From 260cb78e3a129a4cebffe0f407510b4ccf10b976 Mon Sep 17 00:00:00 2001
From: Floris Bruynooghe <flub@devork.be>
Date: Sun, 16 Jan 2022 19:07:06 +0100
Subject: [PATCH] Re-write the blob filename creation loop

This was written in a way which attempted to avoid easily creating an
infinite loop.  But really that's a python idiom and doesn't work very
well in Rust.  Worse, as shown by #2972 it is really easy to still get
this wrong.  Instead do this the rust way, this way the compiler can
also reason properly about the branches and what is unreachable
removing some bogus dead code.
---
 src/blob.rs | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/src/blob.rs b/src/blob.rs
index 239a06ac7..3ba92b73a 100644
--- a/src/blob.rs
+++ b/src/blob.rs
@@ -93,9 +93,11 @@ impl<'a> BlobObject<'a> {
         stem: &str,
         ext: &str,
     ) -> Result<(String, fs::File), BlobError> {
-        let max_attempt = 15;
+        const MAX_ATTEMPT: u32 = 16;
+        let mut attempt = 0;
         let mut name = format!("{}{}", stem, ext);
-        for attempt in 1..=max_attempt {
+        loop {
+            attempt += 1;
             let path = dir.join(&name);
             match fs::OpenOptions::new()
                 .create_new(true)
@@ -105,7 +107,7 @@ impl<'a> BlobObject<'a> {
             {
                 Ok(file) => return Ok((name, file)),
                 Err(err) => {
-                    if attempt == max_attempt {
+                    if attempt >= MAX_ATTEMPT {
                         return Err(BlobError::CreateFailure {
                             blobdir: dir.to_path_buf(),
                             blobname: name,
@@ -119,12 +121,6 @@ impl<'a> BlobObject<'a> {
                 }
             }
         }
-        // This is supposed to be unreachable, but the compiler doesn't know.
-        Err(BlobError::CreateFailure {
-            blobdir: dir.to_path_buf(),
-            blobname: name,
-            cause: std::io::Error::new(std::io::ErrorKind::Other, "supposedly unreachable"),
-        })
     }
 
     /// Creates a new blob object with unique name by copying an existing file.