]> wimlib.net Git - wimlib/blobdiff - src/write.c
write_pipable_wim(): Fix/improve comment
[wimlib] / src / write.c
index 3cac5a2868a7d8ef7c9f3ea90e853e3de824b9fe..1a429039b38dd80fb3141705ef8d1a5aa8c7ac84 100644 (file)
 #  include <pthread.h>
 #endif
 
-#include <unistd.h>
-#include <fcntl.h>
 #include <errno.h>
+#include <fcntl.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <unistd.h>
 
 #ifdef HAVE_ALLOCA_H
 #  include <alloca.h>
-#else
-#  include <stdlib.h>
 #endif
 
-#include <limits.h>
 
 #ifndef __WIN32__
 #  include <sys/uio.h> /* for `struct iovec' */
@@ -683,7 +682,6 @@ struct message {
        u8 *compressed_chunks[MAX_CHUNKS_PER_MSG];
        unsigned uncompressed_chunk_sizes[MAX_CHUNKS_PER_MSG];
        struct iovec out_chunks[MAX_CHUNKS_PER_MSG];
-       size_t total_out_bytes;
        unsigned num_chunks;
        struct list_head list;
        bool complete;
@@ -693,7 +691,6 @@ struct message {
 static void
 compress_chunks(struct message *msg, compress_func_t compress)
 {
-       msg->total_out_bytes = 0;
        for (unsigned i = 0; i < msg->num_chunks; i++) {
                unsigned len = compress(msg->uncompressed_chunks[i],
                                        msg->uncompressed_chunk_sizes[i],
@@ -711,7 +708,6 @@ compress_chunks(struct message *msg, compress_func_t compress)
                }
                msg->out_chunks[i].iov_base = out_chunk;
                msg->out_chunks[i].iov_len = out_len;
-               msg->total_out_bytes += out_len;
        }
 }
 
@@ -739,32 +735,52 @@ compressor_thread_proc(void *arg)
 }
 #endif /* ENABLE_MULTITHREADED_COMPRESSION */
 
+struct write_streams_progress_data {
+       wimlib_progress_func_t progress_func;
+       union wimlib_progress_info progress;
+       uint64_t next_progress;
+       WIMStruct *prev_wim_part;
+};
+
 static void
-do_write_streams_progress(union wimlib_progress_info *progress,
-                         wimlib_progress_func_t progress_func,
-                         uint64_t size_added,
+do_write_streams_progress(struct write_streams_progress_data *progress_data,
+                         struct wim_lookup_table_entry *lte,
                          bool stream_discarded)
 {
+       union wimlib_progress_info *progress = &progress_data->progress;
+       bool new_wim_part;
+
        if (stream_discarded) {
-               progress->write_streams.total_bytes -= size_added;
-               if (progress->write_streams._private != ~(uint64_t)0 &&
-                   progress->write_streams._private > progress->write_streams.total_bytes)
+               progress->write_streams.total_bytes -= wim_resource_size(lte);
+               if (progress_data->next_progress != ~(uint64_t)0 &&
+                   progress_data->next_progress > progress->write_streams.total_bytes)
                {
-                       progress->write_streams._private = progress->write_streams.total_bytes;
+                       progress_data->next_progress = progress->write_streams.total_bytes;
                }
        } else {
-               progress->write_streams.completed_bytes += size_added;
+               progress->write_streams.completed_bytes += wim_resource_size(lte);
+       }
+       new_wim_part = false;
+       if (lte->resource_location == RESOURCE_IN_WIM &&
+           lte->wim != progress_data->prev_wim_part)
+       {
+               if (progress_data->prev_wim_part) {
+                       new_wim_part = true;
+                       progress->write_streams.completed_parts++;
+               }
+               progress_data->prev_wim_part = lte->wim;
        }
        progress->write_streams.completed_streams++;
-       if (progress_func &&
-           progress->write_streams.completed_bytes >= progress->write_streams._private)
+       if (progress_data->progress_func
+           && (progress->write_streams.completed_bytes >= progress_data->next_progress
+               || new_wim_part))
        {
-               progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS,
-                             progress);
-               if (progress->write_streams._private == progress->write_streams.total_bytes) {
-                       progress->write_streams._private = ~(uint64_t)0;
+               progress_data->progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS,
+                                            progress);
+               if (progress_data->next_progress == progress->write_streams.total_bytes) {
+                       progress_data->next_progress = ~(uint64_t)0;
                } else {
-                       progress->write_streams._private =
+                       progress_data->next_progress =
                                min(progress->write_streams.total_bytes,
                                    progress->write_streams.completed_bytes +
                                        progress->write_streams.total_bytes / 100);
@@ -787,6 +803,7 @@ serial_write_stream(struct wim_lookup_table_entry *lte, void *_ctx)
                                  ctx->write_resource_flags);
 }
 
+
 /* Write a list of streams, taking into account that some streams may be
  * duplicates that are checksummed and discarded on the fly, and also delegating
  * the actual writing of a stream to a function @write_stream_cb, which is
@@ -796,8 +813,7 @@ do_write_stream_list(struct list_head *stream_list,
                     struct wim_lookup_table *lookup_table,
                     int (*write_stream_cb)(struct wim_lookup_table_entry *, void *),
                     void *write_stream_ctx,
-                    wimlib_progress_func_t progress_func,
-                    union wimlib_progress_info *progress)
+                    struct write_streams_progress_data *progress_data)
 {
        int ret = 0;
        struct wim_lookup_table_entry *lte;
@@ -815,19 +831,29 @@ do_write_stream_list(struct list_head *stream_list,
                         * stream in the WIM we are writing.  The stream must be
                         * checksummed to know if we need to write it or not. */
                        struct wim_lookup_table_entry *tmp;
-                       u32 orig_refcnt = lte->out_refcnt;
+                       u32 orig_out_refcnt = lte->out_refcnt;
 
