I'm new to the codebase, but I think this patch reflects real-world usage;
the PostgreSQL code itself always calls the length field "vl_len_", and I
believe int32 is preferred over int4 (yes?)
Jay Levitt
diff --git a/doc/src/sgml/xfunc.sgml b/doc/src/sgml/xfunc.sgml
index a6d2a13..b19801d 100644
--- a/doc/src/sgml/xfunc.sgml
+++ b/doc/src/sgml/xfunc.sgml
@@ -1733,9 +1733,11 @@ typedef struct
<para>
Finally, all variable-length types must also be passed
by reference. All variable-length types must begin
- with a length field of exactly 4 bytes, and all data to
+ with an opaque length field of exactly 4 bytes, which will be set
+ by SET_VARSIZE; never set this field directly! All data to
be stored within that type must be located in the memory
- immediately following that length field. The
+ immediately following the length field, which is customarily
+ named <literal>vl_len_</literal>. The
length field contains the total length of the structure,
that is, it includes the size of the length field
itself.
@@ -1766,7 +1768,7 @@ typedef struct
<programlisting>
typedef struct {
- int4 length;
+ int32 vl_len_;
char data[1];
} text;
</programlisting>
@@ -1799,10 +1801,10 @@ memcpy(destination->data, buffer, 40);
]]>
</programlisting>
- <literal>VARHDRSZ</> is the same as <literal>sizeof(int4)</>, but
+ <literal>VARHDRSZ</> is the same as <literal>sizeof(int32)</>, but
it's considered good style to use the macro <literal>VARHDRSZ</>
to refer to the size of the overhead for a variable-length type.
- Also, the length field <emphasis>must</> be set using the
+ Also, the vl_len_ field <emphasis>must</> be set using the
<literal>SET_VARSIZE</> macro, not by simple assignment.
</para>
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