New API function iso_write_opts_set_part_offset() controls creation of

an MBR with a first partiton table entry that bears non-zero start address.
A second set of volume descriptors and directory tree+tables gets created
which can be used to mount the image at the partition start.
Not yet implemented for second set: ISO 9660:1999, MD5 checksums.

libisofs/buffer.c

@@ -293,7 +293,51 @@ unsigned int iso_ring_buffer_get_times_empty(IsoRingBuffer *buf)
 }
 
 
-/**
+/** Internal via buffer.h
+ *
+ * Get the status of a ring buffer.
+ *
+ * @param buf
+ *      The ring buffer object to inquire
+ * @param size
+ *      Will be filled with the total size of the buffer, in bytes
+ * @param free_bytes
+ *      Will be filled with the bytes currently available in buffer
+ * @return
+ *      < 0 error, > 0 state:
+ *           1="active"    : input and consumption are active
+ *           2="ending"    : input has ended without error
+ *           3="failing"   : input had error and ended,
+ *           5="abandoned" : consumption has ended prematurely
+ *           6="ended"     : consumption has ended without input error
+ *           7="aborted"   : consumption has ended after input error
+ */
+int iso_ring_buffer_get_buf_status(IsoRingBuffer *buf, size_t *size,
+                                   size_t *free_bytes)
+{
+    int ret;
+
+    if (buf == NULL) {
+        return ISO_NULL_POINTER;
+    }
+
+    /* get mutex */
+    pthread_mutex_lock(&buf->mutex);
+    if (size) {
+        *size = buf->cap;
+    }
+    if (free_bytes) {
+        *free_bytes = buf->cap - buf->size;
+    }
+
+    ret = (buf->rend ? 4 : 0) + (buf->wend + 1);
+
+    pthread_mutex_unlock(&buf->mutex);
+    return ret;
+}
+
+/** API via libisofs.h
+ *
  * Get the status of the buffer used by a burn_source.
  *
  * @param b
@@ -321,18 +365,7 @@ int iso_ring_buffer_get_status(struct burn_source *b, size_t *size,
         return ISO_NULL_POINTER;
     }
     buf = ((Ecma119Image*)(b->data))->buffer;
-
+    ret = iso_ring_buffer_get_buf_status(buf, size, free_bytes);
-    /* get mutex */
-    pthread_mutex_lock(&buf->mutex);
-    if (size) {
-        *size = buf->cap;
-    }
-    if (free_bytes) {
-        *free_bytes = buf->cap - buf->size;
-    }
-
-    ret = (buf->rend ? 4 : 0) + (buf->wend + 1);
-
-    pthread_mutex_unlock(&buf->mutex);
     return ret;
 }
+

libisofs/buffer.h

@@ -63,6 +63,28 @@ int iso_ring_buffer_write(IsoRingBuffer *buf, uint8_t *data, size_t count);
  */
 int iso_ring_buffer_read(IsoRingBuffer *buf, uint8_t *dest, size_t count);
 
+/** Backend of API call iso_ring_buffer_get_status()
+ *
+ * Get the status of a ring buffer.
+ *
+ * @param buf
+ *      The ring buffer object to inquire
+ * @param size
+ *      Will be filled with the total size of the buffer, in bytes
+ * @param free_bytes
+ *      Will be filled with the bytes currently available in buffer
+ * @return
+ *      < 0 error, > 0 state:
+ *           1="active"    : input and consumption are active
+ *           2="ending"    : input has ended without error
+ *           3="failing"   : input had error and ended,
+ *           5="abandoned" : consumption has ended prematurely
+ *           6="ended"     : consumption has ended without input error
+ *           7="aborted"   : consumption has ended after input error
+ */
+int iso_ring_buffer_get_buf_status(IsoRingBuffer *buf, size_t *size,
+                                   size_t *free_bytes);
+
 /** 
  * Close the buffer (to be called by the writer).
  * You have to explicity close the buffer when you don't have more data to

libisofs/ecma119.c

@@ -85,6 +85,9 @@ void ecma119_image_free(Ecma119Image *t)
         free(t->checksum_buffer);
     if (t->writers != NULL)
         free(t->writers);
+    if (t->partition_root != NULL)
+        ecma119_node_free(t->partition_root);
+    t->partition_root = NULL;
     free(t);
 }
 
@@ -231,6 +234,7 @@ int ecma119_writer_compute_data_blocks(IsoImageWriter *writer)
 {
     Ecma119Image *target;
     uint32_t path_table_size;
+    size_t ndirs;
 
     if (writer == NULL) {
         return ISO_ASSERT_FAILURE;
@@ -253,6 +257,25 @@ int ecma119_writer_compute_data_blocks(IsoImageWriter *writer)
     target->m_path_table_pos = target->curblock;
     target->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
     target->path_table_size = path_table_size;
+
+    if (target->partition_offset > 0) {
+        /* TWINTREE: take into respect second directory tree */
+        ndirs = target->ndirs;
+        target->ndirs = 0;
+        calc_dir_pos(target, target->partition_root);
+        if (target->ndirs != ndirs) {
+            iso_msg_submit(target->image->id, ISO_ASSERT_FAILURE, 0,
+                    "Number of directories differs in ECMA-119 partiton_tree");
+            return ISO_ASSERT_FAILURE;
+	}
+        /* TWINTREE: take into respect second set of path tables */
+        path_table_size = calc_path_table_size(target->partition_root);
+        target->partition_l_table_pos = target->curblock;
+        target->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
+        target->partition_m_table_pos = target->curblock;
+        target->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
+    }
+
     if (target->md5_session_checksum) {
         /* Account for tree checksum tag */
         target->checksum_tree_tag_pos = target->curblock;
@@ -323,7 +346,8 @@ void write_one_dir_record(Ecma119Image *t, Ecma119Node *node, int file_id,
         node = node->parent;
 
     rec->len_dr[0] = len_dr + (info != NULL ? info->suf_len : 0);
-    iso_bb(rec->block, block, 4);
+    /* TWINTREE: - t->eff_partition_offset */
+    iso_bb(rec->block, block - t->eff_partition_offset, 4);
     iso_bb(rec->length, len, 4);
     if (t->dir_rec_mtime) {
         iso= node->node;
@@ -411,15 +435,29 @@ int ecma119_writer_write_vol_desc(IsoImageWriter *writer)
     vol.vol_desc_version[0] = 1;
     strncpy_pad((char*)vol.system_id, system_id, 32);
     strncpy_pad((char*)vol.volume_id, vol_id, 32);
-    iso_bb(vol.vol_space_size, t->vol_space_size, 4);
+
+    /* TWINTREE: - t->eff_partition_offset */
+    iso_bb(vol.vol_space_size, t->vol_space_size  - t->eff_partition_offset,
+           4);
+
     iso_bb(vol.vol_set_size, (uint32_t) 1, 2);
     iso_bb(vol.vol_seq_number, (uint32_t) 1, 2);
     iso_bb(vol.block_size, (uint32_t) BLOCK_SIZE, 2);
     iso_bb(vol.path_table_size, t->path_table_size, 4);
-    iso_lsb(vol.l_path_table_pos, t->l_path_table_pos, 4);
-    iso_msb(vol.m_path_table_pos, t->m_path_table_pos, 4);
 
