[Qemu-devel] [PULL 009/100] vvfat: introduce offset_to_bootsector, offset_to_fat and offset_to_root_dir

[Kevin Wolf <kwolf@redhat.com>]

From: Hervé Poussineau <hpoussin@reactos.org>

- offset_to_bootsector is the number of sectors up to FAT bootsector
- offset_to_fat is the number of sectors up to first File Allocation Table
- offset_to_root_dir is the number of sectors up to root directory sector

Replace first_sectors_number - 1 by offset_to_bootsector.
Replace first_sectors_number by offset_to_fat.
Replace faked_sectors by offset_to_rootdir.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 block/vvfat.c | 70 ++++++++++++++++++++++++++++++++++++-----------------------
 1 file changed, 43 insertions(+), 27 deletions(-)

diff --git a/block/vvfat.c b/block/vvfat.c
index 18d9559..88d1879 100644
--- a/block/vvfat.c
+++ b/block/vvfat.c
@@ -319,22 +319,24 @@ static void print_mapping(const struct mapping_t* mapping);
 typedef struct BDRVVVFATState {
     CoMutex lock;
     BlockDriverState* bs; /* pointer to parent */
-    unsigned int first_sectors_number; /* 1 for a single partition, 0x40 for a disk with partition table */
     unsigned char first_sectors[0x40*0x200];
 
     int fat_type; /* 16 or 32 */
     array_t fat,directory,mapping;
     char volume_label[11];
 
+    uint32_t offset_to_bootsector; /* 0 for floppy, 0x3f for disk */
+
     unsigned int cluster_size;
     unsigned int sectors_per_cluster;
     unsigned int sectors_per_fat;
     unsigned int sectors_of_root_directory;
     uint32_t last_cluster_of_root_directory;
-    unsigned int faked_sectors; /* how many sectors are faked before file data */
     uint32_t sector_count; /* total number of sectors of the partition */
     uint32_t cluster_count; /* total number of clusters of this partition */
     uint32_t max_fat_value;
+    uint32_t offset_to_fat;
+    uint32_t offset_to_root_dir;
 
     int current_fd;
     mapping_t* current_mapping;
@@ -393,15 +395,15 @@ static void init_mbr(BDRVVVFATState *s, int cyls, int heads, int secs)
     partition->attributes=0x80; /* bootable */
 
     /* LBA is used when partition is outside the CHS geometry */
-    lba  = sector2CHS(&partition->start_CHS, s->first_sectors_number - 1,
+    lba  = sector2CHS(&partition->start_CHS, s->offset_to_bootsector,
                      cyls, heads, secs);
     lba |= sector2CHS(&partition->end_CHS,   s->bs->total_sectors - 1,
                      cyls, heads, secs);
 
     /*LBA partitions are identified only by start/length_sector_long not by CHS*/
-    partition->start_sector_long  = cpu_to_le32(s->first_sectors_number - 1);
+    partition->start_sector_long  = cpu_to_le32(s->offset_to_bootsector);
     partition->length_sector_long = cpu_to_le32(s->bs->total_sectors
-                                                - s->first_sectors_number + 1);
+                                                - s->offset_to_bootsector);
 
     /* FAT12/FAT16/FAT32 */
     /* DOS uses different types when partition is LBA,
@@ -822,12 +824,12 @@ static int read_directory(BDRVVVFATState* s, int mapping_index)
 
 static inline uint32_t sector2cluster(BDRVVVFATState* s,off_t sector_num)
 {
-    return (sector_num-s->faked_sectors)/s->sectors_per_cluster;
+    return (sector_num - s->offset_to_root_dir) / s->sectors_per_cluster;
 }
 
 static inline off_t cluster2sector(BDRVVVFATState* s, uint32_t cluster_num)
 {
-    return s->faked_sectors + s->sectors_per_cluster * cluster_num;
+    return s->offset_to_root_dir + s->sectors_per_cluster * cluster_num;
 }
 
 static int init_directories(BDRVVVFATState* s,
@@ -854,6 +856,9 @@ static int init_directories(BDRVVVFATState* s,
     i = 1+s->sectors_per_cluster*0x200*8/s->fat_type;
     s->sectors_per_fat=(s->sector_count+i)/i; /* round up */
 
