Peter Dimov wrote:
Peter Dimov wrote:
Time for a contest. "Write the best non-blocking comment skipping filter". :-)
Here's my entry.
struct filter { char comment_char_; bool in_comment_;
filter(): comment_char_( '#' ), in_comment_( false ) { }
template< class Source > int get( Source & src ) { int c;
for( ;; ) { if( in_comment_ ) { for( ;; ) { c = src.get();
if( c == eof || c == eagain ) return c; if( c == '\n' ) break; }
in_comment_ = false; }
c = src.get();
if( c != comment_char_ ) return c;
in_comment_ = true; } } };
This one is simple enough to put in the tutorial.
struct filter2 { char comment_char_; bool in_comment_;
filter2(): comment_char_( '#' ), in_comment_( false ) { }
template< class Source > int read( Source & src, char * s, int n ) { int m = src.read( s, n );
if( m <= 0 ) return m;
int r = 0; // dest: [s, s + r)
char const * p = s; // src: [p, p + m)
for( ;; ) { if( in_comment_ ) { char const * q = static_cast<char const *>( memchr( p, '\n', m ) );
if( q == 0 ) { return r; }
m -= q - p + 1; p = q + 1; in_comment_ = false; }
char const * q = static_cast<char const *>( memchr( p, comment_char_, m ) );
if( q == 0 ) { memmove( s + r, p, m ); return r + m; }
memmove( s + r, p, q - p ); r += q - p; m -= q - p + 1; p = q + 1; in_comment_ = true; } } };
Pretty sneaky! Try that with a tab-expanding filter ;-) Jonathan