-    write_one_dir_record(t, t->root, 0, vol.root_dir_record, 1, NULL, 0);
+    if (t->eff_partition_offset > 0) {
+        /* TWINTREE: point to second tables and second root */
+        iso_lsb(vol.l_path_table_pos,
+                t->partition_l_table_pos - t->eff_partition_offset, 4);
+        iso_msb(vol.m_path_table_pos,
+                t->partition_m_table_pos - t->eff_partition_offset, 4);
+        write_one_dir_record(t, t->partition_root, 0,
+                             vol.root_dir_record, 1, NULL, 0);
+    } else {
+        iso_lsb(vol.l_path_table_pos, t->l_path_table_pos, 4);
+        iso_msb(vol.m_path_table_pos, t->m_path_table_pos, 4);
+        write_one_dir_record(t, t->root, 0, vol.root_dir_record, 1, NULL, 0);
+    }
 
     strncpy_pad((char*)vol.vol_set_id, volset_id, 128);
     strncpy_pad((char*)vol.publisher_id, pub_id, 128);
@@ -637,7 +675,9 @@ int write_path_table(Ecma119Image *t, Ecma119Node **pathlist, int l_type)
         rec = (struct ecma119_path_table_record*) buf;
         rec->len_di[0] = dir->parent ? (uint8_t) strlen(dir->iso_name) : 1;
         rec->len_xa[0] = 0;
-        write_int(rec->block, dir->info.dir->block, 4);
+        /* TWINTREE: - t->eff_partition_offset */
+        write_int(rec->block, dir->info.dir->block - t->eff_partition_offset,
+                  4);
         write_int(rec->parent, parent + 1, 2);
         if (dir->parent) {
             memcpy(rec->dir_id, dir->iso_name, rec->len_di[0]);
@@ -676,7 +716,13 @@ int write_path_tables(Ecma119Image *t)
     if (pathlist == NULL) {
         return ISO_OUT_OF_MEM;
     }
-    pathlist[0] = t->root;
+
+    /* TWINTREE: t->partition_root */
+    if (t->eff_partition_offset > 0) {
+        pathlist[0] = t->partition_root;
+    } else {
+        pathlist[0] = t->root;
+    }
     cur = 1;
 
     for (i = 0; i < t->ndirs; i++) {
@@ -703,11 +749,54 @@ int write_path_tables(Ecma119Image *t)
     return ret;
 }
 
+
 /**
- * Write both the directory structure (ECMA-119, 6.8) and the L and M
+ * Write the directory structure (ECMA-119, 6.8) and the L and M
  * Path Tables (ECMA-119, 6.9).
  */
 static
+int ecma119_writer_write_dirs(IsoImageWriter *writer)
+{
+    int ret;
+    Ecma119Image *t;
+    Ecma119Node *root;
+
+    t = writer->target;
+
+    /* first of all, we write the directory structure */
+    /* TWINTREE: t->root -> root */
+    if (t->eff_partition_offset > 0) {
+        root = t->partition_root;
+    } else {
+        root = t->root;
+    }
+    ret = write_dirs(t, root, root);
+    if (ret < 0) {
+        return ret;
+    }
+
+    /* and write the path tables */
+    ret = write_path_tables(t);
+    if (ret < 0)
+        return ret;
+    if (t->md5_session_checksum) {
+        /* Write tree checksum tag */
+        if (t->eff_partition_offset > 0) {
+            /* >>> TWINTREE: >>> For now, checksums and tags are only for the
+                                 first session */;
+        } else {
+            ret = iso_md5_write_tag(t, 3);
+        }
+    }
+    return ret;
+}
+
+/**
+ * Write directory structure and Path Tables of the ECMA-119 tree.
+ * This happens eventually a second time for the duplicates which use
+ * addresses with partition offset.
+ */
+static
 int ecma119_writer_write_data(IsoImageWriter *writer)
 {
     int ret;
@@ -718,21 +807,19 @@ int ecma119_writer_write_data(IsoImageWriter *writer)
     }
     t = writer->target;
 
-    /* first of all, we write the directory structure */
+    ret = ecma119_writer_write_dirs(writer);
-    ret = write_dirs(t, t->root, t->root);
-    if (ret < 0) {
-        return ret;
-    }
-
-    /* and write the path tables */
-    ret = write_path_tables(t);
     if (ret < 0)
         return ret;
-    if (t->md5_session_checksum) {
+
-        /* Write tree checksum tag */
+    if (t->partition_offset > 0) {
-        ret = iso_md5_write_tag(t, 3);
+        /* TWINTREE: */
+        t->eff_partition_offset = t->partition_offset;
+        ret = ecma119_writer_write_dirs(writer);
+        t->eff_partition_offset = 0;
+        if (ret < 0) 
+            return ret;
     }
-    return ret;
+    return ISO_SUCCESS;
 }
 
 static
@@ -768,6 +855,16 @@ int ecma119_writer_create(Ecma119Image *target)
         return ret;
     }
 
+    /* TWINTREE: */
+    if(target->partition_offset > 0) {
+        /* Create second tree */
+        target->eff_partition_offset = target->partition_offset;
+        ret = ecma119_tree_create(target);
+        target->eff_partition_offset = 0;
+        if (ret < 0)
+            return ret;
+    }
+
     /* we need the volume descriptor */
     target->curblock++;
     return ISO_SUCCESS;
@@ -867,12 +964,157 @@ int transplant_checksum_buffer(Ecma119Image *target, int flag)
     return 1;
 }
 
+static
+int write_vol_desc_terminator(Ecma119Image *target)
+{
+    int res;
+    uint8_t buf[BLOCK_SIZE];
+    struct ecma119_vol_desc_terminator *vol;
+
+    vol = (struct ecma119_vol_desc_terminator *) buf;
+
+    vol->vol_desc_type[0] = 255;
+    memcpy(vol->std_identifier, "CD001", 5);
+    vol->vol_desc_version[0] = 1;
+
+    res = iso_write(target, buf, BLOCK_SIZE);
+    return res;
+}
+
+
+/* @param flag bit0= initialize system area by target->opts_overwrite
+               bit1= fifo is not yet draining. Inquire write_count from fifo.
+*/
+static
+int write_head_part1(Ecma119Image *target, int *write_count, int flag)
+{
+    int res, i;
+    uint8_t sa[16 * BLOCK_SIZE];
+    IsoImageWriter *writer;
+    size_t buffer_size = 0, buffer_free = 0, buffer_start_free = 0;
+
+    iso_ring_buffer_get_buf_status(target->buffer, &buffer_size,
+                                   &buffer_start_free);
+    *write_count = 0;
+    /* Write System Area (ECMA-119, 6.2.1) */
+    if ((flag & 1) && target->opts_overwrite != NULL)
+        memcpy(sa, target->opts_overwrite, 16 * BLOCK_SIZE);
+    res = iso_write_system_area(target, sa);
+    if (res < 0)
+        goto write_error;
+    res = iso_write(target, sa, 16 * BLOCK_SIZE);
+    if (res < 0)
+        goto write_error;
+    *write_count = 16;
+
+    /* write volume descriptors, one per writer */
+    iso_msg_debug(target->image->id, "Write volume descriptors");
+    for (i = 0; i < target->nwriters; ++i) {
+        writer = target->writers[i];
+        res = writer->write_vol_desc(writer);
+        if (res < 0) 
+            goto write_error;
+    }
+
+    /* write Volume Descriptor Set Terminator (ECMA-119, 8.3) */
+    res = write_vol_desc_terminator(target);
+    if (res < 0)
+        goto write_error;
+
+    if(flag & 2) {
+      iso_ring_buffer_get_buf_status(target->buffer, &buffer_size,
+                                     &buffer_free);
+      *write_count = ( buffer_start_free - buffer_free ) / BLOCK_SIZE;
+    } else {
+      *write_count = target->bytes_written / BLOCK_SIZE;
+    }
+
+    return ISO_SUCCESS;
+write_error:;
+    return res;
+}
+
+static
+int write_head_part2(Ecma119Image *target, int *write_count, int flag)
+{
+    int res, i;
+    uint8_t buf[BLOCK_SIZE];
+    IsoImageWriter *writer;
+
+    if (target->partition_offset <= 0)
+        return ISO_SUCCESS;
+
+    /* TWINTREE: write padding up to target->partition_offset + 16 */
+    memset(buf, 0, 2048);
+    for(; *write_count < target->partition_offset + 16; (*write_count)++) {
+        res = iso_write(target, buf, BLOCK_SIZE);
+        if (res < 0)
+            goto write_error;
+    }
+
+    /* TWINTREE: write volume descriptors subtracting
+                 target->partiton_offset from any LBA pointer.
+    */
+    target->eff_partition_offset = target->partition_offset;
+    for (i = 0; i < target->nwriters; ++i) {
+        writer = target->writers[i];
+        /* TWINTREE:
+           Not all writers have an entry in the partion volume descriptor set.
+           It must be guaranteed that they write exactly one block.
+        */
+        /* >>> TWINTREE: Enhance ISO1999 writer and add it here */
+        if(writer->write_vol_desc != ecma119_writer_write_vol_desc &&
+           writer->write_vol_desc != joliet_writer_write_vol_desc)
+    continue;
+        res = writer->write_vol_desc(writer);
+        if (res < 0)
+            goto write_error;
+        (*write_count)++;
+    }
+    res = write_vol_desc_terminator(target);
+    if (res < 0)
+        goto write_error;
+    (*write_count)++;
+    target->eff_partition_offset = 0;
+
+    /* >>> TWINTREE: Postponed for now:
+                     Write second superblock checksum tag */;
+
+    return ISO_SUCCESS;
+write_error:;
+    return res;
+}
+
+static
+int write_head_part(Ecma119Image *target, int flag)
+{
+    int res, write_count = 0;
+
+    /* System area and volume descriptors */
+    res = write_head_part1(target, &write_count, 0);
+    if (res < 0)
+        return res;
+
+    /* Write superblock checksum tag */
+    if (target->md5_session_checksum && target->checksum_ctx != NULL) {
+        res = iso_md5_write_tag(target, 2);
+        if (res < 0)
+            return res;
+        write_count++;
+    }
+
+    /* Second set of system area and volume descriptors for partition_offset */
+    res = write_head_part2(target, &write_count, 0);
+    if (res < 0)
+        return res;
+    return ISO_SUCCESS;
+}
+
 static
 void *write_function(void *arg)
 {
     int res;
     size_t i;
-    uint8_t buf[BLOCK_SIZE];
     IsoImageWriter *writer;
 
