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author | kientzle <kientzle@FreeBSD.org> | 2006-07-30 00:29:01 +0000 |
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committer | kientzle <kientzle@FreeBSD.org> | 2006-07-30 00:29:01 +0000 |
commit | f501dbec5fe3a8ec80a115b83f7f07e2671bfc95 (patch) | |
tree | 7a38c3d6e84fc5da7d1e72df478099c6b6a417f6 /lib/libarchive/archive_read_open_fd.c | |
parent | 61dd143cfb0a5bd3bf9dc7304f3f4126ae2e5acd (diff) | |
download | FreeBSD-src-f501dbec5fe3a8ec80a115b83f7f07e2671bfc95.zip FreeBSD-src-f501dbec5fe3a8ec80a115b83f7f07e2671bfc95.tar.gz |
Use 'skip' when ignoring data in tar archives. This dramatically
increases performance when extracting a single entry from a large
uncompressed archive, especially on slow devices such as USB hard
drives.
Requires a number of changes:
* New archive_read_open2() supports a 'skip' client function
* Old archive_read_open() is implemented as a wrapper now, to
continue supporting the old API/ABI.
* _read_open_fd and _read_open_file sprout new 'skip' functions.
* compression layer gets a new 'skip' operation.
* compression_none passes skip requests through to client.
* compression_{gzip,bzip2,compress} simply ignore skip requests.
Thanks to: Benjamin Lutz, who designed and implemented the whole thing.
I'm just committing it. ;-)
TODO: Need to update the documentation a little bit.
Diffstat (limited to 'lib/libarchive/archive_read_open_fd.c')
-rw-r--r-- | lib/libarchive/archive_read_open_fd.c | 48 |
1 files changed, 45 insertions, 3 deletions
diff --git a/lib/libarchive/archive_read_open_fd.c b/lib/libarchive/archive_read_open_fd.c index c5716e7..c1c1452 100644 --- a/lib/libarchive/archive_read_open_fd.c +++ b/lib/libarchive/archive_read_open_fd.c @@ -45,6 +45,7 @@ struct read_fd_data { static int file_close(struct archive *, void *); static int file_open(struct archive *, void *); static ssize_t file_read(struct archive *, void *, const void **buff); +static ssize_t file_skip(struct archive *, void *, size_t request); int archive_read_open_fd(struct archive *a, int fd, size_t block_size) @@ -64,7 +65,7 @@ archive_read_open_fd(struct archive *a, int fd, size_t block_size) return (ARCHIVE_FATAL); } mine->fd = fd; - return (archive_read_open(a, mine, file_open, file_read, file_close)); + return (archive_read_open2(a, mine, file_open, file_read, file_skip, file_close)); } static int @@ -87,10 +88,51 @@ static ssize_t file_read(struct archive *a, void *client_data, const void **buff) { struct read_fd_data *mine = client_data; + ssize_t bytes_read; - (void)a; /* UNUSED */ *buff = mine->buffer; - return (read(mine->fd, mine->buffer, mine->block_size)); + bytes_read = read(mine->fd, mine->buffer, mine->block_size); + if (bytes_read < 0) { + archive_set_error(a, errno, "Error reading fd %d", mine->fd); + } + return (bytes_read); +} + +static ssize_t +file_skip(struct archive *a, void *client_data, size_t request) +{ + struct read_fd_data *mine = client_data; + off_t old_offset, new_offset; + + /* Reduce request to the next smallest multiple of block_size */ + request = (request / mine->block_size) * mine->block_size; + /* + * Hurray for lazy evaluation: if the first lseek fails, the second + * one will not be executed. + */ + if (((old_offset = lseek(mine->fd, 0, SEEK_CUR)) < 0) || + ((new_offset = lseek(mine->fd, request, SEEK_CUR)) < 0)) + { + if (errno == ESPIPE) + { + /* + * Failure to lseek() can be caused by the file + * descriptor pointing to a pipe, socket or FIFO. + * Return 0 here, so the compression layer will use + * read()s instead to advance the file descriptor. + * It's slower of course, but works as well. + */ + return (0); + } + /* + * There's been an error other than ESPIPE. This is most + * likely caused by a programmer error (too large request) + * or a corrupted archive file. + */ + archive_set_error(a, errno, "Error seeking"); + return (-1); + } + return (new_offset - old_offset); } static int |