                        ret = hash_unhashed_stream(lte, lookup_table, &tmp);
                        if (ret)
                                break;
                        if (tmp != lte) {
+                               /* We found a duplicate stream.  'lte' was
+                                * freed, so replace it with the duplicate.  */
                                lte = tmp;
-                               /* We found a duplicate stream. */
-                               if (orig_refcnt != tmp->out_refcnt) {
-                                       /* We have already written, or are going
-                                        * to write, the duplicate stream.  So
-                                        * just skip to the next stream. */
-                                       DEBUG("Discarding duplicate stream of length %"PRIu64,
+
+                               /* 'out_refcnt' was transferred to the
+                                * duplicate, and we can detect if the duplicate
+                                * stream was already referenced for writing by
+                                * checking if its 'out_refcnt' is higher than
+                                * that of the original stream.  In such cases,
+                                * the current stream can be discarded.  We can
+                                * also discard the current stream if it was
+                                * previously marked as filtered (e.g. already
+                                * present in the WIM being written).  */
+                               if (lte->out_refcnt > orig_out_refcnt ||
+                                   lte->filtered) {
+                                       DEBUG("Discarding duplicate stream of "
+                                             "length %"PRIu64,
                                              wim_resource_size(lte));
                                        lte->no_progress = 0;
                                        stream_discarded = true;
@@ -860,10 +886,8 @@ do_write_stream_list(struct list_head *stream_list,
                }
        skip_to_progress:
                if (!lte->no_progress) {
-                       do_write_streams_progress(progress,
-                                                 progress_func,
-                                                 wim_resource_size(lte),
-                                                 stream_discarded);
+                       do_write_streams_progress(progress_data,
+                                                 lte, stream_discarded);
                }
        }
        return ret;
@@ -875,8 +899,7 @@ do_write_stream_list_serial(struct list_head *stream_list,
                            struct filedes *out_fd,
                            int out_ctype,
                            int write_resource_flags,
-                           wimlib_progress_func_t progress_func,
-                           union wimlib_progress_info *progress)
+                           struct write_streams_progress_data *progress_data)
 {
        struct serial_write_stream_ctx ctx = {
                .out_fd = out_fd,
@@ -887,8 +910,7 @@ do_write_stream_list_serial(struct list_head *stream_list,
                                    lookup_table,
                                    serial_write_stream,
                                    &ctx,
-                                   progress_func,
-                                   progress);
+                                   progress_data);
 }
 
 static inline int
@@ -909,21 +931,22 @@ write_stream_list_serial(struct list_head *stream_list,
                         struct filedes *out_fd,
                         int out_ctype,
                         int write_resource_flags,
-                        wimlib_progress_func_t progress_func,
-                        union wimlib_progress_info *progress)
+                        struct write_streams_progress_data *progress_data)
 {
+       union wimlib_progress_info *progress = &progress_data->progress;
        DEBUG("Writing stream list of size %"PRIu64" (serial version)",
              progress->write_streams.total_streams);
        progress->write_streams.num_threads = 1;
-       if (progress_func)
-               progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS, progress);
+       if (progress_data->progress_func) {
+               progress_data->progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS,
+                                            progress);
+       }
        return do_write_stream_list_serial(stream_list,
                                           lookup_table,
                                           out_fd,
                                           out_ctype,
                                           write_resource_flags,
-                                          progress_func,
-                                          progress);
+                                          progress_data);
 }
 
 #ifdef ENABLE_MULTITHREADED_COMPRESSION
@@ -935,7 +958,6 @@ write_wim_chunks(struct message *msg, struct filedes *out_fd,
        struct iovec *vecs;
        struct pwm_chunk_hdr *chunk_hdrs;
        unsigned nvecs;
-       size_t nbytes;
        int ret;
 
        for (unsigned i = 0; i < msg->num_chunks; i++)
@@ -944,7 +966,6 @@ write_wim_chunks(struct message *msg, struct filedes *out_fd,
        if (!(write_resource_flags & WIMLIB_WRITE_RESOURCE_FLAG_PIPABLE)) {
                nvecs = msg->num_chunks;
                vecs = msg->out_chunks;
-               nbytes = msg->total_out_bytes;
        } else {
                /* Special case:  If writing a compressed resource to a pipable
                 * WIM, prefix each compressed chunk with a header that gives
@@ -960,7 +981,6 @@ write_wim_chunks(struct message *msg, struct filedes *out_fd,
                        vecs[i * 2 + 1].iov_base = msg->out_chunks[i].iov_base;
                        vecs[i * 2 + 1].iov_len = msg->out_chunks[i].iov_len;
                }
-               nbytes = msg->total_out_bytes + msg->num_chunks * sizeof(chunk_hdrs[0]);
        }
        ret = full_writev(out_fd, vecs, nvecs);
        if (ret)
@@ -978,8 +998,7 @@ struct main_writer_thread_ctx {
        struct shared_queue *res_to_compress_queue;
        struct shared_queue *compressed_res_queue;
        size_t num_messages;
-       wimlib_progress_func_t progress_func;
-       union wimlib_progress_info *progress;
+       struct write_streams_progress_data *progress_data;
 
        struct list_head available_msgs;
        struct list_head outstanding_streams;
@@ -1221,10 +1240,8 @@ receive_compressed_chunks(struct main_writer_thread_ctx *ctx)
                                      cur_lte->output_resource_entry.flags);
                        }
 
-                       do_write_streams_progress(ctx->progress,
-                                                 ctx->progress_func,
-                                                 wim_resource_size(cur_lte),
-                                                 false);
+                       do_write_streams_progress(ctx->progress_data,
+                                                 cur_lte, false);
 
