132 lines
4.7 KiB
C
132 lines
4.7 KiB
C
// Part of JoeyLib, Copyright (c) 2026 Scott Duensing, under the MIT License.
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// See LICENSE.md for license information.
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// SPDX-License-Identifier: MIT
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//
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// iigsStart -- a GS/OS boot launcher for the headless IIgs harnesses.
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//
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// Installed as /System/Start on a copy of the GS/OS system disk, this runs
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// at boot INSTEAD of the Finder and hands off to one JoeyLib example. The
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// point is that the Finder cannot be driven from a script: measured under
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// gssquared, injected keystrokes reach the $C000 latch but never reach the
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// Finder -- Open-Apple-A, Tab, arrows and bare letters all left the desktop
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// untouched. (The one redraw seen after the first key of a run is the
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// Finder's own settling: byte-identical for three different keys.) Reaching
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// the desktop also costs ~61s of boot that a probe must sit through; this
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// route has the example on screen in ~52s.
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//
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// Two GS/OS calls, in this order:
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// SetPrefixGS -- point prefix 0 at the example's DIRECTORY. GS/OS does
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// NOT do this for a QuitGS launch; prefix 0 was measured still pointing
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// at the boot volume. That is not cosmetic: JoeyLib opens its NTP
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// replayer as bare "ntpplayer", and when that read fails jlpAudioInit
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// returns before ntpArm(), so the sound interrupt vector stays at its
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// ROM default ($E1002C = 5C xxxx FF) and the example is SILENT. The
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// Finder sets prefix 0 itself, which is why this only bites here.
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// QuitGS with pCount = 2 and a pathname -- "quit, and launch this".
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//
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// Build: clang-build.sh -DJOEY_START_PATH='"/JOEYLIB/DRAW"' \
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// -o START iigsStart.c iigsStartQuit.s
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#include <stdint.h>
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// The program to launch. Overridden per-disk from the build.
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#ifndef JOEY_START_PATH
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#define JOEY_START_PATH "/JOEYLIB/DRAW"
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#endif
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// The harness's marker, in the $E1:9DC8-$9DFD window that survives a
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// present (SCB proper ends at $9DC7).
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#define QUIT_MAILBOX ((volatile uint8_t *)0xE19DC8L)
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// A GS/OS class-1 input string is a length WORD followed by the characters.
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#define GSOS_STRING_HEADER 2u
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// The parameter blocks: SetPrefixGS {pCount, prefixNum, prefix} and
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// QuitGS {pCount, pathname, flags}.
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#define PREFIX_PARM_BYTES 8u
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#define PREFIX_PARM_PATH 4u
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#define QUIT_PARM_BYTES 8u
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#define QUIT_PARM_PATH 2u
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#define GSOS_PCOUNT_2 2u
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#define PREFIX_CURRENT 0u // prefix 0 = the current directory
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// Room for the whole path, which is the longest either string gets.
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#define PATH_STRING_BYTES (GSOS_STRING_HEADER + sizeof(JOEY_START_PATH))
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// Markers for the harness.
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#define QUIT_REACHED 0xAAu
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#define QUIT_RETURNED 0xEEu
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static void gsosString(uint8_t *dst, const char *src, uint16_t len);
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void iigsStartQuit(uint8_t *parm);
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void iigsStartSetPrefix(uint8_t *parm);
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static void putLong(uint8_t *dst, uint32_t v);
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// In the launcher's own data, where GS/OS reads them during each call.
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static uint8_t gPrefixParm[PREFIX_PARM_BYTES];
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static uint8_t gPrefixPath[PATH_STRING_BYTES];
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static uint8_t gQuitParm[QUIT_PARM_BYTES];
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static uint8_t gQuitPath[PATH_STRING_BYTES];
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// Write a GS/OS input string: length word, then the characters.
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static void gsosString(uint8_t *dst, const char *src, uint16_t len) {
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uint16_t i;
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dst[0] = (uint8_t)(len & 0xFFu);
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dst[1] = (uint8_t)((len >> 8) & 0xFFu);
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for (i = 0; i < len; i++) {
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dst[GSOS_STRING_HEADER + i] = (uint8_t)src[i];
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}
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}
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static void putLong(uint8_t *dst, uint32_t v) {
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dst[0] = (uint8_t)(v & 0xFFu);
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dst[1] = (uint8_t)((v >> 8) & 0xFFu);
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dst[2] = (uint8_t)((v >> 16) & 0xFFu);
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dst[3] = (uint8_t)((v >> 24) & 0xFFu);
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}
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int main(void) {
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const char *path = JOEY_START_PATH;
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uint16_t len = 0;
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uint16_t dir = 0;
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uint16_t i;
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while (path[len] != '\0') {
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len++;
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}
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// Directory part, including the trailing '/': everything up to the last
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// separator. "/JOEYLIB/DRAW" -> "/JOEYLIB/".
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for (i = 0; i < len; i++) {
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if (path[i] == '/') {
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dir = (uint16_t)(i + 1u);
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}
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}
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gsosString(gPrefixPath, path, dir);
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gPrefixParm[0] = GSOS_PCOUNT_2;
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gPrefixParm[1] = 0u;
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gPrefixParm[2] = PREFIX_CURRENT;
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gPrefixParm[3] = 0u;
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putLong(gPrefixParm + PREFIX_PARM_PATH, (uint32_t)gPrefixPath);
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iigsStartSetPrefix(gPrefixParm);
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gsosString(gQuitPath, path, len);
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gQuitParm[0] = GSOS_PCOUNT_2;
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gQuitParm[1] = 0u;
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putLong(gQuitParm + QUIT_PARM_PATH, (uint32_t)gQuitPath);
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gQuitParm[6] = 0u; // flags
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gQuitParm[7] = 0u;
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*QUIT_MAILBOX = QUIT_REACHED;
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iigsStartQuit(gQuitParm);
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*QUIT_MAILBOX = QUIT_RETURNED;
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// QuitGS only returns on failure. Nothing useful is left to do, so
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// spin: the harness reads the mailbox to see what happened.
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for (;;) {
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}
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}
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