diff --git a/ANNOUNCE b/ANNOUNCE
index 24bae0439..b98b1963e 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.5.0beta55 - November 11, 2010
+Libpng 1.5.0beta55 - November 21, 2010
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -226,7 +226,7 @@ version 1.5.0beta24 [May 7, 2010]
     offset of the png_ptr->rowbuf pointer into png_ptr->big_row_buf.
   Added more blank lines for readability.
 
-version 1.5.0beta25 [November 11, 2010]
+version 1.5.0beta25 [November 21, 2010]
   In pngpread.c: png_push_have_row() add check for new_row > height
   Removed the now-redundant check for out-of-bounds new_row from example.c
 
@@ -436,7 +436,12 @@ Version 1.5.0beta54 [November 10, 2010]
   Require 48 bytes, not 64 bytes, for big_row_buf in overflow checks.
   Used a consistent structure for the pngget.c functions.
 
-Version 1.5.0beta55 [November 11, 2010]
+Version 1.5.0beta55 [November 21, 2010]
+  Revised png_get_uint_32, png_get_int_32, png_get_uint_16 (Cosmin)
+  Moved reading of file signature into png_read_sig (Cosmin)
+  Fixed atomicity of chunk header serialization (Cosmin)
+  Added test for io_state in pngtest.c (Cosmin)
+  Added "#!/bin/sh" at the top of contrib/pngminim/*/gather.sh scripts.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net:
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index a1a6241f6..5d1b44314 100644
--- a/CHANGES
+++ b/CHANGES
@@ -3074,7 +3074,12 @@ Version 1.5.0beta54 [November 10, 2010]
   Require 48 bytes, not 64 bytes, for big_row_buf in overflow checks.
   Used a consistent structure for the pngget.c functions.
 
-Version 1.5.0beta55 [November 11, 2010]
+Version 1.5.0beta55 [November 21, 2010]
+  Revised png_get_uint_32, png_get_int_32, png_get_uint_16 (Cosmin)
+  Moved reading of file signature into png_read_sig (Cosmin)
+  Fixed atomicity of chunk header serialization (Cosmin)
+  Added test for io_state in pngtest.c (Cosmin)
+  Added "#!/bin/sh" at the top of contrib/pngminim/*/gather.sh scripts.
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/libpngpf.3 b/libpngpf.3
index db211e8a5..78d382e30 100644
--- a/libpngpf.3
+++ b/libpngpf.3
@@ -1,4 +1,4 @@
-.TH LIBPNGPF 3 "November 11, 2010"
+.TH LIBPNGPF 3 "November 21, 2010"
 .SH NAME
 libpng \- Portable Network Graphics (PNG) Reference Library 1.5.0beta55
 (private functions)
@@ -685,62 +685,38 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.5.0beta55
 
 \fI\fB
 
-\fI\fB
-
 \fBvoid png_read_push_finish_row (png_structp \fIpng_ptr\fP\fB);\fP
 
 \fI\fB
 
-\fI\fB
-
 \fBvoid png_read_start_row (png_structp \fIpng_ptr\fP\fB);\fP
 
 \fI\fB
 
+\fBvoid png_read_sig (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
+
 \fI\fB
 
 \fBvoid png_read_transform_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
 
 \fI\fB
 
-\fI\fB
-
 \fBpng_fixed_point png_reciprocal (png_fixed_point \fIa\fP\fB);\fP
 
 \fI\fB
 
-\fI\fB
-
-\fI\fB
-
-\fI\fB
-
-\fI\fB
-
 \fBpng_fixed_point png_reciprocal2 (png_fixed_point \fP\fIa\fP\fB, png_fixed_point \fIb\fP\fB);\fP
 
 \fI\fB
 
-\fI\fB
-
-\fI\fB
-
-\fI\fB
-
-\fI\fB
-
 \fBvoid png_reset_crc (png_structp \fIpng_ptr\fP\fB);\fP
 
 \fI\fB
 
-\fI\fB
-
 \fBint png_set_text_2 (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fItext_ptr\fP\fB, int \fInum_text\fP\fB);\fP
 
