Add support for column computation on unbuffered streams.

llvm-svn: 79065

lib/Support/FormattedStream.cpp

@@ -15,27 +15,34 @@
 
 using namespace llvm;
 
-/// ComputeColumn - Examine the current output and figure out which
+/// CountColumns - Examine the given char sequence and figure out which
 /// column we end up in after output.
 ///
-void formatted_raw_ostream::ComputeColumn() {
+static unsigned CountColumns(unsigned Column, const char *Ptr, size_t Size) {
   // Keep track of the current column by scanning the string for
   // special characters
 
-  // The buffer may have been allocated underneath us.
-  if (Scanned == 0 && GetNumBytesInBuffer() != 0) {
-    Scanned = begin();
+  for (const char *End = Ptr + Size; Ptr != End; ++Ptr) {
+    ++Column;
+    if (*Ptr == '\n' || *Ptr == '\r')
+      Column = 0;
+    else if (*Ptr == '\t')
+      // Assumes tab stop = 8 characters.
+      Column += (8 - (Column & 0x7)) & 0x7;
   }
 
-  while (Scanned != end()) {
-    ++ColumnScanned;
-    if (*Scanned == '\n' || *Scanned == '\r')
-      ColumnScanned = 0;
-    else if (*Scanned == '\t')
-      // Assumes tab stop = 8 characters.
-      ColumnScanned += (8 - (ColumnScanned & 0x7)) & 0x7;
-    ++Scanned;
-  }
+  return Column;
+}
+
+/// ComputeColumn - Examine the current output and figure out which
+/// column we end up in after output.
+void formatted_raw_ostream::ComputeColumn() {
+  // The buffer may have been allocated underneath us.
+  if (Scanned == 0) Scanned = begin();
+  // Scan all characters added since our last scan to determine the new column.
+  ColumnScanned = CountColumns(ColumnScanned, Scanned, end() - Scanned);
+  // We're now current with everything in the buffer.
+  Scanned = end();
 }
 
 /// PadToColumn - Align the output to some column number.
@@ -63,9 +70,25 @@ void formatted_raw_ostream::PadToColumn(unsigned NewCol, unsigned MinPad) {
 }
 
 void formatted_raw_ostream::write_impl(const char *Ptr, size_t Size) {
+  // Figure out what's in the buffer and add it to the column count.
   ComputeColumn();
+
+  // Write the data to the underlying stream (which is unbuffered, so
+  // the data will be immediately written out).
   TheStream->write(Ptr, Size);
-  Scanned = begin();
+
+  // If this FormattedStream is unbuffered, scan the string that
+  // was just written to determine the new column.
+  if (Ptr == begin()) {
+    // Buffered mode. The buffer is being flushed; reset the scanning
+    // position to the beginning of the buffer.
+    assert(Ptr + Size == end() && "Buffer is not being fully flushed!");
+    Scanned = begin();
+  } else {
+    // Unbuffered mode. Immediately scan the string that was just
+    // written to determine the new column.
+    ColumnScanned = CountColumns(ColumnScanned, Ptr, Size);
+  }
 }
 
 /// fouts() - This returns a reference to a formatted_raw_ostream for