+    s->offset_to_fat = s->offset_to_bootsector + 1;
+    s->offset_to_root_dir = s->offset_to_fat + s->sectors_per_fat * 2;
+
     array_init(&(s->mapping),sizeof(mapping_t));
     array_init(&(s->directory),sizeof(direntry_t));
 
@@ -867,7 +872,6 @@ static int init_directories(BDRVVVFATState* s,
     /* Now build FAT, and write back information into directory */
     init_fat(s);
 
-    s->faked_sectors=s->first_sectors_number+s->sectors_per_fat*2;
     s->cluster_count=sector2cluster(s, s->sector_count);
 
     mapping = array_get_next(&(s->mapping));
@@ -945,7 +949,8 @@ static int init_directories(BDRVVVFATState* s,
 
     s->current_mapping = NULL;
 
-    bootsector=(bootsector_t*)(s->first_sectors+(s->first_sectors_number-1)*0x200);
+    bootsector = (bootsector_t *)(s->first_sectors
+                                  + s->offset_to_bootsector * 0x200);
     bootsector->jump[0]=0xeb;
     bootsector->jump[1]=0x3e;
     bootsector->jump[2]=0x90;
@@ -956,16 +961,18 @@ static int init_directories(BDRVVVFATState* s,
     bootsector->number_of_fats=0x2; /* number of FATs */
     bootsector->root_entries=cpu_to_le16(s->sectors_of_root_directory*0x10);
     bootsector->total_sectors16=s->sector_count>0xffff?0:cpu_to_le16(s->sector_count);
-    bootsector->media_type=(s->first_sectors_number>1?0xf8:0xf0); /* media descriptor (f8=hd, f0=3.5 fd)*/
+    /* media descriptor: hard disk=0xf8, floppy=0xf0 */
+    bootsector->media_type = (s->offset_to_bootsector > 0 ? 0xf8 : 0xf0);
     s->fat.pointer[0] = bootsector->media_type;
     bootsector->sectors_per_fat=cpu_to_le16(s->sectors_per_fat);
     bootsector->sectors_per_track = cpu_to_le16(secs);
     bootsector->number_of_heads = cpu_to_le16(heads);
-    bootsector->hidden_sectors=cpu_to_le32(s->first_sectors_number==1?0:0x3f);
+    bootsector->hidden_sectors = cpu_to_le32(s->offset_to_bootsector);
     bootsector->total_sectors=cpu_to_le32(s->sector_count>0xffff?s->sector_count:0);
 
     /* LATER TODO: if FAT32, this is wrong */
-    bootsector->u.fat16.drive_number=s->first_sectors_number==1?0:0x80; /* fda=0, hda=0x80 */
+    /* drive_number: fda=0, hda=0x80 */
+    bootsector->u.fat16.drive_number = s->offset_to_bootsector == 0 ? 0 : 0x80;
     bootsector->u.fat16.current_head=0;
     bootsector->u.fat16.signature=0x29;
     bootsector->u.fat16.id=cpu_to_le32(0xfabe1afd);
@@ -1122,7 +1129,6 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
             secs = s->fat_type == 12 ? 18 : 36;
             s->sectors_per_cluster = 1;
         }
-        s->first_sectors_number = 1;
         cyls = 80;
         heads = 2;
     } else {
@@ -1130,7 +1136,7 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
         if (!s->fat_type) {
             s->fat_type = 16;
         }
-        s->first_sectors_number = 0x40;
+        s->offset_to_bootsector = 0x3f;
         cyls = s->fat_type == 12 ? 64 : 1024;
         heads = 16;
         secs = 63;
@@ -1166,7 +1172,7 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
     fprintf(stderr, "vvfat %s chs %d,%d,%d\n",
             dirname, cyls, heads, secs);
 
