Adds lo mod

Author: sanpii

Cargo.toml

@@ -15,14 +15,11 @@ readme = "README.md"
 rust-version = "1.77"
 
 [dependencies]
+bitflags = "2.0"
 libc = "0.2"
 log = "0.4"
 thiserror = "1.0"
 
-[dependencies.bitflags]
-version = "2.0"
-optional = true
-
 [dependencies.pq-sys]
 package = "libpq-sys"
 path = "libpq-sys"
@@ -40,6 +37,6 @@ default = []
 v11 = []
 v12 = ["v11"]
 v13 = ["v12"]
-v14 = ["v13", "bitflags"]
+v14 = ["v13"]
 v15 = ["v14"]
 v16 = ["v15"]

examples/testlo.rs

@@ -0,0 +1,94 @@
+/*
+ * Test using large objects with libpq
+ *
+ * <https://github.com/postgres/postgres/blob/REL_16_0/src/test/examples/testlo.c>
+ */
+
+fn main() -> libpq::errors::Result {
+    let mut args = std::env::args();
+
+    if args.len() < 4 {
+        panic!(
+            "usage: {} database_name in_filename out_filename",
+            args.nth(0).unwrap()
+        );
+    }
+
+    let database = args.nth(1).unwrap();
+    let in_filename = args.next().unwrap();
+    let out_filename = args.next().unwrap();
+
+    /*
+     * set up the connection
+     */
+    let conn = libpq::Connection::set_db(None, None, None, None, Some(&database))?;
+
+    /* Set always-secure search path, so malicious users can't take control. */
+    let res = conn.exec("SELECT pg_catalog.set_config('search_path', '', false)");
+    if res.status() != libpq::Status::TupplesOk {
+        panic!("SET failed: {:?}", conn.error_message());
+    }
+
+    conn.exec("begin");
+    println!("importing file \"{in_filename}\" ...");
+    let lobj_oid = libpq::lo::import(&conn, &in_filename);
+
+    println!("\tas large object {lobj_oid}.");
+
+    println!("picking out bytes 1000-2000 of the large object");
+    pickout(&conn, lobj_oid, 1_000, 1_000)?;
+
+    println!("overwriting bytes 1000-2000 of the large object with X's");
+    overwrite(&conn, lobj_oid, 1_000, 1_000)?;
+
+    println!("exporting large object to file \"{out_filename}\" ...");
+    libpq::lo::export(&conn, &out_filename, lobj_oid)?;
+
+    conn.exec("end");
+
+    Ok(())
+}
+
+fn pickout(
+    conn: &libpq::Connection,
+    lobj_id: libpq::Oid,
+    start: i32,
+    len: usize,
+) -> libpq::errors::Result {
+    let lobj = libpq::lo::open(conn, lobj_id, libpq::lo::Inv::READ)?;
+
+    lobj.lseek(start, libpq::lo::Seek::Set)?;
+
+    let mut nread = 0;
+
+    while len - nread > 0 {
+        let mut buf = lobj.read(len - nread)?;
+        let nbytes = buf.len();
+        buf.insert(nbytes, '\0');
+        eprint!(">>> {buf}");
+        nread += nbytes;
+        if nbytes <= 0 {
+            break; /* no more data? */
+        }
+    }
+    eprintln!("");
+
+    Ok(())
+}
+
+fn overwrite(conn: &libpq::Connection, lobj_id: libpq::Oid, start: i32, len: usize) -> libpq::errors::Result {
+    let lobj = libpq::lo::open(conn, lobj_id, libpq::lo::Inv::WRITE)?;
+
+    lobj.lseek(start, libpq::lo::Seek::Set)?;
+    let mut buf = "X".repeat(len);
+    buf.insert(len - 1, '\0');
+
+    let mut nwritten = 0;
+    while len - nwritten > 0 {
+        let nbytes = lobj.write(&buf[nwritten..len - nwritten])?;
+        nwritten += nbytes;
+    }
+    eprintln!("");
+
+    Ok(())
+}

