Make SkString::appendf safe for long strings.
Bug: skia:7841
Change-Id: I5bc77f5230b63da74e42d756ab4a1fefcfab9926
Reviewed-on: https://skia-review.googlesource.com/123634
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/src/core/SkString.cpp b/src/core/SkString.cpp
index 554cde8..707e8be 100644
--- a/src/core/SkString.cpp
+++ b/src/core/SkString.cpp
@@ -5,48 +5,60 @@
* found in the LICENSE file.
*/
+#include "SkString.h"
+#include <stdarg.h>
+#include <cstdio>
#include "SkAtomics.h"
#include "SkSafeMath.h"
-#include "SkString.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;
-#define ARGS_TO_BUFFER(format, buffer, size, written) \
- do { \
- va_list args; \
- va_start(args, format); \
- written = vsnprintf(buffer, size, format, args); \
- SkASSERT(written >= 0 && written < SkToInt(size)); \
- va_end(args); \
+static const char* apply_format_string(const char* format, va_list args, char* stackBuffer,
+ size_t stackBufferSize, int* length, SkString* heapBuffer) {
+ va_list argsCopy;
+ va_copy(argsCopy, args);
+ *length = std::vsnprintf(stackBuffer, stackBufferSize, format, args);
+ if (*length < 0) {
+ SkDebugf("SkString: vsnprintf reported error.");
+ va_end(argsCopy);
+ *length = 0;
+ return stackBuffer;
+ }
+ if (*length < SkToInt(stackBufferSize)) {
+ va_end(argsCopy);
+ return stackBuffer;
+ }
+ heapBuffer->resize(*length);
+ SkDEBUGCODE(int check =)
+ std::vsnprintf(heapBuffer->writable_str(), *length + 1, format, argsCopy);
+ SkASSERT(check == *length);
+ va_end(argsCopy);
+ return heapBuffer->c_str();
+}
+
+#define ARGS_TO_BUFFER(format, buffer, size, written, result) \
+ SkString overflow; \
+ do { \
+ va_list args; \
+ va_start(args, format); \
+ result = apply_format_string(format, args, buffer, size, &written, &overflow); \
+ va_end(args); \
} while (0)
-#define V_SKSTRING_PRINTF(output, format) \
- do { \
- va_list args; \
- va_start(args, format); \
- char buffer[kBufferSize]; \
- int length = vsnprintf(buffer, sizeof(buffer), format, args); \
- va_end(args); \
- if (length < 0) { \
- break; \
- } \
- if (length < (int)sizeof(buffer)) { \
- output.set(buffer, length); \
- break; \
- } \
- SkString tmp((size_t)length); \
- va_start(args, format); \
- SkDEBUGCODE(int check = ) vsnprintf(tmp.writable_str(), \
- length + 1, format, args); \
- va_end(args); \
- SkASSERT(check == length); \
- output = std::move(tmp); \
- SkASSERT(output[length] == '\0'); \
- } while (false)
+#define V_SKSTRING_PRINTF(output, format) \
+ do { \
+ char buffer[kBufferSize]; \
+ va_list args; \
+ va_start(args, format); \
+ int length; \
+ auto result = apply_format_string(format, args, buffer, kBufferSize, &length, &output); \
+ SkASSERT(result == output.c_str() || result == buffer); \
+ if (result == buffer) { \
+ output.set(buffer, length); \
+ } \
+ } while (0)
///////////////////////////////////////////////////////////////////////////////
@@ -491,15 +503,16 @@
}
void SkString::appendf(const char format[], ...) {
- char buffer[kBufferSize];
+ char buffer[kBufferSize];
int length;
- ARGS_TO_BUFFER(format, buffer, kBufferSize, length);
+ const char* result;
+ ARGS_TO_BUFFER(format, buffer, kBufferSize, length, result);
- this->append(buffer, length);
+ this->append(result, length);
}
void SkString::appendVAList(const char format[], va_list args) {
- char buffer[kBufferSize];
+ char buffer[kBufferSize];
int length = vsnprintf(buffer, kBufferSize, format, args);
SkASSERT(length >= 0 && length < SkToInt(kBufferSize));
@@ -507,15 +520,16 @@
}
void SkString::prependf(const char format[], ...) {
- char buffer[kBufferSize];
+ char buffer[kBufferSize];
int length;
- ARGS_TO_BUFFER(format, buffer, kBufferSize, length);
+ const char* result;
+ ARGS_TO_BUFFER(format, buffer, kBufferSize, length, result);
- this->prepend(buffer, length);
+ this->prepend(result, length);
}
void SkString::prependVAList(const char format[], va_list args) {
- char buffer[kBufferSize];
+ char buffer[kBufferSize];
int length = vsnprintf(buffer, kBufferSize, format, args);
SkASSERT(length >= 0 && length < SkToInt(kBufferSize));