syslog/syslog_rpmsg.c: improve syslog_rpmsg performance

use copy buffer instead of single assignment

Signed-off-by: yuanyongjian <yuanyongjian@xiaomi.com>

drivers/syslog/syslog_rpmsg.c

@@ -80,8 +80,8 @@ struct syslog_rpmsg_s
  ****************************************************************************/
 
 static void syslog_rpmsg_work(FAR void *priv_);
-static void syslog_rpmsg_putchar(FAR struct syslog_rpmsg_s *priv, int ch,
+static void syslog_rpmsg_addbuf(FAR struct syslog_rpmsg_s *priv,
-                                 bool last);
+                                FAR const char *buffer, size_t len);
 static void syslog_rpmsg_device_created(FAR struct rpmsg_device *rdev,
                                         FAR void *priv_);
 static void syslog_rpmsg_device_destroy(FAR struct rpmsg_device *rdev,
@@ -189,10 +189,19 @@ static void syslog_rpmsg_work(FAR void *priv_)
     }
 }
 
-static void syslog_rpmsg_putchar(FAR struct syslog_rpmsg_s *priv, int ch,
+static void syslog_rpmsg_addbuf(FAR struct syslog_rpmsg_s *priv,
-                                 bool last)
+                                FAR const char *buffer, size_t len)
 {
-  if (priv->head + 1 - priv->tail >= priv->size)
+  bool overwritten = false;
+  size_t offset;
+  size_t tail;
+
+  if (len <= 0)
+    {
+     return;
+    }
+
+  if (priv->head + len - priv->tail >= priv->size)
     {
       bool ret = false;
 
@@ -203,26 +212,42 @@ static void syslog_rpmsg_putchar(FAR struct syslog_rpmsg_s *priv, int ch,
 
       if (!ret)
         {
-          /* Overwrite */
+          overwritten = true;
-
-          priv->buffer[SYSLOG_RPMSG_TAILOFF(priv)] = 0;
-          priv->tail++;
         }
     }
 
-  priv->buffer[SYSLOG_RPMSG_HEADOFF(priv)] = ch & 0xff;
+  offset = SYSLOG_RPMSG_HEADOFF(priv);
-  priv->head++;
+  tail = priv->size - offset;
+
+  if (len > tail)
+    {
+      memcpy(&priv->buffer[offset], buffer, tail);
+      memcpy(priv->buffer, buffer + tail, len - tail);
+    }
+  else
+    {
+      memcpy(&priv->buffer[offset], buffer, len);
+    }
+
+  priv->head += len;
+  if (overwritten)
+    {
+      priv->tail = priv->head - priv->size;
+      priv->buffer[priv->tail] = 0;
+      priv->tail++;
+    }
 
   if (priv->flush)
     {
 #if defined(CONFIG_ARCH_LOWPUTC)
-      up_putc(ch);
+      up_nputs(buffer, len);
 #endif
-      priv->flush++;
+
+      priv->flush += len;
       return;
     }
 
-  if (last && !priv->suspend && is_rpmsg_ept_ready(&priv->ept))
+  if (!priv->suspend && is_rpmsg_ept_ready(&priv->ept))
     {
       clock_t delay = SYSLOG_RPMSG_WORK_DELAY;
       size_t space = SYSLOG_RPMSG_SPACE(priv);
@@ -340,11 +365,12 @@ static ssize_t syslog_rpmsg_file_write(FAR struct file *filep,
 
 int syslog_rpmsg_putc(FAR syslog_channel_t *channel, int ch)
 {
-  FAR struct syslog_rpmsg_s *priv = &g_syslog_rpmsg;
   irqstate_t flags;
+  char tmp = ch;
+  UNUSED(channel);
 
   flags = enter_critical_section();
-  syslog_rpmsg_putchar(priv, ch, true);
+  syslog_rpmsg_addbuf(&g_syslog_rpmsg, &tmp, 1);
   leave_critical_section(flags);
 
   return ch;
@@ -363,12 +389,13 @@ int syslog_rpmsg_flush(FAR syslog_channel_t *channel)
       priv->flush = priv->tail;
     }
 
-  while (priv->flush < priv->head)
+  if (priv->flush < priv->head)
     {
+      size_t len = priv->head - priv->flush;
 #if defined(CONFIG_ARCH_LOWPUTC)
-      up_putc(priv->buffer[SYSLOG_RPMSG_FLUSHOFF(priv)]);
+      up_nputs(&priv->buffer[SYSLOG_RPMSG_FLUSHOFF(priv)], len);
 #endif
-      priv->flush++;
+      priv->flush += len;
     }
 
   leave_critical_section(flags);
@@ -380,15 +407,8 @@ ssize_t syslog_rpmsg_write(FAR syslog_channel_t *channel,
                            FAR const char *buffer, size_t buflen)
 {
   FAR struct syslog_rpmsg_s *priv = &g_syslog_rpmsg;
-  irqstate_t flags;
+  irqstate_t flags = enter_critical_section();
-  size_t nwritten;
+  syslog_rpmsg_addbuf(priv, buffer, buflen);
-
-  flags = enter_critical_section();
-  for (nwritten = 1; nwritten <= buflen; nwritten++)
-    {
-      syslog_rpmsg_putchar(priv, *buffer++, nwritten == buflen);
-    }
-
   leave_critical_section(flags);
 
   return buflen;