forked from arti/vt1200
docs(xie): the VT1200 ROM has no DCT (JPEG) scheme -- measured
The question was whether this ROM answers "unsupported" for XieK_DCT. It does, at both layers, and it behaves exactly like an out-of-range scheme value. SetTransport (minor 20), raw wire request, a fresh bitonal photomap per scheme: PCM / G31D / G32D / G42D -> accepted DCT (4) and 5 -> BadIDChoice(14), minor_op 20 So the ROM does not even implement the reference server's IsBitonal_ rules (G42D is accepted on a 256-level photomap, where XieTransport.c would BadMatch), but it does refuse 4 and above. Export (minor 21) with the photomap's compression byte forced to each value (the server never initialises it -- it holds the heap fill 0x55, which is why harness/mame/xie_fix.lua pokes file 0x1B256): 0..3 -> pixmap 4096/4096, no X error 4 -> BadValue, nothing drawn 5 -> BadValue, nothing drawn And the ROM carries no JPEG machinery: no "JPEG"/"DCT" string, and the standard Annex K quantisation table is absent in both zigzag and natural order (no flat 8x8 either). A DCT codec carries one of those; this ROM carries none. "DDX_RENDER: unsupported compression scheme" exists in the ROM but did not fire in these runs, so it belongs to a path these probes do not reach -- recorded as an open detail rather than claimed as the explanation. Probes: xie/xiescheme.c (libXie, one scheme per connection) and xie/xie_schemes_raw.py (raw protocol, exact error codes).
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@@ -111,6 +111,69 @@ JPEG baseline/lossless (X11R6.1, two values) — but the 2.3 protocol that the
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terminal speaks has only the single Scheme-4 DCT code, with no baseline/lossless
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split and no lossless predictor field in the wire struct.
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## What THIS ROM actually does (measured, not inferred)
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Two probes were built for this (`xiescheme.c` via libXie, and
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`xie_schemes_raw.py` which speaks the wire protocol directly):
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### 1. At SetTransport (minor 20), raw request, fresh bitonal photomap each time
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```
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PCM SetTransport -> ACCEPTED
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G31D SetTransport -> ACCEPTED
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G32D SetTransport -> ACCEPTED
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G42D SetTransport -> ACCEPTED
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DCT SetTransport -> REFUSED ERROR code=14 (BadIDChoice) minor_op=20
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5 SetTransport -> REFUSED ERROR code=14 (BadIDChoice) minor_op=20
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```
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So **DCT is answered exactly like an out-of-range scheme value.** Note this is
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also evidence that the ROM does *not* implement the reference server's
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`IsBitonal_` rules: G42D is accepted even on a 256-level photomap, where
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`XieTransport.c` would answer BadMatch.
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### 2. At Export (minor 21), with the photomap's compression byte forced
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The client's `XieExport` to a depth-1 pixmap, for each value of the photomap's
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`compression_scheme` byte (`harness/mame/xie_fix.lua` pokes it at file
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`0x1B256`; the server never initialises it, so it holds the heap fill `0x55`):
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```
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scheme 0 PCM export: pixmap 4096/4096 no X error
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scheme 1 G31D export: pixmap 4096/4096 no X error
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scheme 2 G32D export: pixmap 4096/4096 no X error
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scheme 3 G42D export: pixmap 4096/4096 no X error
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scheme 4 DCT export: FAILED BadValue, minor 21
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scheme 5 (bogus) export: FAILED BadValue, minor 21
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```
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**DCT and a bogus value are treated identically; 0..3 are accepted.** So in this
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ROM the valid set is `0..3` and scheme 4 has no implementation — it is refused,
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not silently mis-decoded.
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### 3. The ROM has no JPEG machinery
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Searched `vt1200_v22.bin` (md5 `b46a3e442ccb86134d2356bd70d22fd2`):
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* no `JPEG` / `DCT` string (the only compression-related strings are
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`DDX_RENDER: unsupported compression scheme`, `error initializing scalution`
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and `5 - Scalution Test`);
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* the standard JPEG Annex K quantisation table is **absent**, in both the
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zigzag order code stores and the natural row order — and no flat 8x8 table
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either. A DCT codec carries one of these; this ROM carries none.
