Initial commit

vendor/github.com/jackc/pgx/v4/large_objects.go

@@ -0,0 +1,121 @@
+package pgx
+
+import (
+	"context"
+	"errors"
+	"io"
+)
+
+// LargeObjects is a structure used to access the large objects API. It is only valid within the transaction where it
+// was created.
+//
+// For more details see: http://www.postgresql.org/docs/current/static/largeobjects.html
+type LargeObjects struct {
+	tx Tx
+}
+
+type LargeObjectMode int32
+
+const (
+	LargeObjectModeWrite LargeObjectMode = 0x20000
+	LargeObjectModeRead  LargeObjectMode = 0x40000
+)
+
+// Create creates a new large object. If oid is zero, the server assigns an unused OID.
+func (o *LargeObjects) Create(ctx context.Context, oid uint32) (uint32, error) {
+	err := o.tx.QueryRow(ctx, "select lo_create($1)", oid).Scan(&oid)
+	return oid, err
+}
+
+// Open opens an existing large object with the given mode. ctx will also be used for all operations on the opened large
+// object.
+func (o *LargeObjects) Open(ctx context.Context, oid uint32, mode LargeObjectMode) (*LargeObject, error) {
+	var fd int32
+	err := o.tx.QueryRow(ctx, "select lo_open($1, $2)", oid, mode).Scan(&fd)
+	if err != nil {
+		return nil, err
+	}
+	return &LargeObject{fd: fd, tx: o.tx, ctx: ctx}, nil
+}
+
+// Unlink removes a large object from the database.
+func (o *LargeObjects) Unlink(ctx context.Context, oid uint32) error {
+	var result int32
+	err := o.tx.QueryRow(ctx, "select lo_unlink($1)", oid).Scan(&result)
+	if err != nil {
+		return err
+	}
+
+	if result != 1 {
+		return errors.New("failed to remove large object")
+	}
+
+	return nil
+}
+
+// A LargeObject is a large object stored on the server. It is only valid within the transaction that it was initialized
+// in. It uses the context it was initialized with for all operations. It implements these interfaces:
+//
+//    io.Writer
+//    io.Reader
+//    io.Seeker
+//    io.Closer
+type LargeObject struct {
+	ctx context.Context
+	tx  Tx
+	fd  int32
+}
+
+// Write writes p to the large object and returns the number of bytes written and an error if not all of p was written.
+func (o *LargeObject) Write(p []byte) (int, error) {
+	var n int
+	err := o.tx.QueryRow(o.ctx, "select lowrite($1, $2)", o.fd, p).Scan(&n)
+	if err != nil {
+		return n, err
+	}
+
+	if n < 0 {
+		return 0, errors.New("failed to write to large object")
+	}
+
+	return n, nil
+}
+
+// Read reads up to len(p) bytes into p returning the number of bytes read.
+func (o *LargeObject) Read(p []byte) (int, error) {
+	var res []byte
+	err := o.tx.QueryRow(o.ctx, "select loread($1, $2)", o.fd, len(p)).Scan(&res)
+	copy(p, res)
+	if err != nil {
+		return len(res), err
+	}
+
+	if len(res) < len(p) {
+		err = io.EOF
+	}
+	return len(res), err
+}
+
+// Seek moves the current location pointer to the new location specified by offset.
+func (o *LargeObject) Seek(offset int64, whence int) (n int64, err error) {
+	err = o.tx.QueryRow(o.ctx, "select lo_lseek64($1, $2, $3)", o.fd, offset, whence).Scan(&n)
+	return n, err
+}
+
+// Tell returns the current read or write location of the large object descriptor.
+func (o *LargeObject) Tell() (n int64, err error) {
+	err = o.tx.QueryRow(o.ctx, "select lo_tell64($1)", o.fd).Scan(&n)
+	return n, err
+}
+
+// Trunctes the large object to size.
+func (o *LargeObject) Truncate(size int64) (err error) {
+	_, err = o.tx.Exec(o.ctx, "select lo_truncate64($1, $2)", o.fd, size)
+	return err
+}
+
+// Close closees the large object descriptor.
+func (o *LargeObject) Close() error {
+	_, err := o.tx.Exec(o.ctx, "select lo_close($1)", o.fd)
+	return err
+}