 \fI\fB
 
-\fI\fB
-
 \fBvoid png_write_cHRM (png_structp \fP\fIpng_ptr\fP\fB, double \fP\fIwhite_x\fP\fB, double \fP\fIwhite_y\fP\fB, double \fP\fIred_x\fP\fB, double \fP\fIred_y\fP\fB, double \fP\fIgreen_x\fP\fB, double \fP\fIgreen_y\fP\fB, double \fP\fIblue_x\fP\fB, double \fIblue_y\fP\fB);\fP
 
 \fI\fB
@@ -921,17 +897,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.5.0beta55
 
 \fI\fB
 
-\fI\fB
-
-\fB\fBvoid png_fixed_error (png_structp \fI\fP\fIpng_ptr\fP\fB,
-
-\fBpng_const_charp \fP\fI\fP\fIname\fP\fB\fP\fB, double \fI\fP\fIvalue\fP\fB\fP\fB);\fP\fP
-
-\fI\fB\fI\fB
-
-\fI\fB
-
-\fI\fB\fI\fB
+\fBvoid png_fixed_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fP\fIname\fP\fB, double \fIvalue\fP\fB);\fP
 
 \fI\fB
 
diff --git a/png.c b/png.c
index eaaa95adc..baa7de7ce 100644
--- a/png.c
+++ b/png.c
@@ -556,13 +556,13 @@ png_get_copyright(png_structp png_ptr)
 #else
 #  ifdef __STDC__
    return PNG_STRING_NEWLINE \
-     "libpng version 1.5.0beta55 - November 11, 2010" PNG_STRING_NEWLINE \
+     "libpng version 1.5.0beta55 - November 21, 2010" PNG_STRING_NEWLINE \
      "Copyright (c) 1998-2010 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
      "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
      "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
      PNG_STRING_NEWLINE;
 #  else
-      return "libpng version 1.5.0beta55 - November 11, 2010\
+      return "libpng version 1.5.0beta55 - November 21, 2010\
       Copyright (c) 1998-2010 Glenn Randers-Pehrson\
       Copyright (c) 1996-1997 Andreas Dilger\
       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -1274,7 +1274,7 @@ png_ascii_from_fp(png_structp png_ptr, png_charp ascii, png_size_t size,
                       * place - after the DP don't adjust 'exp' any
                       * more!
                       */
-                     if (exp != (-1)) 
+                     if (exp != (-1))
                      {
                         if (exp == 0) *ascii++ = 46, --size;
                         /* PLUS 1: TOTAL 4 */
@@ -1800,7 +1800,7 @@ png_log8bit(unsigned int x)
     * always at most 19 bits.
     */
    if ((x &= 0xff) == 0)
-      return 0xffffffff; 
+      return 0xffffffff;
 
    if ((x & 0xf0) == 0)
       log  = 4, x <<= 4;
diff --git a/png.h b/png.h
index ea3fb2b1a..812e8e559 100644
--- a/png.h
+++ b/png.h
@@ -1,7 +1,7 @@
 
 /* png.h - header file for PNG reference library
  *
- * libpng version 1.5.0beta55 - November 11, 2010
+ * libpng version 1.5.0beta55 - November 21, 2010
  * Copyright (c) 1998-2010 Glenn Randers-Pehrson
  * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
  * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
@@ -11,7 +11,7 @@
  * Authors and maintainers:
  *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
  *   libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
- *   libpng versions 0.97, January 1998, through 1.5.0beta55 - November 11, 2010: Glenn
+ *   libpng versions 0.97, January 1998, through 1.5.0beta55 - November 21, 2010: Glenn
  *   See also "Contributing Authors", below.
  *
  * Note about libpng version numbers:
@@ -172,7 +172,7 @@
  *
  * This code is released under the libpng license.
  *
- * libpng versions 1.2.6, August 15, 2004, through 1.5.0beta55, November 11, 2010, are
+ * libpng versions 1.2.6, August 15, 2004, through 1.5.0beta55, November 21, 2010, are
  * Copyright (c) 2004, 2006-2010 Glenn Randers-Pehrson, and are
  * distributed according to the same disclaimer and license as libpng-1.2.5
  * with the following individual added to the list of Contributing Authors:
@@ -284,7 +284,7 @@
  * Y2K compliance in libpng:
  * =========================
  *
- *    November 11, 2010
+ *    November 21, 2010
  *
  *    Since the PNG Development group is an ad-hoc body, we can't make
  *    an official declaration.
@@ -348,7 +348,7 @@
 /* Version information for png.h - this should match the version in png.c */
 #define PNG_LIBPNG_VER_STRING "1.5.0beta55"
 #define PNG_HEADER_VERSION_STRING \
-     " libpng version 1.5.0beta55 - November 11, 2010\n"
+     " libpng version 1.5.0beta55 - November 21, 2010\n"
 
