Adjust handling of blob reference counts

[wimlib] / src / blob_table.c

diff --git a/src/blob_table.c b/src/blob_table.c
index 84835b5a7a03b6ca2d5a7774c55f98c025a2bad2..6cc0a98de30fe059beea7dc529e99a4abdbad4a4 100644 (file)
--- a/src/blob_table.c
+++ b/src/blob_table.c
@@ -105,8 +105,7 @@ new_blob_descriptor(void)
        if (blob == NULL)
                return NULL;
 
-       blob->refcnt = 1;
-
+       /* blob->refcnt = 0  */
        /* blob->blob_location = BLOB_NONEXISTENT  */
        BUILD_BUG_ON(BLOB_NONEXISTENT != 0);
 
@@ -263,10 +262,21 @@ finalize_blob(struct blob_descriptor *blob)
 void
 blob_decrement_refcnt(struct blob_descriptor *blob, struct blob_table *table)
 {
-       if (unlikely(blob->refcnt == 0))  /* See comment above  */
+       blob_subtract_refcnt(blob, table, 1);
+}
+
+void
+blob_subtract_refcnt(struct blob_descriptor *blob, struct blob_table *table,
+                    u32 count)
+{
+       if (unlikely(blob->refcnt < count)) {
+               blob->refcnt = 0; /* See comment above  */
                return;
+       }
+
+       blob->refcnt -= count;
 
-       if (--blob->refcnt != 0)
+       if (blob->refcnt != 0)
                return;
 
        if (blob->unhashed) {
@@ -1255,7 +1265,6 @@ new_blob_from_data_buffer(const void *buffer, size_t size,
        if (existing_blob) {
                wimlib_assert(existing_blob->size == size);
                blob = existing_blob;
-               blob->refcnt++;
        } else {
                void *buffer_copy;
                blob = new_blob_descriptor();
@@ -1275,6 +1284,36 @@ new_blob_from_data_buffer(const void *buffer, size_t size,
        return blob;
 }
 
+struct blob_descriptor *
+after_blob_hashed(struct blob_descriptor *blob,
+                 struct blob_descriptor **back_ptr,
+                 struct blob_table *blob_table)
+{
+       struct blob_descriptor *duplicate_blob;
+
+       list_del(&blob->unhashed_list);
+       blob->unhashed = 0;
+
+       /* Look for a duplicate blob  */
+       duplicate_blob = lookup_blob(blob_table, blob->hash);
+       if (duplicate_blob) {
+               /* We have a duplicate blob.  Transfer the reference counts from
+                * this blob to the duplicate and update the reference to this
+                * blob (from a stream) to point to the duplicate.  The caller
+                * is responsible for freeing @blob if needed.  */
+               wimlib_assert(duplicate_blob->size == blob->size);
+               duplicate_blob->refcnt += blob->refcnt;
+               blob->refcnt = 0;
+               *back_ptr = duplicate_blob;
+               return duplicate_blob;
+       } else {
+               /* No duplicate blob, so we need to insert this blob into the
+                * blob table and treat it as a hashed blob.  */
+               blob_table_insert(blob_table, blob);
+               return blob;
+       }
+}
+
 /*
  * Calculate the SHA-1 message digest of a blob and move its descriptor from the
  * list of unhashed blobs to the blob table, possibly joining it with an
@@ -1295,42 +1334,16 @@ int
 hash_unhashed_blob(struct blob_descriptor *blob, struct blob_table *blob_table,
                   struct blob_descriptor **blob_ret)
 {
-       int ret;
-       struct blob_descriptor *duplicate_blob;
        struct blob_descriptor **back_ptr;
+       int ret;
 
-       wimlib_assert(blob->unhashed);
-
-       /* back_ptr must be saved because @back_inode and @back_stream_id are in
-        * union with the SHA-1 message digest and will no longer be valid once
-        * the SHA-1 has been calculated. */
        back_ptr = retrieve_pointer_to_unhashed_blob(blob);
 
        ret = sha1_blob(blob);
        if (ret)
                return ret;
 
-       list_del(&blob->unhashed_list);
-       blob->unhashed = 0;
-
-       /* Look for a duplicate blob  */
-       duplicate_blob = lookup_blob(blob_table, blob->hash);
-       if (duplicate_blob) {
-               /* We have a duplicate blob.  Transfer the reference counts from
-                * this blob to the duplicate and update the reference to this
-                * blob (from an stream) to point to the duplicate.  The caller
-                * is responsible for freeing @blob if needed.  */
-               wimlib_assert(duplicate_blob->size == blob->size);
-               duplicate_blob->refcnt += blob->refcnt;
-               blob->refcnt = 0;
-               *back_ptr = duplicate_blob;
-               blob = duplicate_blob;
-       } else {
-               /* No duplicate blob, so we need to insert this blob into the
-                * blob table and treat it as a hashed blob. */
-               blob_table_insert(blob_table, blob);
-       }
-       *blob_ret = blob;
+       *blob_ret = after_blob_hashed(blob, back_ptr, blob_table);
        return 0;
 }