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`DDX_RENDER: unsupported compression scheme` exists but did **not** fire in any
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of the runs above (0 occurrences in the MAME debug log for schemes 4 and 5), so
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it belongs to a path these probes do not reach — reported as an open detail
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rather than claimed as the explanation.
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### 4. Cross-check: PCM is the only scheme that helps in practice
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The working display path uses `XieK_PCM` throughout, because the transport is
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`XieK_Tile` on a bitonal image and, per the reference rules above, that admits
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PCM only. On a depth-1 server there is no non-bitonal visual, so `XieK_DCT` is
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unreachable by protocol rule as well as unimplemented.
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## Cross-reference: the DTJ article
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`docs/dec/DTJ-1991-v03-04-bitonal-image-accelerators.pdf` — "Hardware
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@@ -136,3 +199,8 @@ DTJ Vol. 3 No. 4, Fall 1991). Reading it against the headers above:
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So the article's "image board" is the bitonal G3/G4 decompressor, and JPEG/DCT
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is the scheme XIE defines for the continuous-tone data type that the same
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protocol carries — the two correspond exactly to `XieK_G42D` and `XieK_DCT`.
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This is consistent with the measurement above: the ROM has the G3/G4 half
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(`0..3` accepted, scalution test present) and no DCT half (scheme 4 refused,
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no JPEG tables). The terminal is depth 1, so the continuous-tone data type the
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DCT scheme exists for has no visual to land on.
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@@ -0,0 +1,76 @@
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#!/usr/bin/env python3
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"""Ask the server, in raw XIE 2.3 protocol, one question:
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for each XieK_ compression scheme, does SetTransport accept it?
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It builds a fresh bitonal photomap per scheme (a photomap that already has a
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transport must match it on a second SetTransport, which would turn every later
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attempt into a BadMatch for the wrong reason) and then sends a real
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xieSetTransportReq (minor 20, 140 bytes) and prints whatever comes back.
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Usage: xie_schemes_raw.py [host]
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"""
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import os
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import struct
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import sys
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HERE = os.path.dirname(os.path.abspath(__file__))
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sys.path.insert(0, HERE)
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sys.path.insert(0, os.path.join(HERE, "evidence"))
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from probe23 import Cli, describe_all # noqa: E402
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NAMES = {0: "PCM", 1: "G31D", 2: "G32D", 3: "G42D", 4: "DCT", 5: "(5)"}
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def make_photomap(c, slot, levels=2):
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"""xieCreatePhotoReq: bitonal 64x64, 1 component, 2 levels.
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A distinct resource id per call -- reusing one after the first photomap owns
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it is a BadIDChoice, which would mask the answer we are after.
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"""
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pid = c.new_id(0x0AAAA + slot * 0x100)
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w = [2, pid, 64, 64, 0, 0, levels, 0, 0, 0x00000100, 0]
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out = c.send(8, 12, b"".join(struct.pack("<I", x) for x in w))
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return pid, describe_all(out)
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def set_transport(c, pid, scheme, mode=1):
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"""xieSetTransportReq, 140 bytes: 3C header + 4 + 4 + 4 + 4 + 24 + 96."""
