streambuf for gzipped files.

git-svn-id: https://mosesdecoder.svn.sourceforge.net/svnroot/mosesdecoder/trunk@778 1f5c12ca-751b-0410-a591-d2e778427230

1 files changed, 80 insertions, 0 deletions

diff --git a/moses/src/gzfilebuf.h b/moses/src/gzfilebuf.h
new file mode 100644
index 000000000..5e0b38c6a
--- /dev/null
+++ b/moses/src/gzfilebuf.h
@@ -0,0 +1,80 @@
+#ifndef _GZFILEBUF_H_
+#define _GZFILEBUF_H_
+
+#include <streambuf>
+#include <zlib.h>
+
+class gzfilebuf : public std::streambuf {
+public:
+  gzfilebuf(const char *filename)
+  { _gzf = gzopen(filename, "rb"); 
+    setg (_buff+sizeof(int),     // beginning of putback area
+          _buff+sizeof(int),     // read position
+          _buff+sizeof(int));    // end position
+  }
+  ~gzfilebuf() { gzclose(_gzf); }
+protected:
+  virtual int_type overflow (int_type c) {
+      throw;
+  }
+
+  // write multiple characters
+  virtual
+  std::streamsize xsputn (const char* s,
+                          std::streamsize num) {
+      throw;
+  }
+
+  virtual std::streampos seekpos ( std::streampos sp, std::ios_base::openmode which = std::ios_base::in | std::ios_base::out ){ throw;
+  }
+
+  //read one character
+  virtual int_type underflow () {
+    // is read position before end of _buff?
+        if (gptr() < egptr()) {
+            return traits_type::to_int_type(*gptr());
+        }
+
+        /* process size of putback area
+         * - use number of characters read
+         * - but at most four
+         */
+        unsigned int numPutback = gptr() - eback();
+        if (numPutback > sizeof(int)) {
+            numPutback = sizeof(int);
+        }
+
+        /* copy up to four characters previously read into
+         * the putback _buff (area of first four characters)
+         */
+        std::memmove (_buff+(sizeof(int)-numPutback), gptr()-numPutback,
+                      numPutback);
+
+        // read new characters
+        int num = gzread(_gzf, _buff+sizeof(int), _buffsize-sizeof(int));
+        if (num <= 0) {
+            // ERROR or EOF
+            return EOF;
+        }
+
+        // reset _buff pointers
+        setg (_buff+(sizeof(int)-numPutback),   // beginning of putback area
+              _buff+sizeof(int),                // read position
+              _buff+sizeof(int)+num);           // end of buffer
+
+        // return next character
+        return traits_type::to_int_type(*gptr());
+  }
+
+  std::streamsize xsgetn (char* s,
+                          std::streamsize num) {
+    return gzread(_gzf,s,num);
+  }
+
+private:
+  gzFile _gzf;
+  static const unsigned int _buffsize = 1024;
+  char _buff[_buffsize];
+};
+
+#endif