From 6322eb58fa7a62e44a222b8901abe81cad9d8649 Mon Sep 17 00:00:00 2001
From: zeekling <lingzhaohui@zeekling.cn>
Date: Sun, 8 Nov 2020 20:30:35 +0800
Subject: [PATCH] =?UTF-8?q?=E9=98=85=E8=AF=BBappend=E5=91=BD=E4=BB=A4?=
 =?UTF-8?q?=E6=BA=90=E7=A0=81?=
MIME-Version: 1.0
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---
 src/db.c       |  1 +
 src/t_string.c | 14 ++++++++------
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/db.c b/src/db.c
index 19b2c48..0cd8998 100644
--- a/src/db.c
+++ b/src/db.c
@@ -352,6 +352,7 @@ int dbDelete(redisDb *db, robj *key) {
 robj *dbUnshareStringValue(redisDb *db, robj *key, robj *o) {
     serverAssert(o->type == OBJ_STRING);
     if (o->refcount != 1 || o->encoding != OBJ_ENCODING_RAW) {
+        // 如果是共享的，则需要解除共享，创建新的字符串
         robj *decoded = getDecodedObject(o);
         o = createRawStringObject(decoded->ptr, sdslen(decoded->ptr));
         decrRefCount(decoded);
diff --git a/src/t_string.c b/src/t_string.c
index 37b2f95..8f6bbc7 100644
--- a/src/t_string.c
+++ b/src/t_string.c
@@ -31,7 +31,7 @@
 #include <math.h> /* isnan(), isinf() */
 
 /*-----------------------------------------------------------------------------
- * String Commands
+ * String Commands 检查字符串的长度是否大于255M
  *----------------------------------------------------------------------------*/
 
 static int checkStringLength(client *c, long long size) {
@@ -452,26 +452,28 @@ void incrbyfloatCommand(client *c) {
     rewriteClientCommandArgument(c,3,aux2);
     decrRefCount(aux2);
 }
-
+/**
+ * append命令实现函数 
+ **/
 void appendCommand(client *c) {
     size_t totlen;
     robj *o, *append;
-
+    // 查找key对应的数据
     o = lookupKeyWrite(c->db,c->argv[1]);
     if (o == NULL) {
-        /* Create the key */
+        /* 如果找不到，则添加 */
         c->argv[2] = tryObjectEncoding(c->argv[2]);
         dbAdd(c->db,c->argv[1],c->argv[2]);
         incrRefCount(c->argv[2]);
         totlen = stringObjectLen(c->argv[2]);
     } else {
-        /* Key exists, check type */
+        /* Key exists, check type，检查是否为string类型 */
         if (checkType(c,o,OBJ_STRING))
             return;
 
         /* "append" is an argument, so always an sds */
         append = c->argv[2];
-        totlen = stringObjectLen(o)+sdslen(append->ptr);
+        totlen = stringObjectLen(o)+sdslen(append->ptr); // 检查长度 
         if (checkStringLength(c,totlen) != C_OK)
             return;