                        /* Since we just finished writing a stream, write any
                         * streams that have been added to the serial_streams
@@ -1238,8 +1255,7 @@ receive_compressed_chunks(struct main_writer_thread_ctx *ctx)
                                                                  ctx->out_fd,
                                                                  ctx->out_ctype,
                                                                  ctx->write_resource_flags,
-                                                                 ctx->progress_func,
-                                                                 ctx->progress);
+                                                                 ctx->progress_data);
                                if (ret)
                                        return ret;
                        }
@@ -1337,8 +1353,7 @@ main_writer_thread_finish(void *_ctx)
                                           ctx->out_fd,
                                           ctx->out_ctype,
                                           ctx->write_resource_flags,
-                                          ctx->progress_func,
-                                          ctx->progress);
+                                          ctx->progress_data);
 }
 
 static int
@@ -1433,14 +1448,14 @@ write_stream_list_parallel(struct list_head *stream_list,
                           struct filedes *out_fd,
                           int out_ctype,
                           int write_resource_flags,
-                          wimlib_progress_func_t progress_func,
-                          union wimlib_progress_info *progress,
+                          struct write_streams_progress_data *progress_data,
                           unsigned num_threads)
 {
        int ret;
        struct shared_queue res_to_compress_queue;
        struct shared_queue compressed_res_queue;
        pthread_t *compressor_threads = NULL;
+       union wimlib_progress_info *progress = &progress_data->progress;
 
        if (num_threads == 0) {
                long nthreads = get_default_num_threads();
@@ -1498,8 +1513,10 @@ write_stream_list_parallel(struct list_head *stream_list,
                }
        }
 
-       if (progress_func)
-               progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS, progress);
+       if (progress_data->progress_func) {
+               progress_data->progress_func(WIMLIB_PROGRESS_MSG_WRITE_STREAMS,
+                                            progress);
+       }
 
        struct main_writer_thread_ctx ctx;
        ctx.stream_list           = stream_list;
@@ -1510,14 +1527,13 @@ write_stream_list_parallel(struct list_head *stream_list,
        ctx.compressed_res_queue  = &compressed_res_queue;
        ctx.num_messages          = queue_size;
        ctx.write_resource_flags  = write_resource_flags;
-       ctx.progress_func         = progress_func;
-       ctx.progress              = progress;
+       ctx.progress_data         = progress_data;
        ret = main_writer_thread_init_ctx(&ctx);
        if (ret)
                goto out_join;
        ret = do_write_stream_list(stream_list, lookup_table,
                                   main_thread_process_next_stream,
-                                  &ctx, progress_func, progress);
+                                  &ctx, progress_data);
        if (ret)
                goto out_destroy_ctx;
 
@@ -1556,8 +1572,7 @@ out_serial_quiet:
                                        out_fd,
                                        out_ctype,
                                        write_resource_flags,
-                                       progress_func,
-                                       progress);
+                                       progress_data);
 
 }
 #endif
@@ -1576,16 +1591,25 @@ write_stream_list(struct list_head *stream_list,
        size_t num_streams = 0;
        u64 total_bytes = 0;
        u64 total_compression_bytes = 0;
-       union wimlib_progress_info progress;
+       struct write_streams_progress_data progress_data;
        int ret;
        int write_resource_flags;
+       unsigned total_parts = 0;
+       WIMStruct *prev_wim_part = NULL;
 
-       if (list_empty(stream_list))
+       if (list_empty(stream_list)) {
+               DEBUG("No streams to write.");
                return 0;
+       }
 
        write_resource_flags = write_flags_to_resource_flags(write_flags);
 
-       DEBUG("write_resource_flags=0x%08x", write_resource_flags);
+       DEBUG("Writing stream list (offset = %"PRIu64", write_resource_flags=0x%08x)",
+             out_fd->offset, write_resource_flags);
+
+       sort_stream_list_by_sequential_order(stream_list,
+                                            offsetof(struct wim_lookup_table_entry,
+                                                     write_streams_list));
 
        /* Calculate the total size of the streams to be written.  Note: this
         * will be the uncompressed size, as we may not know the compressed size
@@ -1600,14 +1624,28 @@ write_stream_list(struct list_head *stream_list,
                {
                        total_compression_bytes += wim_resource_size(lte);
                }
+               if (lte->resource_location == RESOURCE_IN_WIM) {
+                       if (prev_wim_part != lte->wim) {
+                               prev_wim_part = lte->wim;
+                               total_parts++;
+                       }
+               }
        }
-       progress.write_streams.total_bytes       = total_bytes;
-       progress.write_streams.total_streams     = num_streams;
-       progress.write_streams.completed_bytes   = 0;
-       progress.write_streams.completed_streams = 0;
-       progress.write_streams.num_threads       = num_threads;
-       progress.write_streams.compression_type  = out_ctype;
-       progress.write_streams._private          = 0;
+
+       memset(&progress_data, 0, sizeof(progress_data));
+       progress_data.progress_func = progress_func;
+
+       progress_data.progress.write_streams.total_bytes       = total_bytes;
+       progress_data.progress.write_streams.total_streams     = num_streams;
+       progress_data.progress.write_streams.completed_bytes   = 0;
+       progress_data.progress.write_streams.completed_streams = 0;
+       progress_data.progress.write_streams.num_threads       = num_threads;
+       progress_data.progress.write_streams.compression_type  = out_ctype;
+       progress_data.progress.write_streams.total_parts       = total_parts;
+       progress_data.progress.write_streams.completed_parts   = 0;
+
+       progress_data.next_progress = 0;
+       progress_data.prev_wim_part = NULL;
 
 #ifdef ENABLE_MULTITHREADED_COMPRESSION
        if (total_compression_bytes >= 2000000 && num_threads != 1)
@@ -1616,8 +1654,7 @@ write_stream_list(struct list_head *stream_list,
                                                 out_fd,
                                                 out_ctype,
                                                 write_resource_flags,
-                                                progress_func,
-                                                &progress,
+                                                &progress_data,
                                                 num_threads);
        else
 #endif
@@ -1626,8 +1663,7 @@ write_stream_list(struct list_head *stream_list,
                                               out_fd,
                                               out_ctype,
                                               write_resource_flags,
-                                              progress_func,
-                                              &progress);
+                                              &progress_data);
        if (ret == 0)
                DEBUG("Successfully wrote stream list.");
        else
@@ -1681,136 +1717,52 @@ stream_size_table_insert(struct wim_lookup_table_entry *lte, void *_tab)
        return 0;
 }
 
