1 files changed, 39 insertions, 6 deletions

diff --git a/sql/sql_string.cc b/sql/sql_string.cc
index c5544164dbf..f6025390cb2 100644
--- a/sql/sql_string.cc
+++ b/sql/sql_string.cc
@@ -54,11 +54,33 @@ bool String::real_alloc(uint32 length)
 }
 
 
-/*
-** Check that string is big enough. Set string[alloc_length] to 0
-** (for C functions)
-*/
+/**
+   Allocates a new buffer on the heap for this String.
+
+   - If the String's internal buffer is privately owned and heap allocated,
+     one of the following is performed.
+
+     - If the requested length is greater than what fits in the buffer, a new
+       buffer is allocated, data moved and the old buffer freed.
+
+     - If the requested length is less or equal to what fits in the buffer, a
+       null character is inserted at the appropriate position.
 
+   - If the String does not keep a private buffer on the heap, such a buffer
+     will be allocated and the string copied accoring to its length, as found
+     in String::length().
+ 
+   For C compatibility, the new string buffer is null terminated.
+
+   @param alloc_length The requested string size in characters, excluding any
+   null terminator.
+
+   @retval false Either the copy operation is complete or, if the size of the
+   new buffer is smaller than the currently allocated buffer (if one exists),
+   no allocation occured.
+
+   @retval true An error occured when attempting to allocate memory.
+*/
 bool String::realloc(uint32 alloc_length)
 {
   if (Alloced_length <= alloc_length)
@@ -131,6 +153,17 @@ bool String::copy()
   return FALSE;
 }
 
+/**
+   Copies the internal buffer from str. If this String has a private heap
+   allocated buffer where new data does not fit, a new buffer is allocated
+   before copying and the old buffer freed. Character set information is also
+   copied.
+   
+   @param str The string whose internal buffer is to be copied.
+   
+   @retval false Success.
+   @retval true Memory allocation failed.
+*/
 bool String::copy(const String &str)
 {
   if (alloc(str.str_length))
@@ -222,8 +255,8 @@ bool String::copy_aligned(const char *str,uint32 arg_length, uint32 offset,
 			  CHARSET_INFO *cs)
 {
   /* How many bytes are in incomplete character */
-  offset= cs->mbmaxlen - offset; /* How many zeros we should prepend */
-  DBUG_ASSERT(offset && offset != cs->mbmaxlen);
+  offset= cs->mbminlen - offset; /* How many zeros we should prepend */
+  DBUG_ASSERT(offset && offset != cs->mbminlen);
 
   uint32 aligned_length= arg_length + offset;
   if (alloc(aligned_length))