 #define PNG_LIBPNG_VER_SONUM   15
 #define PNG_LIBPNG_VER_DLLNUM  15
@@ -2044,11 +2044,12 @@ PNG_EXPORT(png_const_bytep,png_get_io_chunk_name,(png_structp png_ptr),,200);
       ((png_uint_32)(*((buf) + 2)) << 8) + \
       ((png_uint_32)(*((buf) + 3))))
 #  define png_get_uint_16(buf) \
-     (((png_uint_32)(*(buf)) << 8) + \
-      ((png_uint_32)(*((buf) + 1))))
+     ((png_uint_16) \
+      (((unsigned int)(*(buf)) << 8) + \
+       ((unsigned int)(*((buf) + 1)))))
 #  define png_get_int_32(buf) \
      ((png_int_32)((*(buf) & 0x80) \
-      ? -((png_int_32)((png_get_uint_32(buf) ^ 0xffffffff)+1)) \
+      ? -((png_int_32)((png_get_uint_32(buf) ^ 0xffffffffL) + 1)) \
       : (png_int_32)png_get_uint_32(buf)))
 #endif
 
diff --git a/pngpriv.h b/pngpriv.h
index 3bad2c0ba..69913dd74 100644
--- a/pngpriv.h
+++ b/pngpriv.h
@@ -511,6 +511,9 @@ PNG_EXTERN void png_reset_crc PNGARG((png_structp png_ptr));
 PNG_EXTERN void png_write_data PNGARG((png_structp png_ptr,
     png_const_bytep data, png_size_t length));
 
+/* Read and check the PNG file signature */
+PNG_EXTERN void png_read_sig PNGARG((png_structp png_ptr, png_infop info_ptr));
+
 /* Read the chunk header (length + type name) */
 PNG_EXTERN png_uint_32 png_read_chunk_header PNGARG((png_structp png_ptr));
 
diff --git a/pngread.c b/pngread.c
index d334a8e86..fe180fdfd 100644
--- a/pngread.c
+++ b/pngread.c
@@ -232,32 +232,8 @@ png_read_info(png_structp png_ptr, png_infop info_ptr)
    if (png_ptr == NULL || info_ptr == NULL)
       return;
 
-   /* If we haven't checked all of the PNG signature bytes, do so now. */
-   if (png_ptr->sig_bytes < 8)
-   {
-      png_size_t num_checked = png_ptr->sig_bytes,
-                 num_to_check = 8 - num_checked;
-
-#ifdef PNG_IO_STATE_SUPPORTED
-      png_ptr->io_state = PNG_IO_READING | PNG_IO_SIGNATURE;
-#endif
-
-      png_read_data(png_ptr, &(info_ptr->signature[num_checked]), num_to_check);
-      png_ptr->sig_bytes = 8;
-
-      if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check))
-      {
-         if (num_checked < 4 &&
-             png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4))
-            png_error(png_ptr, "Not a PNG file");
-
-         else
-            png_error(png_ptr, "PNG file corrupted by ASCII conversion");
-      }
-
-      if (num_checked < 3)
-         png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
-   }
+   /* Read and check the PNG file signature. */
+   png_read_sig(png_ptr, info_ptr);
 
    for (;;)
    {
diff --git a/pngrutil.c b/pngrutil.c
index 56e216ed6..18c230362 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -23,12 +23,12 @@
 png_uint_32 PNGAPI
 png_get_uint_31(png_structp png_ptr, png_const_bytep buf)
 {
-   png_uint_32 i = png_get_uint_32(buf);
+   png_uint_32 uval = png_get_uint_32(buf);
 