-
-struct lte_overwrite_prepare_args {
+struct find_streams_ctx {
        WIMStruct *wim;
-       off_t end_offset;
+       int write_flags;
        struct list_head stream_list;
        struct stream_size_table stream_size_tab;
 };
 
-/* First phase of preparing streams for an in-place overwrite.  This is called
- * on all streams, both hashed and unhashed, except the metadata resources. */
-static int
-lte_overwrite_prepare(struct wim_lookup_table_entry *lte, void *_args)
+static void
+lte_reference_for_logical_write(struct wim_lookup_table_entry *lte,
+                               struct find_streams_ctx *ctx,
+                               unsigned nref)
 {
-       struct lte_overwrite_prepare_args *args = _args;
-
-       wimlib_assert(!(lte->resource_entry.flags & WIM_RESHDR_FLAG_METADATA));
-       if (lte->resource_location != RESOURCE_IN_WIM || lte->wim != args->wim)
-               list_add_tail(&lte->write_streams_list, &args->stream_list);
-       lte->out_refcnt = lte->refcnt;
-       stream_size_table_insert(lte, &args->stream_size_tab);
-       return 0;
+       if (lte->out_refcnt == 0) {
+               stream_size_table_insert(lte, &ctx->stream_size_tab);
+               list_add_tail(&lte->write_streams_list, &ctx->stream_list);
+       }
+       lte->out_refcnt += nref;
 }
 
-/* Second phase of preparing streams for an in-place overwrite.  This is called
- * on existing metadata resources and hashed streams, but not unhashed streams.
- *
- * NOTE: lte->output_resource_entry is in union with lte->hash_list_2, so
- * lte_overwrite_prepare_2() must be called after lte_overwrite_prepare(), as
- * the latter uses lte->hash_list_2, while the former expects to set
- * lte->output_resource_entry. */
 static int
-lte_overwrite_prepare_2(struct wim_lookup_table_entry *lte, void *_args)
+do_lte_full_reference_for_logical_write(struct wim_lookup_table_entry *lte,
+                                       void *_ctx)
 {
-       struct lte_overwrite_prepare_args *args = _args;
-
-       if (lte->resource_location == RESOURCE_IN_WIM && lte->wim == args->wim) {
-               /* We can't do an in place overwrite on the WIM if there are
-                * streams after the XML data. */
-               if (lte->resource_entry.offset +
-                   lte->resource_entry.size > args->end_offset)
-               {
-                       if (wimlib_print_errors) {
-                               ERROR("The following resource is after the XML data:");
-                               print_lookup_table_entry(lte, stderr);
-                       }
-                       return WIMLIB_ERR_RESOURCE_ORDER;
-               }
-               copy_resource_entry(&lte->output_resource_entry,
-                                   &lte->resource_entry);
-       }
+       struct find_streams_ctx *ctx = _ctx;
+       lte->out_refcnt = 0;
+       lte_reference_for_logical_write(lte, ctx,
+                                       (lte->refcnt ? lte->refcnt : 1));
        return 0;
 }
 
-/* Given a WIM that we are going to overwrite in place with zero or more
- * additional streams added, construct a list the list of new unique streams
- * ('struct wim_lookup_table_entry's) that must be written, plus any unhashed
- * streams that need to be added but may be identical to other hashed or
- * unhashed streams.  These unhashed streams are checksummed while the streams
- * are being written.  To aid this process, the member @unique_size is set to 1
- * on streams that have a unique size and therefore must be written.
- *
- * The out_refcnt member of each 'struct wim_lookup_table_entry' is set to
- * indicate the number of times the stream is referenced in only the streams
- * that are being written; this may still be adjusted later when unhashed
- * streams are being resolved.
- */
 static int
-prepare_streams_for_overwrite(WIMStruct *wim, off_t end_offset,
-                             struct list_head *stream_list)
-{
-       int ret;
-       struct lte_overwrite_prepare_args args;
-       unsigned i;
-
-       args.wim = wim;
-       args.end_offset = end_offset;
-       ret = init_stream_size_table(&args.stream_size_tab,
-                                    wim->lookup_table->capacity);
-       if (ret)
-               return ret;
-
-       INIT_LIST_HEAD(&args.stream_list);
-       for (i = 0; i < wim->hdr.image_count; i++) {
-               struct wim_image_metadata *imd;
-               struct wim_lookup_table_entry *lte;
-
-               imd = wim->image_metadata[i];
-               image_for_each_unhashed_stream(lte, imd)
-                       lte_overwrite_prepare(lte, &args);
-       }
-       for_lookup_table_entry(wim->lookup_table, lte_overwrite_prepare, &args);
-       list_transfer(&args.stream_list, stream_list);
-
-       for (i = 0; i < wim->hdr.image_count; i++) {
-               ret = lte_overwrite_prepare_2(wim->image_metadata[i]->metadata_lte,
-                                             &args);
-               if (ret)
-                       goto out_destroy_stream_size_table;
-       }
-       ret = for_lookup_table_entry(wim->lookup_table,
-                                    lte_overwrite_prepare_2, &args);
-out_destroy_stream_size_table:
-       destroy_stream_size_table(&args.stream_size_tab);
-       return ret;
-}
-
-
-struct find_streams_ctx {
-       struct list_head stream_list;
-       struct stream_size_table stream_size_tab;
-};
-
-static void
 inode_find_streams_to_write(struct wim_inode *inode,
                            struct wim_lookup_table *table,
-                           struct list_head *stream_list,
-                           struct stream_size_table *tab)
+                           struct find_streams_ctx *ctx)
 {
        struct wim_lookup_table_entry *lte;
-       for (unsigned i = 0; i <= inode->i_num_ads; i++) {
+       unsigned i;
+
+       for (i = 0; i <= inode->i_num_ads; i++) {
                lte = inode_stream_lte(inode, i, table);
-               if (lte) {
-                       if (lte->out_refcnt == 0) {
-                               if (lte->unhashed)
-                                       stream_size_table_insert(lte, tab);
-                               list_add_tail(&lte->write_streams_list, stream_list);
-                       }
-                       lte->out_refcnt += inode->i_nlink;
-               }
+               if (lte)
+                       lte_reference_for_logical_write(lte, ctx, inode->i_nlink);
+               else if (!is_zero_hash(inode_stream_hash(inode, i)))
+                       return WIMLIB_ERR_RESOURCE_NOT_FOUND;
        }
+       return 0;
 }
 
