1 files changed, 98 insertions, 0 deletions
diff --git a/util/bufreader.h b/util/bufreader.h
new file mode 100644
index 0000000..a0dcefa
--- /dev/null
+++ b/util/bufreader.h
@@ -0,0 +1,98 @@
+// @file bufreader.h parse a memory region into usable pieces
+
+/**
+*    Copyright (C) 2009 10gen Inc.
+*
+*    This program is free software: you can redistribute it and/or  modify
+*    it under the terms of the GNU Affero General Public License, version 3,
+*    as published by the Free Software Foundation.
+*
+*    This program is distributed in the hope that it will be useful,
+*    but WITHOUT ANY WARRANTY; without even the implied warranty of
+*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*    GNU Affero General Public License for more details.
+*
+*    You should have received a copy of the GNU Affero General Public License
+*    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+namespace mongo {
+
+    /** helper to read and parse a block of memory
+        methods throw the eof exception if the operation would pass the end of the
+        buffer with which we are working.
+    */
+    class BufReader : boost::noncopyable {
+    public:
+        class eof : public std::exception {
+        public:
+            virtual const char * what() { return "BufReader eof"; }
+        };
+
+        BufReader(const void *p, unsigned len) : _start(p), _pos(p), _end(((char *)_pos)+len) { }
+
+        bool atEof() const { return _pos == _end; }
+
+        /** read in the object specified, and advance buffer pointer */
+        template <typename T>
+        void read(T &t) {
+            T* cur = (T*) _pos;
+            T *next = cur + 1;
+            if( _end < next ) throw eof();
+            t = *cur;
+            _pos = next;
+        }
+
+        /** verify we can look at t, but do not advance */
+        template <typename T>
+        void peek(T &t) {
+            T* cur = (T*) _pos;
+            T *next = cur + 1;
+            if( _end < next ) throw eof();
+            t = *cur;
+        }
+
+        /** return current offset into buffer */
+        unsigned offset() const { return (char*)_pos - (char*)_start; }
+
+        /** return remaining bytes */
+        unsigned remaining() const { return (char*)_end -(char*)_pos; }
+
+        /** back up by nbytes */
+        void rewind(unsigned nbytes) {
+            _pos = ((char *) _pos) - nbytes;
+            assert( _pos >= _start );
+        }
+
+        /** return current position pointer, and advance by len */
+        const void* skip(unsigned len) {
+            const char *nxt = ((char *) _pos) + len;
+            if( _end < nxt ) throw eof();
+            const void *p = _pos;
+            _pos = nxt;
+            return p;
+        }
+
+        void readStr(string& s) {
+            StringBuilder b;
+            while( 1 ) {
+                char ch;
+                read(ch);
+                if( ch == 0 )
+                    break;
+                b << ch;
+            }
+            s = b.str();
+        }
+
+        const void* pos() { return _pos; }
+
+    private:
+        const void *_start;
+        const void *_pos;
+        const void *_end;
+    };
+
+}