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Doc clarifications regarding use of varlena.

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Jay Levitt, reviewed by Tom Lane.
This commit is contained in:
Robert Haas 2012-03-22 15:45:42 -04:00
parent e83f827f5a
commit fdf719cd28
1 changed files with 3 additions and 2 deletions
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doc/src/sgml/xfunc.sgml
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@ -1767,7 +1767,8 @@ typedef struct
<para> <para>
Finally, all variable-length types must also be passed Finally, all variable-length types must also be passed
by reference. All variable-length types must begin 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 be stored within that type must be located in the memory
immediately following that length field. The immediately following that length field. The
length field contains the total length of the structure, length field contains the total length of the structure,
@ -1833,7 +1834,7 @@ memcpy(destination->data, buffer, 40);
]]> ]]>
</programlisting> </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</> it's considered good style to use the macro <literal>VARHDRSZ</>
to refer to the size of the overhead for a variable-length type. 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 length field <emphasis>must</> be set using the