 static int
@@ -1820,6 +1772,7 @@ image_find_streams_to_write(WIMStruct *wim)
        struct wim_image_metadata *imd;
        struct wim_inode *inode;
        struct wim_lookup_table_entry *lte;
+       int ret;
 
        ctx = wim->private;
        imd = wim_get_current_image_metadata(wim);
@@ -1830,55 +1783,174 @@ image_find_streams_to_write(WIMStruct *wim)
        /* Go through this image's inodes to find any streams that have not been
         * found yet. */
        image_for_each_inode(inode, imd) {
-               inode_find_streams_to_write(inode, wim->lookup_table,
-                                           &ctx->stream_list,
-                                           &ctx->stream_size_tab);
+               ret = inode_find_streams_to_write(inode, wim->lookup_table, ctx);
+               if (ret)
+                       return ret;
        }
        return 0;
 }
 
-/* Given a WIM that from which one or all of the images is being written, build
- * the list of unique streams ('struct wim_lookup_table_entry's) that must be
- * written, plus any unhashed streams that need to be written but may be
- * identical to other hashed or unhashed streams being written.  These unhashed
- * streams are checksummed while the streams are being written.  To aid this
- * process, the member @unique_size is set to 1 on streams that have a unique
- * size and therefore must be written.
+/*
+ * Build a list of streams (via `struct wim_lookup_table_entry's) included in
+ * the "logical write" of the WIM, meaning all streams that are referenced at
+ * least once by dentries in the the image(s) being written.  'out_refcnt' on
+ * each stream being included in the logical write is set to the number of
+ * references from dentries in the image(s).  Furthermore, 'unique_size' on each
+ * stream being included in the logical write is set to indicate whether that
+ * stream has a unique size relative to the streams being included in the
+ * logical write.  Still furthermore, 'part_number' on each stream being
+ * included in the logical write is set to the part number given in the
+ * in-memory header of @p wim.
  *
- * The out_refcnt member of each 'struct wim_lookup_table_entry' is set to
- * indicate the number of times the stream is referenced in only the streams
- * that are being written; this may still be adjusted later when unhashed
- * streams are being resolved.
+ * This is considered a "logical write" because it does not take into account
+ * filtering out streams already present in the WIM (in the case of an in place
+ * overwrite) or present in other WIMs (in case of creating delta WIM).
  */
 static int
-prepare_stream_list(WIMStruct *wim, int image, struct list_head *stream_list)
+prepare_logical_stream_list(WIMStruct *wim, int image, bool streams_ok,
+                           struct find_streams_ctx *ctx)
 {
        int ret;
-       struct find_streams_ctx ctx;
+       struct wim_lookup_table_entry *lte;
 
-       DEBUG("Preparing list of streams to write for image %d.", image);
+       if (streams_ok && (image == WIMLIB_ALL_IMAGES ||
+                          (image == 1 && wim->hdr.image_count == 1)))
+       {
+               /* Fast case:  Assume that all streams are being written and
+                * that the reference counts are correct.  */
+               struct wim_lookup_table_entry *lte;
+               struct wim_image_metadata *imd;
+               unsigned i;
+
+               for_lookup_table_entry(wim->lookup_table,
+                                      do_lte_full_reference_for_logical_write, ctx);
+               for (i = 0; i < wim->hdr.image_count; i++) {
+                       imd = wim->image_metadata[i];
+                       image_for_each_unhashed_stream(lte, imd)
+                               do_lte_full_reference_for_logical_write(lte, ctx);
+               }
+       } else {
+               /* Slow case:  Walk through the images being written and
+                * determine the streams referenced.  */
+               for_lookup_table_entry(wim->lookup_table, lte_zero_out_refcnt, NULL);
+               wim->private = ctx;
+               ret = for_image(wim, image, image_find_streams_to_write);
+               if (ret)
+                       return ret;
+       }
 
