[PATCH] base64: improve encoding I/O efficiency

[Pádraig Brady]

Replace fputs() calls with fputc() to improve performance.
Since the I/O overhead is significant to the relatively
simple processing done by this utility, use the simpler
function to output '\n'.
Time to process a 100MiB file was measured to
decrease from 0.417s to 0.383s, i.e. an 8% improvement.

Related to these changes, is a processing improvement in
gnulib, which increases throughput by 60% when processing
full buffers, which improves processing of a 100MiB file
with standard wrapped output, down to 0.256s.
http://lists.gnu.org/archive/html/bug-gnulib/2013-11/msg00057.html

Also increase the encoding buffer size from 3 to 30KiB.
This was seen to give a further 8% improvement, taking
processing time down to 0.235s is the wrapped output case.
The decoding size buffer is not adjusted,
due to the noted caveat with --ignore-garbage.

* src/base64.c (BLOCKSIZE): Split into ENC_ and DEC_ variants,
with the former increased from 3KiB to 30KiB.
(wrap_write): Use the simpler fputc() rather than fputs()
to output the '\n' character.  Also check against EOF
rather than < 0 for errors.
(do_encode): Likewise.
* NEWS: Mention the large increase in performance, which
with the I/O improvements in coreutils and the processing
improvement in gnulib, amount to about a 60% throughput increase.
---
 NEWS         |    2 ++
 src/base64.c |   40 +++++++++++++++++++++-------------------
 2 files changed, 23 insertions(+), 19 deletions(-)

diff --git a/NEWS b/NEWS
index 7028c0d..fafe06d 100644
--- a/NEWS
+++ b/NEWS
@@ -88,6 +88,8 @@ GNU coreutils NEWS                                    -*- 
outline -*-
 
 ** Improvements
 
+  base64 encoding throughtput for bulk data is increased by about 60%.
+
   stat and tail work better with EFIVARFS, EXOFS, F2FS, SNFS and UBIFS.
   stat -f --format=%T now reports the file system type, and tail -f now uses
   inotify for files on those file systems, rather than the default (for unknown
diff --git a/src/base64.c b/src/base64.c
index 0a40068..d1bdf3e 100644
--- a/src/base64.c
+++ b/src/base64.c
@@ -30,6 +30,7 @@
 #include "xstrtol.h"
 #include "quote.h"
 #include "quotearg.h"
+#include "verify.h"
 #include "xfreopen.h"
 
 #include "base64.h"
@@ -89,15 +90,16 @@ from any other non-alphabet bytes in the encoded 
stream.\n"),
   exit (status);
 }
 
+#define ENC_BLOCKSIZE (1024*3*10)
+#define ENC_B64BLOCKSIZE BASE64_LENGTH (ENC_BLOCKSIZE)
 /* Note that increasing this may decrease performance if --ignore-garbage
-   is used, because of the memmove operation below. */
-#define BLOCKSIZE 3072
-#define B64BLOCKSIZE BASE64_LENGTH (BLOCKSIZE)
+   is used, because of the memmove operation below.  */
+#define DEC_BLOCKSIZE (1024*3)
+#define DEC_B64BLOCKSIZE BASE64_LENGTH (DEC_BLOCKSIZE)
 
 /* Ensure that BLOCKSIZE is a multiple of 3 and 4.  */
-#if BLOCKSIZE % 12 != 0
-# error "invalid BLOCKSIZE"
-#endif
+verify (ENC_BLOCKSIZE % 12 == 0);
+verify (DEC_BLOCKSIZE % 12 == 0);
 
 static void
 wrap_write (const char *buffer, size_t len,
@@ -120,7 +122,7 @@ wrap_write (const char *buffer, size_t len,
 
         if (to_write == 0)
           {
-            if (fputs ("\n", out) < 0)
+            if (fputc ('\n', out) == EOF)
               error (EXIT_FAILURE, errno, _("write error"));
             *current_column = 0;
           }
@@ -138,8 +140,8 @@ static void
 do_encode (FILE *in, FILE *out, uintmax_t wrap_column)
 {
   size_t current_column = 0;
-  char inbuf[BLOCKSIZE];
-  char outbuf[B64BLOCKSIZE];
+  char inbuf[ENC_BLOCKSIZE];
+  char outbuf[ENC_B64BLOCKSIZE];
   size_t sum;
 
   do
@@ -149,14 +151,14 @@ do_encode (FILE *in, FILE *out, uintmax_t wrap_column)
       sum = 0;
       do
         {
-          n = fread (inbuf + sum, 1, BLOCKSIZE - sum, in);
+          n = fread (inbuf + sum, 1, ENC_BLOCKSIZE - sum, in);
           sum += n;
         }
-      while (!feof (in) && !ferror (in) && sum < BLOCKSIZE);
+      while (!feof (in) && !ferror (in) && sum < ENC_BLOCKSIZE);
 
       if (sum > 0)
         {
-          /* Process input one block at a time.  Note that BLOCKSIZE %
+          /* Process input one block at a time.  Note that ENC_BLOCKSIZE %
              3 == 0, so that no base64 pads will appear in output. */
           base64_encode (inbuf, sum, outbuf, BASE64_LENGTH (sum));
 
@@ -164,10 +166,10 @@ do_encode (FILE *in, FILE *out, uintmax_t wrap_column)
                       &current_column, out);
         }
     }
-  while (!feof (in) && !ferror (in) && sum == BLOCKSIZE);
+  while (!feof (in) && !ferror (in) && sum == ENC_BLOCKSIZE);
 
   /* When wrapping, terminate last line. */
-  if (wrap_column && current_column > 0 && fputs ("\n", out) < 0)
+  if (wrap_column && current_column > 0 && fputc ('\n', out) == EOF)
     error (EXIT_FAILURE, errno, _("write error"));
 
   if (ferror (in))
@@ -177,8 +179,8 @@ do_encode (FILE *in, FILE *out, uintmax_t wrap_column)
 static void
 do_decode (FILE *in, FILE *out, bool ignore_garbage)
 {
-  char inbuf[B64BLOCKSIZE];
-  char outbuf[BLOCKSIZE];
+  char inbuf[DEC_B64BLOCKSIZE];
+  char outbuf[DEC_BLOCKSIZE];
   size_t sum;
   struct base64_decode_context ctx;
 
@@ -193,7 +195,7 @@ do_decode (FILE *in, FILE *out, bool ignore_garbage)
       sum = 0;
       do
         {
-          n = fread (inbuf + sum, 1, B64BLOCKSIZE - sum, in);
+          n = fread (inbuf + sum, 1, DEC_B64BLOCKSIZE - sum, in);
 
           if (ignore_garbage)
             {
@@ -210,7 +212,7 @@ do_decode (FILE *in, FILE *out, bool ignore_garbage)
           if (ferror (in))
             error (EXIT_FAILURE, errno, _("read error"));
         }
-      while (sum < B64BLOCKSIZE && !feof (in));
+      while (sum < DEC_B64BLOCKSIZE && !feof (in));
 
       /* The following "loop" is usually iterated just once.
          However, when it processes the final input buffer, we want
@@ -220,7 +222,7 @@ do_decode (FILE *in, FILE *out, bool ignore_garbage)
         {
           if (k == 1 && ctx.i == 0)
             break;
-          n = BLOCKSIZE;
+          n = DEC_BLOCKSIZE;
           ok = base64_decode_ctx (&ctx, inbuf, (k == 0 ? sum : 0), outbuf, &n);
 
           if (fwrite (outbuf, 1, n, out) < n)
-- 
1.7.7.6