2 files changed, 31 insertions, 2 deletions
diff --git a/klm/util/file_piece.cc b/klm/util/file_piece.cc
index 4d143857..9de30fc4 100644
--- a/klm/util/file_piece.cc
+++ b/klm/util/file_piece.cc
@@ -51,7 +51,7 @@ FilePiece::FilePiece(int fd, const char *name, std::ostream *show_progress, std:
 
 FilePiece::FilePiece(std::istream &stream, const char *name, std::size_t min_buffer) :
   total_size_(kBadSize), page_(SizePage()) {
-  InitializeNoRead("istream", min_buffer);
+  InitializeNoRead(name ? name : "istream", min_buffer);
 
   fallback_to_read_ = true;
   data_.reset(MallocOrThrow(default_map_size_), default_map_size_, scoped_memory::MALLOC_ALLOCATED);
@@ -95,6 +95,32 @@ unsigned long int FilePiece::ReadULong() {
   return ReadNumber<unsigned long int>();
 }
 
+std::size_t FilePiece::Raw(void *to, std::size_t limit) {
+  if (!limit) return 0;
+  std::size_t in_buf = static_cast<std::size_t>(position_end_ - position_);
+  if (in_buf) {
+    std::size_t amount = std::min(in_buf, limit);
+    memcpy(to, position_, amount);
+    position_ += amount;
+    return amount;
+  }
+
+  std::size_t read_return;
+  if (fallback_to_read_) {
+    read_return = fell_back_.Read(to, limit);
+    progress_.Set(fell_back_.RawAmount());
+  } else {
+    uint64_t desired_begin = mapped_offset_ + static_cast<uint64_t>(position_ - data_.begin());
+    SeekOrThrow(file_.get(), desired_begin);
+    read_return = ReadOrEOF(file_.get(), to, limit);
+    // Good thing we never rewind.  This makes desired_begin calculate the right way the next time.
+    mapped_offset_ += static_cast<uint64_t>(read_return);
+    progress_ += read_return;
+  }
+  at_end_ |= (read_return == 0);
+  return read_return;
+}
+
 // Factored out so that istream can call this.
 void FilePiece::InitializeNoRead(const char *name, std::size_t min_buffer) {
   file_name_ = name;
diff --git a/klm/util/file_piece.hh b/klm/util/file_piece.hh
index c07c6011..1b110287 100644
--- a/klm/util/file_piece.hh
+++ b/klm/util/file_piece.hh
@@ -64,7 +64,10 @@ class FilePiece {
     long int ReadLong();
     unsigned long int ReadULong();
 
-    // Skip spaces defined by isspace.
+    // Fake read() function.  Reads up to limit bytes, returning the amount read.  Returns 0 on EOF || limit == 0. 
+    std::size_t Raw(void *to, std::size_t limit);
+
+    // Skip spaces defined by being in delim.
     void SkipSpaces(const bool *delim = kSpaces) {
       for (; ; ++position_) {
         if (position_ == position_end_) Shift();