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copied!<p>If you dig through the headers you'll find this in <code>server/c.h</code>:</p> <pre><code>/* ---------------- * Variable-length datatypes all share the 'struct varlena' header. *... */ struct varlena { char vl_len_[4]; /* Do not touch this field directly! */ char vl_dat[1]; }; #define VARHDRSZ ((int32) sizeof(int32)) /* * These widely-used datatypes are just a varlena header and the data bytes. * There is no terminating null or anything like that --- the data length is * always VARSIZE(ptr) - VARHDRSZ. */ typedef struct varlena bytea; typedef struct varlena text; </code></pre> <p>so there's your definition of the <code>text</code> data type. Note this rather important part of the comment:</p> <blockquote> <p>There is no terminating null or anything like that</p> </blockquote> <p>That indicates that you absolutely do not want to treat <code>fileName->data</code> as a C string unless you like segfaults. You need a way to convert a <code>text</code> to a nul-terminated C string that you can hand to <code>stat</code>; there is a function for that: <code>text_to_cstring</code>.</p> <p>The only documentation for <code>text_to_cstring</code> that I can find is <a href="http://doxygen.postgresql.org/varlena_8c_source.html#l00121" rel="nofollow noreferrer">this comment in the source</a>:</p> <pre><code>/* * text_to_cstring * * Create a palloc'd, null-terminated C string from a text value. * * We support being passed a compressed or toasted text value. * This is a bit bogus since such values shouldn't really be referred to as * "text *", but it seems useful for robustness. If we didn't handle that * case here, we'd need another routine that did, anyway. */ </code></pre> <p>There is also <a href="http://www.postgresql.org/docs/current/static/spi-examples.html" rel="nofollow noreferrer">an example that uses it</a>:</p> <pre><code>char *command; /*...*/ /* Convert given text object to a C string */ command = text_to_cstring(sql); /*...*/ pfree(command); </code></pre> <p>You should be able to do something like this:</p> <pre><code>struct stat buf; char *fileName = text_to_cstring(PG_GETARG_TEXT_P(0)); int i = stat(fileName, &buf); pfree(fileName); </code></pre>

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