-   if (i > PNG_UINT_31_MAX)
+   if (uval > PNG_UINT_31_MAX)
       png_error(png_ptr, "PNG unsigned integer out of range");
 
-   return (i);
+   return (uval);
 }
 
 #if defined(PNG_READ_gAMA_SUPPORTED) || defined(PNG_READ_cHRM_SUPPORTED)
@@ -42,10 +42,10 @@ png_get_uint_31(png_structp png_ptr, png_const_bytep buf)
 static png_fixed_point /* PRIVATE */
 png_get_fixed_point(png_structp png_ptr, png_const_bytep buf)
 {
-   png_uint_32 u = png_get_uint_32(buf);
+   png_uint_32 uval = png_get_uint_32(buf);
 
-   if (u <= PNG_UINT_31_MAX)
-      return (png_fixed_point)u; /* known to be in range */
+   if (uval <= PNG_UINT_31_MAX)
+      return (png_fixed_point)uval; /* known to be in range */
 
    /* The caller can turn off the warning by passing NULL. */
    if (png_ptr != NULL)
@@ -58,19 +58,21 @@ png_get_fixed_point(png_structp png_ptr, png_const_bytep buf)
 #ifdef PNG_READ_INT_FUNCTIONS_SUPPORTED
 /* NOTE: the read macros will obscure these definitions, so that if
  * PNG_USE_READ_MACROS is set the library will not use them internally,
- * but the APIs will still be available externally.
+ * but the APIs will still be available externally.  The parentheses
+ * around "PNGAPI function_name" are necessary because ...
  */
+
 /* Grab an unsigned 32-bit integer from a buffer in big-endian format. */
 png_uint_32 (PNGAPI
 png_get_uint_32)(png_const_bytep buf)
 {
-   png_uint_32 i =
+   png_uint_32 uval =
        ((png_uint_32)(*(buf    )) << 24) +
        ((png_uint_32)(*(buf + 1)) << 16) +
        ((png_uint_32)(*(buf + 2)) <<  8) +
        ((png_uint_32)(*(buf + 3))      ) ;
 
-   return (i);
+   return uval;
 }
 
 /* Grab a signed 32-bit integer from a buffer in big-endian format.  The
@@ -81,26 +83,60 @@ png_get_uint_32)(png_const_bytep buf)
 png_int_32 (PNGAPI
 png_get_int_32)(png_const_bytep buf)
 {
-   png_uint_32 u = png_get_uint_32(buf);
-   if ((u & 0x80000000) == 0) /* non-negative */
-      return u;
+   png_uint_32 uval = png_get_uint_32(buf);
+   if ((uval & 0x80000000L) == 0) /* non-negative */
+      return uval;
 
-   u = (u ^ 0xffffffff) + 1;  /* 2's complement: -x = ~x+1 */
-   return -(png_int_32)u;
+   uval = (uval ^ 0xffffffffL) + 1;  /* 2's complement: -x = ~x+1 */
+   return -(png_int_32)uval;
 }
 
 /* Grab an unsigned 16-bit integer from a buffer in big-endian format. */
 png_uint_16 (PNGAPI
 png_get_uint_16)(png_const_bytep buf)
 {
-   png_uint_16 i =
-       ((png_uint_32)(*buf) << 8) +
-       ((png_uint_32)(*(buf + 1)));
+   unsigned int val =
+       ((unsigned int)(*buf) << 8) +
+       ((unsigned int)(*(buf + 1)));
 
-   return (i);
+   return (png_uint_16)val;
 }
+
 #endif /* PNG_READ_INT_FUNCTIONS_SUPPORTED */
 
