From a31fae7960ed0ada95813cd5e0160c194cb81ebb Mon Sep 17 00:00:00 2001
From: Dirk Engling <erdgeist@erdgeist.org>
Date: Sun, 18 Aug 2024 12:52:07 +0200
Subject: Make zlib wrapper in v4 exporter more robust and easier to read

---
 src/export/extract_version_4.c | 40 ++++++++++++++++++++++++++--------------
 1 file changed, 26 insertions(+), 14 deletions(-)

diff --git a/src/export/extract_version_4.c b/src/export/extract_version_4.c
index 1dbaf40..e014e23 100644
--- a/src/export/extract_version_4.c
+++ b/src/export/extract_version_4.c
@@ -7,44 +7,56 @@
 #include "mystdlib.h"
 
 #define XORLEN (29)
+#define HUGEINBLOCK (128*1024)
 #define HUGEBLOCK (4*1024*1024)
 
 int main(int argc, char **argv) {
   unsigned const char xorkey [XORLEN] = "Just for Fun. Linus Torvalds.";
-  unsigned char input  [XORLEN];
+  unsigned char input  [HUGEINBLOCK];
   unsigned char output [HUGEBLOCK];
   char respath[32]; /* file_XXXXX\0 */
   int zres = 0, filenum = 0, resfile;
-  size_t i, offs = 0, reported = 0;
+  size_t offs = 0, reported = 0;
   ssize_t temp = 0;
   MAP in;
 
   if( argc != 2 ) exit(111);
   in = map_file( argv[1], 1 );
 
-  z_stream z; memset( &z, 0, sizeof(z));
+  z_stream z;
 
   while( offs < in->size ) {
-    size_t inlen = offs + XORLEN < in->size ? XORLEN : in->size - offs;
-    for( i=0; i<inlen; ++i ) input[i] = in->addr[offs+i] ^ xorkey[i];
+    /* std::min(remain, HUGEINBLOCK) */
+    size_t inlen = in->size - offs;
+    if (inlen > sizeof(input))
+        inlen = sizeof(input);
+
+    /* Copy in block large enough */
+    memcpy(input, in->addr + offs, inlen);
+
+    /* De-"crypt" */
+    for (size_t i = 0; i < sizeof(xorkey); ++i )
+      input[i] ^= xorkey[i];
+
+    /* Prepare decompression struct */
+    memset( &z, 0, sizeof(z));
     z.next_in  = input;  z.avail_in = inlen;
     z.next_out = output; z.avail_out = HUGEBLOCK;
-    inflateInit( &z ); zres = inflate( &z, Z_NO_FLUSH );
-    if( (zres != Z_OK) && (zres != Z_STREAM_END) )
-      goto error_continue;
+    inflateInit( &z );
+    zres = Z_OK;
 
-    z.next_in  = in->addr + offs + inlen;
-    z.avail_in = (unsigned int)(in->size - offs - inlen);
-    while( zres == Z_OK ) zres = inflate( &z, Z_NO_FLUSH );
+    while( zres == Z_OK )
+      zres = inflate( &z, Z_NO_FLUSH );
 
     if( zres != Z_STREAM_END ) {
-error_continue:
-      inflateEnd(&z); memset( &z, 0, sizeof(z));
+      inflateEnd(&z);
       offs++;
       continue;
     }
 
-    sprintf( respath, "file_%05X", filenum++ );
+    // fprintf( stderr, "%08X\n", (unsigned int)(offs));
+    //old_offs = offs;
+    snprintf( respath, sizeof(respath), "file_%05X", filenum++ );
 
     resfile = open( respath, O_RDWR | O_CREAT, 0644 );
     if( resfile < 0 ) {
-- 
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