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Added differencing read/write code

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This commit is contained in:
shermp
2018-12-24 18:39:51 +13:00
parent 79ba37541b
commit 90c2ce76db
1 changed files with 57 additions and 23 deletions
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80
minivhd.c
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@@ -586,8 +586,10 @@ int vhd_read_sectors(VHDMeta *vhdm, FILE *f, int offset, int nr_sectors, void *b
{
transfer_sectors = total_sectors - offset;
}
if (vhdm->type == VHD_DYNAMIC)
if (vhdm->type != VHD_FIXED)
{
VHDMeta *curr_vhdm = vhdm;
FILE *curr_f = f;
int sbsz = VHD_SECT_BM_SIZE / VHD_SECTOR_SZ;
int prev_blk = -1;
int curr_blk;
@@ -596,24 +598,50 @@ int vhd_read_sectors(VHDMeta *vhdm, FILE *f, int offset, int nr_sectors, void *b
ls = offset + (transfer_sectors - 1);
for (s = offset; s <= ls; s++)
{
curr_blk = s / vhdm->sparse_spb;
/* If the data block doesn't yet exist, fill the buffer with zero data */
if (vhdm->sparse_bat_arr[curr_blk] == VHD_SPARSE_BLK)
curr_blk = s / curr_vhdm->sparse_spb;
/* If our file is a differencing VHD, find the appropriate file
to read data from */
while(curr_vhdm->type == VHD_DIFF)
{
memset(buff_ptr, 0, VHD_SECTOR_SZ);
vhd_read_sector_bitmap(curr_vhdm, curr_f, curr_blk);
if (!VHD_TESTBIT(curr_vhdm->sparse_bitmap_arr[curr_blk].bitmap, sib))
{
curr_f = curr_vhdm->parent.f;
curr_vhdm = curr_vhdm->parent.meta;
}
else
{
break;
}
}
if (curr_vhdm->type == VHD_FIXED)
{
uint64_t addr = (uint64_t)s * VHD_SECTOR_SZ;
fseeko64(curr_f, addr, SEEK_SET);
fread(buffer, VHD_SECTOR_SZ, 1, curr_f);
}
else
{
if (curr_blk != prev_blk)
/* If the data block doesn't yet exist, fill the buffer with zero data */
if (curr_vhdm->sparse_bat_arr[curr_blk] == VHD_SPARSE_BLK)
{
sib = s % vhdm->sparse_spb;
uint32_t file_sect_offs = vhdm->sparse_bat_arr[curr_blk] + sbsz + sib;
fseeko64(f, (off64_t)file_sect_offs * VHD_SECTOR_SZ, SEEK_SET);
prev_blk = curr_blk;
memset(buff_ptr, 0, VHD_SECTOR_SZ);
}
else
{
if (curr_blk != prev_blk || vhdm->type == VHD_DIFF)
{
sib = s % curr_vhdm->sparse_spb;
uint32_t file_sect_offs = curr_vhdm->sparse_bat_arr[curr_blk] + sbsz + sib;
fseeko64(curr_f, (off64_t)file_sect_offs * VHD_SECTOR_SZ, SEEK_SET);
prev_blk = curr_blk;
}
fread(buff_ptr, VHD_SECTOR_SZ, 1, curr_f);
}
fread(buff_ptr, VHD_SECTOR_SZ, 1, f);
}
buff_ptr += VHD_SECTOR_SZ;
curr_f = f;
curr_vhdm = vhdm;
}
}
@@ -639,7 +667,7 @@ int vhd_write_sectors(VHDMeta *vhdm, FILE *f, int offset, int nr_sectors, void *
{
transfer_sectors = total_sectors - offset;
}
if (vhdm->type == VHD_DYNAMIC)
if (vhdm->type != VHD_FIXED)
{
int sbsz = VHD_SECT_BM_SIZE / VHD_SECTOR_SZ;
int prev_blk, curr_blk;
@@ -653,17 +681,7 @@ int vhd_write_sectors(VHDMeta *vhdm, FILE *f, int offset, int nr_sectors, void *
/* We need to create a data block if it does not yet exist. */
if (vhdm->sparse_bat_arr[curr_blk] == VHD_SPARSE_BLK)
{
/* If the sector to write contains all zeros, hold off on block creation and therefore
writing to file for this sector. */
if (memcmp(buff_ptr, VHD_ZERO_SECTOR, VHD_SECTOR_SZ) == 0)
{
buff_ptr += VHD_SECTOR_SZ;
continue;
}
else
{
vhd_create_blk(vhdm, f, curr_blk);
}
vhd_create_blk(vhdm, f, curr_blk);
}
if (curr_blk != prev_blk)
{
@@ -674,6 +692,22 @@ int vhd_write_sectors(VHDMeta *vhdm, FILE *f, int offset, int nr_sectors, void *
}
fwrite(buff_ptr, VHD_SECTOR_SZ, 1, f);
buff_ptr += VHD_SECTOR_SZ;
if (vhdm->type == VHD_DIFF)
{
VHD_SETBIT(vhdm->sparse_bitmap_arr[curr_blk].bitmap, sib);
}
}
if (vhdm->type == VHD_DIFF)
{
int start_blk = offset / vhdm->sparse_spb;
int end_blk = (offset + (transfer_sectors - 1)) / vhdm->sparse_spb;
int b;
for (b = start_blk; b <= end_blk; b++)
{
off64_t addr = (off64_t)vhdm->sparse_bat_arr[b] * VHD_SECTOR_SZ;
fseeko64(f, addr, SEEK_SET);
fwrite(vhdm->sparse_bitmap_arr[b].bitmap, sizeof vhdm->sparse_bitmap_arr[b].bitmap, 1, f);
}
}
}
else