-       for_lookup_table_entry(wim->lookup_table, lte_zero_out_refcnt, NULL);
+       list_for_each_entry(lte, &ctx->stream_list, write_streams_list)
+               lte->part_number = wim->hdr.part_number;
+       return 0;
+}
+
+static int
+process_filtered_stream(struct wim_lookup_table_entry *lte, void *_ctx)
+{
+       struct find_streams_ctx *ctx = _ctx;
+       u16 filtered = 0;
+
+       /* Calculate and set lte->filtered.  */
+       if (lte->resource_location == RESOURCE_IN_WIM) {
+               if (lte->wim == ctx->wim &&
+                   (ctx->write_flags & WIMLIB_WRITE_FLAG_OVERWRITE))
+                       filtered |= FILTERED_SAME_WIM;
+               if (lte->wim != ctx->wim &&
+                   (ctx->write_flags & WIMLIB_WRITE_FLAG_SKIP_EXTERNAL_WIMS))
+                       filtered |= FILTERED_EXTERNAL_WIM;
+       }
+       lte->filtered = filtered;
+
+       /* Filtered streams get inserted into the stream size table too, unless
+        * they already were.  This is because streams that are checksummed
+        * on-the-fly during the write should not be written if they are
+        * duplicates of filtered stream.  */
+       if (lte->filtered && lte->out_refcnt == 0)
+               stream_size_table_insert(lte, &ctx->stream_size_tab);
+       return 0;
+}
+
+static int
+mark_stream_not_filtered(struct wim_lookup_table_entry *lte, void *_ignore)
+{
+       lte->filtered = 0;
+       return 0;
+}
+
+/* Given the list of streams to include in a logical write of a WIM, handle
+ * filtering out streams already present in the WIM or already present in
+ * external WIMs, depending on the write flags provided.  */
+static void
+handle_stream_filtering(struct find_streams_ctx *ctx)
+{
+       struct wim_lookup_table_entry *lte, *tmp;
+
+       if (!(ctx->write_flags & (WIMLIB_WRITE_FLAG_OVERWRITE |
+                                 WIMLIB_WRITE_FLAG_SKIP_EXTERNAL_WIMS)))
+       {
+               for_lookup_table_entry(ctx->wim->lookup_table,
+                                      mark_stream_not_filtered, ctx);
+               return;
+       }
+
+       for_lookup_table_entry(ctx->wim->lookup_table,
+                              process_filtered_stream, ctx);
+
+       /* Streams in logical write list that were filtered can be removed.  */
+       list_for_each_entry_safe(lte, tmp, &ctx->stream_list,
+                                write_streams_list)
+               if (lte->filtered)
+                       list_del(&lte->write_streams_list);
+}
+
+/* Prepares list of streams to write for the specified WIM image(s).  This wraps
+ * around prepare_logical_stream_list() to handle filtering out streams already
+ * present in the WIM or already present in external WIMs, depending on the
+ * write flags provided.
+ *
+ * Note: some additional data is stored in each `struct wim_lookup_table_entry':
+ *
+ * - 'out_refcnt' is set to the number of references found for the logical write.
+ *    This will be nonzero on all streams in the list returned by this function,
+ *    but will also be nonzero on streams not in the list that were included in
+ *    the logical write list, but filtered out from the returned list.
+ * - 'filtered' is set to nonzero if the stream was filtered.  Filtered streams
+ *   are not included in the list of streams returned by this function.
+ * - 'unique_size' is set if the stream has a unique size among all streams in
+ *   the logical write plus any filtered streams in the entire WIM that could
+ *   potentially turn out to have the same checksum as a yet-to-be-checksummed
+ *   stream being written.
+ */
+static int
+prepare_stream_list(WIMStruct *wim, int image, int write_flags,
+                   struct list_head *stream_list)
+{
+       int ret;
+       bool streams_ok;
+       struct find_streams_ctx ctx;
+
+       INIT_LIST_HEAD(&ctx.stream_list);
        ret = init_stream_size_table(&ctx.stream_size_tab,
                                     wim->lookup_table->capacity);
        if (ret)
                return ret;
-       for_lookup_table_entry(wim->lookup_table, stream_size_table_insert,
-                              &ctx.stream_size_tab);
-       INIT_LIST_HEAD(&ctx.stream_list);
-       wim->private = &ctx;
-       ret = for_image(wim, image, image_find_streams_to_write);
-       destroy_stream_size_table(&ctx.stream_size_tab);
+       ctx.write_flags = write_flags;
+       ctx.wim = wim;
+
+       streams_ok = ((write_flags & WIMLIB_WRITE_FLAG_STREAMS_OK) != 0);
+
+       ret = prepare_logical_stream_list(wim, image, streams_ok, &ctx);
        if (ret)
-               return ret;
+               goto out_destroy_table;
+
+       handle_stream_filtering(&ctx);
        list_transfer(&ctx.stream_list, stream_list);
-       return 0;
+       ret = 0;
+out_destroy_table:
+       destroy_stream_size_table(&ctx.stream_size_tab);
+       return ret;
 }
 
-/* Writes the streams for the specified @image in @wim to @wim->out_fd.
- * Alternatively, if @stream_list_override is specified, it is taken to be the
- * list of streams to write (connected with 'write_streams_list') and @image is
- * ignored.  */
 static int
 write_wim_streams(WIMStruct *wim, int image, int write_flags,
                  unsigned num_threads,
@@ -1890,22 +1962,24 @@ write_wim_streams(WIMStruct *wim, int image, int write_flags,
        struct list_head *stream_list;
        struct wim_lookup_table_entry *lte;
 
-       if (stream_list_override) {
-               stream_list = stream_list_override;
-               list_for_each_entry(lte, stream_list, write_streams_list) {
-                       if (lte->refcnt)
-                               lte->out_refcnt = lte->refcnt;
-                       else
-                               lte->out_refcnt = 1;
-               }
-       } else {
+       if (stream_list_override == NULL) {
+               /* Normal case: prepare stream list from image(s) being written.
+                */
                stream_list = &_stream_list;
-               ret = prepare_stream_list(wim, image, stream_list);
+               ret = prepare_stream_list(wim, image, write_flags, stream_list);
                if (ret)
                        return ret;
+       } else {
+               /* Currently only as a result of wimlib_split() being called:
+                * use stream list already explicitly provided.  Use existing
+                * reference counts.  */
+               stream_list = stream_list_override;
+               list_for_each_entry(lte, stream_list, write_streams_list) {
+                       lte->out_refcnt = (lte->refcnt ? lte->refcnt : 1);
+                       lte->part_number = wim->hdr.part_number;
+               }
        }
-       list_for_each_entry(lte, stream_list, write_streams_list)
-               lte->part_number = wim->hdr.part_number;
+
        return write_stream_list(stream_list,
                                 wim->lookup_table,
                                 &wim->out_fd,
@@ -1924,8 +1998,10 @@ write_wim_metadata_resources(WIMStruct *wim, int image, int write_flags,
        int end_image;
        int write_resource_flags;
 