+/* Read and check the PNG file signature */
+void /* PRIVATE */
+png_read_sig(png_structp png_ptr, png_infop info_ptr)
+{
+   png_size_t num_checked, num_to_check;
+
+   /* Exit if the user application does not expect a signature. */
+   if (png_ptr->sig_bytes >= 8)
+      return;
+
+   num_checked = png_ptr->sig_bytes;
+   num_to_check = 8 - num_checked;
+
+#ifdef PNG_IO_STATE_SUPPORTED
+   png_ptr->io_state = PNG_IO_READING | PNG_IO_SIGNATURE;
+#endif
+
+   /* The signature must be serialized in a single I/O call. */
+   png_read_data(png_ptr, &(info_ptr->signature[num_checked]), num_to_check);
+   png_ptr->sig_bytes = 8;
+
+   if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check))
+   {
+      if (num_checked < 4 &&
+          png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4))
+         png_error(png_ptr, "Not a PNG file");
+      else
+         png_error(png_ptr, "PNG file corrupted by ASCII conversion");
+   }
+   if (num_checked < 3)
+      png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
+}
+
 /* Read the chunk header (length + type name).
  * Put the type name into png_ptr->chunk_name, and return the length.
  */
@@ -111,33 +147,29 @@ png_read_chunk_header(png_structp png_ptr)
    png_uint_32 length;
 
 #ifdef PNG_IO_STATE_SUPPORTED
-   /* Inform the I/O callback that the chunk header is being read.
-    * PNG_IO_CHUNK_HDR requires a single I/O call.
-    */
    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_HDR;
 #endif
 
-   /* Read the length and the chunk name */
+   /* Read the length and the chunk name.
+    * This must be performed in a single I/O call.
+    */
    png_read_data(png_ptr, buf, 8);
    length = png_get_uint_31(png_ptr, buf);
 
-   /* Put the chunk name into png_ptr->chunk_name */
+   /* Put the chunk name into png_ptr->chunk_name. */
    png_memcpy(png_ptr->chunk_name, buf + 4, 4);
 
    png_debug2(0, "Reading %s chunk, length = %u",
        png_ptr->chunk_name, length);
 
-   /* Reset the crc and run it over the chunk name */
+   /* Reset the crc and run it over the chunk name. */
    png_reset_crc(png_ptr);
    png_calculate_crc(png_ptr, png_ptr->chunk_name, 4);
 
-   /* Check to see if chunk name is valid */
+   /* Check to see if chunk name is valid. */
    png_check_chunk_name(png_ptr, png_ptr->chunk_name);
 
 #ifdef PNG_IO_STATE_SUPPORTED
-   /* Inform the I/O callback that chunk data will (possibly) be read.
-    * PNG_IO_CHUNK_DATA does NOT require a specific number of I/O calls.
-    */
    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_DATA;
 #endif
 
@@ -222,11 +254,10 @@ png_crc_error(png_structp png_ptr)
    }
 
 #ifdef PNG_IO_STATE_SUPPORTED
-   /* Inform the I/O callback that the chunk CRC is being read */
-   /* PNG_IO_CHUNK_CRC requires the I/O to be done at once */
    png_ptr->io_state = PNG_IO_READING | PNG_IO_CHUNK_CRC;
 #endif
 
+   /* The chunk CRC must be serialized in a single I/O call. */
    png_read_data(png_ptr, crc_bytes, 4);
 
    if (need_crc)
@@ -279,7 +310,7 @@ png_inflate(png_structp png_ptr, png_bytep data, png_size_t size,
             png_ptr->zstream.avail_in = (uInt)size;
             size = 0;
          }
-   
+
          else
          {
             png_ptr->zstream.avail_in = ZLIB_IO_MAX;
@@ -3284,18 +3315,10 @@ png_read_finish_row(png_structp png_ptr)
          {
             while (!png_ptr->idat_size)
             {
-               png_byte chunk_length[4];
-
                png_crc_finish(png_ptr, 0);
-
-               png_read_data(png_ptr, chunk_length, 4);
-               png_ptr->idat_size = png_get_uint_31(png_ptr, chunk_length);
-               png_reset_crc(png_ptr);
-               png_crc_read(png_ptr, png_ptr->chunk_name, 4);
-
+               png_ptr->idat_size = png_read_chunk_header(png_ptr);
                if (png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
                   png_error(png_ptr, "Not enough image data");
-
             }
 