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w = [0] * 34
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w[0] = pid
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w[1] = 0 # compression_parameter
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w[2] = scheme | (mode << 8) | (1 << 16) # scheme|mode|comp_org
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w[3] = 1 # plane_mask
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w[4] = 1 # pixel_stride[0] = 1
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w[10] = 8 # scanline_stride[0] = 8
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return c.send(20, 35, b"".join(struct.pack("<I", x) for x in w))
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def main(argv):
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c = Cli()
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c.send(1, 2, struct.pack("<HH", 2, 3)) # init session
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levels = int(argv[1]) if len(argv) > 1 else 2
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schemes = [int(argv[2])] if len(argv) > 2 else (0, 1, 2, 3, 4, 5)
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mode = int(argv[3]) if len(argv) > 3 else 1
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print("levels=%d mode=%d (%s)" % (levels, mode,
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"GetStream" if mode == 1 else "PutStream"))
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for scheme in schemes:
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pid, created = make_photomap(c, scheme, levels)
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if "ERROR" in created:
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print("%-5s create FAILED: %s" % (NAMES[scheme], created))
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continue
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r = set_transport(c, pid, scheme, mode)
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kind = describe_all(r)
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if "ERROR" in kind:
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verdict = "REFUSED"
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elif "NO REPLY" in kind or "NO PACKETS" in kind:
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verdict = "ACCEPTED"
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else:
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verdict = "?"
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print("%-5s SetTransport -> %-8s %s" % (NAMES[scheme], verdict, kind))
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if __name__ == "__main__":
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main(sys.argv)
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+173
@@ -0,0 +1,173 @@
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/*
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* What does THIS ROM answer for each XieK_ compression scheme?
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*
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* Built against DEC XIE 2.3 (libXie from DEC's own sources). For every scheme
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* value 0..5 it issues a real SetTransport (via XieSetStream) in GetStream mode
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* on a bitonal photomap, and then on a grayscale photomap if the server will
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* create one -- and reports the protocol error the server returns.
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*
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* Xlib's default handler exits on an error, so a catching handler is installed.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <X11/Xlib.h>
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#include <X11/Xutil.h>
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#include <X11/extensions/XieLib.h>
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/* the client never calls the DDX dispatch table; satisfy the linker */
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unsigned long (*xieDdxProc[1])() = { 0 };
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static int last_error;
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static int last_req_minor;
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static char last_text[64];
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static int catch(Display *dpy, XErrorEvent *e)
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{
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last_error = e->error_code;
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last_req_minor = e->minor_code;
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XGetErrorText(dpy, e->error_code, last_text, sizeof last_text);
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return 0;
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}
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static const char *scheme_name(int s)
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{
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switch (s) {
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case XieK_PCM: return "PCM ";
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case XieK_G31D: return "G31D ";
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case XieK_G32D: return "G32D ";
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case XieK_G42D: return "G42D ";
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case XieK_DCT: return "DCT ";
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default: return "5 ";
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}
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}
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/* Create a photomap and push pixel data into it so it is a real image. */
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static XiePhotomap make_map(Display *dpy, Window win, int bits, int ncomp,
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int cls, const char *tag)
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{
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XieImage img;
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XiePhotomap pm;
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unsigned long lvl[3];
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unsigned int fill;
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int w = 64, h = 64, nbytes;
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lvl[0] = lvl[1] = lvl[2] = (unsigned long) bits;
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last_error = 0;
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img = XieCreateImage((unsigned long) w, (unsigned long) h,
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XieK_PCM, (unsigned char) XieK_BandByPlane,
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(unsigned char) cls, ncomp, lvl,
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(unsigned char) XieK_PP0, (unsigned char) XieK_LP270);
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XSync(dpy, False);
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if (!img || last_error) {
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printf(" [%s] XieCreateImage FAILED err=%d (%s)\n", tag, last_error,
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last_error ? last_text : "no error, null handle");
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return 0;
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}
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if (!uBase_(img, 0)) {
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nbytes = (int) uArSize_(img, 0);
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if (nbytes <= 0) nbytes = (w + 7) / 8 * h;
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uBase_(img, 0) = (unsigned char *) calloc(1, (size_t) nbytes);
