1 files changed, 112 insertions, 0 deletions
diff --git a/mysys/my_vle.c b/mysys/my_vle.c
new file mode 100644
index 00000000000..5b93ba69bd9
--- /dev/null
+++ b/mysys/my_vle.c
@@ -0,0 +1,112 @@
+/* 
+   Copyright (C) 2005 MySQL AB
+
+   This program is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+   USA
+*/
+
+/*
+  Variable length encoding.
+
+  A method to store an arbitrary-size non-negative integer. We let the
+  most significant bit of the number indicate that the next byte
+  should be contatenated to form the real number.
+*/
+
+#include "my_vle.h"
+
+/*
+  Function to encode an unsigned long as VLE. The bytes for the VLE
+  will be written to the location pointed to by 'out'.  The maximum
+  number of bytes written will be 'max'.
+
+  PARAMETERS
+
+    out  Pointer to beginning of where to store VLE bytes.
+    max  Maximum number of bytes to write.
+    n    Number to encode.
+
+  RETURN VALUE
+    On success, one past the end of the array containing the VLE
+    bytes.  On failure, the 'out' pointer is returned.
+*/
+
+byte*
+my_vle_encode(byte* out, my_size_t max, ulong n) 
+{
+  byte buf[my_vle_sizeof(n)];
+  byte *ptr= buf;
+  my_size_t len;
+
+  do
+  {
+    *ptr++= (byte) (n & 0x7F);
+    n>>= 7;
+  }
+  while (n > 0);
+
+  len= ptr - buf;
+  
+  if (len <= max)
+  {
+    /*
+      The bytes are stored in reverse order in 'buf'. Let's write them
+      in correct order to the output buffer and set the MSB at the
+      same time.
+    */
+    while (ptr-- > buf)
+    {
+      byte v= *ptr;
+      if (ptr > buf)
+        v|= 0x80;
+      *out++= v;
+    }
+  }
+
+  return out;
+}
+
+/*
+  Function to decode a VLE representation of an integral value.
+
+
+  PARAMETERS
+
+    result_ptr  Pointer to an unsigned long where the value will be written.
+    vle         Pointer to the VLE bytes.
+
+  RETURN VALUE
+
+    One-past the end of the VLE bytes. The routine will never read
+    more than sizeof(*result_ptr) + 1 bytes.
+*/
+
+byte const*
+my_vle_decode(ulong *result_ptr, byte const *vle) 
+{
+  ulong result= 0;
+  my_size_t cnt= 1;
+
+  do
+  {
+    result<<= 7;
+    result|= (*vle & 0x7F);
+  }
+  while ((*vle++ & 0x80) && ++cnt <= sizeof(*result_ptr) + 1);
+
+  if (cnt <= sizeof(*result_ptr) + 1)
+    *result_ptr= result;
+
+  return vle;
+}