BufferedIO#getbyte: optimistically read the next byte

This method is a big hotspot for parsing, by not pessimistically
checking the size of the buffer we save a few method calls on
the green path.

Co-authored-by: Aaron Patterson <[email protected]>

Author: byroot

benchmark/drivers_ruby.md

@@ -7,53 +7,53 @@ redis-server: `Redis server v=7.0.12 sha=00000000:0 malloc=libc bits=64 build=a1
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:     5369.2 i/s
-                ruby:     3095.8 i/s - 1.73x  slower
+             hiredis:     5470.4 i/s
+                ruby:     3246.7 i/s - 1.68x  slower
 
 ```
 
 ### large string x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:      303.9 i/s
-                ruby:      217.9 i/s - 1.39x  slower
+             hiredis:      304.4 i/s
+                ruby:      230.2 i/s - 1.32x  slower
 
 ```
 
 ### small list x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:     2706.0 i/s
-                ruby:     1325.4 i/s - 2.04x  slower
+             hiredis:     2643.4 i/s
+                ruby:     1312.4 i/s - 2.01x  slower
 
 ```
 
 ### large list
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:     6827.5 i/s
-                ruby:     1755.0 i/s - 3.89x  slower
+             hiredis:     6761.3 i/s
+                ruby:     1796.0 i/s - 3.76x  slower
 
 ```
 
 ### small hash x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:     3453.2 i/s
-                ruby:     1359.5 i/s - 2.54x  slower
+             hiredis:     3293.2 i/s
+                ruby:     1435.0 i/s - 2.29x  slower
 
 ```
 
 ### large hash
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:     1655.5 i/s
-                ruby:     1666.5 i/s - same-ish: difference falls within error
+             hiredis:     1765.3 i/s
+                ruby:     1782.7 i/s - same-ish: difference falls within error
 
 ```
 

benchmark/drivers_yjit.md

@@ -7,53 +7,53 @@ redis-server: `Redis server v=7.0.12 sha=00000000:0 malloc=libc bits=64 build=a1
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:     6795.5 i/s
-                ruby:     5696.7 i/s - 1.19x  slower
+             hiredis:     6810.9 i/s
+                ruby:     5613.1 i/s - 1.21x  slower
 
 ```
 
 ### large string x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:      291.0 i/s
-                ruby:      339.3 i/s - same-ish: difference falls within error
+             hiredis:      312.1 i/s
+                ruby:      316.3 i/s - same-ish: difference falls within error
 
 ```
 
 ### small list x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:     3661.1 i/s
-                ruby:     2351.8 i/s - 1.56x  slower
+             hiredis:     3644.1 i/s
+                ruby:     2474.0 i/s - 1.47x  slower
 
 ```
 
 ### large list
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:     6839.3 i/s
-                ruby:     5330.8 i/s - 1.28x  slower
+             hiredis:     6884.4 i/s
+                ruby:     5473.2 i/s - 1.26x  slower
 
 ```
 
 ### small hash x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:     3966.9 i/s
-                ruby:     3243.4 i/s - 1.22x  slower
+             hiredis:     4033.9 i/s
+                ruby:     3236.3 i/s - 1.25x  slower
 
 ```
 
 ### large hash
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:     4609.7 i/s
-                ruby:     4612.8 i/s - same-ish: difference falls within error
+             hiredis:     4753.7 i/s
+                ruby:     4637.7 i/s - same-ish: difference falls within error
 
 ```
 

lib/redis_client/ruby_connection/buffered_io.rb

@@ -82,8 +82,10 @@ def write(string)
       end
 
       def getbyte
-        ensure_remaining(1)
-        byte = @buffer.getbyte(@offset)
+        unless byte = @buffer.getbyte(@offset)
+          ensure_remaining(1)
+          byte = @buffer.getbyte(@offset)
+        end
         @offset += 1
         byte
       end