[glib] gchecksum: fix strict-aliasing warnings in the MD5 code

[Dan Winship <danw src gnome org>]

commit a81a0622027a21b71ba11677933f07b646cca151
Author: Dan Winship <danw gnome org>
Date:   Wed Apr 4 10:21:24 2012 -0400

    gchecksum: fix strict-aliasing warnings in the MD5 code
    
    https://bugzilla.gnome.org/show_bug.cgi?id=673191

 glib/gchecksum.c |   39 +++++++++++++++++++++------------------
 1 files changed, 21 insertions(+), 18 deletions(-)
---
diff --git a/glib/gchecksum.c b/glib/gchecksum.c
index e860243..f543d96 100644
--- a/glib/gchecksum.c
+++ b/glib/gchecksum.c
@@ -67,7 +67,10 @@ typedef struct
   guint32 buf[4];
   guint32 bits[2];
 
-  guchar data[MD5_DATASIZE];
+  union {
+    guchar data[MD5_DATASIZE];
+    guint32 data32[MD5_DATASIZE / 4];
+  } u;
 
   guchar digest[MD5_DIGEST_LEN];
 } Md5sum;
@@ -329,13 +332,13 @@ md5_sum_update (Md5sum       *md5,
 
   md5->bits[1] += length >> 29;
 
-  /* bytes already in Md5sum->data */
+  /* bytes already in Md5sum->u.data */
   bit = (bit >> 3) & 0x3f;
 
   /* handle any leading odd-sized chunks */
   if (bit)
     {
-      guchar *p = (guchar *) md5->data + bit;
+      guchar *p = md5->u.data + bit;
 
       bit = MD5_DATASIZE - bit;
       if (length < bit)
@@ -346,8 +349,8 @@ md5_sum_update (Md5sum       *md5,
 
       memcpy (p, data, bit);
 
-      md5_byte_reverse (md5->data, 16);
-      md5_transform (md5->buf, (guint32 *) md5->data);
+      md5_byte_reverse (md5->u.data, 16);
+      md5_transform (md5->buf, md5->u.data32);
 
       data += bit;
       length -= bit;
@@ -356,17 +359,17 @@ md5_sum_update (Md5sum       *md5,
   /* process data in 64-byte chunks */
   while (length >= MD5_DATASIZE)
     {
-      memcpy (md5->data, data, MD5_DATASIZE);
+      memcpy (md5->u.data, data, MD5_DATASIZE);
 
-      md5_byte_reverse (md5->data, 16);
-      md5_transform (md5->buf, (guint32 *) md5->data);
+      md5_byte_reverse (md5->u.data, 16);
+      md5_transform (md5->buf, md5->u.data32);
 
       data += MD5_DATASIZE;
       length -= MD5_DATASIZE;
     }
 
   /* handle any remaining bytes of data */
-  memcpy (md5->data, data, length);
+  memcpy (md5->u.data, data, length);
 }
 
 /* closes a checksum */
@@ -382,7 +385,7 @@ md5_sum_close (Md5sum *md5)
   /* Set the first char of padding to 0x80.
    * This is safe since there is always at least one byte free
    */
-  p = md5->data + count;
+  p = md5->u.data + count;
   *p++ = 0x80;
 
   /* Bytes of padding needed to make 64 bytes */
@@ -394,11 +397,11 @@ md5_sum_close (Md5sum *md5)
       /* Two lots of padding:  Pad the first block to 64 bytes */
       memset (p, 0, count);
 
-      md5_byte_reverse (md5->data, 16);
-      md5_transform (md5->buf, (guint32 *) md5->data);
+      md5_byte_reverse (md5->u.data, 16);
+      md5_transform (md5->buf, md5->u.data32);
 
       /* Now fill the next block with 56 bytes */
-      memset (md5->data, 0, MD5_DATASIZE - 8);
+      memset (md5->u.data, 0, MD5_DATASIZE - 8);
     }
   else
     {
@@ -406,20 +409,20 @@ md5_sum_close (Md5sum *md5)
       memset (p, 0, count - 8);
     }
 
-  md5_byte_reverse (md5->data, 14);
+  md5_byte_reverse (md5->u.data, 14);
 
   /* Append length in bits and transform */
-  ((guint32 *) md5->data)[14] = md5->bits[0];
-  ((guint32 *) md5->data)[15] = md5->bits[1];
+  md5->u.data32[14] = md5->bits[0];
+  md5->u.data32[15] = md5->bits[1];
 
-  md5_transform (md5->buf, (guint32 *) md5->data);
+  md5_transform (md5->buf, md5->u.data32);
   md5_byte_reverse ((guchar *) md5->buf, 4);
 
   memcpy (md5->digest, md5->buf, 16);
 
   /* Reset buffers in case they contain sensitive data */
   memset (md5->buf, 0, sizeof (md5->buf));
-  memset (md5->data, 0, sizeof (md5->data));
+  memset (md5->u.data, 0, sizeof (md5->u.data));
 }
 
 static gchar *