From 6279a820646c856b93056e714b697c6254c7881e Mon Sep 17 00:00:00 2001
From: David Schmenk <dschmenk@sbcglobal.net>
Date: Sun, 24 Nov 2024 07:57:51 -0800
Subject: [PATCH] Prep DCGR slideshow

---
 src/utilsrc/apple/dcgrshow.pla | 82 ++++++++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 src/utilsrc/apple/dcgrshow.pla

diff --git a/src/utilsrc/apple/dcgrshow.pla b/src/utilsrc/apple/dcgrshow.pla
new file mode 100644
index 0000000..492fa44
--- /dev/null
+++ b/src/utilsrc/apple/dcgrshow.pla
@@ -0,0 +1,82 @@
+include "inc/cmdsys.plh"
+include "inc/dcgrlib.plh"
+include "inc/dcgrutils.plh"
+include "inc/args.plh"
+include "inc/fileio.plh"
+include "inc/matchfiles.plh"
+include "inc/lz4.plh"
+
+sysflags resxtxt1|reshgr1|resxhgr1|reshgr2
+
+def lz4ReadBlock(flags, dstbuf)#2
+    word size[2], block, len
+
+    len = fileio:read(inref, @size, 4)
+    if len <> 4 or size[0] == 0 or size[1] & $7FFF
+        return NULL, 0
+    fin
+    block = dstbuf
+    if block
+        len = fileio:read(inref, block, size[0])
+        if len <> size[0]
+            return NULL, 0
+        fin
+    else
+        return NULL, 0
+    fin
+    if size[1] & $8000
+        //
+        // Uncompressed block
+        //
+        data = block
+    else
+        //
+        // Decompress block
+        //
+        len  = heapavail - 256 // Allocate almost entire heap to decompress into
+        data = heapalloc(len)
+        if data
+            len = lz4Unpack(block, block + size[0], data, data + len)
+            memcpy(block, data, len)
+            data = block
+        else
+            len = 0
+        fin
+    fin
+    if flags & $10 // Block Checksum
+        fileio:read(inref, @size, 4)
+    fin
+    return len
+end
+def lz4ReadFrame#0
+    word data, len
+    byte header[t_header], opt
+
+    fileio:read(inref, @header, t_header)
+    if header:magic[1] <> $184D or header:magic[0] <> $2204
+        puts("Not LZ4 file.\n")
+        return
+    fin
+    if header.FLG & $C0 <> $40
+        puts("Wrong LZ4 version.\n")
+        return
+    fin
+    if header.BD & $70 <> $40
+        puts("Not 64K block size.\n")
+        return
+    fin
+    opt = 1
+    if header.FLG & $08 // Content Size
+        opt = opt + 8
+    fin
+    if header.FLG & $01 // Dictionary ID
+        opt = opt + 4
+    fin
+    fileio:read(inref, heapmark, opt) // Read rest of header and throw away
+    repeat
+        len = lz4ReadBlock(header.FLG, $2000)
+    until len == 0
+    if header.FLG & $04 // Content Checksun
+        fileio:read(inref, heapmark, 4)
+    fin
+end