From 046a2ad999260eceb656fa5d06f081f1c8a1518b Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
Date: Wed, 17 Jun 2020 04:11:27 +0200
Subject: [PATCH] Better varint reader

---
 implementations/rust/src/value/reader.rs | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/implementations/rust/src/value/reader.rs b/implementations/rust/src/value/reader.rs
index 56842c5..2a938b3 100644
--- a/implementations/rust/src/value/reader.rs
+++ b/implementations/rust/src/value/reader.rs
@@ -380,11 +380,13 @@ impl<'de, S: BinarySource<'de>> BinaryReader<'de, S> {
     }
 
     fn varint(&mut self) -> IOResult<usize> {
-        let v = self.read()?;
-        if v < 128 {
-            Ok(usize::from(v))
-        } else {
-            Ok(self.varint()? * 128 + usize::from(v - 128))
+        let mut shift = 0;
+        let mut acc: usize = 0;
+        loop {
+            let v = self.read()?;
+            acc = acc | (((v & 0x7f) as usize) << shift);
+            shift = shift + 7;
+            if v & 0x80 == 0 { return Ok(acc) }
         }
     }