Basic capability to list contents of an archive without extracting to disk.

README.md

@@ -147,13 +147,13 @@ Standard Usage
 
     Decompression and Archive extraction
     ------------------------------------
-       pcompress -d <compressed file or '-'> [-m] [-K] [<target file or directory>]
+       pcompress -d <compressed file or '-'> [-m] [-K] [-i] [<target file or directory>]
 
        -m        Enable restoring *all* permissions, ACLs, Extended Attributes etc.
                  Equivalent to the '-p' option in tar. Ownership is only extracted if run as
                  root user.
-
        -K        Do not overwrite newer files.
+       -i        Only list contents of the archive, do not extract.
 
        -m and -K are only meaningful if the compressed file is an archive. For single file
        compressed mode these options are ignored.

archive/pc_archive.c

@@ -1205,6 +1205,7 @@ copy_data_out(struct archive *ar, struct archive *aw, struct archive_entry *entr
 			return (r);
 		}
 	}
+	return (ARCHIVE_OK);
 }
 
 static int
@@ -1235,6 +1236,34 @@ archive_extract_entry(struct archive *a, struct archive_entry *entry,
 	return (r);
 }
 
+static int
+copy_data_skip(struct archive *ar, struct archive_entry *entry, int typ)
+{
+	int64_t offset;
+	const void *buff;
+	size_t size;
+	int r;
+
+	for (;;) {
+		r = archive_read_data_block(ar, &buff, &size, &offset);
+		if (r == ARCHIVE_EOF)
+			return (ARCHIVE_OK);
+		if (r != ARCHIVE_OK)
+			return (r);
+	}
+	return (ARCHIVE_OK);
+}
+
+static int
+archive_list_entry(struct archive *a, struct archive_entry *entry, int typ)
+{
+	printf("%s\n", archive_entry_pathname(entry));
+	if (!archive_entry_size_is_set(entry) || archive_entry_size(entry) > 0) {
+		return (copy_data_skip(a, entry, typ));
+	}
+	return (ARCHIVE_OK);
+}
+
 /*
  * Extract Thread function. Read an uncompressed archive from the decompressor stage
  * and extract members to disk.
@@ -1248,6 +1277,11 @@ extractor_thread_func(void *dat) {
 	struct archive_entry *entry;
 	struct archive *awd, *arc;
 
+	/* Silence compiler. */
+	awd = NULL;
+	got_cwd = 0;
+
+	if (!pctx->list_mode) {
 		flags = ARCHIVE_EXTRACT_TIME;
 		flags |= ARCHIVE_EXTRACT_SECURE_SYMLINKS;
 		flags |= ARCHIVE_EXTRACT_SECURE_NODOTDOT;
@@ -1275,10 +1309,11 @@ extractor_thread_func(void *dat) {
 			got_cwd = 0;
 		}
 
-	ctr = 1;
 		awd = archive_write_disk_new();
 		archive_write_disk_set_options(awd, flags);
 		archive_write_disk_set_standard_lookup(awd);
+	}
+	ctr = 1;
 	arc = (struct archive *)(pctx->archive_ctx);
 	archive_read_open(arc, pctx, arc_open_callback, extract_read_callback, extract_close_callback);
 
@@ -1286,10 +1321,12 @@ extractor_thread_func(void *dat) {
 	 * Change directory after opening the archive, otherwise archive_read_open() can fail
 	 * for relative paths.
 	 */
+	if (!pctx->list_mode) {
 		if (chdir(pctx->to_filename) == -1) {
 			log_msg(LOG_ERR, 1, "Cannot change to dir: %s", pctx->to_filename);
 			goto done;
 		}
+	}
 
 	/*
 	 * Read archive entries and extract to disk.
@@ -1342,7 +1379,11 @@ extractor_thread_func(void *dat) {
 		}
 #endif
 
+		if (!pctx->list_mode) {
 			rv = archive_extract_entry(arc, entry, awd, typ);
+		} else {
+			rv = archive_list_entry(arc, entry, typ);
+		}
 		if (rv != ARCHIVE_OK) {
 			log_msg(LOG_WARN, 0, "%s: %s", archive_entry_pathname(entry),
 			    archive_error_string(arc));
@@ -1359,9 +1400,11 @@ extractor_thread_func(void *dat) {
 		ctr++;
 	}
 
+	if (!pctx->list_mode) {
 		if (got_cwd) {
 			rv = chdir(cwd);
 		}
+	}
 	archive_read_free(arc);
 	archive_write_free(awd);
 done:

pcompress.c

@@ -137,7 +137,8 @@ usage(pc_ctx_t *pctx)
 "       %s -d <compressed file or '-'> [-m] [-K] [<target file or directory>]\n\n"
 "       -m        Enable restoring *all* permissions, ACLs, Extended Attributes etc.\n"
 "                 Equivalent to the '-p' option in tar.\n"
-"       -K        Do not overwrite newer files.\n\n"
+"       -K        Do not overwrite newer files.\n"
+"       -i        Only list contents of the archive, do not extract.\n\n"
 "       -m and -K are only meaningful if the compressed file is an archive. For single file\n"
 "       compressed mode these options are ignored.\n\n"
 "       <compressed file>\n"
@@ -848,6 +849,11 @@ start_decompress(pc_ctx_t *pctx, const char *filename, char *to_filename)
 	} else {
 		const char *origf;
 
+		if (pctx->list_mode) {
+			log_msg(LOG_ERR, 0, "Nothing to list. The compressed file is not an archive.");
+			err = 1;
+			goto uncomp_done;
+		}
 		if (to_filename == NULL) {
 			char *pos;
 
@@ -2827,11 +2833,13 @@ init_pc_context(pc_ctx_t *pctx, int argc, char *argv[])
 	ff.enable_packjpg = 0;
 
 	pthread_mutex_lock(&opt_parse);
-	while ((opt = getopt(argc, argv, "dc:s:l:pt:MCDGEe:w:LPS:B:Fk:avmKjx")) != -1) {
+	while ((opt = getopt(argc, argv, "dc:s:l:pt:MCDGEe:w:LPS:B:Fk:avmKjxi")) != -1) {
 		int ovr;
 		int64_t chunksize;
 
 		switch (opt) {
+		    case 'i':
+			pctx->list_mode = 1; // List mode also sets decompress flag
 		    case 'd':
 			pctx->do_uncompress = 1;
 			break;

pcompress.h

@@ -239,6 +239,7 @@ typedef struct pc_ctx {
 	int btype, ctype;
 	int min_chunk;
 	int enable_packjpg;
+	int list_mode;
 
 	unsigned int chunk_num;
 	uint64_t largest_chunk, smallest_chunk, avg_chunk;