     Ecma119Image *target = (Ecma119Image*)arg;
@@ -881,50 +1123,9 @@ void *write_function(void *arg)
     target->bytes_written = (off_t) 0;
     target->percent_written = 0;
 
-    /* Write System Area (ECMA-119, 6.2.1) */
+    res = write_head_part(target, 0);
-    {
+    if (res < 0)
-        uint8_t sa[16 * BLOCK_SIZE];
+        goto write_error;
-        res = iso_write_system_area(target, sa);
-        if (res < 0) {
-            goto write_error;
-        }
-        res = iso_write(target, sa, 16 * BLOCK_SIZE);
-        if (res < 0) {
-            goto write_error;
-        }
-    }
-
-    /* write volume descriptors, one per writer */
-    iso_msg_debug(target->image->id, "Write volume descriptors");
-    for (i = 0; i < target->nwriters; ++i) {
-        writer = target->writers[i];
-        res = writer->write_vol_desc(writer);
-        if (res < 0) {
-            goto write_error;
-        }
-    }
-
-    /* write Volume Descriptor Set Terminator (ECMA-119, 8.3) */
-    {
-        struct ecma119_vol_desc_terminator *vol;
-        vol = (struct ecma119_vol_desc_terminator *) buf;
-
-        vol->vol_desc_type[0] = 255;
-        memcpy(vol->std_identifier, "CD001", 5);
-        vol->vol_desc_version[0] = 1;
-
-        res = iso_write(target, buf, BLOCK_SIZE);
-        if (res < 0) {
-            goto write_error;
-        }
-    }
-
-    /* Write superblock checksum tag */
-    if (target->md5_session_checksum && target->checksum_ctx != NULL) {
-        res = iso_md5_write_tag(target, 2);
-        if (res < 0)
-            goto write_error;
-    }
 
     /* write data for each writer */
     for (i = 0; i < target->nwriters; ++i) {
@@ -947,6 +1148,10 @@ void *write_function(void *arg)
 #endif
 
     write_error: ;
+
+    /* TWINTREE: */
+    target->eff_partition_offset = 0;
+
     if (res == ISO_CANCELED) {
         /* canceled */
         iso_msg_submit(target->image->id, ISO_IMAGE_WRITE_CANCELED, 0, NULL);
@@ -1064,15 +1269,20 @@ int checksum_prepare_nodes(Ecma119Image *target, IsoNode *node, int flag)
     return ISO_SUCCESS;
 }
 
+/*
+*/
+#define Libisofs_twintreE yes
 
 static
 int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
 {
     int ret, i, voldesc_size, nwriters, image_checksums_mad = 0, tag_pos;
     Ecma119Image *target;
+    IsoImageWriter *writer;
     int el_torito_writer_index = -1, file_src_writer_index = -1;
     int system_area_options = 0;
     char *system_area = NULL;
+    int write_count = 0, write_count_mem;
 
     /* 1. Allocate target and copy opts there */
     target = calloc(1, sizeof(Ecma119Image));
@@ -1172,6 +1382,18 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
     target->vol_effective_time = opts->vol_effective_time;
     strcpy(target->vol_uuid, opts->vol_uuid);
 
+    /* TWINTREE: */
+    target->partition_offset = opts->partition_offset;
+    target->partition_secs_per_head = opts->partition_secs_per_head;
+    target->partition_heads_per_cyl = opts->partition_heads_per_cyl;
+    target->eff_partition_offset = 0;
+    target->partition_root = NULL;
+    target->partition_l_table_pos = 0;
+    target->partition_m_table_pos = 0;
+    target->j_part_root = NULL;
+    target->j_part_l_path_table_pos = 0;
+    target->j_part_m_path_table_pos = 0;
+
     target->input_charset = strdup(iso_get_local_charset(0));
     if (target->input_charset == NULL) {
         ret = ISO_OUT_OF_MEM;
@@ -1203,7 +1425,7 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
     target->checksum_array_pos = 0;
     target->checksum_range_start = 0;
     target->checksum_range_size = 0;
-    target->opts_overwrite = 0;
+    target->opts_overwrite = NULL;
 
     /*
      * 2. Based on those options, create needed writers: iso, joliet...
@@ -1215,6 +1437,13 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
      */
     target->curblock = target->ms_block + 16;
 
+    if (opts->overwrite != NULL && target->ms_block != 0 &&
+        target->ms_block < target->partition_offset + 32) {
+        /* TWINTREE: not enough room for superblock relocation */
+        ret = ISO_OVWRT_MS_TOO_SMALL;
+        goto target_cleanup;
+    }
+
     /* the number of writers is dependent of the extensions */
     nwriters = 1 + 1 + 1; /* ECMA-119 + padding + files */
 
@@ -1306,6 +1535,37 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
         if (ret < 0)
             goto target_cleanup;
     }
+    
+    if (target->partition_offset > 0) {
+        /* >>> TWINTREE: After volume descriptors and superblock tag are
+                         accounted for: account for second volset */
+
+        if (target->ms_block + target->partition_offset + 16
+            < target->curblock) {
+            /* TWINTREE: Overflow of partition system area */
+            ret = ISO_PART_OFFST_TOO_SMALL;
+            goto target_cleanup;
+        }
+        target->curblock = target->ms_block + target->partition_offset + 16;
+
+        /* TWINTREE: Account for partition tree volume descriptors */
+        for (i = 0; i < target->nwriters; ++i) {
+            /* Not all writers have an entry in the partition
+               volume descriptor set.
+            */
+            writer = target->writers[i];
+            /* >>> TWINTREE: Enhance ISO1999 writer and add it here */
+            if(writer->write_vol_desc != ecma119_writer_write_vol_desc &&
+               writer->write_vol_desc != joliet_writer_write_vol_desc)
+        continue;
+            target->curblock++;
+        }
+        target->curblock++; /* + Terminator */
+
+        /* >>> TWINTREE: eventually later : second superblock checksum tag */;
+
+    }
+
 
     /*
      * 3.
@@ -1345,13 +1605,54 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
 #endif /* Libisofs_patch_ticket_145 */
 
