open_xms_store (j_common_ptr cinfo, backing_store_ptr info,
long total_bytes_needed)
{
XMScontext ctx;
/* Get address of XMS driver */
jxms_getdriver((XMSDRIVER far *) & xms_driver);
if (xms_driver == NULL)
return FALSE; /* no driver to be had */
/* Get version number, must be >= 2.00 */
ctx.ax = 0x0000;
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
if (ctx.ax < (unsigned short) 0x0200)
return FALSE;
/* Try to get space (expressed in kilobytes) */
ctx.dx = (unsigned short) ((total_bytes_needed + 1023L) >> 10);
ctx.ax = 0x0900;
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
if (ctx.ax != 1)
return FALSE;
/* Succeeded, save the handle and away we go */
info->handle.xms_handle = ctx.dx;
info->read_backing_store = read_xms_store;
info->write_backing_store = write_xms_store;
info->close_backing_store = close_xms_store;
TRACEMS1(cinfo, 1, JTRC_XMS_OPEN, ctx.dx);
return TRUE; /* succeeded */
}
write_xms_store (j_common_ptr cinfo, backing_store_ptr info,
void FAR * buffer_address,
long file_offset, long byte_count)
{
XMScontext ctx;
XMSspec spec;
char endbuffer[2];
/* The XMS driver can't cope with an odd length, so handle the last byte
* specially if byte_count is odd. We don't expect this to be common.
*/
spec.length = byte_count & (~ 1L);
spec.src_handle = 0;
spec.src.ptr = buffer_address;
spec.dst_handle = info->handle.xms_handle;
spec.dst.offset = file_offset;
ctx.ds_si = (void far *) & spec;
ctx.ax = 0x0b00; /* EMB move */
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
if (ctx.ax != 1)
ERREXIT(cinfo, JERR_XMS_WRITE);
if (ODD(byte_count)) {
read_xms_store(cinfo, info, (void FAR *) endbuffer,
file_offset + byte_count - 1L, 2L);
endbuffer[0] = ((char FAR *) buffer_address)[byte_count - 1L];
write_xms_store(cinfo, info, (void FAR *) endbuffer,
file_offset + byte_count - 1L, 2L);
}
}
METHODDEF void
read_xms_store (backing_store_ptr info, void FAR * buffer_address,
long file_offset, long byte_count)
{
XMScontext ctx;
XMSspec spec;
char endbuffer[2];
/* The XMS driver can't cope with an odd length, so handle the last byte
* specially if byte_count is odd. We don't expect this to be common.
*/
spec.length = byte_count & (~ 1L);
spec.src_handle = info->handle.xms_handle;
spec.src.offset = file_offset;
spec.dst_handle = 0;
spec.dst.ptr = buffer_address;
ctx.ds_si = (void far *) & spec;
ctx.ax = 0x0b00; /* EMB move */
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
if (ctx.ax != 1)
ERREXIT(methods, "read from extended memory failed");
if (ODD(byte_count)) {
read_xms_store(info, (void FAR *) endbuffer,
file_offset + byte_count - 1L, 2L);
((char FAR *) buffer_address)[byte_count - 1L] = endbuffer[0];
}
}
close_xms_store (j_common_ptr cinfo, backing_store_ptr info)
{
XMScontext ctx;
ctx.dx = info->handle.xms_handle;
ctx.ax = 0x0a00;
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
TRACEMS1(cinfo, 1, JTRC_XMS_CLOSE, info->handle.xms_handle);
/* we ignore any error return from the driver */
}
METHODDEF void
close_xms_store (backing_store_ptr info)
{
XMScontext ctx;
ctx.dx = info->handle.xms_handle;
ctx.ax = 0x0a00;
jxms_calldriver(xms_driver, (XMScontext far *) & ctx);
TRACEMS1(methods, 1, "Freed XMS handle %u", info->handle.xms_handle);
/* we ignore any error return from the driver */
}
