From 87040f1822a2da07ef5c378cf1344614b07109f1 Mon Sep 17 00:00:00 2001
From: Jinqing Kuang <kuangjinqingcn@gmail.com>
Date: Tue, 18 Feb 2025 17:13:35 +0800
Subject: [PATCH] enh(stream): replace magic numbers in u64toaFastLut with
 macros

Replace magic numbers in the u64toaFastLut function with macros for
better readability and maintainability. Add unit test to ensure the
correctness of the refactor.
---
 source/util/src/tlog.c   | 41 +++++++++++++++++++++++++++-------------
 source/util/test/log.cpp | 25 ++++++++++++++++++++++++
 2 files changed, 53 insertions(+), 13 deletions(-)

diff --git a/source/util/src/tlog.c b/source/util/src/tlog.c
index 0e3e236b36..2460c7c650 100644
--- a/source/util/src/tlog.c
+++ b/source/util/src/tlog.c
@@ -1502,31 +1502,46 @@ bool taosAssertRelease(bool condition) {
 }
 #endif
 
+#define NUM_BASE 100
+#define DIGIT_LENGTH 2
+#define MAX_DIGITS 24
+
 char* u64toaFastLut(uint64_t val, char* buf) {
+  // Look-up table for 2-digit numbers
   static const char* lut =
       "0001020304050607080910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455"
       "5657585960616263646566676869707172737475767778798081828384858687888990919293949596979899";
 
-  char  temp[24];
-  char* p = temp;
+  char  temp[MAX_DIGITS];
+  char* p = temp + tListLen(temp);
 
-  while (val >= 100) {
-    strncpy(p, lut + (val % 100) * 2, 2);
-    val /= 100;
-    p += 2;
+  // Process the digits greater than or equal to 100
+  while (val >= NUM_BASE) {
+    // Get the last 2 digits from the look-up table and add to the buffer
+    p -= DIGIT_LENGTH;
+    strncpy(p, lut + (val % NUM_BASE) * DIGIT_LENGTH, DIGIT_LENGTH);
+    val /= NUM_BASE;
   }
 
+  // Process the remaining 1 or 2 digits
   if (val >= 10) {
-    strncpy(p, lut + val * 2, 2);
-    p += 2;
+    // If the number is 10 or more, get the 2 digits from the look-up table
+    p -= DIGIT_LENGTH;
+    strncpy(p, lut + val * DIGIT_LENGTH, DIGIT_LENGTH);
   } else if (val > 0 || p == temp) {
-    *(p++) = val + '0';
+    // If the number is less than 10, add the single digit to the buffer
+    p -= 1;
+    *p = val + '0';
   }
 
-  while (p != temp) {
-    *buf++ = *--p;
+  int64_t len = temp + tListLen(temp) - p;
+  if (len > 0) {
+    memcpy(buf, p, len);
+  } else {
+    buf[0] = '0';
+    len = 1;
   }
+  buf[len] = '\0';
 
-  *buf = '\0';
-  return buf;
+  return buf + len;
 }
diff --git a/source/util/test/log.cpp b/source/util/test/log.cpp
index 1899aac2c4..ae1be94e40 100644
--- a/source/util/test/log.cpp
+++ b/source/util/test/log.cpp
@@ -139,3 +139,28 @@ TEST(log, misc) {
 
   taosCloseLog();
 }
+
+TEST(log, test_u64toa) {
+  char buf[64] = {0};
+  char *p = buf;
+
+  p = u64toaFastLut(0, buf);
+  EXPECT_EQ(p, buf + 1);
+  EXPECT_EQ(strcmp(buf, "0"), 0);
+
+  p = u64toaFastLut(1, buf);
+  EXPECT_EQ(p, buf + 1);
+  EXPECT_EQ(strcmp(buf, "1"), 0);
+
+  p = u64toaFastLut(12, buf);
+  EXPECT_EQ(p, buf + 2);
+  EXPECT_EQ(strcmp(buf, "12"), 0);
+
+  p = u64toaFastLut(12345, buf);
+  EXPECT_EQ(p, buf + 5);
+  EXPECT_EQ(strcmp(buf, "12345"), 0);
+
+  p = u64toaFastLut(1234567890, buf);
+  EXPECT_EQ(p, buf + 10);
+  EXPECT_EQ(strcmp(buf, "1234567890"), 0);
+}