Stop using ceill() to compute padded data size

The well-known idiom to compute a required number of data blocks
of size B to contain data of length d is:

     (d + (B-1))/B

The code we use, with ceill(), computes the same value, but does
it in an unorthodox way. This makes a reviewer to doubt himself
and even run tests to make sure we're really computing the
obvious thing.

Apropos the reviewer confusion, the code in Phazr.IO looks weird.
It uses (word_size - hamming_distance) to compute the necessary
number of blocks... but then returns the amount of memory needed
to store blocks of a different size (word_size). We left all of it
alone and return exactly the same values that the old computation
returned.

All these computations were the only thing in the code that used
-lm, so drop that too.

Coincidentially, this patch solves the crash of distro-built
packages of liberasurecode (see Red Hat bug #1454543). But it's
a side effect. Expect a proper patch soon.

Change-Id: Ib297f6df304abf5ca8c27d3392b1107a525e0be0

5 files changed, 8 insertions, 11 deletions

diff --git a/configure.ac b/configure.ac
index c3509d2..d0230a0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -88,7 +88,7 @@ dnl Check for C library headers
 AC_HEADER_STDC
 AC_CHECK_HEADERS(sys/types.h stdio.h stdlib.h stddef.h stdarg.h \
                  malloc.h memory.h string.h strings.h inttypes.h \
-                 stdint.h ctype.h math.h iconv.h signal.h dlfcn.h \
+                 stdint.h ctype.h iconv.h signal.h dlfcn.h \
                  pthread.h unistd.h limits.h errno.h syslog.h)
 AC_CHECK_FUNCS(malloc calloc realloc free openlog)
 
diff --git a/include/erasurecode/erasurecode_stdinc.h b/include/erasurecode/erasurecode_stdinc.h
index 903b33e..aaa9e2b 100644
--- a/include/erasurecode/erasurecode_stdinc.h
+++ b/include/erasurecode/erasurecode_stdinc.h
@@ -100,9 +100,6 @@
 #ifdef HAVE_ERRNO_H
 # include <errno.h>
 #endif
-#ifdef HAVE_MATH_H
-# include <math.h>
-#endif
 
 #if defined(__GNUC__) && __GNUC__ >= 4
 # define DECLSPEC       __attribute__ ((visibility("default")))
diff --git a/src/backends/phazrio/libphazr.c b/src/backends/phazrio/libphazr.c
index 74ad8ad..41ed74e 100644
--- a/src/backends/phazrio/libphazr.c
+++ b/src/backends/phazrio/libphazr.c
@@ -88,7 +88,7 @@ struct libphazr_descriptor {
 static int get_padded_blocksize(int w, int hd, int blocksize)
 {
     int word_size = w / 8;
-    return (int) ceill((double) blocksize / (word_size - hd)) * word_size;
+    return ((blocksize + ((word_size - hd) - 1)) / (word_size - hd)) * word_size;
 }
 
 static int pio_matrix_encode(void *desc, char **data, char **parity, int blocksize)
diff --git a/src/erasurecode.c b/src/erasurecode.c
index fb6d5de..d4a06c2 100644
--- a/src/erasurecode.c
+++ b/src/erasurecode.c
@@ -1194,8 +1194,8 @@ int liberasurecode_verify_stripe_metadata(int desc,
 /**
  * This computes the aligned size of a buffer passed into
  * the encode function.  The encode function must pad fragments
- * to be algined with the word size (w) and the last fragment also
- * needs to be aligned.  This computes the sum of the algined fragment
+ * to be aligned with the word size (w) and the last fragment also
+ * needs to be aligned.  This computes the sum of the aligned fragment
  * sizes for a given buffer to encode.
  */
 int liberasurecode_get_aligned_data_size(int desc, uint64_t data_len)
@@ -1218,8 +1218,8 @@ int liberasurecode_get_aligned_data_size(int desc, uint64_t data_len)
 
     alignment_multiple = k * word_size;
 
-    ret = (int) ceill( (double)
-            data_len / alignment_multiple) * alignment_multiple;
+    ret = ((data_len + alignment_multiple - 1) / alignment_multiple)
+            * alignment_multiple;
 
 out:
     return ret;
diff --git a/src/erasurecode_helpers.c b/src/erasurecode_helpers.c
index 40db93c..fd14298 100644
--- a/src/erasurecode_helpers.c
+++ b/src/erasurecode_helpers.c
@@ -199,8 +199,8 @@ int get_aligned_data_size(ec_backend_t instance, int data_len)
         alignment_multiple = k * word_size;
     }
 
-    aligned_size = (int) 
-        ceill((double) data_len / alignment_multiple) * alignment_multiple;
+    aligned_size = ((data_len + alignment_multiple - 1) / alignment_multiple)
+        * alignment_multiple;
 
     return aligned_size;
 }