diff options
Diffstat (limited to '')
| -rw-r--r-- | Makefile.am | 1 | ||||
| -rw-r--r-- | src/fs/io/PeekReader.cxx | 60 | ||||
| -rw-r--r-- | src/fs/io/PeekReader.hxx | 52 |
3 files changed, 113 insertions, 0 deletions
diff --git a/Makefile.am b/Makefile.am index d28e6b599..61369e471 100644 --- a/Makefile.am +++ b/Makefile.am @@ -507,6 +507,7 @@ FS_LIBS = libfs.a libfs_a_SOURCES = \ src/fs/io/Reader.hxx \ + src/fs/io/PeekReader.cxx src/fs/io/PeekReader.hxx \ src/fs/io/FileReader.cxx src/fs/io/FileReader.hxx \ src/fs/io/BufferedReader.cxx src/fs/io/BufferedReader.hxx \ src/fs/io/TextFile.cxx src/fs/io/TextFile.hxx \ diff --git a/src/fs/io/PeekReader.cxx b/src/fs/io/PeekReader.cxx new file mode 100644 index 000000000..2e8042ab6 --- /dev/null +++ b/src/fs/io/PeekReader.cxx @@ -0,0 +1,60 @@ +/* + * Copyright (C) 2003-2014 The Music Player Daemon Project + * http://www.musicpd.org + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#include "config.h" +#include "PeekReader.hxx" + +#include <algorithm> + +#include <assert.h> +#include <string.h> + +const void * +PeekReader::Peek(size_t size, Error &error) +{ + assert(size > 0); + assert(size < sizeof(buffer)); + assert(buffer_size == 0); + assert(buffer_position == 0); + + do { + size_t nbytes = next.Read(buffer + buffer_size, + size - buffer_size, error); + if (nbytes == 0) + return nullptr; + + buffer_size += nbytes; + } while (buffer_size < size); + + return buffer; +} + +size_t +PeekReader::Read(void *data, size_t size, Error &error) +{ + size_t buffer_remaining = buffer_size - buffer_position; + if (buffer_remaining > 0) { + size_t nbytes = std::min(buffer_remaining, size); + memcpy(data, buffer + buffer_position, nbytes); + buffer_position += nbytes; + return nbytes; + } + + return next.Read(data, size, error); +} diff --git a/src/fs/io/PeekReader.hxx b/src/fs/io/PeekReader.hxx new file mode 100644 index 000000000..27e7ff7c1 --- /dev/null +++ b/src/fs/io/PeekReader.hxx @@ -0,0 +1,52 @@ +/* + * Copyright (C) 2003-2014 The Music Player Daemon Project + * http://www.musicpd.org + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * 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 General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + */ + +#ifndef MPD_PEEK_READER_HXX +#define MPD_PEEK_READER_HXX + +#include "check.h" +#include "Reader.hxx" + +#include <stdint.h> + +class AutoGunzipReader; + +/** + * A filter that allows the caller to peek the first few bytes without + * consuming them. The first call must be Peek(), and the following + * Read() will deliver the same bytes again. + */ +class PeekReader final : public Reader { + Reader &next; + + size_t buffer_size, buffer_position; + + uint8_t buffer[64]; + +public: + PeekReader(Reader &_next) + :next(_next), buffer_size(0), buffer_position(0) {} + + const void *Peek(size_t size, Error &error); + + /* virtual methods from class Reader */ + virtual size_t Read(void *data, size_t size, Error &error) override; +}; + +#endif |