     /* create the ring buffer */
+    if (opts->overwrite != NULL &&
+        opts->fifo_size / 2048 < 32 + target->partition_offset) {
+        /* TWINTREE:
+           The ring buffer must be large enough to take opts->overwrite
+        */
+        ret = ISO_OVWRT_FIFO_TOO_SMALL;
+    }
     ret = iso_ring_buffer_new(opts->fifo_size, &target->buffer);
     if (ret < 0) {
         goto target_cleanup;
     }
 
     /* check if we need to provide a copy of volume descriptors */
-    if (opts->overwrite) {
+    if (opts->overwrite != NULL) {
+
+        /* >>> TWINTREE: >>>
+           opts->overwrite must be larger by partion_offset
+           This storage is provided by the application.
+        */
+
+
+#ifdef Libisofs_twintreE
+
+        /*
+         * In the PVM to be written in the 16th sector of the disc, we
+         * need to specify the full size.
+         */
+        target->vol_space_size = target->curblock;
+
+        /* System area and volume descriptors */
+        target->opts_overwrite = (char *) opts->overwrite;
+        ret = write_head_part1(target, &write_count, 1 | 2);
+        target->opts_overwrite = NULL;
+        if (ret < 0)
+            goto target_cleanup;
+
+        /* copy the volume descriptors to the overwrite buffer... */
+        voldesc_size *= BLOCK_SIZE;
+        ret = iso_ring_buffer_read(target->buffer, opts->overwrite,
+                                   write_count * BLOCK_SIZE);
+        if (ret < 0) {
+            iso_msg_debug(target->image->id,
+                          "Error reading overwrite volume descriptors");
+            goto target_cleanup;
+        }
+
+#else /* Libisofs_twintreE */
+
         /*
          * Get a copy of the volume descriptors to be written in a DVD+RW
          * disc
@@ -1378,7 +1679,7 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
             }
         }
 
-        /* write the system area */
+        /* write the system area to the start of the overwrite buffer */
         ret = iso_write_system_area(target, opts->overwrite);
         if (ret < 0) {
             iso_msg_debug(target->image->id,
@@ -1386,11 +1687,9 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
             goto target_cleanup;
         }
 
-        /* skip the first 16 blocks (system area) */
+        /* copy the volume descriptors to the overwrite buffer... */
         buf = opts->overwrite + 16 * BLOCK_SIZE;
         voldesc_size *= BLOCK_SIZE;
-
-        /* copy the volume descriptors to the overwrite buffer... */
         ret = iso_ring_buffer_read(target->buffer, buf, voldesc_size);
         if (ret < 0) {
             iso_msg_debug(target->image->id,
@@ -1405,6 +1704,11 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
         memcpy(vol->std_identifier, "CD001", 5);
         vol->vol_desc_version[0] = 1;
 
+        write_count = voldesc_size / BLOCK_SIZE + 16;
+        write_count_mem= write_count;
+
+#endif /* ! Libisofs_twintreE */
+
         /* Write relocated superblock checksum tag */
         tag_pos = voldesc_size / BLOCK_SIZE + 16 + 1;
         if (target->md5_session_checksum) {
@@ -1422,9 +1726,10 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
                     goto target_cleanup;
             }
             tag_pos++;
+            write_count++;
         } 
 
-        /* Clean out eventual checksum tags */
+        /* Clean out eventual obsolete checksum tags */
         for (i = tag_pos; i < 32; i++) {
             int tag_type;
             uint32_t pos, range_start, range_size, next_tag;
@@ -1436,6 +1741,22 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
             if (ret > 0)
                 opts->overwrite[i * 2048] = 0;
         }
+
+        /* TWINTREE: Write second set of volume descriptors */
+        write_count_mem= write_count;
+        ret = write_head_part2(target, &write_count, 0);
+        if (ret < 0)
+            goto target_cleanup;
+
+        /* TWINTREE: read written data into opts->overwrite */
+        ret = iso_ring_buffer_read(target->buffer,
+                                opts->overwrite + write_count_mem * BLOCK_SIZE,
+                                (write_count - write_count_mem) * BLOCK_SIZE);
+        if (ret < 0) {
+            iso_msg_debug(target->image->id,
+                          "Error reading overwrite volume descriptors");
+            goto target_cleanup;
+        }
     }
 
     /*
@@ -1702,7 +2023,10 @@ int iso_write_opts_new(IsoWriteOpts **opts, int profile)
     wopts->vol_modification_time = 0;
     wopts->vol_expiration_time = 0;
     wopts->vol_effective_time = 0;
-    wopts->vol_uuid[0]= 0;
+    wopts->vol_uuid[0] = 0;
+    wopts->partition_offset = 0;
+    wopts->partition_secs_per_head = 0;
+    wopts->partition_heads_per_cyl = 0;
 
     *opts = wopts;
     return ISO_SUCCESS;
@@ -2130,3 +2454,15 @@ int iso_write_opts_set_pvd_times(IsoWriteOpts *opts,
     return ISO_SUCCESS;
 }
 
+int iso_write_opts_set_part_offset(IsoWriteOpts *opts,
+                                   uint32_t block_offset_2k,
+                                   int secs_512_per_head, int heads_per_cyl)
+{
+    if (block_offset_2k > 0 && block_offset_2k < 16)
+        return ISO_PART_OFFST_TOO_SMALL;
+    opts->partition_offset = block_offset_2k;
+    opts->partition_secs_per_head = secs_512_per_head;
+    opts->partition_heads_per_cyl = heads_per_cyl;
+    return ISO_SUCCESS;
+}
+                                  

libisofs/ecma119.h

@@ -314,6 +314,15 @@ struct iso_write_opts {
      */
     char vol_uuid[17];
 
+    /* TWINTREE: The number of unclaimed 2K blocks before
+                 start of partition 1 as of the MBR in system area.
+                 Must be 0 or >= 16. (Actually >= #voldescr + checksum tag) */
+    uint32_t partition_offset;
+    /* TWINTREE: Partition table parameter: 1 to 63, 0= disabled/default */
+    int partition_secs_per_head;
+    /* TWINTREE: 1 to 255, 0= disabled/default */
+    int partition_heads_per_cyl;
+
 };
 
 typedef struct ecma119_image Ecma119Image;
@@ -404,8 +413,9 @@ struct ecma119_image
     off_t total_size;
     uint32_t vol_space_size;
 
-    /* Bytes already written, just for progress notification */
+    /* Bytes already written to image output */
     off_t bytes_written;
+    /* just for progress notification */
     int percent_written;
 
     /*
@@ -531,6 +541,30 @@ struct ecma119_image
      * by unconverted string with timezone 0
      */
     char vol_uuid[17];
+
+    /* TWINTREE: The number of unclaimed 2K blocks before
+                 start of partition 1 as of the MBR in system area. */
+    uint32_t partition_offset;
+    /* TWINTREE: Partition table parameter: 1 to 63, 0= disabled/default */
+    int partition_secs_per_head;
+    /* TWINTREE: 1 to 255, 0= disabled/default */
+    int partition_heads_per_cyl;
+
+    /* TWINTREE: The currently applicable LBA offset. To be subtracted from
+                 any LBA that is mentioned in volume descriptors or
+                 ECMA-119 tree. Either 0 or .partition_offset */
+    uint32_t eff_partition_offset;
+
+    /* TWINTREE: The second ECMA-119 directory tree and path tables */
+    Ecma119Node *partition_root;
+    uint32_t partition_l_table_pos;
+    uint32_t partition_m_table_pos;
+
+    /* TWINTREE: The second Joliet directory tree and path tables */
+    JolietNode *j_part_root;
+    uint32_t j_part_l_path_table_pos;
+    uint32_t j_part_m_path_table_pos;
+
 };
 