             png_ptr->zstream.avail_in = (uInt)png_ptr->zbuf_size;
@@ -3307,6 +3330,7 @@ png_read_finish_row(png_structp png_ptr)
             png_crc_read(png_ptr, png_ptr->zbuf, png_ptr->zstream.avail_in);
             png_ptr->idat_size -= png_ptr->zstream.avail_in;
          }
+
          ret = inflate(&png_ptr->zstream, Z_PARTIAL_FLUSH);
 
          if (ret == Z_STREAM_END)
@@ -3319,6 +3343,7 @@ png_read_finish_row(png_structp png_ptr)
             png_ptr->flags |= PNG_FLAG_ZLIB_FINISHED;
             break;
          }
+
          if (ret != Z_OK)
             png_error(png_ptr, png_ptr->zstream.msg ? png_ptr->zstream.msg :
                 "Decompression Error");
diff --git a/pngtest.c b/pngtest.c
index f5733f0b9..fcdc0887b 100644
--- a/pngtest.c
+++ b/pngtest.c
@@ -299,6 +299,48 @@ static int wrote_question = 0;
  * than changing the library.
  */
 
+#ifdef PNG_IO_STATE_SUPPORTED
+void
+pngtest_check_io_state(png_structp png_ptr, png_size_t data_length,
+   png_uint_32 io_op);
+void
+pngtest_check_io_state(png_structp png_ptr, png_size_t data_length,
+   png_uint_32 io_op)
+{
+   png_uint_32 io_state = png_get_io_state(png_ptr);
+   int err = 0;
+
+   /* Check if the current operation (reading / writing) is as expected. */
+   if ((io_state & PNG_IO_MASK_OP) != io_op)
+      png_error(png_ptr, "Incorrect operation in I/O state");
+
+   /* Check if the buffer size specific to the current location
+    * (file signature / header / data / crc) is as expected.
+    */
+   switch (io_state & PNG_IO_MASK_LOC)
+   {
+   case PNG_IO_SIGNATURE:
+      if (data_length > 8)
+         err = 1;
+      break;
+   case PNG_IO_CHUNK_HDR:
+      if (data_length != 8)
+         err = 1;
+      break;
+   case PNG_IO_CHUNK_DATA:
+      break;  /* no restrictions here */
+   case PNG_IO_CHUNK_CRC:
+      if (data_length != 4)
+         err = 1;
+      break;
+   default:
+      err = 1;  /* uninitialized */
+   }
+   if (err)
+      png_error(png_ptr, "Bad I/O state or buffer size");
+}
+#endif
+
 #ifndef USE_FAR_KEYWORD
 static void PNGCBAPI
 pngtest_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
@@ -317,8 +359,12 @@ pngtest_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
 
    if (check != length)
    {
-      png_error(png_ptr, "Read Error!");
+      png_error(png_ptr, "Read Error");
    }
+
+#ifdef PNG_IO_STATE_SUPPORTED
+   pngtest_check_io_state(png_ptr, length, PNG_IO_READING);
+#endif
 }
 #else
 /* This is the model-independent version. Since the standard I/O library
@@ -366,7 +412,11 @@ pngtest_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
    }
 
    if (check != length)
-      png_error(png_ptr, "read Error");
+      png_error(png_ptr, "Read Error");
+
+#ifdef PNG_IO_STATE_SUPPORTED
+   pngtest_check_io_state(png_ptr, length, PNG_IO_READING);
+#endif
 }
 #endif /* USE_FAR_KEYWORD */
 