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uArSize_(img, 0) = nbytes;
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OwnData_(img) = 1;
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}
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nbytes = (int) uArSize_(img, 0);
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fill = ((bits + 7) / 8) == 1 ? 0xAA : 0x00;
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memset(uBase_(img, 0), fill, (size_t) nbytes);
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pm = XieCreatePhoto(dpy, XieK_Photomap, (unsigned long) w, (unsigned long) h,
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(unsigned char) cls, ncomp, lvl,
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(unsigned char) XieK_ZeroDark, 1.0,
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(unsigned char) XieK_BandByPlane,
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(unsigned char) XieK_BandByPlane);
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XSync(dpy, False);
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if (!pm || last_error) {
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printf(" [%s] XieCreatePhoto FAILED err=%d\n", tag, last_error);
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return 0;
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}
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XiePutTile(pm, img, XieK_AllPlanes, 0, 0, 0, 0,
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(unsigned long) w, (unsigned long) h);
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XSync(dpy, False);
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if (last_error) {
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/* SetTransport only needs the photomap to exist, so carry on and let the
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* transport test report whatever the server says. */
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printf(" [%s] XiePutTile failed err=%d (%s) -- continuing with an empty map\n",
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tag, last_error, last_text);
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last_error = 0;
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}
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printf(" [%s] photomap ready (arSize=%d)\n", tag, nbytes);
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return pm;
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}
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static void try_scheme(Display *dpy, XiePhoto pm, int scheme, int mode,
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const char *mode_name)
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{
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int i;
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for (i = 0; i < 8; i++) last_text[i] = 0;
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last_error = 0;
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last_req_minor = -1;
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XieSetStream(pm, 0, (unsigned char) mode, (unsigned char) scheme,
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0L, (unsigned char) XieK_BandByPlane, 1L, 8L);
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XSync(dpy, False);
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if (last_error)
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printf(" %s in %-9s -> ERROR %d %s (minor %d)\n",
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scheme_name(scheme), mode_name, last_error, last_text,
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last_req_minor);
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else
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printf(" %s in %-9s -> ACCEPTED\n", scheme_name(scheme), mode_name);
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}
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int main(int argc, char **argv)
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{
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Display *dpy;
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Window win;
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XSetWindowAttributes swa;
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XiePhotomap bm, gm;
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const char *disp = argc > 1 ? argv[1] : "192.168.99.2:0";
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dpy = XOpenDisplay(disp);
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if (!dpy) { fprintf(stderr, "cannot open %s\n", disp); return 1; }
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XSetErrorHandler(catch);
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printf("display %s, root depth %d\n", disp,
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DefaultDepth(dpy, DefaultScreen(dpy)));
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swa.background_pixel = 0;
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win = XCreateWindow(dpy, DefaultRootWindow(dpy), 150, 200, 64, 64, 0,
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CopyFromParent, InputOutput, CopyFromParent,
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CWBackPixel, &swa);
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XSync(dpy, False);
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{
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int scheme = argc > 2 ? atoi(argv[2]) : XieK_PCM;
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int bits = (argc > 3 && !strcmp(argv[3], "gray")) ? 256 : 2;
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int cls = (bits == 2) ? XieK_Bitonal : XieK_GrayScale;
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const char *tag = (bits == 2) ? "bitonal" : "gray";
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printf("\n--- %s photomap, scheme %s ---\n", tag, scheme_name(scheme));
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bm = make_map(dpy, win, bits, 1, cls, tag);
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if (bm) {
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try_scheme(dpy, bm, scheme, XieK_GetStream, "GetStream");
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/* and, if that was accepted, actually ask for the data */
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if (!last_error) {
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unsigned char *buf = 0;
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unsigned long got = 0;
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last_error = 0;
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printf(" XieSetStream accepted; calling XieGetStream...\n");
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XieGetStream(bm, 0, &buf, 65536L, &got);
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XSync(dpy, False);
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if (last_error)
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printf(" XieGetStream -> ERROR %d %s\n", last_error, last_text);
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else
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printf(" XieGetStream -> ok, %lu bytes, first %02X %02X %02X %02X\n",
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got, buf ? buf[0] : 0, buf ? buf[1] : 0,
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buf ? buf[2] : 0, buf ? buf[3] : 0);
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}
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}
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}
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XCloseDisplay(dpy);
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return 0;
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}
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Block a user