File 0001-bits-change-bit_copy_chain.patch of Package libredwg

From bb97cadde05277f089b730a7aff4cffa4c9f8afa Mon Sep 17 00:00:00 2001
From: Reini Urban <rurban@cpan.org>
Date: Mon, 15 Aug 2022 10:23:08 +0200
Subject: [PATCH] bits: change bit_copy_chain

copy only the rest of the 2nd dat, not the whole.
and don't reset it to 0, keep its position.
---
 src/bits.c   | 14 +++++++-------
 src/encode.c |  5 ++++-
 2 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/bits.c b/src/bits.c
index a7a8ca98..4c9ca878 100644
--- a/src/bits.c
+++ b/src/bits.c
@@ -3353,25 +3353,25 @@ bool does_cross_unicode_datversion (Bit_Chain *restrict dat)
     return false;
 }
 
-/* Copy the whole content of tmp_data to dat, and reset tmp_dat.
+/* Copy the rest content of tmp_data to dat.
    WARN: This might change dat->chain  */
 void bit_copy_chain (Bit_Chain *restrict dat, Bit_Chain *restrict tmp_dat)
 {
   unsigned long i;
-  unsigned long dat_bits = bit_position (tmp_dat);
-  unsigned long size = tmp_dat->byte;
+  unsigned long size = tmp_dat->size - tmp_dat->byte;
   while (dat->byte + size > dat->size)
     bit_chain_alloc (dat);
   // check if dat is byte aligned, tmp_dat always is. we can use memcpy then.
-  if (!dat->bit)
+  if (!dat->bit && !tmp_dat->bit)
     {
       assert(!tmp_dat->bit);
-      memcpy (&dat->chain[dat->byte], &tmp_dat->chain[0], size);
+      memcpy (&dat->chain[dat->byte], &tmp_dat->chain[tmp_dat->byte], size);
       dat->byte += size;
     }
   else
     {
-      bit_set_position (tmp_dat, 0);
+      unsigned long dat_bits = bit_position (tmp_dat);
+      //bit_set_position (tmp_dat, 0);
       for (i = 0; i < size; i++)
         {
           bit_write_RC (dat, bit_read_RC (tmp_dat));
@@ -3380,6 +3380,6 @@ void bit_copy_chain (Bit_Chain *restrict dat, Bit_Chain *restrict tmp_dat)
         {
           bit_write_B (dat, bit_read_B (tmp_dat));
         }
+      bit_set_position (tmp_dat, dat_bits);
     }
-  bit_set_position (tmp_dat, 0);
 }
diff --git a/src/encode.c b/src/encode.c
index d533e1fa..d4a63e16 100644
--- a/src/encode.c
+++ b/src/encode.c
@@ -846,13 +846,16 @@ obj_flush_hdlstream (Dwg_Object *restrict obj, Bit_Chain *restrict dat,
 {
   unsigned long datpos = bit_position (dat);
   unsigned long hdlpos = bit_position (hdl_dat);
+  unsigned long hdlsize = (hdl_dat->size * 8) - hdlpos;
   unsigned long objpos = obj->address * 8;
 #if 0
   unsigned char* oldchain = dat->chain;
 #endif
-  LOG_TRACE ("Flush handle stream of size %lu (@%lu.%u) to @%lu.%lu\n", hdlpos,
+  LOG_TRACE ("Flush handle stream of %lu bits (@%lu.%u) to @%lu.%lu\n", hdlsize,
              hdl_dat->byte, hdl_dat->bit, (datpos - objpos) / 8,
              (datpos - objpos) % 8);
+  if (hdlpos > 10000U)
+    LOG_ERROR("Possible hdl_data overflow")
   // This might change dat->chain
   bit_copy_chain (dat, hdl_dat);
 }
-- 
2.37.1