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+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file file_io.h
+/// \brief I/O types and functions
+//
+// Author: Lasse Collin
+//
+// This file has been put into the public domain.
+// You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+// Some systems have suboptimal BUFSIZ. Use a bit bigger value on them.
+// We also need that IO_BUFFER_SIZE is a multiple of 8 (sizeof(uint64_t))
+#if BUFSIZ <= 1024
+# define IO_BUFFER_SIZE 8192
+#else
+# define IO_BUFFER_SIZE (BUFSIZ & ~7U)
+#endif
+
+
+/// is_sparse() accesses the buffer as uint64_t for maximum speed.
+/// The u32 and u64 members must only be access through this union
+/// to avoid strict aliasing violations. Taking a pointer of u8
+/// should be fine as long as uint8_t maps to unsigned char which
+/// can alias anything.
+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;
+
+
+typedef struct {
+ /// Name of the source filename (as given on the command line) or
+ /// pointer to static "(stdin)" when reading from standard input.
+ const char *src_name;
+
+ /// Destination filename converted from src_name or pointer to static
+ /// "(stdout)" when writing to standard output.
+ char *dest_name;
+
+ /// File descriptor of the source file
+ int src_fd;
+
+ /// File descriptor of the target file
+ int dest_fd;
+
+ /// True once end of the source file has been detected.
+ bool src_eof;
+
+ /// For --flush-timeout: True if at least one byte has been read
+ /// since the previous flush or the start of the file.
+ bool src_has_seen_input;
+
+ /// For --flush-timeout: True when flushing is needed.
+ bool flush_needed;
+
+ /// If true, we look for long chunks of zeros and try to create
+ /// a sparse file.
+ bool dest_try_sparse;
+
+ /// This is used only if dest_try_sparse is true. This holds the
+ /// number of zero bytes we haven't written out, because we plan
+ /// to make that byte range a sparse chunk.
+ off_t dest_pending_sparse;
+
+ /// Stat of the source file.
+ struct stat src_st;
+
+ /// Stat of the destination file.
+ struct stat dest_st;
+
+} file_pair;
+
+
+/// \brief Initialize the I/O module
+extern void io_init(void);
+
+
+#ifndef TUKLIB_DOSLIKE
+/// \brief Write a byte to user_abort_pipe[1]
+///
+/// This is called from a signal handler.
+extern void io_write_to_user_abort_pipe(void);
+#endif
+
+
+/// \brief Disable creation of sparse files when decompressing
+extern void io_no_sparse(void);
+
+
+#ifdef ENABLE_SANDBOX
+/// \brief main() calls this if conditions for sandboxing have been met.
+extern void io_allow_sandbox(void);
+#endif
+
+
+/// \brief Open the source file
+extern file_pair *io_open_src(const char *src_name);
+
+
+/// \brief Open the destination file
+extern bool io_open_dest(file_pair *pair);
+
+
+/// \brief Closes the file descriptors and frees possible allocated memory
+///
+/// The success argument determines if source or destination file gets
+/// unlinked:
+/// - false: The destination file is unlinked.
+/// - true: The source file is unlinked unless writing to stdout or --keep
+/// was used.
+extern void io_close(file_pair *pair, bool success);
+
+
+/// \brief Reads from the source file to a buffer
+///
+/// \param pair File pair having the source file open for reading
+/// \param buf Destination buffer to hold the read data
+/// \param size Size of the buffer; assumed be smaller than SSIZE_MAX
+///
+/// \return On success, number of bytes read is returned. On end of
+/// file zero is returned and pair->src_eof set to true.
+/// On error, SIZE_MAX is returned and error message printed.
+extern size_t io_read(file_pair *pair, io_buf *buf, size_t size);
+
+
+/// \brief Fix the position in src_fd
+///
+/// This is used when --single-thream has been specified and decompression
+/// is successful. If the input file descriptor supports seeking, this
+/// function fixes the input position to point to the next byte after the
+/// decompressed stream.
+///
+/// \param pair File pair having the source file open for reading
+/// \param rewind_size How many bytes of extra have been read i.e.
+/// how much to seek backwards.
+extern void io_fix_src_pos(file_pair *pair, size_t rewind_size);
+
+
+/// \brief Seek to the given absolute position in the source file
+///
+/// This calls lseek() and also clears pair->src_eof.
+///
+/// \param pair Seekable source file
+/// \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_seek_src(file_pair *pair, uint64_t pos);
+
+
+/// \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, uint64_t pos);
+
+
+/// \brief Writes a buffer to the destination file
+///
+/// \param pair File pair having the destination file open for writing
+/// \param buf Buffer containing the data to be written
+/// \param size Size of the buffer; assumed be smaller than SSIZE_MAX
+///
+/// \return On success, zero is returned. On error, -1 is returned
+/// and error message printed.
+extern bool io_write(file_pair *pair, const io_buf *buf, size_t size);