failure
+ */
+static int convert_to_crlf_line_endings(const char *fn) {
+  FILE *fh = fopen(fn, "rb");
+  if (fh == NULL) {
+    return 1;
+  }
+  FILE *tmp = tmpfile();
+  if (tmp == NULL) {
+    fclose(fh);
+    return 1;
+  }
+  int c;
+  while ((c = fgetc(fh)) != EOF) {
+    fputc(c, tmp);
+  }
+  fclose(fh);
+  rewind(tmp);
+
+  fh = fopen(fn, "wb");
+  if (fh == NULL) {
+    fclose(tmp);
+    return 1;
+  }
+  int prev = EOF;
+  while ((c = fgetc(tmp)) != EOF) {
+    if (c == '\n' && prev != '\r') {
+      fputc('\r', fh);
+    }
+    fputc(c, fh);
+    prev = c;
+  }
+  fclose(tmp);
+  return fclose(fh) != 0;
+}
+
 
 int main(int argc, char **argv){
 
@@ -564,6 +622,11 @@ int main(int argc, char **argv){
     interval *real_roots    = NULL;
     real_point_t *real_pts  = NULL;
 
+    /* output files are written with "\n" line endings; if the input file
+     * uses "\r\n", the output file is converted afterwards to match it */
+    int crlf_output = files->in_file != NULL && files->out_file != NULL
+                      && has_crlf_line_ending(files->in_file);
+
     /* main msolve functionality */
     int ret = core_msolve(la_option, use_signatures, nr_threads, info_level,
                           initial_hts, max_pairs, elim_block_len, update_ht,
@@ -576,6 +639,10 @@ int main(int argc, char **argv){
                           &param, mpz_paramp, &nb_real_roots, &real_roots,
                           &real_pts);
 
+    if (crlf_output && convert_to_crlf_line_endings(files->out_file)) {
+        fprintf(ERRSTREAM, "Cannot convert line endings of output file\n");
+    }
+
     /* free parametrization */
     if(param != NULL && gens->field_char){
         free_fglm_param(param);

test/diff/diff_line-endings.sh

@@ -0,0 +1,48 @@
+#!/usr/bin/env bash
+
+source test/diff/diff_source.sh
+
+# the output file should use the same line endings as the input file:
+# for each pair of inputs differing only by their line endings, the output
+# for the dos input must be the output for the unix input with "\r\n"
+
+prefix=input_files/line_endings
+
+check_line_endings() {
+    local dos=$1
+    local unix=$2
+    local excode=$3
+
+    $(pwd)/msolve -f $prefix/$dos.ms -o test/diff/$dos.res \
+          --random-seed $seed $4
+    if [ $? -gt 0 ]; then
+        print_exit $excode
+    fi
+
+    $(pwd)/msolve -f $prefix/$unix.ms -o test/diff/$unix.res \
+          --random-seed $seed $4
+    if [ $? -gt 0 ]; then
+        print_exit $(($excode+1))
+    fi
+
+    if grep -q $'\r' test/diff/$unix.res; then
+        print_exit $(($excode+2))
+    fi
+
+    awk '{ printf "%s\r\n", $0 }' test/diff/$unix.res | \
+        cmp -s - test/diff/$dos.res
+    if [ $? -gt 0 ]; then
+        print_exit $(($excode+3))
+    fi
+
+    rm test/diff/$dos.res test/diff/$unix.res
+}
+
+check_line_endings in1_dos in1_unix 1
+check_line_endings in2_dos_noeol in2_unix 5
+check_line_endings in3_dos in3_unix 9
+check_line_endings in4_dos in4_unix 13
+check_line_endings in1_dos in1_unix 17 "-g 2"
+check_line_endings in1_dos in1_unix 21 "-P 1"
+
+normal_exit