 #define BP(a,b) [(b) - (a) + 1]

libisofs/ecma119_tree.c

@@ -714,6 +714,7 @@ static
 int mangle_tree(Ecma119Image *img, int recurse)
 {
     int max_file, max_dir;
+    Ecma119Node *root;
 
     if (img->max_37_char_filenames) {
         max_file = max_dir = 37;
@@ -723,10 +724,16 @@ int mangle_tree(Ecma119Image *img, int recurse)
     } else {
         max_file = max_dir = 31;
     }
-    if (recurse) {
+    /* TWINTREE: */
-        return mangle_dir(img, img->root, max_file, max_dir);
+    if (img->eff_partition_offset > 0) {
+        root = img->partition_root;
     } else {
-        return mangle_single_dir(img, img->root, max_file, max_dir);
+        root = img->root;
+    }
+    if (recurse) {
+        return mangle_dir(img, root, max_file, max_dir);
+    } else {
+        return mangle_single_dir(img, root, max_file, max_dir);
     }
 }
 
@@ -844,11 +851,18 @@ int reorder_tree(Ecma119Image *img, Ecma119Node *dir, int level, int pathlen)
 {
     int ret;
     size_t max_path;
+    Ecma119Node *root;
 
     max_path = pathlen + 1 + max_child_name_len(dir);
 
     if (level > 8 || max_path > 255) {
-        ret = reparent(dir, img->root);
+        /* TWINTREE: */
+        if (img->eff_partition_offset > 0) {
+            root = img->partition_root;
+        } else {
+            root = img->root;
+        }
+        ret = reparent(dir, root);
         if (ret < 0) {
             return ret;
         }
@@ -1055,10 +1069,16 @@ int ecma119_tree_create(Ecma119Image *img)
         }
         return ret;
     }
-    img->root = root;
+    /* TWINTREE: */
+    if (img->eff_partition_offset > 0) {
+        img->partition_root = root;
+    } else {
+        img->root = root;
+    }
 
     iso_msg_debug(img->image->id, "Matching hardlinks...");
-    ret = match_hardlinks(img, img->root, 0);
+    /* TWINTREE: img->root -> root */
+    ret = match_hardlinks(img, root, 0);
     if (ret < 0) {
         return ret;
     }
@@ -1075,7 +1095,8 @@ int ecma119_tree_create(Ecma119Image *img)
     if (img->rockridge && !img->allow_deep_paths) {
 
         /* reorder the tree, acording to RRIP, 4.1.5 */
-        ret = reorder_tree(img, img->root, 1, 0);
+        /* TWINTREE: img->root -> root */
+        ret = reorder_tree(img, root, 1, 0);
         if (ret < 0) {
             return ret;
         }

libisofs/eltorito.c

@@ -942,7 +942,7 @@ int catalog_stream_new(Ecma119Image *target, IsoStream **stream)
         return ISO_OUT_OF_MEM;
     }
     data = calloc(1, sizeof(struct catalog_stream));
-    if (str == NULL) {
+    if (data == NULL) {
         free(str);
         return ISO_OUT_OF_MEM;
     }
@@ -1107,6 +1107,7 @@ int eltorito_writer_compute_data_blocks(IsoImageWriter *writer)
         }
         ret = iso_stream_open(original);
         if (ret < 0) {
+            free(buf);
             return ret;
         }
         ret = iso_stream_read(original, buf, size);
@@ -1157,7 +1158,10 @@ int eltorito_writer_write_vol_desc(IsoImageWriter *writer)
     memcpy(vol.std_identifier, "CD001", 5);
     vol.vol_desc_version[0] = 1;
     memcpy(vol.boot_sys_id, "EL TORITO SPECIFICATION", 23);
-    iso_lsb(vol.boot_catalog, t->cat->sections[0].block, 4);
+
+    /* TWINTREE:  t->cat->sections[0].block - t->eff_partition_offset */
+    iso_lsb(vol.boot_catalog,
+            t->cat->sections[0].block - t->eff_partition_offset, 4);
 
     return iso_write(t, &vol, sizeof(struct ecma119_boot_rec_vol_desc));
 }

libisofs/joliet.c

@@ -556,17 +556,20 @@ int joliet_tree_create(Ecma119Image *t)
     }
 
     /* the Joliet tree is stored in Ecma119Image target */
-    t->joliet_root = root;
+    /* TWINTREE: */
+    if (t->eff_partition_offset > 0) {
+        t->j_part_root = root;
+    } else {
+        t->joliet_root = root;
+    }
 
     iso_msg_debug(t->image->id, "Sorting the Joliet tree...");
     sort_tree(root);
 
     iso_msg_debug(t->image->id, "Mangling Joliet names...");
-    ret = mangle_tree(t, t->joliet_root);
+    ret = mangle_tree(t, root);
-    if (ret < 0) {
+    if (ret < 0)
         return ret;
-    }
-
     return ISO_SUCCESS;
 }
 
@@ -673,6 +676,7 @@ int joliet_writer_compute_data_blocks(IsoImageWriter *writer)
 {
     Ecma119Image *t;
     uint32_t path_table_size;
+    size_t ndirs;
 
     if (writer == NULL) {
         return ISO_OUT_OF_MEM;
@@ -696,6 +700,24 @@ int joliet_writer_compute_data_blocks(IsoImageWriter *writer)
     t->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
     t->joliet_path_table_size = path_table_size;
 
+    if (t->partition_offset > 0) {
+        /* TWINTREE: take into respect second directory tree */
+        ndirs = t->joliet_ndirs;
+        t->joliet_ndirs = 0;
+        calc_dir_pos(t, t->j_part_root);
+        if (t->joliet_ndirs != ndirs) {
+            iso_msg_submit(t->image->id, ISO_ASSERT_FAILURE, 0,
+                    "Number of directories differs in Joliet partiton_tree");
+            return ISO_ASSERT_FAILURE;
+        }
+        /* TWINTREE: take into respect second set of path tables */
+        path_table_size = calc_path_table_size(t->j_part_root);
+        t->j_part_l_path_table_pos = t->curblock;
+        t->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
+        t->j_part_m_path_table_pos = t->curblock;
+        t->curblock += DIV_UP(path_table_size, BLOCK_SIZE);
+    }
+
     return ISO_SUCCESS;
 }
 
@@ -758,7 +780,8 @@ void write_one_dir_record(Ecma119Image *t, JolietNode *node, int file_id,
         node = node->parent;
 
     rec->len_dr[0] = len_dr;
-    iso_bb(rec->block, block, 4);
+    /* TWINTREE: - t->eff_partition_offset */
+    iso_bb(rec->block, block - t->eff_partition_offset, 4);
     iso_bb(rec->length, len, 4);
     iso_datetime_7(rec->recording_time, t->now, t->always_gmt);
     rec->flags[0] = ((node->type == JOLIET_DIR) ? 2 : 0) | (multi_extend ? 0x80 : 0);
@@ -794,7 +817,6 @@ void ucsncpy_pad(uint16_t *dest, const uint16_t *src, size_t max)
     }
 }
 
-static
 int joliet_writer_write_vol_desc(IsoImageWriter *writer)
 {
     IsoImage *image;
@@ -836,15 +858,27 @@ int joliet_writer_write_vol_desc(IsoImageWriter *writer)
     /* make use of UCS-2 Level 3 */
     memcpy(vol.esc_sequences, "%/E", 3);
 
-    iso_bb(vol.vol_space_size, t->vol_space_size, 4);
+    /* TWINTREE: - t->eff_partition_offset */
+    iso_bb(vol.vol_space_size, t->vol_space_size  - t->eff_partition_offset,
+           4);
+
     iso_bb(vol.vol_set_size, (uint32_t) 1, 2);
     iso_bb(vol.vol_seq_number, (uint32_t) 1, 2);
     iso_bb(vol.block_size, (uint32_t) BLOCK_SIZE, 2);
     iso_bb(vol.path_table_size, t->joliet_path_table_size, 4);
-    iso_lsb(vol.l_path_table_pos, t->joliet_l_path_table_pos, 4);
-    iso_msb(vol.m_path_table_pos, t->joliet_m_path_table_pos, 4);
 
