archive-zip: write extended timestamp

File modification times in ZIP files are encoded in DOS format: local
time with a granularity of two seconds.  Add an extra field to all
archive entries to also record the mtime in Unix' fashion, as UTC with
a granularity of one second.

This has the desirable side-effect of convincing Info-ZIP unzip 6.00
to respect general purpose flag 11, which is used to indicate that a
file name is encoded in UTF-8.  Any extra field would do, actually,
but the extended timestamp is a reasonably small one (22 bytes per
entry).  Archives created by Info-ZIP zip 3.0 contain it, too (but
with ctime and atime as well).

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/archive-zip.c b/archive-zip.c
index 0f763e8022e24f37fd31be341fef4536709a63d8..55f66b4060c64789bdb443f6c71f82a75ef22d0b 100644 (file)
--- a/archive-zip.c
+++ b/archive-zip.c
@@ -76,6 +76,14 @@ struct zip_dir_trailer {
        unsigned char _end[1];
 };
 
+struct zip_extra_mtime {
+       unsigned char magic[2];
+       unsigned char extra_size[2];
+       unsigned char flags[1];
+       unsigned char mtime[4];
+       unsigned char _end[1];
+};
+
 /*
  * On ARM, padding is added at the end of the struct, so a simple
  * sizeof(struct ...) reports two bytes more than the payload size
@@ -85,6 +93,9 @@ struct zip_dir_trailer {
 #define ZIP_DATA_DESC_SIZE     offsetof(struct zip_data_desc, _end)
 #define ZIP_DIR_HEADER_SIZE    offsetof(struct zip_dir_header, _end)
 #define ZIP_DIR_TRAILER_SIZE   offsetof(struct zip_dir_trailer, _end)
+#define ZIP_EXTRA_MTIME_SIZE   offsetof(struct zip_extra_mtime, _end)
+#define ZIP_EXTRA_MTIME_PAYLOAD_SIZE \
+       (ZIP_EXTRA_MTIME_SIZE - offsetof(struct zip_extra_mtime, flags))
 
 static void copy_le16(unsigned char *dest, unsigned int n)
 {
@@ -186,6 +197,7 @@ static int write_zip_entry(struct archiver_args *args,
 {
        struct zip_local_header header;
        struct zip_dir_header dirent;
+       struct zip_extra_mtime extra;
        unsigned long attr2;
        unsigned long compressed_size;
        unsigned long crc;
@@ -266,8 +278,13 @@ static int write_zip_entry(struct archiver_args *args,
                }
        }
 
+       copy_le16(extra.magic, 0x5455);
+       copy_le16(extra.extra_size, ZIP_EXTRA_MTIME_PAYLOAD_SIZE);
+       extra.flags[0] = 1;     /* just mtime */
+       copy_le32(extra.mtime, args->time);
+
        /* make sure we have enough free space in the dictionary */
-       direntsize = ZIP_DIR_HEADER_SIZE + pathlen;
+       direntsize = ZIP_DIR_HEADER_SIZE + pathlen + ZIP_EXTRA_MTIME_SIZE;
        while (zip_dir_size < zip_dir_offset + direntsize) {
                zip_dir_size += ZIP_DIRECTORY_MIN_SIZE;
                zip_dir = xrealloc(zip_dir, zip_dir_size);
@@ -283,7 +300,7 @@ static int write_zip_entry(struct archiver_args *args,
        copy_le16(dirent.mdate, zip_date);
        set_zip_dir_data_desc(&dirent, size, compressed_size, crc);
        copy_le16(dirent.filename_length, pathlen);
-       copy_le16(dirent.extra_length, 0);
+       copy_le16(dirent.extra_length, ZIP_EXTRA_MTIME_SIZE);
        copy_le16(dirent.comment_length, 0);
        copy_le16(dirent.disk, 0);
        copy_le16(dirent.attr1, 0);
@@ -301,11 +318,13 @@ static int write_zip_entry(struct archiver_args *args,
        else
                set_zip_header_data_desc(&header, size, compressed_size, crc);
        copy_le16(header.filename_length, pathlen);
-       copy_le16(header.extra_length, 0);
+       copy_le16(header.extra_length, ZIP_EXTRA_MTIME_SIZE);
        write_or_die(1, &header, ZIP_LOCAL_HEADER_SIZE);
        zip_offset += ZIP_LOCAL_HEADER_SIZE;
        write_or_die(1, path, pathlen);
        zip_offset += pathlen;
+       write_or_die(1, &extra, ZIP_EXTRA_MTIME_SIZE);
+       zip_offset += ZIP_EXTRA_MTIME_SIZE;
        if (stream && method == 0) {
                unsigned char buf[STREAM_BUFFER_SIZE];
                ssize_t readlen;
@@ -402,6 +421,8 @@ static int write_zip_entry(struct archiver_args *args,
        zip_dir_offset += ZIP_DIR_HEADER_SIZE;
        memcpy(zip_dir + zip_dir_offset, path, pathlen);
        zip_dir_offset += pathlen;
+       memcpy(zip_dir + zip_dir_offset, &extra, ZIP_EXTRA_MTIME_SIZE);
+       zip_dir_offset += ZIP_EXTRA_MTIME_SIZE;
        zip_dir_entries++;
 
        return 0;