postgresql/contrib/lo/lo.c

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/*
* PostgreSQL type definitions for managed LargeObjects.
*
* $Id: lo.c,v 1.1 1998/06/16 07:07:11 momjian Exp $
*
*/
#include <stdio.h>
#include <postgres.h>
#include <utils/palloc.h>
/* Required for largeobjects */
#include <libpq/libpq-fs.h>
#include <libpq/be-fsstubs.h>
/* Required for SPI */
#include <executor/spi.h>
/* Required for triggers */
#include <commands/trigger.h>
/* required for tolower() */
/*
* This is the internal storage format for managed large objects
*
*/
typedef Oid Blob;
/*
* Various forward declarations:
*/
Blob *lo_in(char *str); /* Create from String */
char *lo_out(Blob * addr); /* Output oid as String */
Oid lo_oid(Blob * addr); /* Return oid as an oid */
Blob *lo(Oid oid); /* Return Blob based on oid */
HeapTuple lo_manage(void); /* Trigger handler */
/*
* This creates a large object, and set's its OID to the value in the
* supplied string.
*
* If the string is empty, then a new LargeObject is created, and its oid
* is placed in the resulting lo.
*/
Blob *
lo_in(char *str)
{
Blob *result;
Oid oid;
int count;
if (strlen(str) > 0)
{
count = sscanf(str, "%d", &oid);
if (count < 1)
{
elog(ERROR, "lo_in: error in parsing \"%s\"", str);
return (NULL);
}
if(oid < 0)
{
elog(ERROR, "lo_in: illegal oid \"%s\"", str);
return (NULL);
}
}
else
{
/*
* There is no Oid passed, so create a new one
*/
oid = lo_creat(INV_READ|INV_WRITE);
if(oid == InvalidOid)
{
elog(ERROR,"lo_in: InvalidOid returned from lo_creat");
return (NULL);
}
}
result = (Blob *) palloc(sizeof(Blob));
*result = oid;
return (result);
}
/*
* This simply outputs the Oid of the Blob as a string.
*/
char *
lo_out(Blob * addr)
{
char *result;
if (addr == NULL)
return (NULL);
result = (char *) palloc(32);
sprintf(result,"%d",*addr);
return (result);
}
/*
* This function converts Blob to oid.
*
* eg: select lo_export(raster::oid,'/path/file') from table;
*
*/
Oid
lo_oid(Blob * addr)
{
if(addr == NULL)
return InvalidOid;
return (Oid)(*addr);
}
/*
* This function is used so we can convert oid's to lo's
*
* ie: insert into table values(lo_import('/path/file')::lo);
*
*/
Blob *
lo(Oid oid)
{
Blob *result = (Blob *) palloc(sizeof(Blob));
*result = oid;
return (result);
}
/*
* This handles the trigger that protects us from orphaned large objects
*/
HeapTuple
lo_manage(void)
{
int attnum; /* attribute number to monitor */
char **args; /* Args containing attr name */
TupleDesc tupdesc; /* Tuple Descriptor */
HeapTuple rettuple; /* Tuple to be returned */
bool isdelete; /* are we deleting? */
HeapTuple newtuple=NULL; /* The new value for tuple */
HeapTuple trigtuple; /* The original value of tuple */
if (!CurrentTriggerData)
elog(ERROR, "lo: triggers are not initialized");
/*
* Fetch some values from CurrentTriggerData
*/
newtuple = CurrentTriggerData->tg_newtuple;
trigtuple = CurrentTriggerData->tg_trigtuple;
tupdesc = CurrentTriggerData->tg_relation->rd_att;
args = CurrentTriggerData->tg_trigger->tgargs;
/* tuple to return to Executor */
if (TRIGGER_FIRED_BY_UPDATE(CurrentTriggerData->tg_event))
rettuple = newtuple;
else
rettuple = trigtuple;
/* Are we deleting the row? */
isdelete = TRIGGER_FIRED_BY_DELETE(CurrentTriggerData->tg_event);
/* Were done with it */
CurrentTriggerData = NULL;
/* Get the column were interested in */
attnum = SPI_fnumber(tupdesc,args[0]);
/*
* Handle updates
*
* Here, if the value of the monitored attribute changes, then the
* large object associated with the original value is unlinked.
*/
if(newtuple!=NULL) {
char *orig = SPI_getvalue(trigtuple,tupdesc,attnum);
char *newv = SPI_getvalue(newtuple,tupdesc,attnum);
if((orig != newv && (orig==NULL || newv==NULL)) || (orig!=NULL && newv!=NULL && strcmp(orig,newv)))
lo_unlink(atoi(orig));
if(newv)
pfree(newv);
if(orig)
pfree(orig);
}
/*
* Handle deleting of rows
*
* Here, we unlink the large object associated with the managed attribute
*
*/
if(isdelete) {
char *orig = SPI_getvalue(trigtuple,tupdesc,attnum);
if(orig != NULL) {
lo_unlink(atoi(orig));
pfree(orig);
}
}
return (rettuple);
}