bmap::copy truncates file

ftruncate was executed into the main function and it should be done into
the copying process

Signed-off-by: Rafael Garcia Ruiz <[email protected]>

bmap-rs/Cargo.toml

@@ -10,5 +10,4 @@ edition = "2018"
 bmap = { path = "../bmap" }
 anyhow = "1"
 structopt = "0.3"
-nix = "0.25"
 flate2 = "1"

bmap-rs/src/main.rs

@@ -1,11 +1,9 @@
 use anyhow::{anyhow, bail, Context, Result};
 use bmap::{Bmap, Discarder, SeekForward};
 use flate2::read::GzDecoder;
-use nix::unistd::ftruncate;
 use std::ffi::OsStr;
 use std::fs::File;
 use std::io::Read;
-use std::os::unix::io::AsRawFd;
 use std::path::{Path, PathBuf};
 use structopt::StructOpt;
 
@@ -104,8 +102,6 @@ fn copy(c: Copy) -> Result<()> {
         .create(true)
         .open(c.dest)?;
 
-    ftruncate(output.as_raw_fd(), bmap.image_size() as i64).context("Failed to truncate file")?;
-
     let mut input = setup_input(&c.image)?;
     bmap::copy(&mut input, &mut output, &bmap)?;
     println!("Done: Syncing...");

bmap/Cargo.toml

@@ -16,3 +16,4 @@ sha2 = { version = "0.10.6", features = [ "asm" ] }
 strum = { version = "0.24.1", features = [ "derive"] }
 digest = "0.10.5"
 flate2 = "1.0.20"
+nix = "0.25"

bmap/src/lib.rs

@@ -2,11 +2,13 @@ mod bmap;
 pub use crate::bmap::*;
 mod discarder;
 pub use crate::discarder::*;
+use nix::unistd::ftruncate;
 use sha2::{Digest, Sha256};
 use thiserror::Error;
 
 use std::io::Result as IOResult;
 use std::io::{Read, Seek, SeekFrom, Write};
+use std::os::unix::prelude::AsRawFd;
 
 /// Trait that can only seek further forwards
 pub trait SeekForward {
@@ -35,12 +37,14 @@ pub enum CopyError {
 pub fn copy<I, O>(input: &mut I, output: &mut O, map: &Bmap) -> Result<(), CopyError>
 where
     I: Read + SeekForward,
-    O: Write + SeekForward,
+    O: Write + SeekForward + AsRawFd,
 {
     let mut hasher = match map.checksum_type() {
         HashType::Sha256 => Sha256::new(),
     };
 
+    let _ = ftruncate(output.as_raw_fd(), map.image_size() as i64);
+
     let mut v = Vec::new();
     // TODO benchmark a reasonable size for this
     v.resize(8 * 1024 * 1024, 0);