@@ -396,6 +446,10 @@ pngtest_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
    {
       png_error(png_ptr, "Write Error");
    }
+
+#ifdef PNG_IO_STATE_SUPPORTED
+   pngtest_check_io_state(png_ptr, length, PNG_IO_WRITING);
+#endif
 }
 #else
 /* This is the model-independent version. Since the standard I/O library
@@ -448,6 +502,10 @@ pngtest_write_data(png_structp png_ptr, png_bytep data, png_size_t length)
    {
       png_error(png_ptr, "Write Error");
    }
+
+#ifdef PNG_IO_STATE_SUPPORTED
+   pngtest_check_io_state(png_ptr, length, PNG_IO_WRITING);
+#endif
 }
 #endif /* USE_FAR_KEYWORD */
 
diff --git a/pngvalid.c b/pngvalid.c
index 56347414b..510f99f58 100644
--- a/pngvalid.c
+++ b/pngvalid.c
@@ -214,7 +214,7 @@ sample(png_const_bytep row, png_byte colour_type, png_byte bit_depth,
     png_uint_32 x, unsigned int sample)
 {
    png_uint_32 index, result;
-   
+
    /* Find a sample index for the desired sample: */
    x *= bit_depth;
    index = x;
@@ -554,7 +554,7 @@ store_log(png_store* ps, png_structp pp, png_const_charp message, int is_error)
          pos = safecat(buffer, sizeof buffer, 0, "error: ");
       else
          pos = safecat(buffer, sizeof buffer, 0, "warning: ");
-         
+
       store_message(ps, pp, buffer, sizeof buffer, pos, message);
       fputs(buffer, stderr);
       fputc('\n', stderr);
@@ -927,7 +927,7 @@ store_write_reset(png_store *ps)
     * spurious errors in the case of memory corruption above, but this is safe.
     */
    store_pool_delete(ps, &ps->write_memory_pool);
-   
+
    store_freenew(ps);
 }
 
@@ -978,7 +978,7 @@ store_read_reset(png_store *ps)
    if (ps->pread != NULL)
    {
       anon_context(ps);
-      
+
       Try
          png_destroy_read_struct(&ps->pread, &ps->piread, NULL);
 
@@ -1068,7 +1068,7 @@ set_store_for_read(png_store *ps, png_infopp ppi, png_uint_32 id,
 
       Throw ps;
    }
-      
+
    store_read_set(ps, id);
 
