From 65d558b8ccfb472c67784a209c4acde0212d687c Mon Sep 17 00:00:00 2001
From: "Steven G. Johnson" <stevenj@alum.mit.edu>
Date: Wed, 12 Jul 2023 19:03:29 -0400
Subject: [PATCH 1/2] don't forget to shift anchor at end of buffer

---
 src/bufferedinputstream.jl | 5 +++--
 test/runtests.jl           | 9 +++++++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/bufferedinputstream.jl b/src/bufferedinputstream.jl
index 722b207..466d7aa 100644
--- a/src/bufferedinputstream.jl
+++ b/src/bufferedinputstream.jl
@@ -81,10 +81,11 @@ function shiftdata!(stream::BufferedInputStream)
     if stream.immobilized
         return 0
     else
-        if stream.anchor > 0 && stream.available - stream.anchor + 1 > 0
+        if stream.anchor > 0
+            @assert stream.position ≥ stream.anchor # negative seek is not currently allowed
             shift = stream.anchor - 1
             n = stream.available - shift
-            copyto!(stream.buffer, 1, stream.buffer, stream.anchor, n)
+            n > 0 && copyto!(stream.buffer, 1, stream.buffer, stream.anchor, n)
             stream.anchor -= shift
         elseif stream.available - stream.position + 1 > 0
             shift = stream.position - 1
diff --git a/test/runtests.jl b/test/runtests.jl
index 0800edd..aca5b74 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -255,6 +255,15 @@ end
         end
 
         @test all(Bool[test_anchor() for _ in 1:100])
+
+        # issue #78
+        let io = BufferedInputStream(IOBuffer("α∆"), 1)
+            @test read(io, Char) == 'α'
+            mark(io)
+            @test [read(io, UInt8) for _=1:3] == [0xe2, 0x88, 0x86]
+            reset(io)
+            @test read(io, Char) == '∆'
+        end
     end
 
     @testset "seek" begin

From beba2f65c0a2c9c22849ce19e5721a6f34cce843 Mon Sep 17 00:00:00 2001
From: "Steven G. Johnson" <stevenj@alum.mit.edu>
Date: Wed, 12 Jul 2023 19:10:35 -0400
Subject: [PATCH 2/2] rm incorrect comment

---
 src/bufferedinputstream.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/bufferedinputstream.jl b/src/bufferedinputstream.jl
index 466d7aa..3eaeb90 100644
--- a/src/bufferedinputstream.jl
+++ b/src/bufferedinputstream.jl
@@ -82,7 +82,7 @@ function shiftdata!(stream::BufferedInputStream)
         return 0
     else
         if stream.anchor > 0
-            @assert stream.position ≥ stream.anchor # negative seek is not currently allowed
+            @assert stream.position ≥ stream.anchor
             shift = stream.anchor - 1
             n = stream.available - shift
             n > 0 && copyto!(stream.buffer, 1, stream.buffer, stream.anchor, n)