core: Support writing the sign/encrypt output directly to a file

* src/engine-gpg.c (gpg_encrypt): Pass output file name to gpg if output
has file name set.
(gpg_encrypt_sign): Ditto.
(gpg_sign): Ditto.

* tests/run-encrypt.c (show_usage): New option --output.
(main): Parse new option. Set file name on output if --output is given.
Do not print output if --output is given.
* tests/run-sign.c (show_usage): New option --output.
(main): Parse new option. Set file name on output if --output is given.
Do not print output if --output is given.
--

This change makes it possible to tell gpg (and gpgtar) to write the
output (i.e. the signed/encrypted data or the signature or the created
archive) directly to a file with given file name instead of piping
the output back to gpgme.

GnuPG-bug-id: 6530

doc/gpgme.texi

@@ -6332,10 +6332,12 @@ GnuPG 2.4.1.
 @deftypefun gpgme_error_t gpgme_op_sign (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_data_t @var{plain}}, @w{gpgme_data_t @var{sig}}, @w{gpgme_sig_mode_t @var{mode}})
 The function @code{gpgme_op_sign} creates a signature for the text in
 the data object @var{plain} and returns it in the data object
-@var{sig}.  The type of the signature created is determined by the
+@var{sig} or writes it directly to the file set with
-@acronym{ASCII} armor (or, if that is not set, by the encoding
+@code{gpgme_data_set_file_name} for the data object @var{sig}.  The type
-specified for @var{sig}), the text mode attributes set for the context
+of the signature created is determined by the @acronym{ASCII} armor (or,
-@var{ctx} and the requested signature mode @var{mode}.
+if that is not set, by the encoding specified for @var{sig}), the text
+mode attributes set for the context @var{ctx} and the requested signature
+mode @var{mode}.
 
 If signature mode @code{GPGME_SIG_MODE_ARCHIVE} is requested, then a
 signed archive is created from the files and directories given as
@@ -6510,10 +6512,12 @@ and then passed to the encryption operation.
 @deftypefun gpgme_error_t gpgme_op_encrypt (@w{gpgme_ctx_t @var{ctx}}, @w{gpgme_key_t @var{recp}[]}, @w{gpgme_encrypt_flags_t @var{flags}}, @w{gpgme_data_t @var{plain}}, @w{gpgme_data_t @var{cipher}})
 The function @code{gpgme_op_encrypt} encrypts the plaintext in the
 data object @var{plain} for the recipients @var{recp} and stores the
-ciphertext in the data object @var{cipher}.  The type of the
+ciphertext in the data object @var{cipher} or writes it directly to the
-ciphertext created is determined by the @acronym{ASCII} armor (or, if
+file set with @code{gpgme_data_set_file_name} for the data object
-that is not set, by the encoding specified for @var{cipher}) and the
+@var{cipher}.  The type of the ciphertext created is determined by the
-text mode attributes set for the context @var{ctx}.
+@acronym{ASCII} armor (or, if that is not set, by the encoding specified
+for @var{cipher}) and the text mode attributes set for the context
+@var{ctx}.
 
 If the flag @code{GPGME_ENCRYPT_ARCHIVE} is set, then an encrypted
 archive is created from the files and directories given as NUL-separated

src/engine-gpg.c

@@ -2367,9 +2367,17 @@ gpg_encrypt (void *engine, gpgme_key_t recp[], const char *recpstring,
   if (!err)
     err = add_arg (gpg, "--output");
   if (!err)
+    {
+      const char *output = gpgme_data_get_file_name (ciph);
+      if (output)
+        err = add_arg (gpg, output);
+      else
+        {
           err = add_arg (gpg, "-");
           if (!err)
             err = add_data (gpg, ciph, 1, 1);
+        }
+    }
   if (gpg->flags.use_gpgtar)
     {
       const char *file_name = gpgme_data_get_file_name (plain);
@@ -2479,9 +2487,17 @@ gpg_encrypt_sign (void *engine, gpgme_key_t recp[],
   if (!err)
     err = add_arg (gpg, "--output");
   if (!err)
+    {
+      const char *output = gpgme_data_get_file_name (ciph);
+      if (output)
+        err = add_arg (gpg, output);
+      else
+        {
           err = add_arg (gpg, "-");
           if (!err)
             err = add_data (gpg, ciph, 1, 1);
+        }
+    }
   if (gpg->flags.use_gpgtar)
     {
       const char *file_name = gpgme_data_get_file_name (plain);
@@ -3559,6 +3575,7 @@ gpg_sign (void *engine, gpgme_data_t in, gpgme_data_t out,
 {
   engine_gpg_t gpg = engine;
   gpgme_error_t err;
+  const char *output = NULL;
 
   (void)include_certs;
 
@@ -3599,6 +3616,17 @@ gpg_sign (void *engine, gpgme_data_t in, gpgme_data_t out,
   if (!err)
     err = append_args_from_sig_notations (gpg, ctx, NOTATION_FLAG_SIG);
 
