redis_server_protocol: add append_decimal to IOBufappender

src/brpc/redis_reply.cpp

@@ -40,8 +40,6 @@ const char* RedisReplyTypeToString(RedisReplyType type) {
 }
 
 bool RedisReply::SerializeTo(butil::IOBufAppender* appender) {
-    char prefix_buf[24];   // should be enough for '<type><integer>\r\n"
-    size_t len = 0;
     switch (_type) {
         case REDIS_REPLY_ERROR:
             // fall through
@@ -55,40 +53,32 @@ bool RedisReply::SerializeTo(butil::IOBufAppender* appender) {
             appender->append("\r\n");
             break;
         case REDIS_REPLY_INTEGER:
-            prefix_buf[0] = ':';
-            len = butil::AppendDecimal(&prefix_buf[1], _data.integer);
-            prefix_buf[len + 1] = '\r';
-            prefix_buf[len + 2] = '\n';
-            appender->append(prefix_buf, len + 3 /* 1 for ':', 2 for "\r\n" */);
+            appender->push_back(':');
+            appender->append_decimal(_data.integer);
+            appender->append("\r\n");
             break;
         case REDIS_REPLY_STRING:
-            prefix_buf[0] = '$';
-            len = butil::AppendDecimal(&prefix_buf[1], _length);
-            prefix_buf[len + 1] = '\r';
-            prefix_buf[len + 2] = '\n';
-            appender->append(prefix_buf, len + 3 /* 1 for ':', 2 for "\r\n" */);
-            if (_length == npos) {
-                break;
-            }
-            if (_length < (int)sizeof(_data.short_str)) {
-                appender->append(_data.short_str, _length);
-            } else {
-                appender->append(_data.long_str, _length);
-            }
+            appender->push_back('$');
+            appender->append_decimal(_length);
             appender->append("\r\n");
+            if (_length != npos) {
+                if (_length < (int)sizeof(_data.short_str)) {
+                    appender->append(_data.short_str, _length);
+                } else {
+                    appender->append(_data.long_str, _length);
+                }
+                appender->append("\r\n");
+            }
             break;
         case REDIS_REPLY_ARRAY:
-            prefix_buf[0] = '*';
-            len = butil::AppendDecimal(&prefix_buf[1], _length);
-            prefix_buf[len + 1] = '\r';
-            prefix_buf[len + 2] = '\n';
-            appender->append(prefix_buf, len + 3 /* 1 for ':', 2 for "\r\n" */);
-            if (_length == npos) {
-                break;
-            }
-            for (int i = 0; i < _length; ++i) {
-                if (!_data.array.replies[i].SerializeTo(appender)) {
-                    return false;
+            appender->push_back('*');
+            appender->append_decimal(_length);
+            appender->append("\r\n");
+            if (_length != npos) {
+                for (int i = 0; i < _length; ++i) {
+                    if (!_data.array.replies[i].SerializeTo(appender)) {
+                        return false;
+                    }
                 }
             }
             break;

src/butil/iobuf.h

@@ -669,6 +669,11 @@ public:
     // Returns 0 on success, -1 otherwise.
     int append(const void* data, size_t n);
     int append(const butil::StringPiece& str);
+
+    // Format integer |d| to back side of the internal buffer, which is much faster
+    // than snprintf(..., "%lu", d).
+    // Returns 0 on success, -1 otherwise.
+    int append_decimal(long d);
     
     // Push the character to back side of the internal buffer.
     // Costs ~3ns while IOBuf.push_back costs ~13ns on Intel(R) Xeon(R) CPU

src/butil/iobuf_inl.h

@@ -285,6 +285,25 @@ inline int IOBufAppender::append(const StringPiece& str) {
     return append(str.data(), str.size());
 }
 
+inline int IOBufAppender::append_decimal(long d) {
+    char buf[24];  // enough for decimal 64-bit integers
+    size_t n = sizeof(buf);
+    bool negative = false;
+    if (d < 0) {
+        negative = true;
+        d = -d;
+    }
+    do {
+        const long q = d / 10;
+        buf[--n] = d - q * 10 + '0';
+        d = q;
+    } while (d);
+    if (negative) {
+        buf[--n] = '-';
+    }
+    return append(buf + n, sizeof(buf) - n);
+}
+
 inline int IOBufAppender::push_back(char c) {
     if (_data == _data_end) {
         if (add_block() != 0) {