-    write_one_dir_record(t, t->joliet_root, 0, vol.root_dir_record, 1, 0);
+    if (t->eff_partition_offset > 0) {
+        /* TWINTREE: point to second tables and second root */
+        iso_lsb(vol.l_path_table_pos,
+                t->j_part_l_path_table_pos - t->eff_partition_offset, 4);
+        iso_msb(vol.m_path_table_pos,
+                t->j_part_m_path_table_pos - t->eff_partition_offset, 4);
+        write_one_dir_record(t, t->j_part_root, 0, vol.root_dir_record, 1, 0);
+    } else {
+        iso_lsb(vol.l_path_table_pos, t->joliet_l_path_table_pos, 4);
+        iso_msb(vol.m_path_table_pos, t->joliet_m_path_table_pos, 4);
+        write_one_dir_record(t, t->joliet_root, 0, vol.root_dir_record, 1, 0);
+    }
 
     ucsncpy_pad((uint16_t*)vol.vol_set_id, volset_id, 128);
     ucsncpy_pad((uint16_t*)vol.publisher_id, pub_id, 128);
@@ -984,7 +1018,9 @@ int write_path_table(Ecma119Image *t, JolietNode **pathlist, int l_type)
         rec = (struct ecma119_path_table_record*) buf;
         rec->len_di[0] = dir->parent ? (uint8_t) ucslen(dir->name) * 2 : 1;
         rec->len_xa[0] = 0;
-        write_int(rec->block, dir->info.dir->block, 4);
+        /* TWINTREE: - t->eff_partition_offset */
+        write_int(rec->block, dir->info.dir->block - t->eff_partition_offset,
+                  4);
         write_int(rec->parent, parent + 1, 2);
         if (dir->parent) {
             memcpy(rec->dir_id, dir->name, rec->len_di[0]);
@@ -1023,7 +1059,13 @@ int write_path_tables(Ecma119Image *t)
     if (pathlist == NULL) {
         return ISO_OUT_OF_MEM;
     }
-    pathlist[0] = t->joliet_root;
+
+    /* TWINTREE: t->partition_root */
+    if (t->eff_partition_offset > 0) {
+        pathlist[0] = t->j_part_root;
+    } else {
+        pathlist[0] = t->joliet_root;
+    }
     cur = 1;
 
     for (i = 0; i < t->joliet_ndirs; i++) {
@@ -1051,18 +1093,22 @@ int write_path_tables(Ecma119Image *t)
 }
 
 static
-int joliet_writer_write_data(IsoImageWriter *writer)
+int joliet_writer_write_dirs(IsoImageWriter *writer)
 {
     int ret;
     Ecma119Image *t;
+    JolietNode *root;
 
-    if (writer == NULL) {
-        return ISO_NULL_POINTER;
-    }
     t = writer->target;
 
     /* first of all, we write the directory structure */
-    ret = write_dirs(t, t->joliet_root);
+    /* TWINTREE: t->root -> root */
+    if (t->eff_partition_offset > 0) {
+        root = t->j_part_root;
+    } else {
+        root = t->joliet_root;
+    }
+    ret = write_dirs(t, root);
     if (ret < 0) {
         return ret;
     }
@@ -1073,12 +1119,41 @@ int joliet_writer_write_data(IsoImageWriter *writer)
     return ret;
 }
 
+static
+int joliet_writer_write_data(IsoImageWriter *writer)
+{
+    int ret;
+    Ecma119Image *t;
+
+    if (writer == NULL) {
+        return ISO_NULL_POINTER;
+    }
+    t = writer->target;
+
+    ret = joliet_writer_write_dirs(writer);
+    if (ret < 0)
+        return ret;
+
+    if (t->partition_offset > 0) {
+        /* TWINTREE: */
+        t->eff_partition_offset = t->partition_offset;
+        ret = joliet_writer_write_dirs(writer);
+        t->eff_partition_offset = 0;
+        if (ret < 0)
+            return ret;
+    }
+    return ISO_SUCCESS;
+}
+
 static
 int joliet_writer_free_data(IsoImageWriter *writer)
 {
     /* free the Joliet tree */
     Ecma119Image *t = writer->target;
     joliet_node_free(t->joliet_root);
+    if (t->j_part_root != NULL)
+        joliet_node_free(t->j_part_root);
+    t->j_part_root = NULL;
     return ISO_SUCCESS;
 }
 
@@ -1109,6 +1184,17 @@ int joliet_writer_create(Ecma119Image *target)
     /* add this writer to image */
     target->writers[target->nwriters++] = writer;
 
+   /* TWINTREE: */
+    if(target->partition_offset > 0) {
+        /* Create second tree */
+        target->eff_partition_offset = target->partition_offset;
+        ret = joliet_tree_create(target);
+        if (ret < 0) {
+            return ret;
+        }
+        target->eff_partition_offset = 0;
+    }
+
     /* we need the volume descriptor */
     target->curblock++;
     return ISO_SUCCESS;

libisofs/joliet.h

@@ -54,4 +54,10 @@ struct joliet_node
  */
 int joliet_writer_create(Ecma119Image *target);
 
+
+/* TWINTREE: Not to be called but only for comparison with target->writers[i]
+*/
+int joliet_writer_write_vol_desc(IsoImageWriter *writer);
+
+
 #endif /* LIBISO_JOLIET_H */

libisofs/libisofs.h

@@ -1693,9 +1693,12 @@ int iso_write_opts_set_ms_block(IsoWriteOpts *opts, uint32_t ms_block);
  * - Together with iso_write_opts_set_appendable(opts, 0) the buffer allows
  *   to write the first session on overwriteable media to start addresses
  *   other than 0.
+ *   This address must not be smaller than 32 blocks plus the eventual
+ *   partition offset as defined by iso_write_opts_set_part_offset().
  *   libisoburn in most cases writes the first session on overwriteable media
- *   and disk files to LBA 32 in order to preserve its descriptors from the
+ *   and disk files to LBA (32 + partition_offset) in order to preserve its
- *   subsequent overwriting by the descriptor buffer of later sessions.
+ *   descriptors from the subsequent overwriting by the descriptor buffer of
+ *   later sessions.
  *
  * @param opts
  *      The option set to be manipulated.
@@ -1713,7 +1716,7 @@ int iso_write_opts_set_ms_block(IsoWriteOpts *opts, uint32_t ms_block);
 int iso_write_opts_set_overwrite_buf(IsoWriteOpts *opts, uint8_t *overwrite);
 
 /**
- * Set the size, in number of blocks, of the FIFO buffer used between the
+ * Set the size, in number of blocks, of the ring buffer used between the
  * writer thread and the burn_source. You have to provide at least a 32
  * blocks buffer. Default value is set to 2MB, if that is ok for you, you
  * don't need to call this function.
@@ -1761,6 +1764,8 @@ int iso_write_opts_set_system_area(IsoWriteOpts *opts, char data[32768],
  * Explicitely set the four timestamps of the emerging Primary Volume
  * Descriptor. Default with all parameters is 0.
  * ECMA-119 defines them as:
+ * @param opts
+ *        The option set to be manipulated.
  * @param vol_creation_time
  *        When "the information in the volume was created."
  *        A value of 0 means that the timepoint of write start is to be used.
@@ -1782,6 +1787,8 @@ int iso_write_opts_set_system_area(IsoWriteOpts *opts, char data[32768],
  *        is fully predictable and free of timezone pitfalls.
  *        It should express a reasonable time in form  YYYYMMDDhhmmsscc
  *        E.g.:  "2010040711405800" = 7 Apr 2010 11:40:58 (+0 centiseconds)
+ * @return
+ *        ISO_SUCCESS or error
  *
  * @since 0.6.30
  */
@@ -1791,6 +1798,44 @@ int iso_write_opts_set_pvd_times(IsoWriteOpts *opts,
                         char *vol_uuid);
 
