>From e59c2d9516c07a7be5d82c815970e1d9013d23de Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <address@hidden>
Date: Thu, 20 Mar 2014 10:00:13 +0000
Subject: [PATCH] split: avoid unecessary input buffering

Input buffering is best avoided because it introduces
delayed processing of output for intermittent input,
especially when the output size is less than that of
the input buffer.  This is significant when output
is being further processed which could happen if split
is writing to precreated fifos, or through --filter.

If input is arriving fast from a pipe then this will
already be buffered before we read it, so fast arriving
input shouldn't be a performance issue.

* src/split.c (lines_split): s/full_read/safe_read/.
(lines_bytes_split): Likewise.
(bytes_split): Likewise.
(lines_chunk_split): Likewise.
(bytes_chunk_extract): Likewise.
* NEWS: Mention the improvement.
---
 NEWS        |    3 +++
 src/split.c |   29 +++++++++++++----------------
 2 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/NEWS b/NEWS
index c2caa42..f68ab4f 100644
--- a/NEWS
+++ b/NEWS
@@ -45,6 +45,9 @@ GNU coreutils NEWS                                    -*- outline -*-
   causing name look-up errors.  Also look-ups are first done outside the chroot,
   in case the look-up within the chroot fails due to library conflicts etc.
 
+  split avoids unnecessary input buffering, immediately writing input to output
+  which is significant with --filter or when writing to fifos or stdout etc.
+
   stat and tail work better with HFS+ and HFSX.  stat -f --format=%T now reports
   the file system type, and tail -f now uses inotify for files, rather than the
   default of issuing a warning and reverting to polling.
diff --git a/src/split.c b/src/split.c
index 29d3dbf..dacacaa 100644
--- a/src/split.c
+++ b/src/split.c
@@ -33,7 +33,6 @@
 #include "error.h"
 #include "fd-reopen.h"
 #include "fcntl--.h"
-#include "full-read.h"
 #include "full-write.h"
 #include "ioblksize.h"
 #include "quote.h"
@@ -526,8 +525,8 @@ bytes_split (uintmax_t n_bytes, char *buf, size_t bufsize, uintmax_t max_files)
 
   do
     {
-      n_read = full_read (STDIN_FILENO, buf, bufsize);
-      if (n_read < bufsize && errno)
+      n_read = safe_read (STDIN_FILENO, buf, bufsize);
+      if (n_read == SAFE_READ_ERROR)
         error (EXIT_FAILURE, errno, "%s", infile);
       bp_out = buf;
       to_read = n_read;
@@ -562,7 +561,7 @@ bytes_split (uintmax_t n_bytes, char *buf, size_t bufsize, uintmax_t max_files)
             }
         }
     }
-  while (n_read == bufsize);
+  while (n_read);
 
   /* Ensure NUMBER files are created, which truncates
      any existing files or notifies any consumers on fifos.
@@ -584,8 +583,8 @@ lines_split (uintmax_t n_lines, char *buf, size_t bufsize)
 
   do
     {
-      n_read = full_read (STDIN_FILENO, buf, bufsize);
-      if (n_read < bufsize && errno)
+      n_read = safe_read (STDIN_FILENO, buf, bufsize);
+      if (n_read == SAFE_READ_ERROR)
         error (EXIT_FAILURE, errno, "%s", infile);
       bp = bp_out = buf;
       eob = bp + n_read;
@@ -614,7 +613,7 @@ lines_split (uintmax_t n_lines, char *buf, size_t bufsize)
             }
         }
     }
-  while (n_read == bufsize);
+  while (n_read);
 }
 
 /* Split into pieces that are as large as possible while still not more
@@ -633,8 +632,8 @@ line_bytes_split (uintmax_t n_bytes, char *buf, size_t bufsize)
 
   do
     {
-      n_read = full_read (STDIN_FILENO, buf, bufsize);
-      if (n_read < bufsize && errno)
+      n_read = safe_read (STDIN_FILENO, buf, bufsize);
+      if (n_read == SAFE_READ_ERROR)
         error (EXIT_FAILURE, errno, "%s", infile);
       size_t n_left = n_read;
       char *sob = buf;
@@ -718,7 +717,7 @@ line_bytes_split (uintmax_t n_bytes, char *buf, size_t bufsize)
             }
         }
     }
-  while (n_read == bufsize);
+  while (n_read);
 
   /* Handle no eol at end of file.  */
   if (n_hold)
@@ -762,8 +761,8 @@ lines_chunk_split (uintmax_t k, uintmax_t n, char *buf, size_t bufsize,
   while (n_written < file_size)
     {
       char *bp = buf, *eob;
-      size_t n_read = full_read (STDIN_FILENO, buf, bufsize);
-      if (n_read < bufsize && errno)
+      size_t n_read = safe_read (STDIN_FILENO, buf, bufsize);
+      if (n_read == SAFE_READ_ERROR)
         error (EXIT_FAILURE, errno, "%s", infile);
       else if (n_read == 0)
         break; /* eof.  */
@@ -857,8 +856,8 @@ bytes_chunk_extract (uintmax_t k, uintmax_t n, char *buf, size_t bufsize,
 
   while (start < end)
     {
-      size_t n_read = full_read (STDIN_FILENO, buf, bufsize);
-      if (n_read < bufsize && errno)
+      size_t n_read = safe_read (STDIN_FILENO, buf, bufsize);
+      if (n_read == SAFE_READ_ERROR)
         error (EXIT_FAILURE, errno, "%s", infile);
       else if (n_read == 0)
         break; /* eof.  */
@@ -998,8 +997,6 @@ lines_rr (uintmax_t k, uintmax_t n, char *buf, size_t bufsize)
   while (true)
     {
       char *bp = buf, *eob;
-      /* Use safe_read() rather than full_read() here
-         so that we process available data immediately.  */
       size_t n_read = safe_read (STDIN_FILENO, buf, bufsize);
       if (n_read == SAFE_READ_ERROR)
         error (EXIT_FAILURE, errno, "%s", infile);
-- 
1.7.7.6