From c22de779ac3956c267bcd9e913c015f072665359 Mon Sep 17 00:00:00 2001
From: Liu Jicong <liujicong@qq.com>
Date: Tue, 11 Jan 2022 16:55:40 +0800
Subject: [PATCH] add tmemmem

---
 source/libs/wal/src/walMeta.c        | 52 ++++++++++++++++++++--------
 source/libs/wal/src/walMgmt.c        |  1 +
 source/libs/wal/test/walMetaTest.cpp |  3 ++
 3 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/source/libs/wal/src/walMeta.c b/source/libs/wal/src/walMeta.c
index ab3aa02f4a..1c08f88dc6 100644
--- a/source/libs/wal/src/walMeta.c
+++ b/source/libs/wal/src/walMeta.c
@@ -13,7 +13,6 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-#define _DEFAULT_SOURCE
 #include "cJSON.h"
 #include "os.h"
 #include "taoserror.h"
@@ -33,6 +32,24 @@ static inline int walBuildMetaName(SWal* pWal, int metaVer, char* buf) {
   return sprintf(buf, "%s/meta-ver%d", pWal->path, metaVer);
 }
 
+void* tmemmem(char* haystack, int hlen, char* needle, int nlen) {
+  char* limit;
+
+  if (nlen == 0 || hlen < nlen) {
+    return false;
+  }
+
+  limit = haystack + hlen - nlen + 1;
+  while ((haystack = (char*)memchr(
+              haystack, needle[0], limit - haystack)) != NULL) {
+    if (memcmp(haystack, needle, nlen) == 0) {
+      return haystack;
+    }
+    haystack++;
+  }
+  return NULL;
+}
+
 static inline int64_t walScanLogGetLastVer(SWal* pWal) {
   ASSERT(pWal->fileInfoSet != NULL);
   int sz = taosArrayGetSize(pWal->fileInfoSet);
@@ -47,7 +64,7 @@ static inline int64_t walScanLogGetLastVer(SWal* pWal) {
 
   struct stat statbuf;
   stat(fnameStr, &statbuf);
-  int readSize = MIN(WAL_MAX_SIZE, statbuf.st_size);
+  int readSize = MIN(WAL_MAX_SIZE + 2, statbuf.st_size);
 
   FileFd fd = taosOpenFileRead(fnameStr);
   if (fd < 0) {
@@ -64,6 +81,7 @@ static inline int64_t walScanLogGetLastVer(SWal* pWal) {
     return -1;
   }
 
+  taosLSeekFile(fd, -readSize, SEEK_END);
   if (readSize != taosReadFile(fd, buf, readSize)) {
     free(buf);
     taosCloseFile(fd);
@@ -71,21 +89,25 @@ static inline int64_t walScanLogGetLastVer(SWal* pWal) {
     return -1;
   }
   
-  char* found = strstr(buf, (const char*)&magic);
-  if (found == NULL) {
-    ASSERT(false);
-    // file has to be deleted
-    free(buf);
-    taosCloseFile(fd);
-    terrno = TSDB_CODE_WAL_FILE_CORRUPTED;
-    return -1;
-  }
-  char *another;
-  while((another = strstr(found + 1, (const char*)&magic)) != NULL) {
+  char* haystack = buf;
+  char* found = NULL;
+  char *candidate = NULL;
+  while((candidate = tmemmem(haystack, readSize - (haystack - buf), (char*)&magic, sizeof(uint64_t))) != NULL) {
     // read and validate
-    SWalHead *logContent = (SWalHead*)another;
+    SWalHead *logContent = (SWalHead*)candidate;
     if (walValidHeadCksum(logContent) == 0 && walValidBodyCksum(logContent) == 0) {
-      found = another;
+      found = candidate;
+    }
+    haystack = candidate + 1;
+  }
+  if (found == buf) {
+    SWalHead *logContent = (SWalHead*)found;
+    if (walValidHeadCksum(logContent) != 0 || walValidBodyCksum(logContent) != 0) {
+      // file has to be deleted
+      free(buf);
+      taosCloseFile(fd);
+      terrno = TSDB_CODE_WAL_FILE_CORRUPTED;
+      return -1;
     }
   }
   taosCloseFile(fd);
diff --git a/source/libs/wal/src/walMgmt.c b/source/libs/wal/src/walMgmt.c
index d12acb52c6..93ec4693a3 100644
--- a/source/libs/wal/src/walMgmt.c
+++ b/source/libs/wal/src/walMgmt.c
@@ -106,6 +106,7 @@ SWal *walOpen(const char *path, SWalCfg *pCfg) {
   // init write buffer
   memset(&pWal->writeHead, 0, sizeof(SWalHead));
   pWal->writeHead.head.headVer = WAL_HEAD_VER;
+  pWal->writeHead.magic = WAL_MAGIC;
 
   if (pthread_mutex_init(&pWal->mutex, NULL) < 0) {
     taosArrayDestroy(pWal->fileInfoSet);
diff --git a/source/libs/wal/test/walMetaTest.cpp b/source/libs/wal/test/walMetaTest.cpp
index a95c75b11d..5774eea8c0 100644
--- a/source/libs/wal/test/walMetaTest.cpp
+++ b/source/libs/wal/test/walMetaTest.cpp
@@ -340,7 +340,10 @@ TEST_F(WalRetentionEnv, repairMeta1) {
   char buf[100];
   sprintf(buf, "%s/meta-ver%d", pathName, 0);
   remove(buf);
+  sprintf(buf, "%s/meta-ver%d", pathName, 1);
+  remove(buf);
   SetUp();
+  //getchar();
 
   ASSERT_EQ(pWal->vers.lastVer, 99);