diff options
| -rw-r--r-- | src/xz/file_io.c | 25 | ||||
| -rw-r--r-- | src/xz/file_io.h | 17 |
2 files changed, 42 insertions, 0 deletions
diff --git a/src/xz/file_io.c b/src/xz/file_io.c index d94e2321..a07501c1 100644 --- a/src/xz/file_io.c +++ b/src/xz/file_io.c @@ -812,6 +812,31 @@ io_read(file_pair *pair, io_buf *buf_union, size_t size) } +extern bool +io_pread(file_pair *pair, io_buf *buf, size_t size, off_t pos) +{ + // Using lseek() and read() is more portable than pread() and + // for us it is as good as real pread(). + if (lseek(pair->src_fd, pos, SEEK_SET) != pos) { + message_error(_("%s: Error seeking the file: %s"), + pair->src_name, strerror(errno)); + return true; + } + + const size_t amount = io_read(pair, buf, size); + if (amount == SIZE_MAX) + return true; + + if (amount != size) { + message_error(_("%s: Unexpected end of file"), + pair->src_name); + return true; + } + + return false; +} + + static bool is_sparse(const io_buf *buf) { diff --git a/src/xz/file_io.h b/src/xz/file_io.h index 58bf7b5e..94d4c174 100644 --- a/src/xz/file_io.h +++ b/src/xz/file_io.h @@ -23,6 +23,7 @@ /// Use an union to make sure that the buffer is properly aligned. typedef union { uint8_t u8[IO_BUFFER_SIZE]; + uint32_t u32[IO_BUFFER_SIZE / sizeof(uint32_t)]; uint64_t u64[IO_BUFFER_SIZE / sizeof(uint64_t)]; } io_buf; @@ -97,6 +98,22 @@ extern void io_close(file_pair *pair, bool success); extern size_t io_read(file_pair *pair, io_buf *buf, size_t size); +/// \brief Read from source file from given offset to a buffer +/// +/// This is remotely similar to standard pread(). This uses lseek() though, +/// so the read offset is changed on each call. +/// +/// \param pair Seekable source file +/// \param buf Destination buffer +/// \param size Amount of data to read +/// \param pos Offset relative to the beginning of the file, +/// from which the data should be read. +/// +/// \return On success, false is returned. On error, error message +/// is printed and true is returned. +extern bool io_pread(file_pair *pair, io_buf *buf, size_t size, off_t pos); + + /// \brief Writes a buffer to the destination file /// /// \param pair File pair having the destination file open for writing |