    if (ppi != NULL)
@@ -1339,21 +1339,21 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
             store_read_imp(&pm->this, pm->buffer, 8); /* size of signature. */
             pm->buffer_count = 8;
             pm->buffer_position = 0;
-   
+
             if (memcmp(pm->buffer, sign, 8) != 0)
                png_error(pm->this.pread, "invalid PNG file signature");
             pm->state = modifier_signature;
             break;
-   
+
          case modifier_signature:
             store_read_imp(&pm->this, pm->buffer, 13+12); /* size of IHDR */
             pm->buffer_count = 13+12;
             pm->buffer_position = 0;
-   
+
             if (png_get_uint_32(pm->buffer) != 13 ||
                 png_get_uint_32(pm->buffer+4) != CHUNK_IHDR)
                png_error(pm->this.pread, "invalid IHDR");
-   
+
             /* Check the list of modifiers for modifications to the IHDR. */
             mod = pm->modifications;
             while (mod != NULL)
@@ -1364,19 +1364,19 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
                   mod->modified = 1;
                   modifier_setbuffer(pm);
                   }
-   
+
                /* Ignore removal or add if IHDR! */
                mod = mod->next;
             }
-   
+
             /* Cache information from the IHDR (the modified one.) */
             pm->bit_depth = pm->buffer[8+8];
             pm->colour_type = pm->buffer[8+8+1];
-   
+
             pm->state = modifier_IHDR;
             pm->flush = 0;
             break;
-   
+
          case modifier_IHDR:
          default:
             /* Read a new chunk and process it until we see PLTE, IDAT or
@@ -1392,7 +1392,7 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
                st -= cb;
                if (st <= 0) return;
             }
-   
+
             /* No more bytes to flush, read a header, or handle a pending
              * chunk.
              */
@@ -1405,14 +1405,14 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
             }
             else
                store_read_imp(&pm->this, pm->buffer, 8);
-   
+
             pm->buffer_count = 8;
             pm->buffer_position = 0;
-   
+
             /* Check for something to modify or a terminator chunk. */
             len = png_get_uint_32(pm->buffer);
             chunk = png_get_uint_32(pm->buffer+4);
-   
+
             /* Terminators first, they may have to be delayed for added
              * chunks
              */
@@ -1420,7 +1420,7 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
                 chunk == CHUNK_IEND)
             {
                mod = pm->modifications;
-   
+
                while (mod != NULL)
                {
                   if ((mod->add == chunk ||
@@ -1431,7 +1431,7 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
                       * this again.
                       */
                      mod->added = 1;
-   
+
                      if ((*mod->modify_fn)(pm, mod, 1/*add*/))
                      {
                         /* Reset the CRC on a new chunk */
@@ -1443,7 +1443,7 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
                            pm->buffer_position = 0;
                            mod->removed = 1;
                            }
-   
+
                         /* The buffer has been filled with something (we assume)
                          * so output this.  Pend the current chunk.
                          */
@@ -1452,10 +1452,10 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
                         break; /* out of while */
                      }
                   }
-   
+
                   mod = mod->next;
                }
-   
+
                /* Don't do any further processing if the buffer was modified -
                 * otherwise the code will end up modifying a chunk that was just
                 * added.
@@ -1463,7 +1463,7 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
                if (mod != NULL)
                   break; /* out of switch */
             }
-   
+
             /* If we get to here then this chunk may need to be modified.  To do
              * this is must be less than 1024 bytes in total size, otherwise
              * it just gets flushed.
@@ -1473,7 +1473,7 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
                store_read_imp(&pm->this, pm->buffer+pm->buffer_count,
                    len+12-pm->buffer_count);
                pm->buffer_count = len+12;
-   
+
                /* Check for a modification, else leave it be. */
                mod = pm->modifications;
                while (mod != NULL)
@@ -1500,14 +1500,14 @@ modifier_read_imp(png_modifier *pm, png_bytep pb, png_size_t st)
                         modifier_setbuffer(pm);
                      }
                   }
-   
+
                   mod = mod->next;
                }
             }
 
             else
                pm->flush = len+12 - pm->buffer_count; /* data + crc */
-   
+
             /* Take the data from the buffer (if there is any). */
             break;
       }
@@ -2073,7 +2073,7 @@ make_error(png_store* ps, png_byte PNG_CONST colour_type, png_byte bit_depth,
          for (pass=1; pass<=npasses; ++pass)
          {
             png_uint_32 y;
-         
+
             for (y=0; y<h; ++y)
             {
                png_byte buffer[STD_ROWMAX];
@@ -2241,7 +2241,7 @@ standard_info_part1(standard_display *dp, png_structp pp, png_infop pi)
     * no transforms, it does for other tests where rowbytes may change after
     * png_read_update_info.
     */
-   if (png_get_rowbytes(pp, pi) != 
+   if (png_get_rowbytes(pp, pi) !=
        standard_rowsize(pp, dp->colour_type, dp->bit_depth))
       png_error(pp, "validate: row size changed");
 
@@ -2750,7 +2750,7 @@ gamma_display_init(gamma_display *dp, png_modifier *pm, png_byte colour_type,
    /* Standard fields */
    standard_display_init(&dp->this, &pm->this, colour_type, bit_depth,
       interlace_type);
-   
+
    /* Parameter fields */
    dp->pm = pm;
    dp->file_gamma = file_gamma;
diff --git a/pngwutil.c b/pngwutil.c
index 454350c70..3377d38c4 100644
--- a/pngwutil.c
+++ b/pngwutil.c
@@ -653,7 +653,7 @@ png_write_IHDR(png_structp png_ptr, png_uint_32 width, png_uint_32 height,
 
    png_ptr->zstream.next_out = png_ptr->zbuf;
    png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
-   /* libpng is not interested in zstream.data_type, so set it 
+   /* libpng is not interested in zstream.data_type, so set it
     * to a predefined value, to avoid its evaluation inside zlib
     */
    png_ptr->zstream.data_type = Z_BINARY;