From: Andrey Rys <rys@lynxlynx.ru>
Date: Fri, 13 Dec 2019 23:46:30 +0000 (+0100)
Subject: -O ftrunc=tail: trim unused tail after processing actual data.
X-Git-Url: https://jxself.org/git/?p=tfcrypt.git;a=commitdiff_plain;h=c0dc5614a87ed6d0eed4906447171ef4c73b306e

-O ftrunc=tail: trim unused tail after processing actual data.

This is a hack actually, it's not much useful in everyday life.
It is for compressing files in place, exploiting stream compressors like this:

        xz -9c -T 4 < file.tar | tfcrypt -P -O ftrunc=tail - file.tar

, or more safer way (since tfcrypt does not buffer):

        tfcrypt -P file.tar | xz -9c -T 4 | tfcrypt -P -O ftrunc=tail - file.tar
---

diff --git a/VERSION b/VERSION
index a787364..8f92bfd 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-34
+35
diff --git a/tfc_error.c b/tfc_error.c
index 905ae40..a40ab0a 100644
--- a/tfc_error.c
+++ b/tfc_error.c
@@ -266,6 +266,7 @@ void usage(void)
 	tfc_say("    oseek=val: seek destination file/device by these val bytes.");
 	tfc_say("    count=val: process only these val bytes, both input and output.");
 	tfc_say("    ftrunc=val: truncate output file to these val bytes before closing it.");
+	tfc_say("    ftrunc=tail: truncate output's tail, leaving only processed data.");
 	tfc_say("    xkey=val: take only val bytes from user keyfile.");
 	tfc_say("    okey=val: seek the key before reading it (usually a device).");
 	tfc_say("    xctr=val: specify size in bytes of initial counter prepended or read.");
diff --git a/tfc_vars.c b/tfc_vars.c
index 4ca3785..1a65ac3 100644
--- a/tfc_vars.c
+++ b/tfc_vars.c
@@ -62,7 +62,7 @@ size_t sksum_turns;
 int do_edcrypt = TFC_DO_ENCRYPT, do_stop, quiet, error_action;
 int counter_opt, mackey_opt, do_mac, do_outfmt = TFC_OUTFMT_B64, rawkey;
 int idx, write_flags;
-tfc_yesno catch_all_errors, ignore_seek_errors, password, overwrite_source, do_fsync, do_pad;
+tfc_yesno catch_all_errors, ignore_seek_errors, password, overwrite_source, do_fsync, do_pad, do_ftrunc = TFC_NO_FTRUNC;
 tfc_yesno do_preserve_time, do_stats_in_gibs, do_statline_dynamic = YES, do_less_stats;
 tfc_yesno no_repeat, do_full_hexdump = YES, verbose, statline_was_shown, show_secrets;
 char *srcfname = TFC_STDIN_NAME, *dstfname = TFC_STDOUT_NAME, *do_mac_file, *counter_file, *sksum_hashlist_file;
diff --git a/tfcrypt.c b/tfcrypt.c
index d673d38..fb3dfb9 100644
--- a/tfcrypt.c
+++ b/tfcrypt.c
@@ -425,14 +425,21 @@ _baddfname:
 					}
 					else if (!strncmp(s, "ftrunc", 6) && *(s+6) == '=') {
 						s += 7;
-						ftrunc_dfd = tfc_humanfsize(s, &stoi);
-						if (!str_empty(stoi)) {
-							ftrunc_dfd = tfc_fnamesize(s, YES);
-							ftrunc_dfd = tfc_modifysize(ftrunc_dfd, strchr(s, ':'));
-							if (ftrunc_dfd == NOFSIZE) xerror(NO, YES, YES,
-							"%s: invalid ftrunc value", s);
+						if (!strcmp(s, "tail")) {
+							do_ftrunc = TFC_FTRUNC_TAIL;
+							ftrunc_dfd = NOFSIZE;
+						}
+						else {
+							do_ftrunc = TFC_DO_FTRUNC;
+							ftrunc_dfd = tfc_humanfsize(s, &stoi);
+							if (!str_empty(stoi)) {
+								ftrunc_dfd = tfc_fnamesize(s, YES);
+								ftrunc_dfd = tfc_modifysize(ftrunc_dfd, strchr(s, ':'));
+								if (ftrunc_dfd == NOFSIZE) xerror(NO, YES, YES,
+								"%s: invalid ftrunc value", s);
+							}
+							else ftrunc_dfd = tfc_modifysize(ftrunc_dfd, strchr(s, ':'));
 						}
-						else ftrunc_dfd = tfc_modifysize(ftrunc_dfd, strchr(s, ':'));
 					}
 					else if (!strncmp(s, "xkey", 4) && *(s+4) == '=') {
 						s += 5;
@@ -1333,7 +1340,10 @@ _nomac:
 
 	if (do_preserve_time) fcopy_matime(dfd, &s_stat);
 	xclose(sfd);
-	if (ftrunc_dfd != NOFSIZE) if (ftruncate(dfd, (off_t)ftrunc_dfd) == -1) xerror(YES, NO, YES, "ftruncate(%d)", dfd);
+	if (do_ftrunc > TFC_NO_FTRUNC) {
+		if (do_ftrunc == TFC_FTRUNC_TAIL) ftrunc_dfd = total_processed_dst;
+		if (ftruncate(dfd, (off_t)ftrunc_dfd) == -1) xerror(YES, NO, YES, "ftruncate(%d)", dfd);
+	}
 	xclose(dfd);
 
 	xexit(exitcode);
diff --git a/tfcrypt.h b/tfcrypt.h
index a313b33..85ed79a 100644
--- a/tfcrypt.h
+++ b/tfcrypt.h
@@ -155,7 +155,7 @@ extern size_t sksum_turns;
 extern int do_edcrypt, do_stop, quiet, error_action;
 extern int counter_opt, mackey_opt, do_mac, do_outfmt, rawkey;
 extern int idx, write_flags;
-extern tfc_yesno catch_all_errors, ignore_seek_errors, password, overwrite_source, do_fsync, do_pad;
+extern tfc_yesno catch_all_errors, ignore_seek_errors, password, overwrite_source, do_fsync, do_pad, do_ftrunc;
 extern tfc_yesno do_preserve_time, do_stats_in_gibs, do_statline_dynamic, do_less_stats;
 extern tfc_yesno no_repeat, do_full_hexdump, verbose, statline_was_shown, show_secrets;
 extern char *srcfname, *dstfname, *do_mac_file, *counter_file, *sksum_hashlist_file;
@@ -229,5 +229,6 @@ enum {
 	TFC_MODE_STREAM, TFC_MODE_XTS, TFC_MODE_ECB, TFC_MODE_CBC, TFC_MODE_OCB
 };
 enum { TFC_CTR_SHOW = 1, TFC_CTR_HEAD, TFC_CTR_RAND, TFC_CTR_ZERO, TFC_CTR_SSET };
+enum { TFC_NO_FTRUNC, TFC_DO_FTRUNC, TFC_FTRUNC_TAIL };
 
 #endif