Possible optimization to SkString

src/core/SkString.cpp

 
 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkString.h"
 #include "SkFixed.h"
 #include "SkThread.h"
 #include "SkUtils.h"
 #include <stdarg.h>
 #include <stdio.h>
 
 // number of bytes (on the stack) to receive the printf result
 static const size_t kBufferSize = 1024;
 
 #ifdef SK_BUILD_FOR_WIN
     #define VSNPRINTF(buffer, size, format, args) \
         _vsnprintf_s(buffer, size, _TRUNCATE, format, args)
     #define SNPRINTF    _snprintf
 #else
     #define VSNPRINTF   vsnprintf
     #define SNPRINTF    snprintf
 #endif
 
-#define ARGS_TO_BUFFER(format, buffer, size)        \
-    do {                                            \
-        va_list args;                               \
-        va_start(args, format);                     \
-        VSNPRINTF(buffer, size, format, args);      \
-        va_end(args);                               \
+#define ARGS_TO_BUFFER(format, buffer, size, written)    \
+    do {                                                 \
+        va_list args;                                    \
+        va_start(args, format);                          \
+        written = VSNPRINTF(buffer, size, format, args); \

[mtklein, 2014/10/23 23:01:36]

Let's SkASSERT(written >= 0 && written < size) here?  The return value is more
like wouldHaveWrittenHadWeTheRoomToDoSo, so it's nice to check it's actually
less than size.

[joshualitt, 2014/10/23 23:13:46]

Acknowledged.

+        va_end(args);                                    \
     } while (0)
 
 ///////////////////////////////////////////////////////////////////////////////
 
 bool SkStrEndsWith(const char string[], const char suffixStr[]) {
     SkASSERT(string);
     SkASSERT(suffixStr);
     size_t  strLen = strlen(string);
     size_t  suffixLen = strlen(suffixStr);
     return  strLen >= suffixLen &&
@@ skipping 505 matching lines @@
 }
 
 void SkString::insertScalar(size_t offset, SkScalar value) {
     char    buffer[SkStrAppendScalar_MaxSize];
     char*   stop = SkStrAppendScalar(buffer, value);
     this->insert(offset, buffer, stop - buffer);
 }
 
 void SkString::printf(const char format[], ...) {
     char    buffer[kBufferSize];
-    ARGS_TO_BUFFER(format, buffer, kBufferSize);
+    int length;
+    ARGS_TO_BUFFER(format, buffer, kBufferSize, length);
+    SkASSERT(length >= 0);
 
-    this->set(buffer, strlen(buffer));
+    this->set(buffer, length);
 }
 
 void SkString::appendf(const char format[], ...) {
     char    buffer[kBufferSize];
-    ARGS_TO_BUFFER(format, buffer, kBufferSize);
+    int length;
+    ARGS_TO_BUFFER(format, buffer, kBufferSize, length);
+    SkASSERT(length >= 0);
 
-    this->append(buffer, strlen(buffer));
+    this->append(buffer, length);
 }
 
 void SkString::appendVAList(const char format[], va_list args) {
     char    buffer[kBufferSize];
-    VSNPRINTF(buffer, kBufferSize, format, args);
+    int length = VSNPRINTF(buffer, kBufferSize, format, args);
+    SkASSERT(length >= 0);
 
-    this->append(buffer, strlen(buffer));
+    this->append(buffer, length);
 }
 
 void SkString::prependf(const char format[], ...) {
     char    buffer[kBufferSize];
-    ARGS_TO_BUFFER(format, buffer, kBufferSize);
+    int length;
+    ARGS_TO_BUFFER(format, buffer, kBufferSize, length);
+    SkASSERT(length >= 0);
 
-    this->prepend(buffer, strlen(buffer));
+    this->prepend(buffer, length);
 }
 
 void SkString::prependVAList(const char format[], va_list args) {
     char    buffer[kBufferSize];
-    VSNPRINTF(buffer, kBufferSize, format, args);
+    int length = VSNPRINTF(buffer, kBufferSize, format, args);
+    SkASSERT(length >= 0);
 
-    this->prepend(buffer, strlen(buffer));
+    this->prepend(buffer, length);
 }
 
 
 ///////////////////////////////////////////////////////////////////////////////
 
 void SkString::remove(size_t offset, size_t length) {
     size_t size = this->size();
 
     if (offset < size) {
         if (length > size - offset) {
@@ skipping 27 matching lines @@
 #ifdef SK_DEBUG
     SkTSwap<const char*>(fStr, other.fStr);
 #endif
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkString SkStringPrintf(const char* format, ...) {
     SkString formattedOutput;
     char buffer[kBufferSize];
-    ARGS_TO_BUFFER(format, buffer, kBufferSize);
+    SK_UNUSED int length;
+    ARGS_TO_BUFFER(format, buffer, kBufferSize, length);
     formattedOutput.set(buffer);
     return formattedOutput;
 }
 
 void SkStrSplit(const char* str, const char* delimiters, SkTArray<SkString>* out) {
     const char* end = str + strlen(str);
     while (str != end) {
         // Find a token.
         const size_t len = strcspn(str, delimiters);
         out->push_back().set(str, len);
         str += len;
         // Skip any delimiters.
         str += strspn(str, delimiters);
     }
 }
 
 #undef VSNPRINTF
 #undef SNPRINTF