LOCAL boolean open_ems_store(j_common_ptr cinfo, backing_store_ptr info, long total_bytes_needed)
{
EMScontext ctx;
/* Is EMS driver there? */
if(!jems_available())
return FALSE;
/* Get status, make sure EMS is OK */
ctx.ax = 0x4000;
jems_calldriver((EMScontext far *) & ctx);
if(HIBYTE(ctx.ax) != 0)
return FALSE;
/* Get version, must be >= 4.0 */
ctx.ax = 0x4600;
jems_calldriver((EMScontext far *) & ctx);
if(HIBYTE(ctx.ax) != 0 || LOBYTE(ctx.ax) < 0x40)
return FALSE;
/* Try to allocate requested space */
ctx.ax = 0x4300;
ctx.bx = (unsigned short)((total_bytes_needed + EMSPAGESIZE - 1L) / EMSPAGESIZE);
jems_calldriver((EMScontext far *) & ctx);
if(HIBYTE(ctx.ax) != 0)
return FALSE;
/* Succeeded, save the handle and away we go */
info->handle.ems_handle = ctx.dx;
info->read_backing_store = read_ems_store;
info->write_backing_store = write_ems_store;
info->close_backing_store = close_ems_store;
TRACEMS1(cinfo, 1, JTRC_EMS_OPEN, ctx.dx);
return TRUE; /* succeeded */
}
close_ems_store (j_common_ptr cinfo, backing_store_ptr info)
{
EMScontext ctx;
ctx.ax = 0x4500;
ctx.dx = info->handle.ems_handle;
jems_calldriver((EMScontext far *) & ctx);
TRACEMS1(cinfo, 1, JTRC_EMS_CLOSE, info->handle.ems_handle);
/* we ignore any error return from the driver */
}
METHODDEF void
close_ems_store (backing_store_ptr info)
{
EMScontext ctx;
ctx.ax = 0x4500;
ctx.dx = info->handle.ems_handle;
jems_calldriver((EMScontext far *) & ctx);
TRACEMS1(methods, 1, "Freed EMS handle %u", info->handle.ems_handle);
/* we ignore any error return from the driver */
}
METHODDEF void
write_ems_store(j_common_ptr cinfo, backing_store_ptr info, void FAR * buffer_address, long file_offset, long byte_count)
{
EMScontext ctx;
EMSspec spec;
spec.length = byte_count;
SRC_TYPE(spec) = 0;
SRC_HANDLE(spec) = 0;
SRC_PTR(spec) = buffer_address;
DST_TYPE(spec) = 1;
DST_HANDLE(spec) = info->handle.ems_handle;
DST_PAGE(spec) = (unsigned short)(file_offset / EMSPAGESIZE);
DST_OFFSET(spec) = (unsigned short)(file_offset % EMSPAGESIZE);
ctx.ds_si = (void far *)&spec;
ctx.ax = 0x5700; /* move memory region */
jems_calldriver((EMScontext far *) & ctx);
if(HIBYTE(ctx.ax) != 0)
ERREXIT(cinfo, JERR_EMS_WRITE);
}
METHODDEF void
read_ems_store (backing_store_ptr info, void FAR * buffer_address,
long file_offset, long byte_count)
{
EMScontext ctx;
EMSspec spec;
spec.length = byte_count;
SRC_TYPE(spec) = 1;
SRC_HANDLE(spec) = info->handle.ems_handle;
SRC_PAGE(spec) = (unsigned short) (file_offset / EMSPAGESIZE);
SRC_OFFSET(spec) = (unsigned short) (file_offset % EMSPAGESIZE);
DST_TYPE(spec) = 0;
DST_HANDLE(spec) = 0;
DST_PTR(spec) = buffer_address;
ctx.ds_si = (void far *) & spec;
ctx.ax = 0x5700; /* move memory region */
jems_calldriver((EMScontext far *) & ctx);
if (HIBYTE(ctx.ax) != 0)
ERREXIT(methods, "read from expanded memory failed");
}