 
+/* CAUTION : Not yet completely implemented for checksums in the second tree
+ *           set and not yet tested for multi-session with overwrite buffer. 
+ *           Already usable for single session including bootability and
+ *           Joliet directory tree.
+ *
+ * Control production of a second set of volume descriptors (superblock)
+ * and directory trees, together with a partition table entry in the MBR which
+ * has non-zero start address.
+ * The second volume descriptor set and trees will allow to mount the ISO image
+ * at the start of the first partition, while it is still possible to mount it
+ * via the normal first volume descriptor set and tree at the start of the
+ * image resp. storage device.
+ * This makes few sense on optical media. But on USB sticks it creates a
+ * conventional partition table which makes it mountable on e.g. Linux via
+ * /dev/sdb and /dev/sdb1 alike.
+ *
+ * @param opts
+ *        The option set to be manipulated.
+ * @param block_offset_2k
+ *        The offset of the partition start relative to device start.
+ *        This is counted in 2 kB blocks. The partition table will show the
+ *        according number of 512 byte sectors.
+ *        Default is 0 which causes no second set and trees.
+ *        If it is not 0 then it must not be smaller than 16.
+ * @param secs_512_per_head
+ *        Number of 512 byte sectors per head. 1 to 63. 0=automatic.
+ * @param heads_per_cyl
+ *        Number of heads per cylinder. 1 to 255. 0=automatic.
+ * @return
+ *        ISO_SUCCESS or error
+ *
+ * @since 0.6.36
+ */
+int iso_write_opts_set_part_offset(IsoWriteOpts *opts,
+                                   uint32_t block_offset_2k,
+                                   int secs_512_per_head, int heads_per_cyl);
+
+
 /**
  * Inquire the start address of the file data blocks after having used
  * IsoWriteOpts with iso_image_create_burn_source().
@@ -6071,8 +6116,35 @@ int iso_md5_match(char first_md5[16], char second_md5[16]);
 */
 #define ISO_SCDBACKUP_TAG_NOT_0   0xD030FE99
 
+/**
+ * The setting of iso_write_opts_set_ms_block() leaves not enough room
+ * for the prescibed size of iso_write_opts_set_overwrite_buf().
+ * (FAILURE, HIGH, -360)
+ * @since 0.6.36
+ */
+#define ISO_OVWRT_MS_TOO_SMALL    0xE830FE98
 
-/* ! PLACE NEW ERROR CODES HERE ! */
+/**
+ * The partition offset is not 0 and leaves not not enough room for
+ * system area, volume descriptors, and checksum tags of the first tree.
+ * (FAILURE, HIGH, -361)
+ */
+#define ISO_PART_OFFST_TOO_SMALL   0xE830FE97
+
+/**
+ * The ring buffer is smaller than 64 kB + partition offset.
+ * (FAILURE, HIGH, -362)
+ */
+#define ISO_OVWRT_FIFO_TOO_SMALL   0xE830FE96
+
+
+/* Internal developer note: 
+   Place new error codes directly above this comment. 
+   Newly introduced errors must get a message entry in
+   libisofs/message.c, function iso_error_to_msg()
+*/
+
+/* ! PLACE NEW ERROR CODES ABOVE. NOT AFTER THIS LINE ! */
 
 
 /** Read error occured with IsoDataSource (SORRY,HIGH, -513) */
@@ -6088,7 +6160,7 @@ int iso_md5_match(char first_md5[16], char second_md5[16]);
 #define ISO_DATA_SOURCE_FATAL     0xF030FCFF
 
 
-/* ! PLACE NEW ERROR CODES ABOVE. NOT HERE ! */
+/* ! PLACE NEW ERROR CODES SEVERAL LINES ABOVE. NOT HERE ! */
 
 
 /* ------------------------------------------------------------------------- */

libisofs/libisofs.ver

@@ -272,6 +272,7 @@ iso_write_opts_set_no_force_dots;
 iso_write_opts_set_omit_version_numbers;
 iso_write_opts_set_output_charset;
 iso_write_opts_set_overwrite_buf;
+iso_write_opts_set_part_offset;
 iso_write_opts_set_pvd_times;
 iso_write_opts_set_record_md5;
 iso_write_opts_set_relaxed_vol_atts;

libisofs/messages.c

@@ -286,6 +286,12 @@ const char *iso_error_to_msg(int errcode)
         return "Session does not start at LBA 0. scdbackup checksum tag not written.";
     case ISO_BOOT_NO_CATALOG:
         return "No boot catalog created yet";
+    case ISO_OVWRT_MS_TOO_SMALL:
+        return "Multi-session offset too small for overwrite buffer";
+    case ISO_PART_OFFST_TOO_SMALL:
+        return "Partition offset too small for first tree root.";
+    case ISO_OVWRT_FIFO_TOO_SMALL:
+        return "The ring buffer is too small for overwrite buffer";
     default:
         return "Unknown error";
     }

libisofs/rockridge.c

@@ -184,7 +184,9 @@ int rrip_add_PL(Ecma119Image *t, Ecma119Node *n, struct susp_info *susp)
     PL[3] = 1;
 
     /* write the location of the real parent, already computed */
-    iso_bb(&PL[4], n->info.dir->real_parent->info.dir->block, 4);
+    /* TWINTREE: - t->eff_partition_offset */
+    iso_bb(&PL[4],
+       n->info.dir->real_parent->info.dir->block - t->eff_partition_offset, 4);
     return susp_append(t, susp, PL);
 }
 
@@ -277,7 +279,9 @@ int rrip_add_CL(Ecma119Image *t, Ecma119Node *n, struct susp_info *susp)
     CL[1] = 'L';
     CL[2] = 12;
     CL[3] = 1;
-    iso_bb(&CL[4], n->info.real_me->info.dir->block, 4);
+    /* TWINTREE: - t->eff_partition_offset */
+    iso_bb(&CL[4], n->info.real_me->info.dir->block - t->eff_partition_offset,
+           4);
     return susp_append(t, susp, CL);
 }
 
@@ -697,7 +701,9 @@ int susp_add_CE(Ecma119Image *t, size_t ce_len, struct susp_info *susp)
     CE[1] = 'E';
     CE[2] = 28;
     CE[3] = 1;
-    iso_bb(&CE[4], susp->ce_block, 4);
+
+    /* TWINTREE: susp->ce_block - t->eff_partition_offset */
+    iso_bb(&CE[4], susp->ce_block - t->eff_partition_offset, 4);
     iso_bb(&CE[12], susp->ce_len, 4);
     iso_bb(&CE[20], (uint32_t) ce_len, 4);
 

libisofs/system_area.c

@@ -32,12 +32,42 @@ int make_isohybrid_mbr(int bin_lba, int *img_blocks, char *mbr, int flag);
  * Be cautious with changing parameters. Only few combinations are tested.
  *
  */
-int make_isolinux_mbr(int32_t *img_blocks, uint32_t boot_lba,
+int make_isolinux_mbr(uint32_t *img_blocks, uint32_t boot_lba,
                       uint32_t mbr_id, int head_count, int sector_count,
                       int part_offset, int part_number, int fs_type,
                       uint8_t *buf, int flag);
 
 
+/*
+ * @param flag bit0= img_blocks is start address rather than end address:
+                     do not subtract 1
+ */
+static
+void iso_compute_cyl_head_sec(uint32_t *img_blocks, int hpc, int sph,
+                              uint32_t *end_lba, uint32_t *end_sec,
+                              uint32_t *end_head, uint32_t *end_cyl, int flag)
+{
+    uint32_t secs;
+
+    /* Partition table unit is 512 bytes per sector, ECMA-119 unit is 2048 */
+    if (*img_blocks >= 0x40000000)
+      *img_blocks = 0x40000000 - 1;        /* truncate rather than roll over */
+    if (flag & 1)
+        secs = *end_lba = *img_blocks * 4;            /* first valid 512-lba */
+    else
+        secs = *end_lba = *img_blocks * 4 - 1;         /* last valid 512-lba */
+    *end_cyl = secs / (sph * hpc);
+    secs -= *end_cyl * sph * hpc;
+    *end_head = secs / sph;
+    *end_sec = secs - *end_head * sph + 1;   /* Sector count starts by 1 */
+    if (*end_cyl >= 1024) {
+        *end_cyl = 1023;
+        *end_head = hpc - 1;
+        *end_sec = sph;
+    }
+}
+
+
 /* This is the gesture of grub-mkisofs --protective-msdos-label as explained by
    Vladimir Serbinenko <phcoder@gmail.com>, 2 April 2010, on grub-devel@gnu.org
    "Currently we use first and not last entry. You need to:
@@ -53,38 +83,35 @@ int make_isolinux_mbr(int32_t *img_blocks, uint32_t boot_lba,
    should go into bytes 458-461. But with a start lba of 1, this is the
    same number.
    See also http://en.wikipedia.org/wiki/Master_boot_record
+
+   flag   bit0= do not write 0x55, 0xAA to 510,511
+          bit1= do not mark partition as bootable
 */
 static
-int make_grub_msdos_label(int img_blocks, uint8_t *buf, int flag)
+int make_grub_msdos_label(uint32_t img_blocks, uint8_t *buf, int flag)
 {
     uint8_t *wpt;
-    unsigned long end_lba, secs, end_sec, end_head, end_cyl;
+    uint32_t end_lba, end_sec, end_head, end_cyl;
     int sph = 63, hpc = 255, i;
 
-    /* Partition table unit is 512 bytes per sector, ECMA-119 unit is 2048 */
+    iso_compute_cyl_head_sec(&img_blocks, hpc, sph,
-    if (img_blocks >= 0x40000000)
+                             &end_lba, &end_sec, &end_head, &end_cyl, 0);
-      img_blocks = 0x40000000 - 1;         /* truncate rather than roll over */
-    secs = end_lba = img_blocks * 4 - 1;   /* last valid 512-lba */
-    end_cyl = secs / (sph * hpc);
-    secs -= end_cyl * sph * hpc;
-    end_head = secs / sph;
-    end_sec = secs - end_head * sph + 1;   /* Sector count starts by 1 */
-    if (end_cyl >= 1024) {
-        end_cyl = 1023;
-        end_head = hpc - 1;
-        end_sec = sph;
-    }
 
     /* 1) Zero-fill 446-510 */
     wpt = buf + 446;
     memset(wpt, 0, 64);
 
-    /* 2) Put 0x55, 0xAA into 510-512 (actually 510-511) */
+    if (!(flag & 1)) {
-    buf[510] = 0x55;
+        /* 2) Put 0x55, 0xAA into 510-512 (actually 510-511) */
-    buf[511] = 0xAA;
+        buf[510] = 0x55;
-
+        buf[511] = 0xAA;
-    /* 3) Put 0x80 (for bootable partition), */
+    }
-    *(wpt++) = 0x80;
+    if (!(flag & 2)) {
+      /* 3) Put 0x80 (for bootable partition), */
+      *(wpt++) = 0x80;
+    } else {
+      *(wpt++) = 0;
+    }
 
     /* 0, 2, 0 (C/H/S of the start), */
     *(wpt++) = 0;
@@ -120,10 +147,63 @@ int make_grub_msdos_label(int img_blocks, uint8_t *buf, int flag)
 }
 
 
+static
+int iso_offset_partition_start(uint32_t img_blocks, uint32_t partition_offset,
+                               int sph_in, int hpc_in, uint8_t *buf, int flag)
+{
+    uint8_t *wpt;
+    uint32_t end_lba, end_sec, end_head, end_cyl;
+    uint32_t start_lba, start_sec, start_head, start_cyl;
+    int sph = 63, hpc = 255, i;
+
+    if (sph_in > 0)
+      sph = sph_in;
+    if (hpc_in > 0)
+      hpc = hpc_in;
+    iso_compute_cyl_head_sec(&partition_offset, hpc, sph,
+                           &start_lba, &start_sec, &start_head, &start_cyl, 1);
+    iso_compute_cyl_head_sec(&img_blocks, hpc, sph,
+                             &end_lba, &end_sec, &end_head, &end_cyl, 0);
+    wpt = buf + 446;
+
+    wpt++;
+
+    /* C/H/S of the start */
+    *(wpt++) = start_head;
+    *(wpt++) = start_sec | ((start_cyl & 0x300) >> 2);
+    *(wpt++) = end_cyl & 0xff;
+
+    /* (partition type) */
+    wpt++;
+
+    /* 3 bytes of C/H/S end */
+    *(wpt++) = end_head;
+    *(wpt++) = end_sec | ((end_cyl & 0x300) >> 2);
+    *(wpt++) = end_cyl & 0xff;
+    
+    /* LBA start in little endian */
+    for (i = 0; i < 4; i++)
+       *(wpt++) = (start_lba >> (8 * i)) & 0xff;
+
+    /* Number of sectors in partition, little endian */
+    end_lba = end_lba - start_lba + 1;
+    for (i = 0; i < 4; i++)
+       *(wpt++) = (end_lba >> (8 * i)) & 0xff;
+
+    /* at 446-462 */
+    if (wpt - buf != 462) {
+        fprintf(stderr,
+    "libisofs: program error in iso_offset_partition_start: \"assert 462\"\n");
+        return ISO_ASSERT_FAILURE;
+    }
+    return ISO_SUCCESS;
+}
+
+
 int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
 {
-    int ret;
+    int ret, int_img_blocks;
-    int img_blocks;
+    uint32_t img_blocks;
 
     if ((t == NULL) || (buf == NULL)) {
         return ISO_NULL_POINTER;
@@ -142,8 +222,13 @@ int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
         /* Check for isolinux image with magic number of 3.72 and produce
            an MBR from our built-in template. (Deprecated since 31 Mar 2010)
         */
+        if (img_blocks < 0x80000000) {
+            int_img_blocks= img_blocks;
+        } else {
+            int_img_blocks= 0x7ffffff0;
+        }
         ret = make_isohybrid_mbr(t->bootsrc[0]->sections[0].block,
-                                 &img_blocks, (char*)buf, 0);
+                                 &int_img_blocks, (char*)buf, 0);
         if (ret != 1) {
             /* error, it should never happen */
             return ISO_ASSERT_FAILURE;
@@ -151,9 +236,9 @@ int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
         return ISO_SUCCESS;
     }
     if (t->system_area_options & 1) {
-        /* Write GRUB protective msdos label, i.e. a isimple partition table */
+        /* Write GRUB protective msdos label, i.e. a simple partition table */
         ret = make_grub_msdos_label(img_blocks, buf, 0);
-        if (ret != 1) /* error should never happen */
+        if (ret != ISO_SUCCESS) /* error should never happen */
             return ISO_ASSERT_FAILURE;
     } else if(t->system_area_options & 2) {
         /* Patch externally provided system area as isohybrid MBR */
@@ -167,6 +252,23 @@ int iso_write_system_area(Ecma119Image *t, uint8_t *buf)
                                 (uint32_t) 0, 64, 32, 0, 1, 0x17, buf, 1);
         if (ret != 1)
             return ret;
+    } else if(t->partition_offset > 0) {
+        /* Write a simple partition table. */
+        /* >>> TWINTREE: ??? Shall the partition stay marked as bootable ? */
+        ret = make_grub_msdos_label(img_blocks, buf, 2);
+        if (ret != ISO_SUCCESS) /* error should never happen */
+            return ISO_ASSERT_FAILURE;
     }
+
+    if (t->partition_offset > 0) {
+        /* TWINTREE: adjust partition table to partition offset */
+        img_blocks = t->curblock;                  /* value might be altered */
+        ret = iso_offset_partition_start(img_blocks, t->partition_offset,
+                                         t->partition_secs_per_head,
+                                         t->partition_heads_per_cyl, buf, 0);
+        if (ret != ISO_SUCCESS) /* error should never happen */
+            return ISO_ASSERT_FAILURE;
+    }
+
     return ISO_SUCCESS;
 }