-    s->sector_count = cyls * heads * secs - (s->first_sectors_number - 1);
+    s->sector_count = cyls * heads * secs - s->offset_to_bootsector;
 
     if (qemu_opt_get_bool(opts, "rw", false)) {
         if (!bdrv_is_read_only(bs)) {
@@ -1196,7 +1202,8 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail;
     }
 
-    s->sector_count = s->faked_sectors + s->sectors_per_cluster*s->cluster_count;
+    s->sector_count = s->offset_to_root_dir
+                    + s->sectors_per_cluster * s->cluster_count;
 
     /* Disable migration when vvfat is used rw */
     if (s->qcow) {
@@ -1212,7 +1219,7 @@ static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
         }
     }
 
-    if (s->first_sectors_number == 0x40) {
+    if (s->offset_to_bootsector > 0) {
         init_mbr(s, cyls, heads, secs);
     }
 
@@ -1425,15 +1432,24 @@ static int vvfat_read(BlockDriverState *bs, int64_t sector_num,
             }
 DLOG(fprintf(stderr, "sector %d not allocated\n", (int)sector_num));
         }
-        if(sector_num<s->faked_sectors) {
-            if(sector_num<s->first_sectors_number)
-                memcpy(buf+i*0x200,&(s->first_sectors[sector_num*0x200]),0x200);
-            else if(sector_num-s->first_sectors_number<s->sectors_per_fat)
-                memcpy(buf+i*0x200,&(s->fat.pointer[(sector_num-s->first_sectors_number)*0x200]),0x200);
-            else if(sector_num-s->first_sectors_number-s->sectors_per_fat<s->sectors_per_fat)
-                memcpy(buf+i*0x200,&(s->fat.pointer[(sector_num-s->first_sectors_number-s->sectors_per_fat)*0x200]),0x200);
+        if (sector_num < s->offset_to_root_dir) {
+            if (sector_num < s->offset_to_fat) {
+                memcpy(buf + i * 0x200,
+                       &(s->first_sectors[sector_num * 0x200]),
+                       0x200);
+            } else if (sector_num < s->offset_to_fat + s->sectors_per_fat) {
+                memcpy(buf + i * 0x200,
+                       &(s->fat.pointer[(sector_num
+                                       - s->offset_to_fat) * 0x200]),
+                       0x200);
+            } else if (sector_num < s->offset_to_root_dir) {
+                memcpy(buf + i * 0x200,
+                       &(s->fat.pointer[(sector_num - s->offset_to_fat
+                                       - s->sectors_per_fat) * 0x200]),
+                       0x200);
+            }
         } else {
-            uint32_t sector=sector_num-s->faked_sectors,
+            uint32_t sector = sector_num - s->offset_to_root_dir,
             sector_offset_in_cluster=(sector%s->sectors_per_cluster),
             cluster_num=sector/s->sectors_per_cluster;
             if(cluster_num > s->cluster_count || read_cluster(s, cluster_num) != 0) {
@@ -2045,7 +2061,7 @@ DLOG(checkpoint());
         memcpy(s->fat2, s->fat.pointer, size);
     }
     check = vvfat_read(s->bs,
-            s->first_sectors_number, s->fat2, s->sectors_per_fat);
+            s->offset_to_fat, s->fat2, s->sectors_per_fat);
     if (check) {
         fprintf(stderr, "Could not copy fat\n");
         return 0;
@@ -2864,7 +2880,7 @@ DLOG(checkpoint());
      * - do not allow to write non-ASCII filenames
      */
 
-    if (sector_num < s->first_sectors_number)
+    if (sector_num < s->offset_to_fat)
         return -1;
 
     for (i = sector2cluster(s, sector_num);
-- 
1.8.3.1