+  if (!err)
+    {
+      output = gpgme_data_get_file_name (out);
+      if (output)
+        {
+          err = add_arg (gpg, "--output");
+          if (!err)
+            err = add_arg (gpg, output);
+        }
+    }
+
   /* Tell the gpg object about the data.  */
   if (gpg->flags.use_gpgtar)
     {
@@ -3634,7 +3662,7 @@ gpg_sign (void *engine, gpgme_data_t in, gpgme_data_t out,
         err = add_data (gpg, in, -1, 0);
     }
 
-  if (!err)
+  if (!err && !output)
     err = add_data (gpg, out, 1, 1);
 
   if (!err)

tests/run-encrypt.c

@@ -152,6 +152,7 @@ show_usage (int ex)
          "  --symmetric        encrypt symmetric (OpenPGP only)\n"
          "  --archive          encrypt given file or directory into an archive\n"
          "  --directory DIR    switch to directory DIR before encrypting into an archive\n"
+         "  --output FILE      write output to FILE instead of stdout\n"
          "  --diagnostics      print diagnostics\n"
          "  --cancel N         cancel after N progress lines\n"
          , stderr);
@@ -177,6 +178,7 @@ main (int argc, char **argv)
   int keycount = 0;
   char *keystring = NULL;
   const char *directory = NULL;
+  const char *output = NULL;
   int i;
   gpgme_encrypt_flags_t flags = GPGME_ENCRYPT_ALWAYS_TRUST;
   gpgme_off_t offset;
@@ -294,6 +296,14 @@ main (int argc, char **argv)
           directory = *argv;
           argc--; argv++;
         }
+      else if (!strcmp (*argv, "--output"))
+        {
+          argc--; argv++;
+          if (!argc)
+            show_usage (1);
+          output = *argv;
+          argc--; argv++;
+        }
       else if (!strcmp (*argv, "--diagnostics"))
         {
           diagnostics = 1;
@@ -410,6 +420,11 @@ main (int argc, char **argv)
 
   err = gpgme_data_new (&out);
   fail_if_err (err);
+  if (output)
+    {
+      err = gpgme_data_set_file_name (out, output);
+      fail_if_err (err);
+    }
 
   if (sign)
     err = gpgme_op_encrypt_sign_ext (ctx, keycount ? keys : NULL, keystring,
@@ -451,9 +466,12 @@ main (int argc, char **argv)
       exit (1);
     }
 
+  if (!output)
+    {
       fputs ("Begin Output:\n", stdout);
       print_data (out);
       fputs ("End Output.\n", stdout);
+    }
   gpgme_data_release (out);
 
   gpgme_data_release (in);

tests/run-sign.c

@@ -89,6 +89,7 @@ show_usage (int ex)
          "  --clear          create a clear text signature\n"
          "  --archive        create a signed archive with the given file or directory\n"
          "  --directory DIR  switch to directory DIR before creating the archive\n"
+         "  --output FILE    write output to FILE instead of stdout\n"
          "  --diagnostics    print diagnostics\n"
          , stderr);
   exit (ex);
@@ -103,6 +104,7 @@ main (int argc, char **argv)
   gpgme_ctx_t ctx;
   const char *key_string = NULL;
   const char *directory = NULL;
+  const char *output = NULL;
   gpgme_protocol_t protocol = GPGME_PROTOCOL_OpenPGP;
   gpgme_sig_mode_t sigmode = GPGME_SIG_MODE_NORMAL;
   gpgme_data_t in, out;
@@ -196,6 +198,14 @@ main (int argc, char **argv)
           directory = *argv;
           argc--; argv++;
         }
+      else if (!strcmp (*argv, "--output"))
+        {
+          argc--; argv++;
+          if (!argc)
+            show_usage (1);
+          output = *argv;
+          argc--; argv++;
+        }
       else if (!strcmp (*argv, "--diagnostics"))
         {
           diagnostics = 1;
@@ -283,6 +293,11 @@ main (int argc, char **argv)
 
   err = gpgme_data_new (&out);
   fail_if_err (err);
+  if (output)
+    {
+      err = gpgme_data_set_file_name (out, output);
+      fail_if_err (err);
+    }
 
   err = gpgme_op_sign (ctx, in, out, sigmode);
   result = gpgme_op_sign_result (ctx);
@@ -319,9 +334,12 @@ main (int argc, char **argv)
   if ((s = gpgme_get_ctx_flag (ctx, "redraw")) && *s)
     fputs ("Screen redraw suggested\n", stdout);
 
+  if (!output)
+    {
       fputs ("Begin Output:\n", stdout);
       print_data (out);
       fputs ("End Output.\n", stdout);
+    }
   gpgme_data_release (out);
 
   gpgme_data_release (in);