Simplify leveldb::ChromiumLogger::Logv().

This basically reimplemented base::StringPrintV(). Use that directly
instead.

Bug: none
Change-Id: I2e1a7de3a56d609b26899532d76cb64ca5bb7842
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4814667
Auto-Submit: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Joshua Bell <jsbell@chromium.org>
Commit-Queue: Joshua Bell <jsbell@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1188593}

third_party/leveldatabase/chromium_logger.h

@@ -5,14 +5,16 @@
 #ifndef THIRD_PARTY_LEVELDATABASE_CHROMIUM_LOGGER_H_
 #define THIRD_PARTY_LEVELDATABASE_CHROMIUM_LOGGER_H_
 
-#include <cstdarg>
+#include <string>
 #include <utility>
 
+#include "base/containers/span.h"
 #include "base/files/file.h"
 #include "base/format_macros.h"
-#include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
+#include "third_party/leveldatabase/src/include/leveldb/env.h"
 
 namespace leveldb {
 
@@ -23,87 +25,22 @@ class ChromiumLogger : public Logger {
   ~ChromiumLogger() override = default;
 
   void Logv(const char* format, va_list arguments) override {
-    // Record the time as close to the Logv() call as possible.
     base::Time::Exploded now_exploded;
     base::Time::Now().LocalExplode(&now_exploded);
 
-    const base::PlatformThreadId thread_id = base::PlatformThread::CurrentId();
-
-    // We first attempt to print into a stack-allocated buffer. If this attempt
-    // fails, we make a second attempt with a dynamically allocated buffer.
-    constexpr const int kStackBufferSize = 512;
-    char stack_buffer[kStackBufferSize];
-    static_assert(sizeof(stack_buffer) == static_cast<size_t>(kStackBufferSize),
-                  "sizeof(char) is expected to be 1 in C++");
-
-    int dynamic_buffer_size = 0;  // Computed in the first iteration.
-    for (int iteration = 0; iteration < 2; ++iteration) {
-      const int buffer_size =
-          (iteration == 0) ? kStackBufferSize : dynamic_buffer_size;
-      char* const buffer =
-          (iteration == 0) ? stack_buffer : new char[dynamic_buffer_size];
-
-      // Print the header into the buffer.
-      int buffer_offset = base::snprintf(
-          buffer, buffer_size,
-          "%04d/%02d/%02d-%02d:%02d:%02d.%03d %" PRIx64 " ",
-          now_exploded.year,
-          now_exploded.month,
-          now_exploded.day_of_month,
-          now_exploded.hour,
-          now_exploded.minute,
-          now_exploded.second,
-          now_exploded.millisecond,
-          static_cast<uint64_t>(thread_id));
-
-      // The header can be at most 45 characters (10 date + 12 time + 3 spacing
-      // + 20 thread ID), which should fit comfortably into the static buffer.
-      DCHECK_LE(buffer_offset, 45);
-      static_assert(45 < kStackBufferSize,
-                    "stack-allocated buffer may not fit the message header");
-      DCHECK_LT(buffer_offset, buffer_size);
-
-      // Print the message into the buffer.
-      std::va_list arguments_copy;
-      va_copy(arguments_copy, arguments);
-      buffer_offset += std::vsnprintf(buffer + buffer_offset,
-                                      buffer_size - buffer_offset, format,
-                                      arguments_copy);
-      va_end(arguments_copy);
-
-      // The code below may append a newline at the end of the buffer, which
-      // requires an extra character.
-      if (buffer_offset >= buffer_size - 1) {
-        // The message did not fit into the buffer.
-        if (iteration == 0) {
-          // Re-run the loop and use a dynamically-allocated buffer. The buffer
-          // will be large enough for the log message, an extra newline and a
-          // null terminator.
-          dynamic_buffer_size = buffer_offset + 2;
-          continue;
-        }
-
-        // The dynamically-allocated buffer was incorrectly sized. This should
-        // not happen, assuming a correct implementation of (v)snprintf. Fail
-        // in tests, recover by truncating the log message in production.
-        NOTREACHED();
-        buffer_offset = buffer_size - 1;
-      }
-
-      // Add a newline if necessary.
-      if (buffer[buffer_offset - 1] != '\n') {
-        buffer[buffer_offset] = '\n';
-        ++buffer_offset;
-      }
-
-      DCHECK_LE(buffer_offset, buffer_size);
-      file_.WriteAtCurrentPos(buffer, buffer_offset);
-
-      if (iteration != 0) {
-        delete[] buffer;
-      }
-      break;
+    std::string str =
+        base::StringPrintf(
+            "%04d/%02d/%02d-%02d:%02d:%02d.%03d %" PRIx64 " ",
+            now_exploded.year, now_exploded.month, now_exploded.day_of_month,
+            now_exploded.hour, now_exploded.minute, now_exploded.second,
+            now_exploded.millisecond,
+            static_cast<uint64_t>(base::PlatformThread::CurrentId())) +
+        base::StringPrintV(format, arguments);
+    if (str.back() != '\n') {
+      str.push_back('\n');
     }
+
+    file_.WriteAtCurrentPosAndCheck(base::as_bytes(base::make_span(str)));
   }
 
  private: