Closes #1508 Write wrapper for [v]snprintf. Mimics linux version.

The windows wrapper will always null terminate.
It will return >= size if overflow, although it might return less than linux on overflow.
When overflowing by more than 1, it just indicates an overflow of 1.

git-svn-id: file:///svn/toku/tokudb@9714 c7de825b-a66e-492c-adef-691d508d4ae1

windows/misc.h

@@ -51,11 +51,6 @@ long long int strtoll(const char *nptr, char **endptr, int base);
 long int random(void);
 void srandom(unsigned int seed);
 
-//snprintf
-//TODO: Put in its own file, or define a snprintf function based on _vsnprintf
-//in its own file
-#define snprintf(str, size, fmt, ...) _snprintf(str, size, fmt, __VA_ARGS__)
-
 //strtoll has a different name in windows.
 #define strtoll     _strtoi64
 #define strtoull    _strtoui64
@@ -73,6 +68,10 @@ char *realpath(const char *path, char *resolved_path);
 int unsetenv(const char *name);
 int setenv(const char *name, const char *value, int overwrite);
 
+int vsnprintf(char *str, size_t size, const char *format, va_list ap);
+
+int snprintf(char *str, size_t size, const char *format, ...);
+
 #if defined(__cplusplus)
 };
 #endif

windows/tests/test-snprintf.c

@@ -12,7 +12,7 @@
 void
 check_snprintf(int i) {
     char buf_before[8];
-    char target[8];
+    char target[5];
     char buf_after[8];
     memset(target, 0xFF, sizeof(target));
     memset(buf_before, 0xFF, sizeof(buf_before));
@@ -23,7 +23,8 @@ check_snprintf(int i) {
     for (j = 0; j < i; j++) n *= 10;
 
     int bytes = snprintf(target, sizeof target, "%"PRId64, n);
-    assert(bytes==i+1);
+    assert(bytes==i+1 ||
+           (i+1>=sizeof target && bytes>=sizeof target));
     if (bytes>=sizeof target) {
         //Overflow prevented by snprintf
         assert(target[sizeof target - 1] == '\0');

windows/windows.c

@@ -214,3 +214,27 @@ toku_os_is_absolute_name(const char* path) {
     return (path[0] == '\\' || 
             (isalpha(path[0]) && path[1]==':' && path[2]=='\\'));
 }
+
+int
+vsnprintf(char *str, size_t size, const char *format, va_list ap) {
+    int r = _vsnprintf(str, size, format, ap);
+    if (str && size>0) {
+        str[size-1] = '\0';         //Always null terminate.
+        if (r<0 && errno==ERANGE);
+            r = strlen(str)+1;      //Mimic linux return value.
+                                    //May be too small, but it does
+                                    //at least indicate overflow
+        }
+    }
+    return r;
+}
+
+int
+snprintf(char *str, size_t size, const char *format, ...) {
+    va_list ap;
+    va_start(ap, format);
+    int r = vsnprintf(str, size, format, ap);
+    va_end(ap);
+    return r;
+}
+