-       if (write_flags & WIMLIB_WRITE_FLAG_NO_METADATA)
+       if (write_flags & WIMLIB_WRITE_FLAG_NO_METADATA) {
+               DEBUG("Not writing any metadata resources.");
                return 0;
+       }
 
        write_resource_flags = write_flags_to_resource_flags(write_flags);
 
@@ -1947,10 +2023,23 @@ write_wim_metadata_resources(WIMStruct *wim, int image, int write_flags,
                struct wim_image_metadata *imd;
 
                imd = wim->image_metadata[i - 1];
+               /* Build a new metadata resource only if image was modified from
+                * the original (or was newly added).  Otherwise just copy the
+                * existing one.  */
                if (imd->modified) {
+                       DEBUG("Image %u was modified; building and writing new "
+                             "metadata resource", i);
                        ret = write_metadata_resource(wim, i,
                                                      write_resource_flags);
+               } else if (write_flags & WIMLIB_WRITE_FLAG_OVERWRITE) {
+                       DEBUG("Image %u was not modified; re-using existing "
+                             "metadata resource.", i);
+                       copy_resource_entry(&imd->metadata_lte->output_resource_entry,
+                                           &imd->metadata_lte->resource_entry);
+                       ret = 0;
                } else {
+                       DEBUG("Image %u was not modified; copying existing "
+                             "metadata resource.", i);
                        ret = write_wim_resource(imd->metadata_lte,
                                                 &wim->out_fd,
                                                 wim->compression_type,
@@ -2164,8 +2253,10 @@ lock_wim(WIMStruct *wim, int fd)
 #endif
 
 /*
+ * write_pipable_wim():
+ *
  * Perform the intermediate stages of creating a "pipable" WIM (i.e. a WIM
- * capable of being applied from a pipe).  Such a WIM looks like:
+ * capable of being applied from a pipe).
  *
  * Pipable WIMs are a wimlib-specific modification of the WIM format such that
  * images can be applied from them sequentially when the file data is sent over
@@ -2174,7 +2265,7 @@ lock_wim(WIMStruct *wim, int fd)
  *
  * - Magic characters in header are "WLPWM\0\0\0" (wimlib pipable WIM) instead
  *   of "MSWIM\0\0\0".  This lets wimlib know that the WIM is pipable and also
- *   should stop other software from trying to read the file as a normal WIM.
+ *   stops other software from trying to read the file as a normal WIM.
  *
  * - The header at the beginning of the file does not contain all the normal
  *   information; in particular it will have all 0's for the lookup table and
@@ -2196,10 +2287,13 @@ lock_wim(WIMStruct *wim, int fd)
  *   uncompressed stream size, and flags that indicate whether the stream is
  *   compressed.  The data of uncompressed streams then follows literally, while
  *   the data of compressed streams follows in a modified format.  Compressed
- *   streams have no chunk table, since the chunk table cannot be written until
- *   all chunks have been compressed; instead, each compressed chunk is prefixed
- *   by a `struct pwm_chunk_hdr' that gives its size.  However, the offsets are
- *   given in the chunk table as if these chunk headers were not present.
+ *   streams do not begin with a chunk table, since the chunk table cannot be
+ *   written until all chunks have been compressed.  Instead, each compressed
+ *   chunk is prefixed by a `struct pwm_chunk_hdr' that gives its size.
+ *   Furthermore, the chunk table is written at the end of the resource instead
+ *   of the start.  Note: chunk offsets are given in the chunk table as if the
+ *   `struct pwm_chunk_hdr's were not present; also, the chunk table is only
+ *   used if the WIM is being read from a seekable file (not a pipe).
  *
  * - Metadata resources always come before other file resources (streams).
  *   (This does not by itself constitute an incompatibility with normal WIMs,
@@ -2216,15 +2310,20 @@ lock_wim(WIMStruct *wim, int fd)
  *
  *   Layout of pipable WIM:
  *
- * ----------+----------+--------------------+----------------+--------------+------------+--------+
- * | Header  | XML data | Metadata resources | File resources | Lookup table | XML data   | Header |
- * ----------+----------+--------------------+----------------+--------------+------------+--------+
+ * ---------+----------+--------------------+----------------+--------------+-----------+--------+
+ * | Header | XML data | Metadata resources | File resources | Lookup table | XML data  | Header |
+ * ---------+----------+--------------------+----------------+--------------+-----------+--------+
  *
  *   Layout of normal WIM:
  *
- * +---------+--------------------+----------------+--------------+----------+
- * | Header  | Metadata resources | File resources | Lookup table | XML data |
- * +---------+--------------------+----------------+--------------+----------+
+ * +--------+-----------------------------+-------------------------+
+ * | Header | File and metadata resources | Lookup table | XML data |
+ * +--------+-----------------------------+-------------------------+
+ *
+ * An optional integrity table can follow the final XML data in both normal and
+ * pipable WIMs.  However, due to implementation details, wimlib currently can
+ * only include an integrity table in a pipable WIM when writing it to a
+ * seekable file (not a pipe).
  *
  * Do note that since pipable WIMs are not supported by Microsoft's software,
  * wimlib does not create them unless explicitly requested (with
@@ -2338,7 +2437,8 @@ write_wim_part(WIMStruct *wim,
                DEBUG("Number of threads: %u", num_threads);
        DEBUG("Progress function: %s", (progress_func ? "yes" : "no"));
        DEBUG("Stream list:       %s", (stream_list_override ? "specified" : "autodetect"));
-       DEBUG("GUID:              %s", (guid ? "specified" : "generate new"));
+       DEBUG("GUID:              %s", ((guid || wim->guid_set_explicitly) ?
+                                       "specified" : "generate new"));
 
