RESP3: parse sequence sizes with getbyte

All RESP3 types start with a single line containing a postive
integer that announce the size of the data.

e.g. `*42\r\n....`.

Before this commit we would read one line, hence allocate
a String, then parse it with `Kernel.Integer`.

By instead reading bytes one by one and rebuilding the integer
we save that string allocation, which has a significant impact.

The `gets_integer` method also optimistically assumes the buffer
already contains the line, which saves some methods calls in the
happy path.

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

Author: byroot

.rubocop.yml

@@ -66,6 +66,12 @@ Metrics/ParameterLists:
 Metrics/PerceivedComplexity:
   Enabled: false
 
+Style/InfiniteLoop:
+  Enabled: false
+
+Style/WhileUntilModifier:
+  Enabled: false
+
 Style/Alias:
   EnforcedStyle: prefer_alias_method
 

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:     5416.0 i/s
-                ruby:     2923.7 i/s - 1.85x  slower
+             hiredis:     5346.6 i/s
+                ruby:     2984.3 i/s - 1.79x  slower
 
 ```
 
 ### large string x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:      286.7 i/s
-                ruby:      302.3 i/s - same-ish: difference falls within error
+             hiredis:      304.2 i/s
+                ruby:      204.1 i/s - 1.49x  slower
 
 ```
 
 ### small list x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:     2596.0 i/s
-                ruby:     1155.6 i/s - 2.25x  slower
+             hiredis:     2612.0 i/s
+                ruby:     1240.8 i/s - 2.11x  slower
 
 ```
 
 ### large list
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:     6797.0 i/s
-                ruby:     1388.9 i/s - 4.89x  slower
+             hiredis:     6772.7 i/s
+                ruby:     1540.7 i/s - 4.40x  slower
 
 ```
 
 ### small hash x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:     3459.8 i/s
-                ruby:     1170.4 i/s - 2.96x  slower
+             hiredis:     3293.2 i/s
+                ruby:     1234.0 i/s - 2.67x  slower
 
 ```
 
 ### large hash
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) [arm64-darwin23]
-             hiredis:     1345.9 i/s
-                ruby:     1329.5 i/s - same-ish: difference falls within error
+             hiredis:     1421.7 i/s
+                ruby:     1481.0 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:     6775.6 i/s
-                ruby:     5212.3 i/s - 1.30x  slower
+             hiredis:     6723.1 i/s
+                ruby:     5507.5 i/s - 1.22x  slower
 
 ```
 
 ### large string x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:      306.1 i/s
-                ruby:      335.5 i/s - same-ish: difference falls within error
+             hiredis:      290.8 i/s
+                ruby:      335.2 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:     3566.7 i/s
-                ruby:     1999.6 i/s - 1.78x  slower
+             hiredis:     3686.7 i/s
+                ruby:     2437.1 i/s - 1.51x  slower
 
 ```
 
 ### large list
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:     6563.1 i/s
-                ruby:     2984.7 i/s - 2.20x  slower
+             hiredis:     6725.9 i/s
+                ruby:     4990.0 i/s - 1.35x  slower
 
 ```
 
 ### small hash x 100
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:     3870.9 i/s
-                ruby:     2387.4 i/s - 1.62x  slower
+             hiredis:     3893.0 i/s
+                ruby:     2994.7 i/s - 1.30x  slower
 
 ```
 
 ### large hash
 
 ```
 ruby 3.3.0 (2023-12-25 revision 5124f9ac75) +YJIT [arm64-darwin23]
-             hiredis:     2641.9 i/s
-                ruby:     2575.8 i/s - same-ish: difference falls within error
+             hiredis:     4303.3 i/s
+                ruby:     4244.6 i/s - same-ish: difference falls within error
 
 ```
 

lib/redis_client/ruby_connection/buffered_io.rb

@@ -99,6 +99,29 @@ def gets_chomp
         line
       end
 
+      def gets_integer
+        int = 0
+        offset = @offset
+        while true
+          chr = @buffer.getbyte(offset)
+
+          if chr
+            if chr == 13 # "\r".ord
+              @offset = offset + 2
+              break
+            else
+              int = (int * 10) + chr - 48
+            end
+            offset += 1
+          else
+            ensure_line
+            return gets_integer
+          end
+        end
+
+        int
+      end
+
       def read_chomp(bytes)
         ensure_remaining(bytes + EOL_SIZE)
         str = @buffer.byteslice(@offset, bytes)
@@ -108,6 +131,13 @@ def read_chomp(bytes)
 
       private
 
+      def ensure_line
+        fill_buffer(false) if @offset >= @buffer.bytesize
+        until @buffer.index(EOL, @offset)
+          fill_buffer(false)
+        end
+      end
+
       def ensure_remaining(bytes)
         needed = bytes - (@buffer.bytesize - @offset)
         if needed > 0
@@ -117,7 +147,8 @@ def ensure_remaining(bytes)
 
       def fill_buffer(strict, size = @chunk_size)
         remaining = size
-        empty_buffer = @offset >= @buffer.bytesize
+        start = @offset - @buffer.bytesize
+        empty_buffer = start >= 0
 
         loop do
           bytes = if empty_buffer
@@ -126,15 +157,6 @@ def fill_buffer(strict, size = @chunk_size)
             @io.read_nonblock([remaining, @chunk_size].max, exception: false)
           end
           case bytes
-          when String
-            if empty_buffer
-              @offset = 0
-              empty_buffer = false
-            else
-              @buffer << bytes
-            end
-            remaining -= bytes.bytesize
-            return if !strict || remaining <= 0
           when :wait_readable
             unless @io.to_io.wait_readable(@read_timeout)
               raise ReadTimeoutError, "Waited #{@read_timeout} seconds" unless @blocking_reads
@@ -144,7 +166,14 @@ def fill_buffer(strict, size = @chunk_size)
           when nil
             raise EOFError
           else
-            raise "Unexpected `read_nonblock` return: #{bytes.inspect}"
+            if empty_buffer
+              @offset = start
+              empty_buffer = false
+            else
+              @buffer << bytes
+            end
+            remaining -= bytes.bytesize
+            return if !strict || remaining <= 0
           end
         end
       end

lib/redis_client/ruby_connection/resp3.rb

@@ -165,16 +165,16 @@ def parse_boolean(io)
     end
 
     def parse_array(io)
-      parse_sequence(io, parse_integer(io))
+      parse_sequence(io, io.gets_integer)
     end
 
     def parse_set(io)
-      parse_sequence(io, parse_integer(io))
+      parse_sequence(io, io.gets_integer)
     end
 
     def parse_map(io)
       hash = {}
-      parse_integer(io).times do
+      io.gets_integer.times do
         hash[parse(io)] = parse(io)
       end
       hash
@@ -217,7 +217,7 @@ def parse_null(io)
     end
 
     def parse_blob(io)
-      bytesize = parse_integer(io)
+      bytesize = io.gets_integer
       return if bytesize < 0 # RESP2 nil type
 
       str = io.read_chomp(bytesize)