From 0628853b432605a0bbdcbc34fe29387135711aa0 Mon Sep 17 00:00:00 2001
From: Avril <flanchan@cumallover.me>
Date: Mon, 25 Apr 2022 08:21:40 +0100
Subject: [PATCH] Working memfile implementation
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Fortune for collect's current commit: Future blessing − 末吉
---
 Cargo.lock     |  2 +-
 Cargo.toml     |  2 +-
 src/main.rs    | 70 ++++++++++++++++++++++++++++++++++++++++++++++++--
 src/memfile.rs | 14 ++++++----
 4 files changed, 79 insertions(+), 9 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 8beefb0..5e65c26 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -84,7 +84,7 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "collect"
-version = "0.1.0"
+version = "0.2.0"
 dependencies = [
  "bitflags",
  "bytes",
diff --git a/Cargo.toml b/Cargo.toml
index ed743dc..1022970 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,7 +6,7 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [features]
-default = ["jemalloc", "logging", "tracing/release_max_level_warn"] #, "memfile" ]
+default = ["jemalloc", "memfile", "logging", "tracing/release_max_level_warn"] #, "memfile" ]
 
 # TODO: mmap, memfd_create() ver
 memfile = ["bitflags", "lazy_static", "stackalloc"]
diff --git a/src/main.rs b/src/main.rs
index fa557bf..713a194 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -261,11 +261,77 @@ fn non_map_work() -> eyre::Result<()>
 #[cfg(feature="memfile")] 
 fn map_work() -> eyre::Result<()>
 {
+    extern "C" {
+	fn getpagesize() -> libc::c_int;
+    }
+    /// 8 pages
+    const DEFAULT_BUFFER_SIZE: fn () -> Option<std::num::NonZeroUsize> = || { unsafe { std::num::NonZeroUsize::new((getpagesize() as usize) * 8) } }; 
     
     if_trace!(trace!("strategy: mapped memory file"));
 
-    let file = memfile::create_memfile(Some("this is a test file"), 4096)?;
-    unimplemented!("Feature not yet implemented")
+    use std::borrow::Borrow;
+
+    #[inline(always)] 
+    fn tell_file<T>(file: &mut T) -> io::Result<u64>
+	where T: io::Seek + ?Sized
+    {
+	file.stream_position()
+    }
+
+    #[inline(always)] 
+    fn unwrap_int_string<T, E>(i: impl Borrow<Result<T, E>>) -> String
+    where T: std::fmt::Display,
+    E: std::fmt::Display
+    {
+	i.borrow().as_ref().map(ToString::to_string)
+	    .unwrap_or_else(|e| format!("<unknown: {e}>"))
+    }
+
+    let (mut file, read) = {
+	let stdin = io::stdin();
+
+	let buffsz = try_get_size(&stdin).or_else(DEFAULT_BUFFER_SIZE);
+	if_trace!(trace!("Attempted determining input size: {:?}", buffsz));
+	let mut file = memfile::create_memfile(Some("collect-buffer"), 
+					       buffsz.map(|x| x.get()).unwrap_or(0))	    
+	    .with_section(|| format!("{:?}", buffsz).header("Deduced input buffer size"))
+	    .wrap_err(eyre!("Failed to create in-memory buffer"))?;
+
+	let read = io::copy(&mut stdin.lock(), &mut file)
+	    .with_section(|| format!("{:?}", file).header("Memory buffer file"))?;
+	
+	{
+	    use io::*;
+	    file.seek(SeekFrom::Start(0))
+		.with_section(|| read.header("Actual read bytes"))
+		.wrap_err(eyre!("Failed to seek back to start of memory buffer file for output")
+			  .with_section(|| unwrap_int_string(file.stream_position()).header("Memfile position"))
+			  /*.with_section(|| file.stream_len().map(|x| x.to_string())
+					.unwrap_or_else(|e| format!("<unknown: {e}>")).header("Memfile full length"))*/)?;
+	}
+	
+	(file, usize::try_from(read)
+	 .wrap_err(eyre!("Failed to convert read bytes to `usize`")
+		   .with_section(|| read.header("Number of bytes was"))
+		   .with_section(|| u128::abs_diff(read.into(), usize::MAX as u128).header("Difference between `read` and `usize::MAX` is"))
+		   .with_suggestion(|| "It is likely you are running on a 32-bit ptr width machine and this input exceeds that of the maximum 32-bit unsigned integer value")
+		   .with_note(|| usize::MAX.header("Maximum value of `usize`")))?)
+    };
+    if_trace!(info!("collected {read} from stdin. starting write."));
+
+    let written =
+	io::copy(&mut file, &mut io::stdout().lock())
+	.with_section(|| read.header("Bytes read from stdin"))
+	.with_section(|| unwrap_int_string(tell_file(&mut file)).header("Current buffer position"))
+	.wrap_err("Failed to write buffer to stdout")?;
+    if_trace!(info!("written {written} to stdout."));
+
+    if read != written as usize {
+	return Err(io::Error::new(io::ErrorKind::BrokenPipe, format!("read {read} bytes, but only wrote {written}")))
+	    .wrap_err("Writing failed: size mismatch");
+    }
+    
+    Ok(())
 }
 
 #[cfg_attr(feature="logging", instrument(err))]
diff --git a/src/memfile.rs b/src/memfile.rs
index f41559c..18a8bba 100644
--- a/src/memfile.rs
+++ b/src/memfile.rs
@@ -224,11 +224,15 @@ impl RawFile
 
 	    let fd = attempt_call!(-1, memfd_create(bname as *const _, MEMFD_CREATE_FLAGS), Create(name.map(str::to_owned), MEMFD_CREATE_FLAGS))
 		.map(Self::take_ownership_of_unchecked)?; // Ensures `fd` is dropped if any subsequent calls fail
-	    
-	    attempt_call!(-1
-			  , fallocate(fd.0.get(), 0, 0, len.try_into()
-				      .map_err(|_| Allocate(None, len))?)
-			  , Allocate(Some(fd.fileno().clone()), len))?;
+
+	    if len > 0 {
+		attempt_call!(-1
+			      , fallocate(fd.0.get(), 0, 0, len.try_into()
+					  .map_err(|_| Allocate(None, len))?)
+			      , Allocate(Some(fd.fileno().clone()), len))?;
+	    } else {
+		if_trace!(trace!("No length provided, skipping fallocate() call"));
+	    }
 
 	    Ok(fd)
 	})