Simpler implementation

include/ent.h

@@ -0,0 +1,17 @@
+#ifndef _ENT_H
+#define _ENT_H
+
+#include <stddef.h>
+
+/*
+ * Fills buf with high-quality entropy.
+ *
+ * buflen is the number of bytes, no greater than 256.
+ *
+ * Returns 0 on success. On failure, returns -1 and sets errno to
+ * indicate the error.
+ */
+int
+ent_getentropy(void* buf, size_t buflen);
+
+#endif /* _ENT_H */

include/ent/detail.h

@@ -1,26 +0,0 @@
-#ifndef _LIBENT_DETAIL_H
-#define _LIBENT_DETAIL_H
-
-#if defined _WIN32 || defined __CYGWIN__
-# ifdef WIN_EXPORT
-#  ifdef __GNUC__
-#   define ENT_EXPORT __attribute__ ((dllexport))
-#  else
-#   define ENT_EXPORT __declspec(dllexport)
-#  endif
-# else
-#  ifdef __GNUC__
-#   define ENT_EXPORT __attribute__ ((dllimport))
-#  else
-#   define ENT_EXPORT __declspec(dllimport)
-#  endif
-# endif
-#else
-# if __GNUC__ >= 4
-#  define ENT_EXPORT __attribute__ ((visibility ("default")))
-# else
-#  define ENT_EXPORT
-# endif
-#endif
-
-#endif /* _LIBENT_DETAIL_H */

include/ent/ent.h

@@ -1,12 +0,0 @@
-#ifndef _LIBENT_ENT_H
-#define _LIBENT_ENT_H
-
-#include <stddef.h>
-
-#include <ent/detail.h>
-
-ENT_EXPORT
-int
-ent_getentropy(void *buf, size_t buflen);
-
-#endif /* _LIBENT_ENT_H */

meson.build

@@ -3,11 +3,33 @@ project('libent', 'c', 'cpp',
         version : '0.0.1',
         license : 'MIT')
 
-inc = include_directories('include')
+conf_data = configuration_data()
+compiler = meson.get_compiler('c')
 
-install_headers('include/ent/ent.h', subdir : 'ent')
+code = '''#include <unistd.h>
+#include <sys/random.h>
+int main() { return getentropy((void*)0, 0); }
+'''
+have_getentropy = compiler.links(code,name : 'system getentropy')
+conf_data.set('USE_GETENTROPY', have_getentropy)
+
+if not have_getentropy
+  code = '''#include <fcntl.h>
+  int main() { return -1 != open("/dev/urandom", O_RDONLY) ? 0 : 1; }
+  '''
+  use_urandom = compiler.run(code, name : 'open /dev/urandom')
+  conf_data.set('USE_URANDOM', use_urandom.returncode() == 0)
+endif
+
+configure_file(output : 'config.h',
+               configuration : conf_data)
+
+inc = include_directories('.', 'include')
+
+install_headers('include/ent.h')
 
 ent_sources = ['src/ent.c']
+
 libent = shared_library('ent',
                         ent_sources,
                         include_directories : inc,

src/ent.c

@@ -1,14 +1,43 @@
-#include <ent/ent.h>
+#include <ent.h>
 
-#if defined __OPENBSD__ || (defined __linux__ && defined _DEFAULT_SOURCE)
+#include <assert.h>
+
+#include "config.h"
+
+#if defined(USE_GETENTROPY)
 # include <unistd.h>
+# if defined(__APPLE__) || defined(__linux__)
+#   include <sys/random.h>
+# endif
 # define getentropy_impl getentropy
-#elif defined __APPLE__ && defined __MACH__
+#elif defined(USE_URANDOM)
+# include <fcntl.h>
+# include <sys/types.h>
 # include <unistd.h>
-# include <sys/random.h>
-# define getentropy_impl getentropy
 #else
-# error "Port: getentropy unimplemented"
+# error "port: getentropy"
+#endif
+
+
+#if defined(USE_URANDOM)
+
+static int
+getentropy_impl(void* buf, size_t buflen)
+{
+  int fd;
+
+  assert(buflen <= 256);
+  if (-1 == (fd = open("/dev/urandom", O_RDONLY))) {
+    return -1;
+  }
+  if (buflen != read(fd, buf, buflen)) {
+    (void) close(fd);
+    return -1;
+  }
+  close(fd);
+  return 0;
+}
+
 #endif
 
 int