split: avoid unnecessary 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 quickly 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, lines_bytes_split, bytes_split,
lines_chunk_split, bytes_chunk_extract): s/full_read/safe_read/.
* THANKS.in: Mention the reporter.
* NEWS: Mention the improvement.

1 files changed, 13 insertions, 16 deletions

diff --git a/src/split.c b/src/split.c
index 29d3dbfe4..dacacaa88 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);