Fix issue when skipping first file in 7zip archive that is a multiple of 65536 bytes

Author: dunhor

Diff for: Makefile.am

@@ -789,6 +789,7 @@ libarchive_test_EXTRA_DIST=\
 	libarchive/test/test_read_format_7zip_encryption.7z.uu \
 	libarchive/test/test_read_format_7zip_encryption_header.7z.uu \
 	libarchive/test/test_read_format_7zip_encryption_partially.7z.uu \
+	libarchive/test/test_read_format_7zip_extract_second.7z.uu \
 	libarchive/test/test_read_format_7zip_lzma1.7z.uu \
 	libarchive/test/test_read_format_7zip_lzma1_2.7z.uu \
 	libarchive/test/test_read_format_7zip_lzma1_lzma2.7z.uu \

Diff for: libarchive/archive_read_support_format_7zip.c

@@ -3462,7 +3462,7 @@ read_stream(struct archive_read *a, const void **buff, size_t size,
 	/*
 	 * Skip the bytes we already has skipped in skip_stream().
 	 */
-	while (skip_bytes) {
+	while (1) {
 		ssize_t skipped;
 
 		if (zip->uncompressed_buffer_bytes_remaining == 0) {
@@ -3482,6 +3482,10 @@ read_stream(struct archive_read *a, const void **buff, size_t size,
 				return (ARCHIVE_FATAL);
 			}
 		}
+
+		if (!skip_bytes)
+			break;
+
 		skipped = get_uncompressed_data(
 			a, buff, (size_t)skip_bytes, 0);
 		if (skipped < 0)

Diff for: libarchive/test/test_read_format_7zip.c

@@ -1257,5 +1257,47 @@ DEFINE_TEST(test_read_format_7zip_win_attrib)
 	assertEqualString("system", archive_entry_fflags_text(ae));
 
 
+	assertEqualInt(ARCHIVE_OK, archive_read_free(a));
+}
+
+DEFINE_TEST(test_read_format_7zip_extract_second)
+{
+	struct archive *a;
+	char buffer[256];
+
+	assert((a = archive_read_new()) != NULL);
+
+	if (ARCHIVE_OK != archive_read_support_filter_lzma(a)) {
+		skipping(
+		    "7zip:lzma decoding is not supported on this platform");
+		assertEqualInt(ARCHIVE_OK, archive_read_free(a));
+		return;
+	}
+
+	assertEqualIntA(a, ARCHIVE_OK, archive_read_support_format_all(a));
+
+	/*
+	 * The test archive has two files: first.txt which is a 65,536 file (the
+	 * size of the uncompressed buffer), and second.txt which has contents
+	 * we will validate. This test ensures we can skip first.txt and still
+	 * be able to read the contents of second.txt
+	 */
+	const char *refname = "test_read_format_7zip_extract_second.7z";
+	extract_reference_file(refname);
+
+	assertEqualIntA(a, ARCHIVE_OK,
+		archive_read_open_filename(a, refname, 10240));
+
+	struct archive_entry *ae;
+
+	assertEqualIntA(a, ARCHIVE_OK, archive_read_next_header(a, &ae));
+	assertEqualString("first.txt", archive_entry_pathname(ae));
+
+	assertEqualIntA(a, ARCHIVE_OK, archive_read_next_header(a, &ae));
+	assertEqualString("second.txt", archive_entry_pathname(ae));
+
+	assertEqualInt(23, archive_read_data(a, buffer, sizeof(buffer)));
+	assertEqualMem("This is from second.txt", buffer, 23);
+
 	assertEqualInt(ARCHIVE_OK, archive_read_free(a));
 }

Diff for: libarchive/test/test_read_format_7zip_extract_second.7z.uu

@@ -0,0 +1,11 @@
+begin 644 test_read_format_7zip_extract_second.7z
+M-WJ\KR<<``-N%=VX!@$````````B`````````*R\U.<`&`Q"DFIGO`[1,RO\
+MN,RA7-QU1L&_]O_/$0MMLIEBUR3'BDX@M2C-5'VG./-4,5@W3Q@*__^7_,[H
+MEO`DB'[ZI>@H2_E>/W.2G$$.P01-X!YN5";SS[3#7Z4Q1G/EF.0'^D*[S8&8
+M[FV9DYX7,SA%^.Q\'?__P!@`````@3,'K@_4WV/Q0A7VLXG$X?GH4=5W^`UM
+M$N_EX$)LE*?K$W5?WLP:X0T[Q%V^?A!0E\VZRBB,)(MO`C`LO[O!3(1YL)<:
+MJ."`';WU;>GP5',%Z=6?*/H9*Z)&\*!2^<F\P&>,RV`R30UOBH8+5.;;2IKF
+M0W://&'?"L?0L2!)`*]F30B0&/_'<4``%P9Z`0F`C``'"P$``2,#`0$%70``
+-@``,@*@*`6]FB2D`````
+`
+end