        /* Internally, this is always called with a valid part number and total
         * parts.  */
@@ -2350,9 +2450,12 @@ write_wim_part(WIMStruct *wim,
             (image < 1 || image > wim->hdr.image_count))
                return WIMLIB_ERR_INVALID_IMAGE;
 
-       /* @wim must specify a standalone WIM.  */
-       if (wim->hdr.total_parts != 1)
-               return WIMLIB_ERR_SPLIT_UNSUPPORTED;
+       /* If we need to write metadata resources, make sure the ::WIMStruct has
+        * the needed information attached (e.g. is not a resource-only WIM,
+        * such as a non-first part of a split WIM).  */
+       if (!wim_has_metadata(wim) &&
+           !(write_flags & WIMLIB_WRITE_FLAG_NO_METADATA))
+               return WIMLIB_ERR_METADATA_NOT_FOUND;
 
        /* Check for contradictory flags.  */
        if ((write_flags & (WIMLIB_WRITE_FLAG_CHECK_INTEGRITY |
@@ -2405,7 +2508,7 @@ write_wim_part(WIMStruct *wim,
        /* Use GUID if specified; otherwise generate a new one.  */
        if (guid)
                memcpy(wim->hdr.guid, guid, WIMLIB_GUID_LEN);
-       else
+       else if (!wim->guid_set_explicitly)
                randomize_byte_array(wim->hdr.guid, WIMLIB_GUID_LEN);
 
        /* Clear references to resources that have not been written yet.  */
@@ -2558,6 +2661,40 @@ any_images_modified(WIMStruct *wim)
        return false;
 }
 
+static int
+check_resource_offset(struct wim_lookup_table_entry *lte, void *_wim)
+{
+       const WIMStruct *wim = _wim;
+       off_t end_offset = *(const off_t*)wim->private;
+
+       if (lte->resource_location == RESOURCE_IN_WIM && lte->wim == wim &&
+           lte->resource_entry.offset + lte->resource_entry.size > end_offset)
+               return WIMLIB_ERR_RESOURCE_ORDER;
+       return 0;
+}
+
+/* Make sure no file or metadata resources are located after the XML data (or
+ * integrity table if present)--- otherwise we can't safely overwrite the WIM in
+ * place and we return WIMLIB_ERR_RESOURCE_ORDER.  */
+static int
+check_resource_offsets(WIMStruct *wim, off_t end_offset)
+{
+       int ret;
+       unsigned i;
+
+       wim->private = &end_offset;
+       ret = for_lookup_table_entry(wim->lookup_table, check_resource_offset, wim);
+       if (ret)
+               return ret;
+
+       for (i = 0; i < wim->hdr.image_count; i++) {
+               ret = check_resource_offset(wim->image_metadata[i]->metadata_lte, wim);
+               if (ret)
+                       return ret;
+       }
+       return 0;
+}
+
 /*
  * Overwrite a WIM, possibly appending streams to it.
  *
@@ -2634,6 +2771,10 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
                if (wim_has_integrity_table(wim))
                        write_flags |= WIMLIB_WRITE_FLAG_CHECK_INTEGRITY;
 
+       /* Set additional flags for overwrite.  */
+       write_flags |= WIMLIB_WRITE_FLAG_OVERWRITE |
+                      WIMLIB_WRITE_FLAG_STREAMS_OK;
+
        /* Make sure that the integrity table (if present) is after the XML
         * data, and that there are no stream resources, metadata resources, or
         * lookup tables after the XML data.  Otherwise, these data would be
@@ -2643,12 +2784,12 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
        old_lookup_table_end = wim->hdr.lookup_table_res_entry.offset +
                               wim->hdr.lookup_table_res_entry.size;
        if (wim->hdr.integrity.offset != 0 && wim->hdr.integrity.offset < old_xml_end) {
-               ERROR("Didn't expect the integrity table to be before the XML data");
+               WARNING("Didn't expect the integrity table to be before the XML data");
                return WIMLIB_ERR_RESOURCE_ORDER;
        }
 
        if (old_lookup_table_end > old_xml_begin) {
-               ERROR("Didn't expect the lookup table to be after the XML data");
+               WARNING("Didn't expect the lookup table to be after the XML data");
                return WIMLIB_ERR_RESOURCE_ORDER;
        }
 
@@ -2677,7 +2818,12 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
                old_wim_end = old_xml_end;
        }
 
-       ret = prepare_streams_for_overwrite(wim, old_wim_end, &stream_list);
+       ret = check_resource_offsets(wim, old_wim_end);
+       if (ret)
+               return ret;
+
+       ret = prepare_stream_list(wim, WIMLIB_ALL_IMAGES, write_flags,
+                                 &stream_list);
        if (ret)
                return ret;
 
@@ -2707,8 +2853,6 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
                goto out_unlock_wim;
        }
 
-       DEBUG("Writing newly added streams (offset = %"PRIu64")",
-             old_wim_end);
        ret = write_stream_list(&stream_list,
                                wim->lookup_table,
                                &wim->out_fd,
@@ -2719,13 +2863,11 @@ overwrite_wim_inplace(WIMStruct *wim, int write_flags,
        if (ret)
                goto out_truncate;
 
-       for (unsigned i = 1; i <= wim->hdr.image_count; i++) {
-               if (wim->image_metadata[i - 1]->modified) {
-                       ret = write_metadata_resource(wim, i, 0);
-                       if (ret)
-                               goto out_truncate;
-               }
-       }
+       ret = write_wim_metadata_resources(wim, WIMLIB_ALL_IMAGES,
+                                          write_flags, progress_func);
+       if (ret)
+               goto out_truncate;
+
        write_flags |= WIMLIB_WRITE_FLAG_REUSE_INTEGRITY_TABLE;
        ret = finish_write(wim, WIMLIB_ALL_IMAGES, write_flags,
                           progress_func, NULL);