From d13002a92d0d216caee9d99114f06025ad21c955 Mon Sep 17 00:00:00 2001
From: Nikita Kniazev <nok.raven@gmail.com>
Date: Thu, 11 Oct 2018 20:31:44 +0300
Subject: [PATCH 1/2] Fixed slow pipe reading on windows

It looks like the OS has the internal buffer around 4KB and with any buffer
over this size `read_pipe` will end the reading loop after first try despite
that reading a pipe may pump a new data and it can be read immediately.
---
 src/engine/execnt.c | 64 ++++++++++++++++-----------------------------
 1 file changed, 22 insertions(+), 42 deletions(-)

diff --git a/src/engine/execnt.c b/src/engine/execnt.c
index 431d11122..4e512f149 100644
--- a/src/engine/execnt.c
+++ b/src/engine/execnt.c
@@ -767,55 +767,35 @@ static void read_pipe
     DWORD bytesInBuffer = 0;
     DWORD bytesAvailable = 0;
 
-    do
+    for (;;)
     {
         /* check if we have any data to read */
         if ( !PeekNamedPipe( in, ioBuffer, IO_BUFFER_SIZE, &bytesInBuffer,
-            &bytesAvailable, NULL ) )
-            bytesAvailable = 0;
+            &bytesAvailable, NULL ) || bytesAvailable == 0 )
+            return;
 
-        /* read in the available data */
-        if ( bytesAvailable > 0 )
+        /* we only read in the available bytes, to avoid blocking */
+        if ( !ReadFile( in, ioBuffer, bytesAvailable <= IO_BUFFER_SIZE ?
+            bytesAvailable : IO_BUFFER_SIZE, &bytesInBuffer, NULL ) || bytesInBuffer == 0 )
+            return;
+
+        /* Clean up some illegal chars. */
+        int i;
+        for ( i = 0; i < bytesInBuffer; ++i )
         {
-            /* we only read in the available bytes, to avoid blocking */
-            if ( ReadFile( in, ioBuffer, bytesAvailable <= IO_BUFFER_SIZE ?
-                bytesAvailable : IO_BUFFER_SIZE, &bytesInBuffer, NULL ) )
-            {
-                if ( bytesInBuffer > 0 )
-                {
-                    /* Clean up some illegal chars. */
-                    int i;
-                    for ( i = 0; i < bytesInBuffer; ++i )
-                    {
-                        if ( ( (unsigned char)ioBuffer[ i ] < 1 ) )
-                            ioBuffer[ i ] = '?';
-                    }
-                    /* Null, terminate. */
-                    ioBuffer[ bytesInBuffer ] = '\0';
-                    /* Append to the output. */
-                    string_append( out, ioBuffer );
-                    /* Copy it to our output if appropriate */
-                    if ( forwarding_mode == FORWARD_PIPE_STDOUT )
-                        out_data( ioBuffer );
-                    else if ( forwarding_mode == FORWARD_PIPE_STDERR )
-                        err_data( ioBuffer );
-                    /* Subtract what we read in. */
-                    bytesAvailable -= bytesInBuffer;
-                }
-                else
-                {
-                    /* Likely read a error, bail out. */
-                    bytesAvailable = 0;
-                }
-            }
-            else
-            {
-                /* Definitely read a error, bail out. */
-                bytesAvailable = 0;
-            }
+            if ( ( (unsigned char)ioBuffer[ i ] < 1 ) )
+                ioBuffer[ i ] = '?';
         }
+        /* Null, terminate. */
+        ioBuffer[ bytesInBuffer ] = '\0';
+        /* Append to the output. */
+        string_append( out, ioBuffer );
+        /* Copy it to our output if appropriate */
+        if ( forwarding_mode == FORWARD_PIPE_STDOUT )
+            out_data( ioBuffer );
+        else if ( forwarding_mode == FORWARD_PIPE_STDERR )
+            err_data( ioBuffer );
     }
-    while ( bytesAvailable > 0 );
 }
 
 #define EARLY_OUTPUT( cmd ) \

From e7e55d0cc950f5d7645c9b59ada9632d83e94f65 Mon Sep 17 00:00:00 2001
From: Nikita Kniazev <nok.raven@gmail.com>
Date: Thu, 11 Oct 2018 23:21:23 +0300
Subject: [PATCH 2/2] Do not read pipe content at available size peeking

Currently the same data is read twice.

The first time a buffer is filled by `PeekNamedPipe` and second time it is
overwritten with the same content by `ReadFile`.
---
 src/engine/execnt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/engine/execnt.c b/src/engine/execnt.c
index 4e512f149..a712e15d3 100644
--- a/src/engine/execnt.c
+++ b/src/engine/execnt.c
@@ -770,7 +770,7 @@ static void read_pipe
     for (;;)
     {
         /* check if we have any data to read */
-        if ( !PeekNamedPipe( in, ioBuffer, IO_BUFFER_SIZE, &bytesInBuffer,
+        if ( !PeekNamedPipe( in, NULL, IO_BUFFER_SIZE, NULL,
             &bytesAvailable, NULL ) || bytesAvailable == 0 )
             return;