examples/testlo64.rs

@@ -0,0 +1,112 @@
+/**
+ * Test using large objects with libpq using 64-bit APIs
+ *
+ * <https://github.com/postgres/postgres/blob/REL_16_0/src/test/examples/testlo64.c>
+ */
+
+fn main() -> libpq::errors::Result {
+    let mut args = std::env::args();
+
+    if args.len() < 5 {
+        panic!(
+            "usage: {} database_name in_filename out_filename out_filename2",
+            args.nth(0).unwrap()
+        );
+    }
+
+    let database = args.nth(1).unwrap();
+    let in_filename = args.next().unwrap();
+    let out_filename = args.next().unwrap();
+    let out_filename2 = args.next().unwrap();
+
+    /*
+     * set up the connection
+     */
+    let conn = libpq::Connection::set_db(None, None, None, None, Some(&database))?;
+
+    /* Set always-secure search path, so malicious users can't take control. */
+    let res = conn.exec("SELECT pg_catalog.set_config('search_path', '', false)");
+    if res.status() != libpq::Status::TupplesOk {
+        panic!("SET failed: {:?}", conn.error_message());
+    }
+
+    conn.exec("begin");
+
+    println!("importing file \"{in_filename}\" ...");
+    let lobj_oid = libpq::lo::import(&conn, &in_filename);
+
+    println!("\tas large object {lobj_oid}.");
+
+    println!("picking out bytes 4294967000-4294968000 of the large object");
+    pickout(&conn, lobj_oid, 4_294_967_000, 1_000)?;
+
+    println!("overwriting bytes 4294967000-4294968000 of the large object with X's");
+    overwrite(&conn, lobj_oid, 4_294_967_000, 1_000)?;
+
+    println!("exporting large object to file \"{out_filename}\" ...");
+    libpq::lo::export(&conn, &out_filename, lobj_oid)?;
+
+    println!("truncating to 3294968000 bytes");
+    my_truncate(&conn, lobj_oid, 3_294_968_000)?;
+
+    println!("exporting truncated large object to file \"{out_filename2}\" ...");
+    libpq::lo::export(&conn, &out_filename2, lobj_oid)?;
+
+    conn.exec("end");
+
+    Ok(())
+}
+
+fn pickout(
+    conn: &libpq::Connection,
+    lobj_id: libpq::Oid,
+    start: i64,
+    len: usize,
+) -> libpq::errors::Result {
+    let lobj = libpq::lo::open(conn, lobj_id, libpq::lo::Inv::READ)?;
+
+    lobj.lseek64(start, libpq::lo::Seek::Set)?;
+
+    if lobj.tell64()? != start {
+        panic!("error in lo_tell64: {:?}", conn.error_message());
+    }
+
+    let mut nread = 0;
+
+    while len - nread > 0 {
+        let mut buf = lobj.read(len - nread)?;
+        let nbytes = buf.len();
+        buf.insert(nbytes, '\0');
+        eprint!(">>> {buf}");
+        nread += nbytes;
+        if nbytes <= 0 {
+            break; /* no more data? */
+        }
+    }
+    eprintln!("");
+
+    Ok(())
+}
+
+fn overwrite(conn: &libpq::Connection, lobj_id: libpq::Oid, start: i64, len: usize) -> libpq::errors::Result {
+    let lobj = libpq::lo::open(conn, lobj_id, libpq::lo::Inv::WRITE)?;
+
+    lobj.lseek64(start, libpq::lo::Seek::Set)?;
+    let mut buf = "X".repeat(len);
+    buf.insert(len - 1, '\0');
+
+    let mut nwritten = 0;
+    while len - nwritten > 0 {
+        let nbytes = lobj.write(&buf[nwritten..len - nwritten])?;
+        nwritten += nbytes;
+    }
+    eprintln!("");
+
+    Ok(())
+}
+
+fn my_truncate(conn: &libpq::Connection, lobj_id: libpq::Oid, len: i64) -> libpq::errors::Result {
+    let lobj = libpq::lo::open(conn, lobj_id, libpq::lo::Inv::WRITE)?;
+
+    lobj.truncate64(len)
+}

src/errors.rs

@@ -8,6 +8,8 @@ pub enum Error {
     NulError(#[from] std::ffi::NulError),
     #[error("{0}")]
     Backend(String),
+    #[error("Large object error")]
+    LargeObject,
     #[error("Unknow error")]
     Unknow,
     #[error("{0}")]

src/lib.rs

@@ -8,6 +8,7 @@ pub mod connection;
 pub mod encrypt;
 pub mod errors;
 pub mod escape;
+pub mod lo;
 pub mod ping;
 #[cfg(feature = "v14")]
 pub mod pipeline;
@@ -31,6 +32,7 @@ mod verbosity;
 pub use connection::Connection;
 pub use encoding::*;
 pub use format::*;
+pub use lo::LargeObject;
 pub use oid::*;
 pub use result::Result;
 pub use state::State;