Bug 965362 - Part 1: Make sure that nsScriptableInputStream::Read reads all of the allowed available bytes from the input stream; r=bsmedberg

xpcom/io/nsScriptableInputStream.cpp

@@ -45,14 +45,13 @@ nsScriptableInputStream::Read(uint32_t aCount, char **_retval) {
     buffer = (char*)moz_malloc(count+1); // make room for '\0'
     if (!buffer) return NS_ERROR_OUT_OF_MEMORY;
 
-    uint32_t amtRead = 0;
-    rv = mInputStream->Read(buffer, count, &amtRead);
+    rv = ReadHelper(buffer, count);
     if (NS_FAILED(rv)) {
         nsMemory::Free(buffer);
         return rv;
     }
 
-    buffer[amtRead] = '\0';
+    buffer[count] = '\0';
     *_retval = buffer;
     return NS_OK;
 }
@@ -69,10 +68,20 @@ nsScriptableInputStream::ReadBytes(uint32_t aCount, nsACString &_retval) {
     }
 
     char *ptr = _retval.BeginWriting();
+    nsresult rv = ReadHelper(ptr, aCount);
+    if (NS_FAILED(rv)) {
+      _retval.Truncate();
+    }
+    return rv;
+}
+
+nsresult
+nsScriptableInputStream::ReadHelper(char* aBuffer, uint32_t aCount)
+{
     uint32_t totalBytesRead = 0;
     while (1) {
       uint32_t bytesRead;
-      nsresult rv = mInputStream->Read(ptr + totalBytesRead,
+      nsresult rv = mInputStream->Read(aBuffer + totalBytesRead,
                                        aCount - totalBytesRead,
                                        &bytesRead);
       if (NS_FAILED(rv)) {
@@ -86,7 +95,6 @@ nsScriptableInputStream::ReadBytes(uint32_t aCount, nsACString &_retval) {
 
       // If we have read zero bytes, we have hit EOF.
       if (bytesRead == 0) {
-        _retval.Truncate();
         return NS_ERROR_FAILURE;
       }
 

xpcom/io/nsScriptableInputStream.h

@@ -33,6 +33,8 @@ public:
 private:
     ~nsScriptableInputStream() {}
 
+    nsresult ReadHelper(char* aBuffer, uint32_t aCount);
+
     nsCOMPtr<nsIInputStream> mInputStream;
 };