xiaoxiang781216 commented on code in PR #5996:
URL: https://github.com/apache/nuttx/pull/5996#discussion_r1059079785


##########
include/stdlib.h:
##########
@@ -132,6 +132,19 @@ extern "C"
 
 void      srand(unsigned int seed);
 int       rand(void);
+void      lcong48(FAR unsigned short int param[7]);
+FAR unsigned short int *seed48(FAR unsigned short int seed16v[3]);
+void      srand48(long int seedval);
+#ifdef CONFIG_HAVE_LONG_LONG
+long int  jrand48(FAR unsigned short int xsubi[3]);
+long int  lrand48(void);
+long int  mrand48(void);
+long int  nrand48(FAR unsigned short int xsubi[3]);
+#ifdef CONFIG_HAVE_DOUBLE

Review Comment:
   ```suggestion
   #  ifdef CONFIG_HAVE_DOUBLE
   ```



##########
libs/libc/stdlib/lib_rand48.c:
##########
@@ -0,0 +1,202 @@
+/****************************************************************************
+ * libs/libc/stdlib/lib_rand48.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdlib.h>
+
+#include <nuttx/lib/lib.h>
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static unsigned short int g_seed48[7] =
+{
+  0,
+  0,
+  0,
+  0xe66d,
+  0xdeec,
+  0x5,
+  0xb
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+#ifdef CONFIG_HAVE_LONG_LONG
+static uint64_t rand48_step(FAR unsigned short int *xi,
+                            FAR unsigned short int *lc)
+{
+  uint64_t a;
+  uint64_t x;
+
+  x = xi[0] | (xi[1] + (0ul << 16)) | (xi[2] + (0ull << 32));

Review Comment:
   why need add the zero shifted by 32/64bit?



##########
libs/libc/stdlib/lib_rand48.c:
##########
@@ -0,0 +1,202 @@
+/****************************************************************************
+ * libs/libc/stdlib/lib_rand48.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdlib.h>
+
+#include <nuttx/lib/lib.h>
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static unsigned short int g_seed48[7] =
+{
+  0,
+  0,
+  0,
+  0xe66d,
+  0xdeec,
+  0x5,
+  0xb
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+#ifdef CONFIG_HAVE_LONG_LONG
+static uint64_t rand48_step(FAR unsigned short int *xi,
+                            FAR unsigned short int *lc)
+{
+  uint64_t a;
+  uint64_t x;
+
+  x = xi[0] | (xi[1] + (0ul << 16)) | (xi[2] + (0ull << 32));
+  a = lc[0] | (lc[1] + (0ul << 16)) | (lc[2] + (0ull << 32));
+  x = a * x + lc[3];
+
+  xi[0] = x;
+  xi[1] = x >> 16;
+  xi[2] = x >> 32;
+  return x & 0xffffffffffffull;
+}
+#endif
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: srand48
+ ****************************************************************************/
+
+void srand48(long seed)
+{
+  unsigned short int p[3];
+
+  p[0] = 0x330e;
+  p[1] = seed;
+  p[2] = seed >> 16;
+  seed48(p);
+}
+
+/****************************************************************************
+ * Name: seed48
+ ****************************************************************************/
+
+FAR unsigned short int *seed48(FAR unsigned short int seed16v[3])
+{
+  static unsigned short int p[3];
+
+  memcpy(p, g_seed48, sizeof p);
+  memcpy(g_seed48, seed16v, sizeof p);

Review Comment:
   ```suggestion
     memcpy(g_seed48, seed16v, sizeof(g_seed48));
   ```



##########
include/stdlib.h:
##########
@@ -132,6 +132,19 @@ extern "C"
 
 void      srand(unsigned int seed);
 int       rand(void);
+void      lcong48(FAR unsigned short int param[7]);
+FAR unsigned short int *seed48(FAR unsigned short int seed16v[3]);
+void      srand48(long int seedval);
+#ifdef CONFIG_HAVE_LONG_LONG
+long int  jrand48(FAR unsigned short int xsubi[3]);
+long int  lrand48(void);
+long int  mrand48(void);
+long int  nrand48(FAR unsigned short int xsubi[3]);
+#ifdef CONFIG_HAVE_DOUBLE
+double    drand48(void);
+double    erand48(FAR unsigned short int xsubi[3]);
+#endif

Review Comment:
   ```suggestion
   #   endif
   ```



##########
libs/libc/stdlib/lib_rand48.c:
##########
@@ -0,0 +1,202 @@
+/****************************************************************************
+ * libs/libc/stdlib/lib_rand48.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdlib.h>
+
+#include <nuttx/lib/lib.h>
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static unsigned short int g_seed48[7] =
+{
+  0,
+  0,
+  0,
+  0xe66d,
+  0xdeec,
+  0x5,
+  0xb
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+#ifdef CONFIG_HAVE_LONG_LONG
+static uint64_t rand48_step(FAR unsigned short int *xi,
+                            FAR unsigned short int *lc)
+{
+  uint64_t a;
+  uint64_t x;
+
+  x = xi[0] | (xi[1] + (0ul << 16)) | (xi[2] + (0ull << 32));
+  a = lc[0] | (lc[1] + (0ul << 16)) | (lc[2] + (0ull << 32));
+  x = a * x + lc[3];
+
+  xi[0] = x;
+  xi[1] = x >> 16;
+  xi[2] = x >> 32;
+  return x & 0xffffffffffffull;
+}
+#endif
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: srand48
+ ****************************************************************************/
+
+void srand48(long seed)
+{
+  unsigned short int p[3];
+
+  p[0] = 0x330e;
+  p[1] = seed;
+  p[2] = seed >> 16;
+  seed48(p);
+}
+
+/****************************************************************************
+ * Name: seed48
+ ****************************************************************************/
+
+FAR unsigned short int *seed48(FAR unsigned short int seed16v[3])
+{
+  static unsigned short int p[3];
+
+  memcpy(p, g_seed48, sizeof p);

Review Comment:
   ```suggestion
     memcpy(p, g_seed48, sizeof(p));
   ```



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