/* retrieve (part of) an object */
public LONGINT64 RetrieveObject(ChmUnitInfo ui, ref byte[] buf, LONGUINT64 addr, LONGINT64 len)
{
/* must be valid file handle */
if (_h.fd == null)
{
return((Int64)0);
}
/* starting address must be in correct range */
if (addr < 0 || addr >= ui.length)
{
return((Int64)0);
}
/* clip length */
if (addr + (ulong)len > ui.length)
{
len = (LONGINT64)(ui.length - addr);
}
/* if the file is uncompressed, it's simple */
if (ui.space == Storage.CHM_UNCOMPRESSED)
{
/* read data */
return(Storage.FetchBytes(ref _h, ref buf,
(UInt64)_h.data_offset + (UInt64)ui.start + (UInt64)addr,
len));
}
/* else if the file is compressed, it's a little trickier */
else /* ui->space == CHM_COMPRESSED */
{
Int64 swath = 0, total = 0;
UInt64 bufpos = 0;
/* if compression is not enabled for this file... */
if (!_h.compression_enabled)
{
return(total);
}
do
{
/* swill another mouthful */
swath = Lzxc.DecompressRegion(ref _h, ref buf, bufpos, ui.start + addr, len);
/* if we didn't get any... */
if (swath == 0)
{
return(total);
}
/* update stats */
total += swath;
len -= swath;
addr += (LONGUINT64)swath;
bufpos += (LONGUINT64)swath;
} while (len != 0);
return(total);
}
}
public static ChmFile Open(string filename)
{
byte[] sbuffer = new byte[256];
uint sremain;
uint sbufpos;
chmItsfHeader itsfHeader = new chmItsfHeader();
chmItspHeader itspHeader = new chmItspHeader();
ChmUnitInfo uiLzxc = new ChmUnitInfo();
chmLzxcControlData ctlData = new chmLzxcControlData();
ChmFile chmf = new ChmFile(filename);
/* allocate handle */
chmf._h.fd = null;
chmf._h.lzx_state = null;
chmf._h.cache_blocks = null;
chmf._h.cache_block_indices = null;
chmf._h.cache_num_blocks = 0;
/* open file */
chmf._h.fd = File.Open(filename, FileMode.Open, FileAccess.Read);
/* initialize mutexes, if needed */
chmf._h.mutex = new Mutex();
chmf._h.lzx_mutex = new Mutex();
chmf._h.cache_mutex = new Mutex();
/* read and verify header */
sremain = Itsf.CHM_ITSF_V3_LEN;
sbufpos = 0;
if (Storage.FetchBytes(ref chmf._h, ref sbuffer, 0, sremain) != sremain ||
!Itsf.UnmarshalItsfHeader(ref sbuffer, ref sbufpos, ref sremain, ref itsfHeader))
{
chmf.Close();
throw new InvalidDataException();
}
/* stash important values from header */
chmf._h.dir_offset = itsfHeader.dir_offset;
chmf._h.dir_len = itsfHeader.dir_len;
chmf._h.data_offset = itsfHeader.data_offset;
/* now, read and verify the directory header chunk */
sremain = Itsp.CHM_ITSP_V1_LEN;
sbufpos = 0;
if (Storage.FetchBytes(ref chmf._h, ref sbuffer,
(UInt64)itsfHeader.dir_offset, sremain) != sremain ||
!Itsp.UnmarshalItpfHeader(ref sbuffer, ref sbufpos, ref sremain, ref itspHeader))
{
chmf.Close();
throw new InvalidDataException();
}
/* grab essential information from ITSP header */
chmf._h.dir_offset += (ulong)itspHeader.header_len;
chmf._h.dir_len -= (ulong)itspHeader.header_len;
chmf._h.index_root = itspHeader.index_root;
chmf._h.index_head = itspHeader.index_head;
chmf._h.block_len = itspHeader.block_len;
/* if the index root is -1, this means we don't have any PMGI blocks.
* as a result, we must use the sole PMGL block as the index root
*/
if (chmf._h.index_root <= -1)
{
chmf._h.index_root = chmf._h.index_head;
}
/* By default, compression is enabled. */
chmf._h.compression_enabled = true;
/* prefetch most commonly needed unit infos */
if (!chmf.ResolveObject(Storage.CHMU_RESET_TABLE, ref chmf._h.rt_unit) ||
chmf._h.rt_unit.space == Storage.CHM_COMPRESSED ||
!chmf.ResolveObject(Storage.CHMU_CONTENT, ref chmf._h.cn_unit) ||
chmf._h.cn_unit.space == Storage.CHM_COMPRESSED ||
!chmf.ResolveObject(Storage.CHMU_LZXC_CONTROLDATA, ref uiLzxc) ||
uiLzxc.space == Storage.CHM_COMPRESSED)
{
chmf._h.compression_enabled = false;
}
/* read reset table info */
if (chmf._h.compression_enabled)
{
sremain = Lzxc.CHM_LZXC_RESETTABLE_V1_LEN;
sbufpos = 0; /* TODO bobc: is sbuffer actually at index 0?? */
if (chmf.RetrieveObject(chmf._h.rt_unit, ref sbuffer,
0, sremain) != sremain ||
!Lzxc.UnmarshalLzxcResetTable(ref sbuffer, ref sbufpos, ref sremain,
ref chmf._h.reset_table))
{
chmf._h.compression_enabled = false;
}
}
/* read control data */
if (chmf._h.compression_enabled)
{
sremain = (uint)uiLzxc.length;
if (uiLzxc.length > (ulong)sbuffer.Length)
{
chmf.Close();
throw new InvalidDataException();
}
sbufpos = 0; /* TODO bobc: is sbuffer actually at index 0?? */
if (chmf.RetrieveObject(uiLzxc, ref sbuffer,
0, sremain) != sremain ||
!Lzxc.UnmarshalLzxcControlData(ref sbuffer, ref sbufpos, ref sremain,
ref ctlData))
{
chmf._h.compression_enabled = false;
}
chmf._h.window_size = ctlData.windowSize;
chmf._h.reset_interval = ctlData.resetInterval;
/* Jed, Mon Jun 28: Experimentally, it appears that the reset block count */
/* must be multiplied by this formerly unknown ctrl data field in */
/* order to decompress some files. */
chmf._h.reset_blkcount = chmf._h.reset_interval /
(chmf._h.window_size / 2) *
ctlData.windowsPerReset;
}
/* initialize cache */
chmf.SetParam(CHM_PARAM_MAX_BLOCKS_CACHED, CHM_MAX_BLOCKS_CACHED);
return(chmf);
}
