shada: Use glibc functions to convert from big endian, add a fallback

1 files changed, 66 insertions, 7 deletions

diff --git a/src/nvim/shada.c b/src/nvim/shada.c
index 73aaa311b4..881e613114 100644
--- a/src/nvim/shada.c
+++ b/src/nvim/shada.c
@@ -5,6 +5,15 @@
 #include <inttypes.h>
 #include <errno.h>
 #include <assert.h>
+#if defined (__GLIBC__)
+# ifndef _BSD_SOURCE
+#  define _BSD_SOURCE 1
+# endif
+# ifndef _DEFAULT_SOURCE
+#  define _DEFAULT_SOURCE 1
+# endif
+# include <endian.h>
+#endif
 
 #include <msgpack.h>
 
@@ -45,6 +54,43 @@
 #define home_replace_save(a, b) \
     ((char *)home_replace_save(a, (char_u *)b))
 
+// From http://www.boost.org/doc/libs/1_43_0/boost/detail/endian.hpp + some 
+// additional checks done after examining `{compiler} -dM -E - < /dev/null` 
+// output.
+#if defined (__GLIBC__)
+# if (__BYTE_ORDER == __BIG_ENDIAN)
+#  define SHADA_BIG_ENDIAN
+# endif
+#elif defined(_BIG_ENDIAN) || defined(_LITTLE_ENDIAN)
+# if defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)
+#  define SHADA_BIG_ENDIAN
+# endif
+// clang-specific
+#elif defined(__BIG_ENDIAN__) || defined(__LITTLE_ENDIAN__)
+# if defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)
+#  define SHADA_BIG_ENDIAN
+# endif
+// pcc-, gcc- and clang-specific
+#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__)
+# if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#  define SHADA_BIG_ENDIAN
+# endif
+#elif defined(__sparc) || defined(__sparc__) \
+   || defined(_POWER) || defined(__powerpc__) \
+   || defined(__ppc__) || defined(__hpux) || defined(__hppa) \
+   || defined(_MIPSEB) || defined(_POWER) \
+   || defined(__s390__)
+# define SHADA_BIG_ENDIAN
+#elif defined(__i386__) || defined(__alpha__) \
+   || defined(__ia64) || defined(__ia64__) \
+   || defined(_M_IX86) || defined(_M_IA64) \
+   || defined(_M_ALPHA) || defined(__amd64) \
+   || defined(__amd64__) || defined(_M_AMD64) \
+   || defined(__x86_64) || defined(__x86_64__) \
+   || defined(_M_X64) || defined(__bfin__)
+// Define nothing
+#endif
+
 /// Possible ShaDa entry types
 ///
 /// @warning Enum values are part of the API and must not be altered.
@@ -1027,6 +1073,22 @@ static void shada_free_shada_entry(ShadaEntry *const entry)
   }
 }
 
+#ifndef __GLIBC__
+static inline uint64_t be64toh(uint64_t big_endian_64_bits)
+{
+#ifdef SHADA_BIG_ENDIAN
+  return big_endian_64_bits;
+#else
+  uint8_t *buf = &big_endian_64_bits;
+  uint64_t ret = 0;
+  for (size_t i = 8; i; i--) {
+    ret |= ((uint64_t) buf[i - 1]) << ((8 - i) * 8);
+  }
+  return ret;
+#endif
+}
+#endif
+
 /// Read next unsigned integer from file
 ///
 /// Errors out if the result is not an unsigned integer.
@@ -1088,8 +1150,9 @@ static int msgpack_read_uint64(FILE *const fp, const int first_char,
         return FAIL;
       }
     }
-    uint8_t buf[8];
-    size_t read_bytes = fread((char *) &(buf[0]), 1, length, fp);
+    uint8_t buf[sizeof(uint64_t)] = {0, 0, 0, 0, 0, 0, 0, 0};
+    size_t read_bytes = fread((char *) &(buf[sizeof(uint64_t)-length]), 1,
+                              length, fp);
     if (ferror(fp)) {
       emsg2("System error while reading ShaDa file: %s",
             strerror(errno));
@@ -1100,11 +1163,7 @@ static int msgpack_read_uint64(FILE *const fp, const int first_char,
             (int64_t) fpos);
       return FAIL;
     }
-    // TODO(ZyX-I): Just cast if current platform is big-endian.
-    *result = 0;
-    for (size_t i = length; i; i--) {
-      *result |= ((uint64_t) buf[i - 1]) << ((length - i) * 8);
-    }
+    *result = be64toh(*((uint64_t *) &(buf[0])));
   }
   return OK;
 }