Make NS_ReadLine() not lie about having more data when the stream ends in \r\n. b=397850 r+sr=cbiesinger a=blocking1.9

netwerk/base/public/nsReadLine.h

@@ -22,6 +22,7 @@
  *
  * Contributor(s):
  *   Christian Biesinger <cbiesinger@web.de>
+ *   Mats Palmgren <mats.palmgren@bredband.net>
  *
  * Alternatively, the contents of this file may be used under the terms of
  * either the GNU General Public License Version 2 or later (the "GPL"), or
@@ -60,21 +61,23 @@
  * Buffer size. This many bytes will be buffered. If a line is longer than this,
  * the partial line will be appended to the out parameter of NS_ReadLine and the
  * buffer will be emptied.
+ * Note: if you change this constant, please update the regression test in
+ * netwerk/test/unit/test_readline.js accordingly (bug 397850).
  */
 #define kLineBufferSize 4096
 
 /**
  * @internal
  * Line buffer structure, buffers data from an input stream.
+ * The buffer is empty when |start| == |end|.
+ * Invariant: |start| <= |end|
  */
 template<typename CharT>
 class nsLineBuffer {
   public:
   CharT buf[kLineBufferSize+1];
   CharT* start;
-  CharT* current;
   CharT* end;
-  PRBool empty;
 };
 
 /**
@@ -105,8 +108,7 @@ NS_InitLineBuffer (nsLineBuffer<CharT> ** aBufferPtr) {
   if (!(*aBufferPtr))
     return NS_ERROR_OUT_OF_MEMORY;
 
-  (*aBufferPtr)->start = (*aBufferPtr)->current = (*aBufferPtr)->end = (*aBufferPtr)->buf;
-  (*aBufferPtr)->empty = PR_TRUE;
+  (*aBufferPtr)->start = (*aBufferPtr)->end = (*aBufferPtr)->buf;
   return NS_OK;
 }
 
@@ -136,76 +138,62 @@ NS_InitLineBuffer (nsLineBuffer<CharT> ** aBufferPtr) {
 template<typename CharT, class StreamType, class StringType>
 nsresult
 NS_ReadLine (StreamType* aStream, nsLineBuffer<CharT> * aBuffer,
-             StringType & aLine, PRBool *more) {
-  nsresult rv = NS_OK;
-  PRUint32 bytesRead;
-  *more = PR_TRUE;
-  PRBool eolStarted = PR_FALSE;
-  CharT eolchar = '\0';
+             StringType & aLine, PRBool *more)
+{
+  CharT eolchar = 0; // the first eol char or 1 after \r\n or \n\r is found
+
   aLine.Truncate();
+
   while (1) { // will be returning out of this loop on eol or eof
-    if (aBuffer->empty) { // buffer is empty.  Read into it.
-      rv = aStream->Read(aBuffer->buf, kLineBufferSize, &bytesRead);
-      if (NS_FAILED(rv)) // read failed
-        return rv;
-      if (bytesRead == 0) { // end of file
+    if (aBuffer->start == aBuffer->end) { // buffer is empty.  Read into it.
+      PRUint32 bytesRead;
+      nsresult rv = aStream->Read(aBuffer->buf, kLineBufferSize, &bytesRead);
+      if (NS_FAILED(rv) || NS_UNLIKELY(bytesRead == 0)) {
         *more = PR_FALSE;
-        return NS_OK;
+        return rv;
       }
+      aBuffer->start = aBuffer->buf;
       aBuffer->end = aBuffer->buf + bytesRead;
-      aBuffer->empty = PR_FALSE;
-      *(aBuffer->end) = '\0'; // null-terminate this thing
+      *(aBuffer->end) = '\0';
     }
-    // walk the buffer looking for an end-of-line
-    while (aBuffer->current < aBuffer->end) {
-      if (eolStarted) {
-          if ((eolchar == '\n' && *(aBuffer->current) == '\r') ||
-              (eolchar == '\r' && *(aBuffer->current) == '\n')) { // line end
-            (aBuffer->current)++;
-            aBuffer->start = aBuffer->current;
-          }
-          eolStarted = PR_FALSE;
-          return NS_OK;
-      } else if (*(aBuffer->current) == '\n' ||
-                 *(aBuffer->current) == '\r') { // line end
-        eolStarted = PR_TRUE;
-        eolchar = *(aBuffer->current);
-        *(aBuffer->current) = '\0';
-        aLine.Append(aBuffer->start);
-        (aBuffer->current)++;
-        aBuffer->start = aBuffer->current;
-      } else {
-        eolStarted = PR_FALSE;
-        (aBuffer->current)++;
+
+    /*
+     * Walk the buffer looking for an end-of-line.
+     * There are 3 cases to consider:
+     *  1. the eol char is the last char in the buffer
+     *  2. the eol char + one more char at the end of the buffer
+     *  3. the eol char + two or more chars at the end of the buffer
+     * we need at least one char after the first eol char to determine if
+     * it's a \r\n or \n\r sequence (and skip over it), and we need one
+     * more char after the end-of-line to set |more| correctly.
+     */
+    CharT* current = aBuffer->start;
+    if (NS_LIKELY(eolchar == 0)) {
+      for ( ; current < aBuffer->end; ++current) {
+        if (*current == '\n' || *current == '\r') {
+          eolchar = *current;
+          *current++ = '\0';
+          aLine.Append(aBuffer->start);
+          break;
+        }
+      }
+    }
+    if (NS_LIKELY(eolchar != 0)) {
+      for ( ; current < aBuffer->end; ++current) {
+        if ((eolchar == '\r' && *current == '\n') ||
+            (eolchar == '\n' && *current == '\r')) {
+          eolchar = 1;
+          continue;
+        }
+        aBuffer->start = current;
+        *more = PR_TRUE;
+        return NS_OK;
       }
     }
 
-    // append whatever we currently have to the string
-    aLine.Append(aBuffer->start);
-
-    // we've run out of buffer.  Begin anew
-    aBuffer->current = aBuffer->start = aBuffer->buf;
-    aBuffer->empty = PR_TRUE;
-    
-    if (eolStarted) {  // have to read another char and possibly skip over it
-      rv = aStream->Read(aBuffer->buf, 1, &bytesRead);
-      if (NS_FAILED(rv)) // read failed
-        return rv;
-      if (bytesRead == 0) { // end of file
-        *more = PR_FALSE;
-        return NS_OK;
-      }
-      if ((eolchar == '\n' && *(aBuffer->buf) == '\r') ||
-          (eolchar == '\r' && *(aBuffer->buf) == '\n')) {
-        // Just return and all is good -- we've skipped the extra newline char
-        return NS_OK;
-      } else {
-        // we have a byte that we should look at later
-        aBuffer->empty = PR_FALSE;
-        aBuffer->end = aBuffer->buf + 1;
-        *(aBuffer->end) = '\0';
-      }
-    }
+    if (eolchar == 0)
+      aLine.Append(aBuffer->start);
+    aBuffer->start = aBuffer->end; // mark the buffer empty
   }
 }