add eager keyword argument (#75)

Author: bicycle1885

src/buffer.jl

@@ -123,12 +123,13 @@ function emptybuffer!(buf::Buffer)
 end
 
 # Make margin with ≥`minsize` and return the size of it.
-function makemargin!(buf::Buffer, minsize::Integer)
+# If eager is true, it tries to move data even when the buffer has enough margin.
+function makemargin!(buf::Buffer, minsize::Integer; eager::Bool = false)
     @assert minsize ≥ 0
     if buffersize(buf) == 0 && buf.markpos == 0
         buf.bufferpos = buf.marginpos = 1
     end
-    if marginsize(buf) < minsize
+    if marginsize(buf) < minsize || eager
         # shift data to left
         if buf.markpos == 0
             datapos = buf.bufferpos

src/noop.jl

@@ -148,16 +148,16 @@ end
 # These methods are overloaded for the `Noop` codec because it has only one
 # buffer for efficiency.
 
-function fillbuffer(stream::NoopStream)
+function fillbuffer(stream::NoopStream; eager::Bool = false)
     changemode!(stream, :read)
     buffer = stream.state.buffer1
     @assert buffer === stream.state.buffer2
     if stream.stream isa TranscodingStream && buffer === stream.stream.state.buffer1
         # Delegate the operation when buffers are shared.
-        return fillbuffer(stream.stream)
+        return fillbuffer(stream.stream, eager = eager)
     end
     nfilled::Int = 0
-    while buffersize(buffer) == 0 && !eof(stream.stream)
+    while ((!eager && buffersize(buffer) == 0) || (eager && makemargin!(buffer, 0, eager = true) > 0)) && !eof(stream.stream)
         makemargin!(buffer, 1)
         nfilled += readdata!(stream.stream, buffer)
     end

src/stream.jl

@@ -556,12 +556,12 @@ end
 # Buffering
 # ---------
 
-function fillbuffer(stream::TranscodingStream)
+function fillbuffer(stream::TranscodingStream; eager::Bool = false)
     changemode!(stream, :read)
     buffer1 = stream.state.buffer1
     buffer2 = stream.state.buffer2
     nfilled::Int = 0
-    while buffersize(buffer1) == 0 && stream.state.mode != :stop
+    while ((!eager && buffersize(buffer1) == 0) || (eager && makemargin!(buffer1, 0, eager = true) > 0)) && stream.state.mode != :stop
         if stream.state.code == :end
             if buffersize(buffer2) == 0 && eof(stream.stream)
                 break