150 lines
4.2 KiB
Go
150 lines
4.2 KiB
Go
package pgx
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import (
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"io"
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"github.com/jackc/pgx/pgtype"
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)
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// LargeObjects is a structure used to access the large objects API. It is only
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// valid within the transaction where it was created.
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//
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// For more details see: http://www.postgresql.org/docs/current/static/largeobjects.html
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type LargeObjects struct {
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// Has64 is true if the server is capable of working with 64-bit numbers
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Has64 bool
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fp *fastpath
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}
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const largeObjectFns = `select proname, oid from pg_catalog.pg_proc
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where proname in (
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'lo_open',
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'lo_close',
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'lo_create',
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'lo_unlink',
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'lo_lseek',
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'lo_lseek64',
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'lo_tell',
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'lo_tell64',
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'lo_truncate',
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'lo_truncate64',
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'loread',
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'lowrite')
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and pronamespace = (select oid from pg_catalog.pg_namespace where nspname = 'pg_catalog')`
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// LargeObjects returns a LargeObjects instance for the transaction.
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func (tx *Tx) LargeObjects() (*LargeObjects, error) {
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if tx.conn.fp == nil {
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tx.conn.fp = newFastpath(tx.conn)
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}
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if _, exists := tx.conn.fp.fns["lo_open"]; !exists {
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res, err := tx.Query(largeObjectFns)
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if err != nil {
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return nil, err
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}
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if err := tx.conn.fp.addFunctions(res); err != nil {
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return nil, err
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}
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}
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lo := &LargeObjects{fp: tx.conn.fp}
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_, lo.Has64 = lo.fp.fns["lo_lseek64"]
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return lo, nil
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}
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type LargeObjectMode int32
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const (
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LargeObjectModeWrite LargeObjectMode = 0x20000
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LargeObjectModeRead LargeObjectMode = 0x40000
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)
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// Create creates a new large object. If id is zero, the server assigns an
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// unused OID.
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func (o *LargeObjects) Create(id pgtype.OID) (pgtype.OID, error) {
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newOID, err := fpInt32(o.fp.CallFn("lo_create", []fpArg{fpIntArg(int32(id))}))
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return pgtype.OID(newOID), err
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}
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// Open opens an existing large object with the given mode.
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func (o *LargeObjects) Open(oid pgtype.OID, mode LargeObjectMode) (*LargeObject, error) {
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fd, err := fpInt32(o.fp.CallFn("lo_open", []fpArg{fpIntArg(int32(oid)), fpIntArg(int32(mode))}))
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return &LargeObject{fd: fd, lo: o}, err
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}
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// Unlink removes a large object from the database.
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func (o *LargeObjects) Unlink(oid pgtype.OID) error {
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_, err := o.fp.CallFn("lo_unlink", []fpArg{fpIntArg(int32(oid))})
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return err
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}
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// A LargeObject is a large object stored on the server. It is only valid within
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// the transaction that it was initialized in. It implements these interfaces:
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//
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// io.Writer
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// io.Reader
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// io.Seeker
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// io.Closer
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type LargeObject struct {
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fd int32
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lo *LargeObjects
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}
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// Write writes p to the large object and returns the number of bytes written
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// and an error if not all of p was written.
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func (o *LargeObject) Write(p []byte) (int, error) {
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n, err := fpInt32(o.lo.fp.CallFn("lowrite", []fpArg{fpIntArg(o.fd), p}))
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return int(n), err
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}
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// Read reads up to len(p) bytes into p returning the number of bytes read.
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func (o *LargeObject) Read(p []byte) (int, error) {
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res, err := o.lo.fp.CallFn("loread", []fpArg{fpIntArg(o.fd), fpIntArg(int32(len(p)))})
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if len(res) < len(p) {
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err = io.EOF
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}
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return copy(p, res), err
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}
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// Seek moves the current location pointer to the new location specified by offset.
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func (o *LargeObject) Seek(offset int64, whence int) (n int64, err error) {
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if o.lo.Has64 {
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n, err = fpInt64(o.lo.fp.CallFn("lo_lseek64", []fpArg{fpIntArg(o.fd), fpInt64Arg(offset), fpIntArg(int32(whence))}))
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} else {
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var n32 int32
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n32, err = fpInt32(o.lo.fp.CallFn("lo_lseek", []fpArg{fpIntArg(o.fd), fpIntArg(int32(offset)), fpIntArg(int32(whence))}))
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n = int64(n32)
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}
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return
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}
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// Tell returns the current read or write location of the large object
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// descriptor.
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func (o *LargeObject) Tell() (n int64, err error) {
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if o.lo.Has64 {
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n, err = fpInt64(o.lo.fp.CallFn("lo_tell64", []fpArg{fpIntArg(o.fd)}))
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} else {
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var n32 int32
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n32, err = fpInt32(o.lo.fp.CallFn("lo_tell", []fpArg{fpIntArg(o.fd)}))
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n = int64(n32)
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}
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return
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}
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// Trunctes the large object to size.
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func (o *LargeObject) Truncate(size int64) (err error) {
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if o.lo.Has64 {
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_, err = o.lo.fp.CallFn("lo_truncate64", []fpArg{fpIntArg(o.fd), fpInt64Arg(size)})
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} else {
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_, err = o.lo.fp.CallFn("lo_truncate", []fpArg{fpIntArg(o.fd), fpIntArg(int32(size))})
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}
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return
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}
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// Close closees the large object descriptor.
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func (o *LargeObject) Close() error {
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_, err := o.lo.fp.CallFn("lo_close", []fpArg{fpIntArg(o.fd)})
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return err
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}
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